0001293971-22-000016 | 10-K | XBRL Viewer

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Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
Consolidated Statements of Cash Flows $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Cash flows from operating activities:
Net loss	$ (819,378)	$ (618,695)	$ (789,608)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of contingent consideration	387	(6,468)	2,747
Depreciation and amortization	19,649	19,356	17,434
Stock-based compensation expense	127,915	156,631	160,629
Unrealized loss (gain) on equity securities	(29,356)	7,217	9,297
Excess inventory reserve	29,924	0	0
Other non-cash items	17,235	458	(11,000)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(5,289)	(10,089)	(13,913)
Inventory	(18,447)	0	0
Operating lease right-of-use assets	30,148	21,281	22,496
Accounts payable	9,286	(20,100)	23,600
Accrued expenses and other liabilities	40,025	4,835	29,617
Operating lease liabilities	(32,142)	(17,380)	(9,944)
Collaboration research advancement	(5,596)	(7,397)	(5,739)
Net cash used in operating activities	(635,639)	(470,351)	(564,384)
Cash flows from investing activities:
Purchase of property, plant and equipment	(14,503)	(28,986)	(71,028)
Purchases of marketable securities	(451,391)	(1,003,525)	(756,570)
Proceeds from maturities of marketable securities	895,333	918,288	1,340,629
Proceeds from sales of marketable securities	31,318	29,878	0
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300	0	0
Purchase of intangible assets	(8,500)	0	(5,224)
Net cash provided by (used in) investing activities	562,557	(84,345)	507,807
Cash flows from financing activities:
Net cash transferred to 2seventy bio at separation	(174,284)	0	0
Proceeds from exercise of stock options and ESPP contributions	5,355	5,179	21,187
Net cash provided by (used in) financing activities	(93,954)	546,715	21,187
Decrease in cash, cash equivalents and restricted cash	(167,036)	(7,981)	(35,390)
Cash, cash equivalents and restricted cash at beginning of year	373,728	381,709	417,099
Cash, cash equivalents and restricted cash at end of year	206,692	373,728	381,709
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	161,160	317,705	327,214
Restricted cash included in receivables and other current assets	2,282	1,500	0
Restricted cash included in restricted cash and other non-current assets	43,250	54,523	54,495
Total cash, cash equivalents and restricted cash	206,692	373,728	381,709
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	411	2,854	5,286
Right-of-use assets obtained in exchange for operating lease liabilities	202,221	19,414	23,939
Reduction of right of use asset and associated lease liability due to lease reassessment	(9,004)	0	0
Issuance of unrestricted stock awards to settle accrued employee compensation	25,074	0	0
Cash paid during the period for interest	0	0	0
Cash paid during the period for income taxes	617	361	637
Private Placement
Cash flows from financing activities:
Proceeds from issuance of common stock	74,975	0	0
Public Offering
Cash flows from financing activities:
Proceeds from issuance of common stock	$ 0	$ 541,536	$ 0

Leases - Summary of Lease Costs and Other Information Pertaining to Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 25,067	$ 18,660	$ 20,005
Total lease cost	25,067	18,660	20,005
Operating cash flows used for operating leases	$ 22,805	$ 17,780	$ 17,205
Weighted average remaining lease term	4 years 8 months 12 days	6 years 3 months 18 days	7 years 3 months 18 days
Weighted average discount rate	5.02%	5.98%	6.66%
Short-term lease, cost	$ 0	$ 0
Variable lease, cost	$ 0	$ 0

Stock-based compensation - Summary of Stock Option Activity Under Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021
Shares (in thousands)
Outstanding at beginning of period (in shares)	6,262,000
Granted (in shares)	1,238,000
Exercised (in shares)	(218,000)
Canceled or forfeited (in shares)	(2,357,000)
Conversion and modification of awards (in shares)	1,339,000
Outstanding at end of period (in shares)	3,586,000
Exercisable at end of period (in shares)	1,835,000
Vested and expected to vest at end of period (in shares)	3,586,000
Weighted- average exercise price per share
Outstanding at beginning of period (in dollars per share)	$ 105.02
Granted (in dollars per share)	27.19
Exercised (in dollars per share)	6.82
Canceled or forfeited (in dollars per share)	81.20
Conversion and modification of awards (in dollars per share)	42.90
Outstanding at end of period (in dollars per share)	39.23
Exercisable at end of period (in dollars per share)	57.09
Vested and expected to vest at end of period (in dollars per share)	$ 39.23
Weighted- average contractual life (in years)
Outstanding at end of period	6 years 9 months 18 days
Exercisable at end of period	5 years 6 months
Vested and expected to vest at end of period	6 years 9 months 18 days
Aggregate intrinsic value (in thousands)
Outstanding at end of period	$ 631
Exercisable at end of period	380
Vested and expected to vest at end of period	$ 631
Option Conversion Awards
Shares (in thousands)
Conversion and modification of awards (in shares)	4,375

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Statement of Financial Position [Abstract]
Costs from public offering	$ 33,645

401(k) Savings plan - Additional Information (Detail) - 401 (k) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Contributions to the 401(k) plan		$ 6.0
Expenses related to 401(k) plan			$ 2.8	$ 3.0	$ 2.9
Forecast
Defined Contribution Plan Disclosure [Line Items]
Contributions to the 401(k) plan	$ 2.8
Forecast \| 2seventy bio
Defined Contribution Plan Disclosure [Line Items]
Contributions to the 401(k) plan	$ 2.0

Net loss per share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net loss per share

The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands):


	Year ended December 31,
	2021	2020	2019
Outstanding stock options (1)	5,534	6,262	5,483
Restricted stock units (1)	3,427	1,495	1,127
ESPP shares and other	—	326	19
	8,961	8,083	6,629

(1) Outstanding stock options and restricted stock units include awards outstanding to employees of 2seventy bio.

Discontinued operations - Revenue and Expenses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net loss from discontinued operations	$ (22,725)	$ (63,982)	$ (85,729)	$ (84,304)	$ (63,553)	$ (57,067)	$ 119,200	$ (56,219)	$ (256,740)	$ (57,639)	$ (234,586)
2seventy bio \| Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues									42,494	250,734	44,674
Research and development									204,287	268,647	255,294
Selling, general and administrative									82,078	46,945	35,518
Share of collaboration loss									10,071	0	0
Change in fair value of contingent consideration									387	(6,468)	2,747
Total operating expenses									299,115	314,520	296,537
Loss from operations									(256,621)	(63,786)	(251,863)
Interest income, net									791	5,770	17,380
Other income (expense), net									910		103
Other income (expense), net										377
Loss before income taxes									(256,740)	(57,639)	(234,586)
Net loss from discontinued operations									(256,740)	(57,639)	(234,586)
2seventy bio \| Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| Service revenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues									18,130	114,064	30,729
2seventy bio \| Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| Collaborative arrangement revenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues									18,602	115,594	5,740
2seventy bio \| Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| Royalty and other revenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues									5,762	21,076	8,205
Cost of royalty and other revenue									$ 2,292	$ 5,396	$ 2,978

Commitments and contingencies - Schedule of Non-cancelable Contractual Obligations (Detail) $ in Thousands	Dec. 31, 2021 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2022	$ 43,903
2023	9,918
2024 and thereafter	0
Total purchase commitments	$ 53,821

Income taxes - Schedule of Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S.	$ (487,404)	$ (431,452)	$ (414,586)
Foreign	(74,976)	(128,918)	(140,981)
Loss before income taxes	$ (562,380)	$ (560,370)	$ (555,567)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 32
-Subparagraph (c)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 30
-Subparagraph (b)
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 25
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

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+ Details

Summary of significant accounting policies and basis of presentation (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Estimated Useful Lives of Assets

Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the assets, which are as follows:


Asset						Estimated useful life
Building						40 years
Computer equipment and software						3 years
Furniture and fixtures						2-5 years
Laboratory equipment						2-5 years
Leasehold improvements						Shorter of the useful life or remaining lease term

Intangible assets (Tables)

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-Lived Intangible Assets

Intangible assets, net of accumulated amortization, are summarized as follows (in thousands):


	As of December 31, 2021
	Cost		Accumulated amortization		Impairment		Net
In-licensed rights	$	5,224	(1,219)		(4,005)		—
Total	$	5,224	$	(1,219)	$	(4,005)	$	—


	As of December 31, 2020(1)
	Cost		Accumulated amortization		Impairment		Net
In-licensed rights	$	5,224	(827)		—		4,397
Total	$	5,224	$	(827)	$	—	$	4,397

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

Leases - Narrative (Details) € in Millions	1 Months Ended									12 Months Ended			22 Months Ended
Leases - Narrative (Details) € in Millions	Apr. 30, 2022 USD ($) ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Nov. 30, 2021 ft² $ / ft²	Oct. 31, 2021 USD ($) ft²	Feb. 28, 2021 USD ($)	Jul. 31, 2020 USD ($)	Mar. 31, 2020 EUR (€)	Apr. 30, 2019 USD ($) ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Nov. 30, 2016	Jun. 30, 2016
Lessee, Lease, Description [Line Items]
Lease arrangements annual rent increase percentage									3.00%
Operating lease, expense										$ 36,200,000	$ 24,200,000	$ 23,300,000
60 Binney Street lease
Lessee, Lease, Description [Line Items]
Collateralized letter of credit					$ 13,800,000
Market capitalization required for release of liability					$ 900,000,000
Lease building space (in sq ft) \| ft²					72,988
Lessee, operating lease, monthly expense					$ 500,000
60 Binney Street lease \| Forecast
Lessee, Lease, Description [Line Items]
Lease building space (in sq ft) \| ft²	58,004
Lessee, operating lease, monthly expense	$ 400,000
50 Binney Street sublease
Lessee, Lease, Description [Line Items]
Collateralized letter of credit		$ 40,100,000							$ 40,100,000
Lease building space (in sq ft) \| ft²									267,278
Rate of area for sublease per square feet (in dollars per sq ft)									99.95
Lessee, operating lease, annual expense									$ 26,700,000
Lease arrangements annual rent increase percentage		3.00%								3.00%
Lessee, operating sublease, payment commencement, term									90 days
Upfront payment for purchase of furniture and equipment		$ 7,500,000							$ 7,500,000	$ 7,500,000
Payment for purchase of furniture and equipment, upon lease commencement									$ 7,500,000
Annual base rent of sub-sublease		28,000,000								28,000,000
50 Binney Street sublease \| Selling, general and administrative
Lessee, Lease, Description [Line Items]
Loss on unrecoverable upfront payment		$ 7,500,000
Assembly Row lease
Lessee, Lease, Description [Line Items]
Lease building space (in sq ft) \| ft²				61,180
Annual lease rent per square foot (in dollars per sq ft) \| $ / ft²				45
Lease rent, annual increase percentage				2.50%
Tenant work allowance (in dollars per sq ft) \| $ / ft²				160
Manufacturing Facility
Lessee, Lease, Description [Line Items]
Lessee, operating lease, annual expense										$ 5,100,000
Lease period						5 years	5 years							5 years	12 years
Milestone paid													$ 12,000,000
Lease extension terms														3 years
Lessee, operating lease, termination fees, term										24 months
Lessee, operating lease, maximum potential annual maintenance and production fees \| €								€ 16.5
Lessee, operating lease, termination notice period						18 months	18 months	12 months
Payment of termination fee \| €			€ 1.0
Lessee, operating lease, maximum potential annual maintenance fees						$ 4,200,000	$ 5,400,000
Lessee, operating lease, termination notice period, after stage 5 commencement						8 months

Stock-based compensation - Schedule of Stock-Based Compensation Expense by Classification (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 98,740	$ 122,596	$ 131,083
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	42,989	49,766	59,378
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 55,751	$ 72,830	$ 71,705

Income taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income taxes

The components of loss before income taxes were as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
U.S.	$	(487,404)	$	(431,452)	$	(414,586)
Foreign	(74,976)		(128,918)		(140,981)
Total	$	(562,380)	$	(560,370)	$	(555,567)

The provision for (benefit from) income taxes were as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
Current:
Federal	$	—	$	—	$	—
State	—		2		7
Foreign	258		684		612
Deferred:
Federal	—		—		(966)
State	—		—		(198)
Foreign	—		—		—
Total income tax expense (benefit)	$	258	$	686	$	(545)

A reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate to the Company’s effective income tax rate as reflected in the financial statements is as follows:


	Year ended December 31,
	2021		2020		2019
Federal income tax expense at statutory rate	21.0	%	21.0	%	21.0	%
State income tax, net of federal benefit	3.9	%	3.1	%	3.7	%
Permanent differences	(0.6)	%	(0.6)	%	(0.8)	%
Stock-based compensation	(3.1)	%	(2.4)	%	(0.7)	%
Research and development credit	4.3	%	6.0	%	5.4	%
Foreign differential	(1.9)	%	(4.6)	%	(3.7)	%
Other	—	%	(0.3)	%	0.8	%
Change in valuation allowance	(23.6)	%	(22.3)	%	(25.6)	%
Effective income tax rate (expense) benefit	—	%	(0.1)	%	0.1	%

For the years ended December 31, 2021, 2020 and 2019, the Company recognized an income tax expense (benefit) of $0.3 million or 0.0%, $0.7 million or (0.1)%, and $(0.5) million or 0.1%, respectively. The Company did not recognize any significant tax expense for the years ended December 31, 2021, 2020, or 2019 as the Company was subject to a full valuation allowance. Tax expense associated with the sale of bRT and the Separation, accounted for as discontinued operations and discussed in Note 3, is $0 for the years ended December 31, 2021, 2020, or 2019 due to the full valuation allowance. Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the Company’s deferred tax assets and liabilities are composed of the following (in thousands):


	Year ended December 31,
	2021		2020 (1)
Deferred tax assets:
U.S. net operating loss carryforwards (federal and state)	$	703,125	$	546,098
Tax credit carryforwards (federal and state)	281,687		246,742
Capitalized license fees and research and development expenses	2,237		1,558
Deferred revenue	604		398
Stock-based compensation	25,181		37,164
Lease liabilities	22,916		14,787
Accruals and other	15,598		12,894
Total deferred tax assets	1,051,348		859,641
Right-of-use assets	(23,053)		(15,044)
Fixed assets	(1,546)		(1,212)
Less valuation allowance	(1,026,749)		(843,385)
Net deferred taxes	$	—	$	—

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has recorded a full valuation allowance against the Company’s otherwise recognizable net deferred tax assets. The valuation allowance increased on a net basis by approximately $183.4 million during the year ended December 31, 2021 due primarily to net operating losses, tax credit carryforwards, and stock-based compensation, offset by the sale of bRT and the Separation. Effective January 1, 2021, the Company adopted ASU 2019-12, which simplifies accounting for income taxes. There was no material impact on the Company's financial position or results of operations upon adoption.

As of December 31, 2021, 2020 and 2019, the Company had U.S. federal net operating loss carryforwards of approximately $2.63 billion, $2.03 billion, and $1.62 billion, respectively, which may be available to offset future income tax liabilities. Of the amount as of December 31, 2021, $1.92 billion will carryforward indefinitely while $711.0 million will expire at various dates through 2037. As of December 31, 2021, 2020 and 2019, the Company also had U.S. state net operating loss

carryforwards of approximately $2.39 billion, $1.89 billion, and $1.56 billion, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2041.

As of December 31, 2021, 2020 and 2019, the Company had federal research and development and orphan drug tax credit carryforwards of approximately $268.3 million, $235.3 million, and $203.1 million, respectively, available to reduce future tax liabilities which expire at various dates through 2041. As of December 31, 2021, 2020 and 2019, the Company had state credit carryforwards of approximately $16.9 million, $14.5 million, and $13.6 million, respectively, available to reduce future tax liabilities which expire at various dates through 2036. During the fourth quarter of 2018, the Company completed an analysis of prior year estimates of U.S. research and development and orphan drug tax credits for the years 2013 through 2017. The analysis resulted in an immaterial adjustment to the Company's income tax benefit, which was offset by an adjustment to the valuation allowance. An analysis of the U.S. research and development and orphan drug credits has not yet been completed for 2019, 2020, or 2021.

In March 2020, the Coronavirus Aid, Relief and Economic Security Act (“CARES Act”) was enacted. This law temporarily suspends and adjusts certain law changes enacted in the Tax Cuts and Jobs Act in 2017. In December 2020, the Consolidated Appropriations Act was enacted. This law modified the employee retention credit under the CARES Act and created credit extenders for certain credits. In March 2021, the American Rescue Plan Act ("ARPA") was enacted and contained extenders to the refundable employee retention credit and provided further limitations to executive compensation effective for tax years beginning after 2026. The Company has concluded that the provisions in the CARES Act, Consolidated Appropriations Act, and ARPA have an immaterial impact on the Company’s income tax expense due to its cumulative losses and full valuation allowance position.

Under the provisions of the Internal Revenue Code, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50 percent, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed several financings since its inception, which it believes has resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code. The Company completed a study through December 2020 confirming no additional ownership changes; any ownership shifts occurring after December 2020 could result in an ownership change under Section 382.

The Company files Federal income tax returns in the United States, and various state and foreign jurisdictions. The federal, state and foreign income tax returns are generally subject to tax examinations for the tax years ended December 31, 2018 through December 31, 2020. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service, or state or foreign tax authorities to the extent utilized in a future period.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):


	Unrecognized tax benefits
Balance as of December 31, 2019	$	15,945
Increases (decreases) for tax positions related to current period	3,149
Increases (decreases) for tax positions related to prior periods	(100)
Balance as of December 31, 2020	18,994
Increases (decreases) for tax positions related to current period	2,949
Increases (decreases) for tax positions related to prior periods	17
Balance as of December 31, 2021	21,960

The unrecognized tax benefits at December 31, 2021, if recognized, would not affect the Company’s effective tax rate due to its full valuation allowance position. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease within the next 12 months. The Company has elected to include interest and penalties related to uncertain tax positions as a component of its provision for income taxes. For the years ended December 31, 2021, 2020 and 2019, the Company’s accrued interest and penalties related to uncertain tax positions were not material.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2021

Commitments and Contingencies Disclosure [Abstract]

Schedule of Non-cancelable Contractual Obligations

The following table presents non-cancelable contractual obligations arising from these arrangements:


Years ended December 31,	Purchase commitment
2022	$	43,903
2023	9,918
2024 and thereafter	—
Total purchase commitments	$	53,821

Restricted cash (Tables)

12 Months Ended

Dec. 31, 2021

Other Assets, Noncurrent [Abstract]

Schedule of collateralized bank account of financial institution

Total restricted cash as of December 31, 2021 and 2020 consisted of the following (in thousands):


	As of December 31,
	2021		2020
50 Binney Street lease	$	40,072	$	40,072
Assembly Row lease	2,753		—
60 Binney Street lease	—		13,763
Other	2,675		2,188
Total restricted cash	$	45,500	$	56,023

Stock-based compensation - Summary of Restricted Stock Units (Detail)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Restricted stock units
Shares (in thousands)
Unvested balance at beginning of period (in shares)	1,495,000
Granted (in shares)	3,359,000
Vested (in shares)	(526,000)
Forfeited (in shares)	(987,000)
Conversion and modification of awards (in shares)	148,000
Unvested balance at end of period (in shares)	3,193,000
Weighted-average grant date fair value
Unvested balance at beginning of period (in dollars per share) \| $ / shares	$ 102.34
Granted (in dollars per share) \| $ / shares	26.43
Vested (in dollars per share) \| $ / shares	112.21
Forfeited (in dollars per share) \| $ / shares	53.58
Conversion and modification of awards (in dollars per share) \| $ / shares	16.84
Unvested balance at end of period (in dollars per share) \| $ / shares	$ 16.21
Restricted stock unit conversion awards
Shares (in thousands)
Conversion and modification of awards (in shares)	3,327

Summary of significant accounting policies and basis of presentation

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of significant accounting policies and basis of presentation

Basis of presentation

The accompanying consolidated financial statements have been prepared by the Company in accordance with accounting principles generally accepted in the United States (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States GAAP as included in the ASC and the Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”).

Certain items in the prior year’s consolidated financial statements have been reclassified to conform to the current presentation. The Company has presented its oncology business together with its manufacturing facility in Durham, North Carolina as discontinued operations in its consolidated financial statements for all periods presented (see Note 3, Discontinued operations). The historical financial statements and footnotes have been recast accordingly.

Amounts reported are computed based on thousands, except percentages, per share amounts, or as otherwise noted. As a result, certain totals may not sum due to rounding.

Principles of consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. 2seventy bio, Inc. ("2seventy bio") was a wholly-owned subsidiary until it became an independent publicly-traded company on November 4, 2021. All intercompany balances and transactions have been eliminated in consolidation.

Discontinued operations

The Company determined that the separation of its oncology business in November 2021 and the sale of its manufacturing facility in Durham, North Carolina in July 2021 represented multiple components of a single disposal plan that met the criteria for classification as a discontinued operation in accordance with ASC Subtopic 205-20, Discontinued Operations (“ASC 205-20”). Accordingly, the accompanying consolidated financial statements for all periods presented have been updated to present the assets and liabilities associated with the oncology business and the manufacturing facility separately as discontinued operations on the consolidated balance sheets and the results of all discontinued operations reported as a separate component of loss in the consolidated statements of operations and comprehensive loss (see Note 3, Discontinued operations).

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results could materially differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements.

Estimates and judgments are used in the following areas, among others: future undiscounted cash flows and subsequent fair value estimates used to assess potential and measure any impairment of long-lived assets, including goodwill and intangible assets, and the measurement of right-of-use assets and lease liabilities, stock-based compensation expense, accrued expenses, income taxes, the assets and liabilities and losses related to discontinued operations and the assessment of the Company's ability to fund its operations for at least the next twelve months from the date of issuance of these financial statements.

Foreign currency translation

The financial statements of the Company’s subsidiaries with functional currencies other than the U.S. dollar are translated into U.S. dollars using period-end exchange rates for assets and liabilities, historical exchange rates for stockholders’ equity and weighted average exchange rates for operating results. Translation gains and losses are included in accumulated other comprehensive income (loss) in stockholders’ equity. Foreign currency transaction gains and losses are included in other income (expense), net in the results of operations.

Segment information

The Company operates in a single segment, focusing on researching, developing and commercializing potentially transformative gene therapies for severe genetic diseases. Consistent with its operational structure, its chief operating decision maker manages and allocates resources at a global, consolidated level. Therefore, results of the Company's operations are reported on a consolidated basis for purposes of segment reporting. All material long-lived assets of the Company reside in the United States.

Cash and cash equivalents

The Company considers all highly liquid investments purchased with original final maturities of 90 days or less from the date of purchase to be cash equivalents. Cash equivalents comprise marketable securities with maturities of less than 90 days when purchased. Cash equivalents are reported at fair value.

Marketable securities

The Company’s marketable securities are maintained by investment managers and consist of U.S. government agency securities and treasuries, equity securities, corporate bonds and commercial paper. Debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive income (loss) as a component of stockholders’ equity until realized. Any premium arising at purchase is amortized to the earliest call date and any discount arising at purchase is accreted to maturity. Amortization and accretion of premiums and discounts are recorded in interest income, net. Equity securities with readily determinable fair values are also carried at fair value with unrealized gains and losses included in other income (expense), net. Realized gains and losses on both debt and equity securities are determined using the specific identification method and are included in other income (expense), net.

The Company classifies equity securities with readily determinable fair values, which would be available for use in its current operations, as current assets even though the Company may not dispose of such marketable securities within the next 12 months. Equity securities are included in the balance of marketable securities on the Company's consolidated balance sheets. The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Marketable securities with a remaining maturity date greater than one year are classified as non-current assets.

Effective January 1, 2020, the Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements (“ASU 2016-13” or “ASC 326”), using the effective date method. As the Company had never recorded any other-than-temporary-impairment adjustments to its available-for-sale debt securities prior to the effective date, no transition provisions are applicable to the Company.

The Company assesses its available-for-sale debt securities under the available-for-sale debt security impairment model in ASC 326 as of each reporting date in order to determine if a portion of any decline in fair value below carrying value recognized on its available-for-sale debt securities is the result of a credit loss. The Company records credit losses in the consolidated statements of operations and comprehensive loss as credit loss expense within other income (expense), net, which is limited to the difference between the fair value and the amortized cost of the security. To date, the Company has not recorded any credit losses on its available-for-sale debt securities.

Accrued interest receivable related to the Company's available-for-sale debt securities is presented within receivables and other current assets on the Company's consolidated balance sheets. The Company has elected the practical expedient available to exclude accrued interest receivable from both the fair value and the amortized cost basis of available-for-sale debt securities for the purposes of identifying and measuring any impairment. The Company writes off accrued interest receivable once it has determined that the asset is not realizable. Any write offs of accrued interest receivable are recorded by reversing interest income, recognizing credit loss expense, or a combination of both. To date, the Company has not written off any accrued interest receivables associated with its marketable securities.

Concentrations of credit risk and off-balance sheet risk

Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents and available-for-sale securities. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s marketable securities, which primarily consist of U.S. government agency securities and treasuries, equity securities, corporate bonds and commercial paper, potentially subject the Company to concentrations of credit risk. The Company has adopted an investment policy that limits the amounts the Company may invest in any one type of investment and requires all investments held by the Company to be at least AA+/Aa1 rated, thereby reducing credit risk exposure.

Fair value of financial instruments

The Company has certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements:

Level 1—Fair values are determined utilizing quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Fair values are determined utilizing quoted prices for identical or similar assets or liabilities in active markets or other market observable inputs such as interest rates, yield curves and foreign currency spot rates.

Level 3—Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Items measured at fair value on a recurring basis include marketable securities (see Note 4, Marketable securities, and Note 5, Fair value measurements). The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term nature.

Business combinations

Business combinations are accounted for using the acquisition method of accounting. Using this method, the tangible and intangible assets acquired and the liabilities assumed are recorded as of the acquisition date at their respective fair values. The Company evaluates a business as an integrated set of activities and assets that is capable of being managed for the purpose of providing a return in the form of dividends, lower costs or other economic benefits and consists of inputs and processes that provide or have the ability to provide outputs. In an acquisition of a business, the excess of the fair value of the consideration transferred over the fair value of the net assets acquired is recorded as goodwill. In an acquisition of net assets that does not constitute a business, no goodwill is recognized.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of the net assets acquired when accounted for using the acquisition method of accounting for business combinations. Goodwill is not amortized but is evaluated for impairment within the Company’s single reporting unit on an annual basis, during the fourth quarter, or more frequently if an event occurs or circumstances change that would more-likely-than-not reduce the fair value of the Company’s reporting unit below its carrying amount. The Company performs a one-step quantitative test and records the amount of goodwill impairment, if any, as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The Company has not recognized any impairment charges related to goodwill to date.

Upon disposal of a portion of a reporting unit that constitutes a business, goodwill is assigned based on the relative fair values of the portion of the reporting unit being disposed and the portion of the reporting unit remaining. This approach requires a determination of the fair value of both the business to be disposed of and the business (or businesses) within the reporting unit that will be retained. As a result of the separation of the Company's oncology business and the sale of the Company's manufacturing facility in Durham, North Carolina, the Company assigned goodwill based on the relative fair value of the business to be disposed of, and such goodwill has been reclassified to discontinued operations.

Intangible assets, net

Intangible assets, net consist of in-licensed rights with finite lives, net of accumulated amortization. The Company amortizes its intangible assets using the straight-line method over their estimated economic lives and periodically reviews for impairment. During the third quarter of 2021, the Company recognized impairment charges related to intangible assets. In accordance with FASB ASC Topic 350, General Intangibles Other than Goodwill (“ASC 350”), the Company reviewed its intangible assets for recoverability. During the third quarter of 2021, the Company determined that the intangible assets were impaired, resulting in the impairment of the remaining carrying value of the intangible assets.

Property, plant and equipment

Property, plant and equipment is stated at cost. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the assets, which are as follows:


Asset						Estimated useful life
Building						40 years
Computer equipment and software						3 years
Furniture and fixtures						2-5 years
Laboratory equipment						2-5 years
Leasehold improvements						Shorter of the useful life or remaining lease term

Impairment of long-lived assets

The Company reviews long-lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the book values of the assets to future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets.

Leases

Effective January 1, 2019, the Company adopted ASC 842 using the required modified retrospective approach and utilizing the effective date as its date of initial application.

At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets and current and non-current lease liabilities, as applicable.

Operating lease liabilities and their corresponding right-of-use assets are initially recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate to discount lease payments, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. To estimate its incremental borrowing rate, a credit rating applicable to the Company is estimated using a synthetic credit rating analysis since the Company does not currently have a rating agency-based credit rating. Prospectively, the Company will adjust the right-of-use assets for straight-line rent expense or any incentives received and remeasure the lease liability at the net present value using the same incremental borrowing rate that was in effect as of the lease commencement or transition date.

The Company has elected not to recognize leases with an original term of one year or less on the balance sheet. The Company typically only includes an initial lease term in its assessment of a lease arrangement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew.

Assumptions made by the Company at the commencement date are re-evaluated upon occurrence of certain events, including a lease modification. A lease modification results in a separate contract when the modification grants the lessee an additional right of use not included in the original lease and when lease payments increase commensurate with the standalone price for the additional right of use. When a lease modification results in a separate contract, it is accounted for in the same manner as a new lease.

In accordance with ASC 842, components of a lease should be split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) must be allocated based on the respective relative fair values to the lease components and non-lease components.

Entities may elect not to separate lease and non-lease components. Rather, entities would account for each lease component and related non-lease component together as a single lease component. The Company has elected to account for lease and non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only.

ASC 842 allows for the use of judgment in determining whether the assumed lease term is for a major part of the remaining economic life of the underlying asset and whether the present value of lease payments represents substantially all of the fair value of the underlying asset. The Company applies the bright line thresholds referenced in ASC 842-10-55-2 to assist in evaluating leases for appropriate classification. The aforementioned bright lines are applied consistently to the Company’s entire portfolio of leases.

Common stock warrants

The Company's common stock warrants are evaluated pursuant to ASC 480, Distinguishing Liabilities from Equity ("ASC 480"), and ASC 815, Derivatives and Hedging ("ASC 815"). Management classifies its freestanding warrants as (i) liabilities, if the warrant terms allow settlement of the warrant exercise in cash, or (ii) equity, if the warrant terms only allow settlement in shares of common stock.

Inventory

Inventories are stated at the lower of cost or net realizable value under the first-expired, first-out ("FEFO") methodology. Given human gene therapy products are a new and novel category of therapeutics and future economic benefit is not probable until regulatory approval for the product has been obtained, the Company has only considered inventory for capitalization upon regulatory approval. Manufacturing costs incurred prior to regulatory approval for pre-launch inventory that did not qualify for capitalization and clinical manufacturing costs are charged to research and development expense in the Company’s consolidated statements of operations and comprehensive loss as costs are incurred. Additionally, inventory that initially qualifies for capitalization but that may ultimately be used for the production of clinical drug product is expensed as research and development expense when it has been designated for the manufacture of clinical drug product.

Inventory consists of cell banks, plasmids, LVV, other materials and compounds sourced from third party suppliers and utilized in the manufacturing process, and drug product, which has been produced for the treatment of specific patients, that are owned by the Company.

Management periodically reviews inventories for excess or obsolescence, considering factors such as sales forecasts compared to quantities on hand and firm purchase commitments as well as remaining shelf life of on hand inventories. The Company writes-down its inventory that is obsolete or otherwise unmarketable to its estimated net realizable value in the period in which the impairment is first identified. Any such adjustments are included as a component of cost of goods sold within cost of product revenue on the Company’s consolidated statements of operations and comprehensive loss.

Revenue recognition

Under ASC Topic 606, Revenue from Contracts with Customers (“Topic 606”), an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines

are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer.

Once a contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations.

The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract).

The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied.

If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment.

If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. The Company assessed each of its revenue generating arrangements in order to determine whether a significant financing component exists and concluded that a significant financing component does not exist in any of its arrangements.

The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time recognition is based on the use of an output or input method.

The Company recognizes revenue within the following financial statement captions:

Product revenue

The Company recognizes product revenue in accordance with Topic 606. Product revenue represents sales of ZYNTEGLO. In 2021, the Company distributed ZYNTEGLO directly to hospitals in Germany. The Company determined that contracted sales with hospitals formed a single performance obligation and it recognizes revenue from product sales at the point in time it satisfies the performance obligation, which is upon transferring control of ZYNTEGLO to the hospital. Control of the product generally transfers upon infusion of the product.

Other revenue

In 2021, the Company entered into a grant agreement with the Bill and Melinda Gates Foundation. The Company recognizes grant revenue in accordance with ASC 958-605, Revenue Recognition Not-for-Profit Entities, when qualifying costs are incurred and barriers to restriction have been overcome. When grant funds are received after costs have been incurred, the Company records revenue and a corresponding grant receivable. Cash received from grants in advance of incurring qualifying costs is recorded as deferred revenue and recognized as revenue when qualifying costs are incurred. In addition, the Company entered into strategic collaborations and recognized an immaterial amount of revenue associated with those collaboration agreements.

Research and development expenses

Research and development costs are charged to expense as costs are incurred in performing research and development activities, including salaries and benefits, facilities costs, overhead costs, clinical study and related clinical manufacturing costs, license and milestone fees, contract services, manufacturing costs for pre-launch inventory that did not qualify for capitalization, and other related costs. Up-front fees and milestones paid to third parties in connection with technologies which have not reached technological feasibility and do not have an alternative future use are expensed as research and development expense as incurred. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company accrues costs for clinical trial activities based upon estimates of the services received and related expenses incurred that have yet to be invoiced by the contract research organizations, clinical study sites, laboratories, consultants, or other clinical trial vendors that perform the activities. Where amounts owed to a collaboration partner exceed the Company’s collaborative arrangement revenues in each quarterly period, such amounts are classified as research and development expense.

Cost of product revenue

Costs to manufacture and deliver the product and those associated with administering the therapy are included in cost of product revenue which are associated with the sale of ZYNTEGLO in Germany. Reserves for excess inventories are also included in cost of product revenue.

Stock-based compensation

The Company’s share-based compensation programs grant awards that have included stock options, restricted stock units, restricted stock awards, unrestricted stock awards and shares issued under its employee stock purchase plan. Grants are awarded to employees and non-employees, including the Company's board of directors.

The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation—Stock Compensation (“ASC 718”). ASC 718 requires all stock-based payments, including grants of stock options and restricted stock units and modifications to existing stock options, to be recognized in the consolidated statements of operations and comprehensive loss based on their fair values.

The Company’s stock-based awards are subject to either service or performance-based vesting conditions. Compensation expense related to awards with service-based vesting conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. Compensation expense related to awards with performance-based vesting conditions is recognized based on the grant date fair value over the requisite service period using the accelerated attribution method to the extent achievement of the performance condition is probable.

The Company estimates the fair value of its option awards using the Black-Scholes option pricing model, which requires the input of subjective assumptions, including (i) the expected stock price volatility, (ii) the calculation of expected term of the award, (iii) the risk-free interest rate, and (iv) expected dividends. Effective January 1, 2020, the Company eliminated the use of a representative peer group and uses only its own historical volatility data in its estimate of expected volatility given that there is now a sufficient amount of historical information regarding the volatility of its own stock price. For both employee and non-employee awards, the measurement date is the date of grant. The Company has estimated the expected term of its employee stock options using the “simplified” method, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the option due to its lack of sufficient historical data. The risk-free interest rates for periods within the expected term of the option are based on the U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The Company has never paid, and does not expect to pay, dividends in the foreseeable future.

The Company accounts for forfeitures as they occur. Stock-based compensation expense recognized in the financial statements is based on awards for which performance or service conditions are expected to be satisfied.

Conversion and modification of equity awards outstanding at date of separation of 2seventy bio

In connection with the separation of 2seventy bio on November 4, 2021, under the provisions of the existing plans, the Company adjusted its outstanding equity awards in accordance with the terms of the Employee Matters Agreement (an equitable adjustment) to preserve the intrinsic value of the awards immediately before and after the separation. These modified awards otherwise retained substantially the same terms and conditions, including term and vesting provisions. The Company will recognize future expense for awards denominated in bluebird stock and 2seventy bio stock granted to the Company's employees as a result of the separation of 2seventy bio. Expense related to awards denominated in bluebird stock granted to 2seventy bio employees will be incurred by 2seventy bio.

Stock-based compensation expense related to modified awards is measured based on the fair value for the awards as of the modification date. Any incremental stock-based compensation expense arising from the excess of the fair value of the awards on the modification date compared to the fair value of the awards immediately before the modification date is recognized at the modification date or ratably over the requisite remaining service period, as appropriate.

Interest income, net

Interest income, net consists primarily of interest income earned on investments, net of amortization of premium and accretion of discount.

Other income (expense), net

Other income (expense), net consists primarily of gains and losses on equity securities held by the Company, gains and losses on disposal of assets, and gains and losses on foreign currency.

Net loss per share

Basic net loss per share is calculated by dividing net loss from continuing operations attributable to common stockholders, net loss from discontinued operations attributable to common stockholders and net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period, including the shares of common stock issuable upon the exercise of warrants that are exercisable for little or no consideration. Diluted net loss per share is calculated by dividing the net loss from continuing operations attributable to common stockholders, net loss from discontinued operations attributable to common stockholders and net loss attributable to common stockholders by the weighted-average number of common equivalent shares outstanding for the period, including the shares of common stock issuable upon the exercise of warrants that are exercisable for little or no consideration as well as any dilutive effect from outstanding stock options, unvested restricted stock, restricted stock units, and employee stock purchase plan stock using the treasury stock method. Given that the Company recorded a net loss for each of the periods presented, there is no difference between basic and diluted net loss per share since the effect of common stock equivalents would be anti-dilutive and are, therefore, excluded from the diluted net loss per share calculation.

The Company follows the two-class method when computing net loss per share in periods when issued shares that meet the definition of participating securities are outstanding. The two-class method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Accordingly, in periods in which the Company reports a net loss attributable to common stockholders when participating securities are outstanding, losses are not allocated to the participating securities.

Income taxes

Income taxes are recorded in accordance with FASB ASC Topic 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if

based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company accrues for potential interest and penalties related to unrecognized tax benefits in income tax expense.

Comprehensive loss

Comprehensive loss is composed of net loss and other comprehensive income (loss). Other comprehensive income (loss) consists of unrealized gains and losses on debt securities, foreign currency translation adjustments and other items.

Restructuring expenses

The Company records costs and liabilities associated with exit and disposal activities in accordance with FASB ASC Topic 420, Exit or Disposal Cost Obligations ("ASC 420"). Such costs are based on estimates of fair value in the period liabilities are incurred. The Company evaluates and adjusts these costs as appropriate for changes in circumstances as additional information becomes available. Refer to Note 18, Reduction in workforce, for more information.

Recent accounting pronouncements

Recently adopted

ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The new standard was effective beginning January 1, 2021. The adoption of ASU 2019-12 did not have a material impact on the Company's financial position or results of operations upon adoption.

ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity

In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”). ASU 2020-06 simplifies the complexity associated with applying U.S. GAAP for certain financial instruments with characteristics of liabilities and equity. More specifically, the amendments focus on the guidance for convertible instruments and derivative scope exception for contracts in an entity's own equity. The Company early adopted the new standard, effective January 1, 2021. The adoption of ASU 2020-06 did not have an impact on the Company's financial position or results of operations upon adoption.

ASU No. 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs

In October 2020, the FASB issued ASU 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs (“ASU 2020-08”) to provide further clarification and update the previously issued guidance in ASU 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20: Premium Amortization on Purchased Callable Debt Securities) (“ASU 2017-08”). ASU 2017-08 shortened the amortization period for certain callable debt securities purchased at a premium by requiring that the premium be amortized to the earliest call date. ASU 2020-08 requires that at each reporting period, to the extent that the amortized cost of an individual callable debt security exceeds the amount repayable by the issuer at the next call date, the excess premium shall be amortized to the next call date. The new standard was effective beginning January 1, 2021. The adoption of ASU 2020-08 did not have a material impact on the Company's financial position or results of operations upon adoption.

ASU No. 2020-10, Codification Improvements

In October 2020, the FASB issued ASU 2020-10, Codification Improvements ("ASU 2020-10"). The amendments in this ASU represent changes to clarify the ASC, correct unintended application of the guidance, or make minor improvements to the ASC that are not expected to have a significant effect on current accounting practice or create a significant administrative cost to most entities. This new standard was effective beginning January 1, 2021. The adoption of ASU 2020-10 did not have a material impact on the Company's financial position or results of operations upon adoption.

Income taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of beginning of period	$ 18,994	$ 15,945
Increases (decreases) for tax positions related to current period	2,949	3,149
Increases (decreases) for tax positions related to prior periods	17
Increases (decreases) for tax positions related to prior periods		(100)
Balance as of end of period	$ 21,960	$ 18,994

Summary of significant accounting policies and basis of presentation - Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2021
Building
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Computer equipment and software
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Furniture and fixtures \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	2 years
Furniture and fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	5 years
Laboratory equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	2 years
Laboratory equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	5 years

Income taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
U.S. net operating loss carryforwards (federal and state)	$ 703,125	$ 546,098
Tax credit carryforwards (federal and state)	281,687	246,742
Capitalized license fees and research and development expenses	2,237	1,558
Deferred revenue	604	398
Stock-based compensation	25,181	37,164
Lease liabilities	22,916	14,787
Accruals and other	15,598	12,894
Total deferred tax assets	1,051,348	859,641
Right-of-use assets	(23,053)	(15,044)
Fixed assets	(1,546)	(1,212)
Less valuation allowance	(1,026,749)	(843,385)
Net deferred taxes	$ 0	$ 0

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Other Comprehensive Income (Loss), Tax	$ 0.0	$ 0.0	$ (1.2)

- Definition

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123586238&loc=d3e39076-109324

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32136-110900

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
-Paragraph 20
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123586238&loc=d3e38679-109324

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442407-227067

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 740
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-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32672-109319

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e640-108580

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

+ Details

Property, plant and equipment, net (Tables)

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Summary of Property, Plant and Equipment Net

Property, plant and equipment, net, consists of the following (in thousands):


	As of December 31,
	2021		2020 (1)
Laboratory equipment	$	29,061	$	27,146
Computer equipment and software	421		447
Office equipment	117		1,077
Leasehold improvements	12		5,949
Construction-in-progress	501		895
Total property, plant and equipment	30,112		35,514
Less accumulated depreciation and amortization	(20,406)		(18,141)
Property, plant and equipment, net	$	9,706	$	17,373

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Fair value measurements - Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Equity securities	$ 3,691	$ 5,653
Corporate bonds
Assets:
Marketable securities	49,307	98,781
Commercial paper
Assets:
Marketable securities	54,065	38,975
Fair value, measurements, recurring
Assets:
Cash and cash equivalents	161,160	260,629
Equity securities	3,691	5,653
Total assets	396,617	741,673
Fair value, measurements, recurring \| U.S. government agency securities and treasuries
Assets:
Marketable securities	128,393	337,635
Fair value, measurements, recurring \| Corporate bonds
Assets:
Marketable securities	49,308	98,781
Fair value, measurements, recurring \| Commercial paper
Assets:
Marketable securities	54,065	38,975
Fair value, measurements, recurring \| Quoted prices in active markets (Level 1)
Assets:
Cash and cash equivalents	161,146	260,629
Equity securities	3,691	5,653
Total assets	164,837	266,282
Fair value, measurements, recurring \| Quoted prices in active markets (Level 1) \| U.S. government agency securities and treasuries
Assets:
Marketable securities	0	0
Fair value, measurements, recurring \| Quoted prices in active markets (Level 1) \| Corporate bonds
Assets:
Marketable securities	0	0
Fair value, measurements, recurring \| Quoted prices in active markets (Level 1) \| Commercial paper
Assets:
Marketable securities	0	0
Fair value, measurements, recurring \| Significant other observable inputs (Level 2)
Assets:
Cash and cash equivalents	14	0
Equity securities	0	0
Total assets	231,780	475,391
Fair value, measurements, recurring \| Significant other observable inputs (Level 2) \| U.S. government agency securities and treasuries
Assets:
Marketable securities	128,393	337,635
Fair value, measurements, recurring \| Significant other observable inputs (Level 2) \| Corporate bonds
Assets:
Marketable securities	49,308	98,781
Fair value, measurements, recurring \| Significant other observable inputs (Level 2) \| Commercial paper
Assets:
Marketable securities	54,065	38,975
Fair value, measurements, recurring \| Significant unobservable inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Equity securities	0	0
Total assets	0	0
Fair value, measurements, recurring \| Significant unobservable inputs (Level 3) \| U.S. government agency securities and treasuries
Assets:
Marketable securities	0	0
Fair value, measurements, recurring \| Significant unobservable inputs (Level 3) \| Corporate bonds
Assets:
Marketable securities	0	0
Fair value, measurements, recurring \| Significant unobservable inputs (Level 3) \| Commercial paper
Assets:
Marketable securities	$ 0	$ 0

Selected quarterly financial data (unaudited)

12 Months Ended

Dec. 31, 2021

Quarterly Financial Information Disclosure [Abstract]

Selected quarterly financial data (Unaudited)

Selected quarterly financial data (unaudited)

The following table contains quarterly financial information for 2021 and 2020. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair presentation of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period.


	2021
	First quarter		Second quarter		Third quarter		Fourth quarter		Total
	(in thousands, except per share data)
Total revenues	$	894	$	143	$	1,019	$	1,606	$	3,662
Total operating expenses	146,988		154,844		155,468		137,273		594,573
Loss from operations	(146,094)		(154,701)		(154,449)		(135,667)		(590,911)
Net loss from continuing operations	(121,504)		(155,973)		(152,834)		(132,327)		(562,638)
Net loss from discontinued operations	(84,304)		(85,729)		(63,982)		(22,725)		(256,740)
Net loss	(205,808)		(241,702)		(216,816)		(155,052)		(819,378)
Net loss per share from continuing operations —basic and diluted	(1.81)		(2.31)		(2.23)		(1.83)		(8.16)
Net loss per share from discontinued operations—basic and diluted	(1.26)		(1.27)		(0.93)		(0.31)		(3.73)
Net loss per share—basic and diluted	$	(3.07)	$	(3.58)	$	(3.16)	$	(2.14)	$	(11.89)


	2020
	First quarter		Second quarter		Third quarter		Fourth quarter		Total
	(in thousands, except per share data)
Total revenues	$	—	$	—	$	—	$	—	$	—
Total operating expenses	144,479		143,650		131,743		139,387		559,259
Loss from operations	(144,479)		(143,650)		(131,743)		(139,387)		(559,259)
Net loss from continuing operations	(146,392)		(140,665)		(137,678)		(136,321)		(561,056)
Net income (loss) from discontinued operations	(56,219)		119,200		(57,067)		(63,553)		(57,639)
Net loss	(202,611)		(21,465)		(194,745)		(199,874)		(618,695)
Net loss per share from continuing operations —basic and diluted	(2.63)		(2.33)		(2.08)		(2.05)		(9.02)
Net income (loss) per share from discontinued operations—basic and diluted	(1.01)		1.97		(0.86)		(0.96)		(0.93)
Net loss per share—basic and diluted	$	(3.64)	$	(0.36)	$	(2.94)	$	(3.01)	$	(9.95)

401(k) Savings plan	12 Months Ended
401(k) Savings plan	Dec. 31, 2021
Retirement Benefits [Abstract]
401(k) Savings plan	401(k) Savings planIn 1997, the Company established a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code (the "401(k) Plan"). The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation on a pretax basis. In March 2022, the Company expects to make matching contributions of approximately $2.8 million related to employee contributions made during 2021. At the same time, the Company anticipates making matching contributions to 2seventy bio employees of $2.0 million for their contributions under the 401(k) Plan during 2021 through the Separation. In March 2021, the Company made $6.0 million of matching contributions related to employee contributions made during 2020. The match contribution is included in accrued expenses and other current liabilities as of December 31, 2021 and 2020. Expense related to the 401(k) Plan from continuing operations totaled $2.8 million, $3.0 million, $2.9 million for the years ended December 31, 2021, 2020, and 2019, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=21916913&loc=d3e273930-122802

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/topic&trid=2235017

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 3
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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+ Details

Income taxes - Narrative (Detail) - USD ($)	12 Months Ended
Income taxes - Narrative (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components Of Income Tax Expense Benefit [Line Items]
Income tax expense (benefit)	$ 258,000	$ 686,000	$ (545,000)
Income tax expense, discontinued operations	$ 0	$ 0	$ 0
Effective income tax rate	0.00%	(0.10%)	0.10%
Approximately valuation allowance increased	$ 183,400,000
Operating loss carryforwards, without expiration dates	1,920,000,000
Operating loss carryforwards, with expiration dates	711,000,000
Income tax examination, penalties and interest accrued	$ 0	$ 0	$ 0
Research Tax Credit Carryforward
Components Of Income Tax Expense Benefit [Line Items]
Limitations on use of net operating losses and tax credit carryforwards, period	3 years
Limitations on use of net operating losses and tax credit carryforwards, percentage	50.00%
U.S.
Components Of Income Tax Expense Benefit [Line Items]
Operating loss carryforwards	$ 2,630,000,000	2,030,000,000.00	1,620,000,000
U.S. \| Research Tax Credit Carryforward
Components Of Income Tax Expense Benefit [Line Items]
Tax credit carryforward amount	268,300,000	235,300,000	203,100,000
State and Local Jurisdiction
Components Of Income Tax Expense Benefit [Line Items]
Operating loss carryforwards	2,390,000,000	1,890,000,000	1,560,000,000
State and Local Jurisdiction \| Research Tax Credit Carryforward
Components Of Income Tax Expense Benefit [Line Items]
Tax credit carryforward amount	$ 16,900,000	$ 14,500,000	$ 13,600,000

Net loss per share (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share


	Year ended December 31,
	2021	2020	2019
Outstanding stock options (1)	5,534	6,262	5,483
Restricted stock units (1)	3,427	1,495	1,127
ESPP shares and other	—	326	19
	8,961	8,083	6,629

(1) Outstanding stock options and restricted stock units include awards outstanding to employees of 2seventy bio.

Leases (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Lease, Cost

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the years ended December 31, 2021 and 2020 (in thousands):


	For the year ended December 31,
	2021			2020 (2)			2019 (2)
Lease cost (1)
Operating lease cost	$	25,067		$	18,660		$	20,005
Total lease cost	$	25,067		$	18,660		$	20,005

Other information
Operating cash flows used for operating leases	$	22,805		$	17,780		$	17,205
Weighted average remaining lease term	4.7 years			6.3 years			7.3 years
Weighted average discount rate	5.02		%	5.98		%	6.66		%

(1) Short-term lease costs and variable lease costs incurred by the Company for the twelve months ended December 31, 2021, 2020 and 2019 were immaterial.

(2) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Summary of Future Minimum Commitments

As of December 31, 2021, future minimum commitments under ASC 842 under the Company’s operating leases were as follows (in thousands):


	As of
Maturity of lease liabilities	December 31, 2021
2022	$	27,037
2023	21,460
2024	18,009
2025	14,639
2026	8,598
2027 and thereafter	12,356
Total lease payments	102,099
Less: imputed interest	(12,515)
Total operating lease liabilities	$	89,584

Reduction in workforce - Narrative (Details) $ in Thousands		1 Months Ended		12 Months Ended
Reduction in workforce - Narrative (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Jul. 31, 2021 USD ($) employee	Apr. 30, 2021 USD ($) employee	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring expense				$ 25,801	$ 0	$ 0
Stock-based compensation expense				98,740	$ 122,596	$ 131,083
April 2021 reduction
Restructuring Cost and Reserve [Line Items]
Number of employees impacted \| employee			50
Restructuring expense			$ 4,600	4,625
July 2021 reduction
Restructuring Cost and Reserve [Line Items]
Number of employees impacted \| employee		90
Restructuring expense		$ 21,200		21,176
July 2021 reduction \| Unrestricted Stock
Restructuring Cost and Reserve [Line Items]
Stock-based compensation expense	$ 2,500
July 2021 reduction \| Unrestricted Stock \| Research And Development And Selling, General And Administrative Expenses
Restructuring Cost and Reserve [Line Items]
Stock-based compensation expense				$ 2,500

Commitments and contingencies

12 Months Ended

Dec. 31, 2021

Commitments and Contingencies Disclosure [Abstract]

Commitments and contingencies

Lease commitments

The Company leases certain office and laboratory space and has embedded leases at contract manufacturing organizations. Refer to Note 10, Leases, for further information on the terms of these lease agreements.

Other funding commitments

The Company is party to various agreements, principally relating to licensed technology, that require future payments relating to milestones that may be met in subsequent periods or royalties on future sales of specified products.

Additionally, the Company is party to various contracts with contract research organizations and contract manufacturers that generally provide for termination on notice, with the exact amounts in the event of termination to be based on the timing of the termination and the terms of the agreement.

Based on our development plans as of December 31, 2021, the Company may be obligated to make future development, regulatory and commercial milestone payments and royalty payments on future sales of specified products associated with the Company's collaboration and license agreements. Payments under these agreements generally become due and payable upon achievement of such milestones or sales. When the achievement of these milestones or sales have not occurred, such contingencies are not recorded in the Company’s financial statements.

The Company has various manufacturing development and license agreements to support clinical and commercial product needs. The following table presents non-cancelable contractual obligations arising from these arrangements:


Years ended December 31,	Purchase commitment
2022	$	43,903
2023	9,918
2024 and thereafter	—
Total purchase commitments	$	53,821

Litigation

From time to time, the Company is party to various claims and complaints arising in the ordinary course of business, including securities class action litigation. The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to the agreements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is generally unlimited. Management does not believe that any ultimate liability resulting from any of these claims will have a material adverse effect on its results of operations, financial position, or liquidity. However, management cannot give any assurance regarding the ultimate outcome of any claims, and their resolution could be material to operating results for any particular period.

The Company also indemnifies each of its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company's request in such capacity, as permitted under Delaware law and in accordance with its certificate of incorporation and by-laws. The term of the indemnification period lasts as long as such officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. This insurance allows the transfer of risk associated with the Company's exposure and may enable it to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, it has not recognized any liabilities relating to these obligations.

Property, plant and equipment, net - Summary of Property, Plant and Equipment Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 30,112	$ 35,514
Less accumulated depreciation and amortization	(20,406)	(18,141)
Property, plant and equipment, net	9,706	17,373
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	29,061	27,146
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	421	447
Office equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	117	1,077
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	12	5,949
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 501	$ 895

Description of the business	12 Months Ended
Description of the business	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the business	Description of the business bluebird bio, Inc. (the “Company” or “bluebird”) was incorporated in Delaware on April 16, 1992, and is headquartered in Cambridge, Massachusetts. The Company is a biotechnology company committed to researching, developing and commercializing potentially transformative gene therapies for severe genetic diseases. Since its inception, the Company has devoted substantially all of its resources to its research and development efforts relating to its product candidates, including activities to manufacture product candidates, conduct clinical studies of its product candidates, perform preclinical research to identify new product candidates and provide selling, general and administrative support for these operations, including commercial-readiness activities. In August 2021, the Company announced its intent to focus its severe genetic disease business on the U.S. market and further invest in research and development for its core programs in β-thalassemia, sickle cell disease ("SCD"), and cerebral adrenoleukodystrophy ("CALD") in that market. As part of the strategy to focus on the U.S. market, it began executing an orderly wind down of its European operations, which will result in a reduction of selling, general and administrative costs and had an impact on the Company's excess inventory analysis, which is based on forecasted consumption levels driven by sales forecasts. In November 2021, the Company completed the separation of its severe genetic disease and oncology programs into two separate, independent publicly traded companies, bluebird bio, Inc. and 2seventy bio, Inc. ("2seventy bio"), a Delaware corporation and wholly-owned subsidiary of the Company prior to the separation. bluebird intends to retain its severe genetic disease programs, with a focus on the U.S. market. The Company’s programs in severe genetic diseases include programs for β-thalassemia, SCD, and CALD. The Company also expects to make focused investments in research and development efforts on optimizing our existing programs as well as on pipeline programs in severe genetic diseases. The Company’s programs in severe genetic diseases include betibeglogene autotemcel ("beti-cel", formerly "LentiGlobin for β-thalassemia gene therapy") as a treatment for β-thalassemia; lovotibeglogene autotemcel ("lovo-cel") as a treatment for SCD; and elivaldogene autotemcel ("eli-cel", formerly "Lenti-D gene therapy") as a treatment for CALD. As of December 31, 2021, the Company had cash, cash equivalents and marketable securities of $396.6 million. The Company has incurred losses since inception and to date has financed its operations primarily through the sale of equity securities and, to a lesser extent, through collaboration agreements and grants from charitable foundations. As of December 31, 2021, the Company had an accumulated deficit of $3.72 billion. During the twelve months ended December 31, 2021, the Company incurred a loss from continuing operations of $562.6 million and used $635.6 million of cash in operations. The Company expects to continue to generate operating losses and negative operating cash flows for the next few years and will need additional funding to support its planned operating activities through profitability. The transition to profitability is dependent upon the successful development, approval, and commercialization of beti-cel, eli-cel, and lovo-cel, and the achievement of a level of revenues adequate to support its cost structure. In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, the Company evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the date that these consolidated financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the Company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that these consolidated financial statements are issued. In performing its analysis, management excluded certain elements of its operating plan that cannot be considered probable. Under ASC 205-40, the future receipt of potential funding from future equity or debt issuances, the release of restricted cash related to the Company’s 50 Binney Street sublease, and the potential sale of priority review vouchers cannot be considered probable at this time because these plans are not entirely within the Company’s control nor have been approved by the Board of Directors as of the date of these consolidated financial statements. The Company's expectation to generate operating losses and negative operating cash flows in the future and the need for additional funding to support its planned operations raise substantial doubt regarding the Company’s ability to continue as a going concern for a period of one year after the date that these consolidated financial statements are issued. Management's plans to alleviate the conditions that raise substantial doubt include reduced 2022 spending, including projected savings through the move of the Company's headquarters to Assembly Row in Somerville, Massachusetts, the orderly wind down of European operations, the potential sale of priority review vouchers that would be issued with anticipated U.S. regulatory approvals of BLAs for beti-cel and eli-cel, and the pursuit of additional cash resources through public or private equity or debt financings. Management has concluded the likelihood that its plan to successfully obtain sufficient funding from one or more of these sources, or adequately reduce expenditures, while reasonably possible, is less than probable. Accordingly, the Company has concluded that substantial doubt exists about the Company’s ability to continue as a going concern for a period of at least 12 months from the date of issuance of these consolidated financial statements. The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described above.

Reduction in workforce

12 Months Ended

Dec. 31, 2021

Restructuring and Related Activities [Abstract]

Reduction in workforce

In April 2021, the Company announced its decision to withdraw ZYNTEGLO from the German market because reimbursement negotiations in Germany did not result in a price for ZYNTEGLO that reflects the value of the one-time gene therapy with potential life-long benefit for people living with β-thalassemia requiring regular transfusions. A total of approximately 50 employees were impacted by this reduction. During the three months ended June 30, 2021, the Company substantially completed the implementation of this reduction and, in accordance with ASC 420, Exit and Disposal Activities, and ASC 712, Nonretirement Postemployment Benefits, recorded approximately $4.6 million of costs including severance, the portion of the employees' 2021 retention bonuses to be paid in cash, and the pro rata portion of the employees' 2021 performance bonus.

In July 2021, the Company made the decision to focus its efforts on the U.S. market for beti-cel, eli-cel, and lovo-cel and is executing an orderly wind down of its European operations. A total of approximately 90 employees were impacted by the reduction in workforce associated with this decision. The Company recorded $21.2 million of expense, in accordance with the related accounting standards mentioned above, for the affected employees. This amount includes expense for severance, the pro rata portion of the employees' 2021 performance bonus, the portion of the European employees' 2021 retention bonuses to be paid in cash, and the portion of retention bonuses to be paid in unrestricted stock awards, which were granted on September 30, 2021. As described in Note 14, Stock-based compensation, the Company recorded $2.5 million of costs associated with the grant of unrestricted stock awards to affected employees as a one-time payment. All costs associated with the April 2021 and July 2021 reductions are reflected within restructuring expense in the Company's consolidated statements of operations and comprehensive loss.

The Company expects that substantially all accrued restructuring charges will be paid in cash by March 31, 2022.

The following table summarizes the accrued liabilities activity recorded in connection with the reduction in workforce for the year ended December 31, 2021 (in thousands):


	Charges		Amount paid		Amounts accrued at December 31, 2021
April 2021 reduction	$	4,625	$	(4,625)	$	—
July 2021 reduction	21,176		(16,503)		4,673
Total	$	25,801	$	(21,128)	$	4,673

During the year ended December 31, 2021, the Company recorded approximately $25.8 million in restructuring expenses. During the year ended December 31, 2021, the Company recorded $2.5 million in research and development expenses and selling, general and administrative expenses related to the grant of unrestricted stock awards to affected employees.

Marketable securities - Summary of Marketable Securities Held (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Equity securities, amortized cost / cost	$ 4,305	$ 20,017
Marketable securities, amortized cost / cost	236,638	495,098
Equity securities, unrealized gains	0	0
Marketable securities, unrealized gains	0	367
Equity securities, unrealized losses	(614)	(14,364)
Marketable securities, unrealized losses	(1,182)	(14,421)
Equity securities	3,691	5,653
Marketable securities, fair value	235,456	481,044
U.S. government agency securities and treasuries
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost / cost	128,902	337,521
Debt securities, unrealized gains	0	151
Debt securities, unrealized losses	(509)	(37)
Debt securities, fair value	128,393	337,635
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost / cost	49,366	98,585
Debt securities, unrealized gains	0	216
Debt securities, unrealized losses	(59)	(20)
Debt securities, fair value	49,307	98,781
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost / cost	54,065	38,975
Debt securities, unrealized gains	0	0
Debt securities, unrealized losses	0	0
Debt securities, fair value	$ 54,065	$ 38,975

Marketable securities (Tables)

12 Months Ended

Dec. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Summary of Marketable Securities Held

The following table summarizes the marketable securities held at December 31, 2021 and 2020 (in thousands):


	Amortized cost / cost		Unrealized gains		Unrealized losses		Fair value
December 31, 2021
U.S. government agency securities and treasuries	$	128,902	$	—	$	(509)	$	128,393
Corporate bonds	49,366		—		(59)		49,307
Commercial paper	54,065		—		—		54,065
Equity securities	4,305		—		(614)		3,691
Total	$	236,638	$	—	$	(1,182)	$	235,456
December 31, 2020 (1)
U.S. government agency securities and treasuries	$	337,521	$	151	$	(37)	$	337,635
Corporate bonds	98,585		216		(20)		98,781
Commercial paper	38,975		—		—		38,975
Equity securities	20,017		—		(14,364)		5,653
Total	$	495,098	$	367	$	(14,421)	$	481,044

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Discontinued operations - Narrative (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares	Nov. 03, 2021 agreement	Oct. 19, 2021	Dec. 31, 2020 $ / shares
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Conversion ratio			0.3333
Common stock, par value (in dollars per share) \| $ / shares	$ 0.01			$ 0.01
Number of transition services agreements \| agreement		2
Initial term of transition services agreement		2 years
Selling, general and administrative expense related to transition services agreement	$ 0.7
Lentiviral Vector Manufacturing Facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net assets transferred to 2seventy bio	111.2
Loss on fixed assets disposal	$ 2.0
2seventy bio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Common stock, par value (in dollars per share) \| $ / shares	$ 0.0001

Net loss per share - Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share (in shares)	8,961	8,083	6,629
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share (in shares)	5,534	6,262	5,483
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share (in shares)	3,427	1,495	1,127
ESPP shares and other
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share (in shares)	0	326	19

Inventory

12 Months Ended

Dec. 31, 2021

Inventory Disclosure [Abstract]

Inventory

Inventory consists of the following (in thousands):


	As of December 31, 2021		As of December 31, 2020
Raw materials	$	—	$	8,967
Finished goods	—		1,731
Inventory	$	—	$	10,698

During the year ended December 31, 2021, the Company recorded a reserve for excess inventories of $29.9 million, which is included within cost of product revenue in the consolidated statements of operations and comprehensive loss. During the year ended December 31, 2020, the Company did not record a reserve for excess inventories.

Accrued expenses and other current liabilities

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	As of December 31,
	2021		2020 (1)
Employee compensation	$	41,095	$	41,192
Accrued goods and services	24,273		14,855
Accrued clinical and contract research organization costs	17,769		20,912
Accrued manufacturing costs	15,722		15,763
Accrued professional fees	1,665		1,541
Deferred revenue, current portion	2,282		1,500
Other	1,152		2,427
Total accrued expenses and other current liabilities	$	103,958	$	98,190

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Accrued employee compensation includes severance costs associated with the Company's orderly wind down of its European operations. As of December 31, 2021, the Company had accrued expenses of $4.7 million related to these restructuring costs. Please refer to Note 17, Reduction in workforce, for further discussion.

Summary of significant accounting policies and basis of presentation (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Basis of presentation

Amounts reported are computed based on thousands, except percentages, per share amounts, or as otherwise noted. As a result, certain totals may not sum due to rounding.

Principles of consolidation

Discontinued operations

Use of estimates

Foreign currency transaction

Foreign currency translation

Segment information

Cash and cash equivalents

Marketable securities

Concentrations of credit risk and off-balance sheet risk

Fair value of financial instruments

Level 1—Fair values are determined utilizing quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 3—Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Business combinations

Goodwill

Intangible assets

Intangible assets, netIntangible assets, net consist of in-licensed rights with finite lives, net of accumulated amortization. The Company amortizes its intangible assets using the straight-line method over their estimated economic lives and periodically reviews for impairment. During the third quarter of 2021, the Company recognized impairment charges related to intangible assets. In accordance with FASB ASC Topic 350, General Intangibles Other than Goodwill (“ASC 350”), the Company reviewed its intangible assets for recoverability. During the third quarter of 2021, the Company determined that the intangible assets were impaired, resulting in the impairment of the remaining carrying value of the intangible assets.

Property, plant and equipment


Asset						Estimated useful life
Building						40 years
Computer equipment and software						3 years
Furniture and fixtures						2-5 years
Laboratory equipment						2-5 years
Leasehold improvements						Shorter of the useful life or remaining lease term

Impairment of long-lived assets

Leases

Effective January 1, 2019, the Company adopted ASC 842 using the required modified retrospective approach and utilizing the effective date as its date of initial application.

Common stock warrants

Common stock warrantsThe Company's common stock warrants are evaluated pursuant to ASC 480, Distinguishing Liabilities from Equity ("ASC 480"), and ASC 815, Derivatives and Hedging ("ASC 815"). Management classifies its freestanding warrants as (i) liabilities, if the warrant terms allow settlement of the warrant exercise in cash, or (ii) equity, if the warrant terms only allow settlement in shares of common stock.

Inventory

Revenue recognition

The Company recognizes revenue within the following financial statement captions:

Product revenue

Other revenue

Research and development expenses

Cost of product revenue

Cost of product revenue Costs to manufacture and deliver the product and those associated with administering the therapy are included in cost of product revenue which are associated with the sale of ZYNTEGLO in Germany. Reserves for excess inventories are also included in cost of product revenue.

Stock-based compensation

Conversion and modification of equity awards outstanding at date of separation of 2seventy bio

Interest income, net

Interest income, netInterest income, net consists primarily of interest income earned on investments, net of amortization of premium and accretion of discount.

Other income (expense), net

Other income (expense), net consists primarily of gains and losses on equity securities held by the Company, gains and losses on disposal of assets, and gains and losses on foreign currency.

Net loss per share

Income taxes

based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

Comprehensive loss

Restructuring expenses

Recent accounting pronouncements

Recently adopted

ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

ASU No. 2020-08, Codification Improvements to Subtopic 310-20, Receivables - Nonrefundable Fees and Other Costs

ASU No. 2020-10, Codification Improvements

Marketable securities

12 Months Ended

Dec. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Marketable securities

The following table summarizes the marketable securities held at December 31, 2021 and 2020 (in thousands):


	Amortized cost / cost		Unrealized gains		Unrealized losses		Fair value
December 31, 2021
U.S. government agency securities and treasuries	$	128,902	$	—	$	(509)	$	128,393
Corporate bonds	49,366		—		(59)		49,307
Commercial paper	54,065		—		—		54,065
Equity securities	4,305		—		(614)		3,691
Total	$	236,638	$	—	$	(1,182)	$	235,456
December 31, 2020 (1)
U.S. government agency securities and treasuries	$	337,521	$	151	$	(37)	$	337,635
Corporate bonds	98,585		216		(20)		98,781
Commercial paper	38,975		—		—		38,975
Equity securities	20,017		—		(14,364)		5,653
Total	$	495,098	$	367	$	(14,421)	$	481,044

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

No available-for-sale debt securities held as of December 31, 2021 or 2020 had remaining maturities greater than five years.

Fair value measurements

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair value measurements

The following table sets forth the Company’s assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2021 and 2020 (in thousands):


	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2021
Assets:
Cash and cash equivalents	$	161,160	$	161,146	$	14	$	—
Marketable securities:
U.S. government agency securities and treasuries	128,393		—		128,393		—
Corporate bonds	49,308		—		49,308		—
Commercial paper	54,065		—		54,065		—
Equity securities	3,691		3,691		—		—
Total assets	$	396,617	$	164,837	$	231,780	$	—
December 31, 2020 (1)
Assets:
Cash and cash equivalents	$	260,629	$	260,629	$	—	$	—
Marketable securities:
U.S. government agency securities and treasuries	337,635		—		337,635		—
Corporate bonds	98,781		—		98,781		—
Commercial paper	38,975		—		38,975		—
Equity securities	5,653		5,653		—		—
Total assets	$	741,673	$	266,282	$	475,391	$	—

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Cash and cash equivalents

As of December 31, 2021, cash and cash equivalents comprise funds in cash and money market accounts. As of December 31, 2020, cash and cash equivalents comprise funds in cash and money market accounts.

Marketable securities

Marketable securities classified as Level 2 within the valuation hierarchy generally consist of U.S. government agency securities and treasuries, corporate bonds, and commercial paper. The Company estimates the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for the same or similar securities, issuer credit spreads, benchmark yields, and other observable inputs. The Company validates the prices provided by its third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances.

The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to the earliest call date for premiums or to maturity for discounts. At December 31, 2021 and 2020, the balance in the Company’s accumulated other comprehensive loss was composed primarily of activity related to the Company’s available-for-sale debt securities. There were no material realized gains or losses recognized on the sale or maturity of available-for-sale securities during the years ended December 31, 2021 or 2020.

Accrued interest receivable on the Company's available-for-sale debt securities totaled $0.3 million and $1.5 million as of December 31, 2021 and 2020, respectively. No accrued interest receivable was written off during the twelve months ended December 31, 2021 or 2020.

The following table summarizes available-for-sale debt securities in a continuous unrealized loss position for less than and greater than twelve months, and for which an allowance for credit losses has not been recorded at December 31, 2021 and 2020 (in thousands):


	Less than 12 months				12 months or greater				Total
Description	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
December 31, 2021
U.S. government agency securities and treasuries	$	108,695	$	(505)	$	2,496	$	(4)	$	111,191	$	(509)
Corporate bonds	45,042		(56)		3,896		(2)		48,938		(58)
Total	$	153,737	$	(561)	$	6,392	$	(6)	$	160,129	$	(567)
December 31, 2020 (1)
U.S. government agency securities and treasuries	$	105,692	$	(37)	$	—	$	—	$	105,692	$	(37)
Corporate bonds	38,299		(20)		603		—		38,902		(20)
Total	$	143,991	$	(57)	$	603	$	—	$	144,594	$	(57)

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

The Company determined that there was no material change in the credit risk of the above investments during the twelve months ended December 31, 2021. As such, an allowance for credit losses was not recognized. As of December 31, 2021, the Company does not intend to sell such securities and it is not more likely than not that the Company will be required to sell the securities before recovery of their amortized cost bases.

The Company holds equity securities with an aggregate fair value of $3.7 million and $5.7 million at December 31, 2021 and 2020, respectively, within current marketable securities on its consolidated balance sheets. In January 2021, the Company sold a portion of its equity securities for proceeds of $31.3 million. The Company recorded gains of $29.4 million and losses of $7.2 million and $9.3 million related to its equity securities during the years ended December 31, 2021, 2020 and 2019, respectively. Gains and losses related to equity securities are included in other income (expense), net in the consolidated statements of operations and comprehensive loss.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Stock-based compensation - Narrative (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		12 Months Ended
	Nov. 04, 2021	Jan. 31, 2022	Jan. 31, 2021	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2021	Jun. 24, 2013	Jun. 03, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in common stock available for issuance under 2013 plan (in shares)			2,700,000
Number of shares available for issuance (in shares)				3,200,000		3,200,000
Incremental fair value from modification	$ 4,500					$ 20,300
Stock-based compensation expense						98,740	$ 122,596	$ 131,083
Stock-based compensation capitalized into inventory						$ 1,000	$ 500
Unrestricted stock awards granted (in shares)						1,238,000
Weighted average grant date fair value of options granted (in dollars per share)						$ 16.32	$ 43.24	$ 83.44
Intrinsic value of stock options exercised						$ 5,100	$ 4,000	$ 29,000
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in common stock available for issuance under 2013 plan (in shares)		2,800,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense						54,660	75,837	79,912
Unrecognized stock- based compensation expense related to unvested stock options, restricted stock awards and employee stock purchase plan				$ 34,200		$ 34,200
Expected weighted-average period related to unvested stock options, restricted stock awards and employee stock purchase plan						2 years 2 months 8 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense						$ 30,767	$ 38,123	50,158
Unvested restricted stock awards outstanding (in shares)				3,193,000		3,193,000	1,495,000
Unrecognized stock- based compensation expense related to unvested stock options, restricted stock awards and employee stock purchase plan				$ 54,300		$ 54,300
Expected weighted-average period related to unvested stock options, restricted stock awards and employee stock purchase plan						2 years 3 months 3 days
Intrinsic value of restricted stock units vested						$ 44,000	$ 30,900	28,400
Employee stock purchase plan and other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for future issuance (in shares)											200,000
Stock-based compensation expense						$ 13,313	$ 8,636	$ 1,013
Increase in shares authorized (in shares)									1,400,000
Employee stock purchase plan and other \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, shares issued in period (less than) (in shares)						100,000	100,000
2013 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for future issuance (in shares)										1,000,000
Percentage of automatic increase in shares reserved and available for issuance determined based on shares outstanding				4.00%		4.00%
2020 Annual Incentive Program \| Unrestricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 10,600
Unrestricted stock awards granted (in shares)			400,000
Stock based compensation			$ 21,200
Retention Program \| Unrestricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrestricted stock awards granted (in shares)				1,000,000	100,000

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 161,160	$ 260,629
Marketable securities	138,343	419,599
Prepaid expenses	25,628	25,718
Inventory	0	10,698
Receivables and other current assets	11,389	3,872
Current assets of discontinued operations	0	495,021
Total current assets	336,520	1,215,537
Marketable securities	97,114	61,445
Property, plant and equipment, net	9,706	17,373
Intangible assets, net	0	4,397
Goodwill	5,646	5,646
Operating lease right-of-use assets	91,532	67,563
Restricted cash and other non-current assets	53,277	65,727
Non-current assets of discontinued operations	0	343,564
Total assets	593,795	1,781,252
Current liabilities:
Accounts payable	25,883	13,811
Accrued expenses and other current liabilities	103,958	98,190
Operating lease liability, current portion	23,152	9,711
Current liabilities of discontinued operations	0	81,876
Total current liabilities	152,993	203,588
Operating lease liability, net of current portion	66,432	55,707
Other non-current liabilities	93	5,759
Non-current liabilities of discontinued operations	0	161,142
Total liabilities	219,518	426,196
Commitments and contingencies Note 11
Stockholders' equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at December 31, 2021 and December 31, 2020	0	0
Common stock, $0.01 par value, 125,000 shares authorized; 71,115 and 66,432 shares issued and outstanding at December 31, 2021 and December 31, 2020, respectively	711	665
Additional paid-in capital	4,096,402	4,260,443
Accumulated other comprehensive loss	(2,911)	(5,505)
Accumulated deficit	(3,719,925)	(2,900,547)
Total stockholders' equity	374,277	1,355,056
Total liabilities and stockholders' equity	$ 593,795	$ 1,781,252

Stock-based compensation - Summary of Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 98,740	$ 122,596	$ 131,083
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	54,660	75,837	79,912
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	30,767	38,123	50,158
Employee stock purchase plan and other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 13,313	$ 8,636	$ 1,013

Discontinued operations - Significant Non-Cash Items and Capital Expenditures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Change in fair value of contingent consideration	$ 387	$ (6,468)	$ 2,747
Depreciation and amortization	4,900	5,100	4,100
Stock-based compensation expense	127,915	156,631	160,629
Investing activities:
Purchase of property, plant and equipment	(14,503)	(28,986)	(71,028)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300	0	0
Purchase of intangible assets	(8,500)	0	(5,224)
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	411	2,854	5,286
Right-of-use assets obtained in exchange for operating lease liabilities	202,221	19,414	23,939
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff \| 2seventy bio
Operating activities:
Change in fair value of contingent consideration	387	(6,468)	2,747
Depreciation and amortization	14,195	13,730	12,995
Stock-based compensation expense	29,175	34,036	29,545
Loss on fixed assets disposal	569	146	108
Loss on sale of Durham, North Carolina manufacturing facility	1,986	0	0
Investing activities:
Purchase of property, plant and equipment	(11,256)	(23,159)	(57,196)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300	0	0
Purchase of intangible assets	(8,500)	0	0
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	778	2,039	3,064
Right-of-use assets obtained in exchange for operating lease liabilities	$ 151,520	$ 4,989	$ 9,745

Marketable securities - Narrative (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Debt securities, available-for-sale, noncurrent	$ 0	$ 0

Property, plant and equipment, net - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 4.9	$ 5.1	$ 4.1

Accrued expenses and other current liabilities - Narrative (Details)	Dec. 31, 2021 USD ($)
Payables and Accruals [Abstract]
Accrued restructuring charges	$ 4,673,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	125,000,000	125,000,000
Common stock, shares issued (in shares)	71,115,000	66,432,000
Common stock, shares outstanding (in shares)	71,115,000	66,432,000

Intangible assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Cost	$ 5,224	$ 5,224
Accumulated amortization	(1,219)	(827)
Impairment	(4,005)	0
Net	0	4,397
In-licensed rights
Finite-Lived Intangible Assets [Line Items]
Cost	5,224	5,224
Accumulated amortization	(1,219)	(827)
Impairment	(4,005)	0
Net	$ 0	$ 4,397

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Total revenues	$ 3,662	$ 0	$ 0
Operating expenses:
Research and development	319,946	319,309	327,119
Selling, general and administrative	209,969	239,950	235,844
Restructuring expense	25,801	0	0
Total operating expenses	594,573	559,259	562,963
Loss from operations	(590,911)	(559,259)	(562,963)
Interest income, net	879	5,770	17,380
Other income (expense), net	27,652	(6,881)	(9,984)
Loss before income taxes	(562,380)	(560,370)	(555,567)
Income tax (expense) benefit	(258)	(686)	545
Net loss from continuing operations	(562,638)	(561,056)	(555,022)
Net income (loss) from discontinued operations	(256,740)	(57,639)	(234,586)
Net loss	$ (819,378)	$ (618,695)	$ (789,608)
Net loss per share from continuing operations - basic (in dollars per share)	$ (8.16)	$ (9.02)	$ (10.06)
Net loss per share from continuing operations - diluted (in dollars per share)	(8.16)	(9.02)	(10.06)
Net loss per share from discontinued operations - basic (in dollars per share)	(3.73)	(0.93)	(4.25)
Net loss per share from discontinued operations - diluted (in dollars per share)	(3.73)	(0.93)	(4.25)
Net loss per share applicable to common stockholders - basic (in dollars per share)	(11.89)	(9.95)	(14.31)
Net loss per share applicable to common stockholders - diluted (in dollars per share)	$ (11.89)	$ (9.95)	$ (14.31)
Weighted-average number of common shares used in computing net loss per share - basic and diluted (in shares)	68,910	62,178	55,191
Other comprehensive income (loss):
Other comprehensive income (loss)	$ 2,364	$ (3,612)	$ 1,734
Comprehensive loss	(817,014)	(622,307)	(787,874)
Product revenue
Revenue:
Revenue	2,850	0	0
Operating expenses:
Cost of product revenue	38,857	0	0
Other revenue
Revenue:
Revenue	$ 812	$ 0	$ 0

Leases

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Leases

The Company leases certain office and laboratory space. Additionally, the Company has embedded leases through its agreements with contract manufacturing organizations.

60 Binney Street lease & sublease

In October 2021, the Company entered into a consent to assignment and amendment to its lease agreement for its 60 Binney Street lease (the "Assignment"). The Assignment transfers the Company's interest in the lease to 2seventy bio and releases the Company from its obligation to maintain the $13.8 million collateralized letter of credit required under the original 60 Binney Street lease. Although the lease was legally transferred to 2seventy bio, the lessor required that the Company remain secondarily liable as a guarantor for payment obligations accruing under the 60 Binney Street lease from the date of Assignment until (i) the Company has completely vacated the premises and (ii) 2seventy bio has reached a market capitalization of $900 million. Upon Separation, the lease assignment was accounted for as the termination of the original lease and the Company de-recognized the right-of-use asset and lease liability related to the 60 Binney Street lease and recognized the fair value of the guarantee pursuant to ASC 405, Liabilities. The fair value of the guarantee was not material.

Concurrent with the Assignment of the 60 Binney Street Lease, the Company entered into a sublease agreement with 2seventy bio for office, laboratory and storage space located at 60 Binney Street (the "60 Binney Street Sublease") while it constructs and outfits its new office and laboratory space. Under the terms of the 60 Binney Street Sublease, the Company will lease 72,988 square feet for $0.5 million per month in base rent for the period beginning from the Assignment through March 2022 and 58,004 square feet for $0.4 million per month in base rent for the period from April 2022 through March 2024. The Company accounted for the 60 Binney Street Sublease as a new lease under ASC 842, and in November 2021, recognized a right-of-use asset and lease liability related to the 60 Binney Street Sublease.

50 Binney Street sublease & sub-sublease

In April 2019, the Company entered into a sublease agreement for office space located at 50 Binney Street in Cambridge, Massachusetts (the “50 Binney Street Sublease”) to supplement the Company’s corporate headquarters located at 60 Binney Street in Cambridge, Massachusetts. Under the terms of the 50 Binney Street Sublease, the Company will lease 267,278 square feet of office space for $99.95 per square foot, or $26.7 million per year in base rent subject to certain operating expenses, taxes and annual rent increases of approximately 3%. The lease will commence when the space is available for use by the Company, which is anticipated to be in the first half of 2022, which reflects the sublessor's exercise of its option to postpone the commencement date of the sublease. The lease term will end on December 31, 2030, unless other specific circumstances specified in the 50 Binney Street Sublease occur. The Company will assess the lease classification of the 50 Binney Street Sublease and commence recognition of the associated rent expense at the lease commencement date.

Upon signing the 50 Binney Street Sublease, the Company executed a $40.1 million cash-collateralized letter of credit, which may be reduced in the future subject to the terms of the 50 Binney Street Sublease and certain reduction requirements specified therein. The $40.1 million of cash collateralizing the letter of credit is classified as restricted cash and other non-current assets on the Company’s consolidated balance sheets. Payments will commence at the earlier of (i) the date which is 90 days following the commencement date and (ii) the date the Company takes occupancy of all or any portion of the premises.

In connection with the execution of the 50 Binney Street Sublease, the Company also entered into a purchase agreement for furniture and equipment (the “Furniture Purchase Agreement”) located on the premises upon lease commencement. Upon execution of the Furniture Purchase Agreement, the Company made an upfront payment of $7.5 million, all of which was recorded within restricted cash and other non-current assets on the Company’s consolidated balance sheets and assessed for recoverability on a recurring basis. The Company will be required to make another $7.5 million payment under the Furniture Purchase Agreement upon lease commencement.

In December 2021, the Company entered into a sub-sublease agreement (the "Sub-Sublease") with Meta Platforms, Inc. (“Meta”). Under the terms of the Sub-Sublease, the Company is subleasing the entirety of the 50 Binney Street premises which it has rights to under the 50 Binney Street Sublease. The Company is sub-subleasing the premises for $28.0 million in the first year with 3% annual increases in each subsequent year. Meta will receive access to 50 Binney Street at the lease commencement date, which is the same point that the Company would receive access under the 50 Binney Street Sublease. The Company remains liable under the 50 Binney Street Sublease, including for maintenance of the $40.1 million collateralized

letter of credit. As a result of the execution of the Sub-Sublease, the Company assessed the $7.5 million deposit related to the Furniture Purchase Agreement for recoverability and determined that the amount was not recoverable. As a result, the Company recorded $7.5 million in the Company's consolidated statements of operations and comprehensive loss as selling, general and administrative expense during the year ended December 31, 2021.

Assembly Row lease

In November 2021, the Company entered into a lease agreement with Assembly Row 5B, LLC ("Landlord") for office space located at 455 Grand Union Boulevard in Somerville, Massachusetts to serve as the Company's future corporate headquarters. Under the terms of the arrangement, the Company will lease approximately 61,180 square feet starting at an annual rate of $45 per square foot, subject to annual increases of 2.5%, plus operating expenses and taxes. In addition, the Company will be eligible for a tenant work allowance of $160 per rentable square foot of the premises. The lease will commence on the date on which the Landlord tenders possession of the premises to the Company with any tenant work required to be performed by the Landlord substantially completed, which is anticipated to occur in the first half of 2022.

Embedded leases

In June 2016, the Company entered into a manufacturing agreement for the future commercial production of the Company’s beti-cel and eli-cel drug products with a contract manufacturing organization. Under this 12-year agreement, the contract manufacturing organization will complete the design, construction, validation and process validation of the leased suites prior to anticipated commercial launch of the product candidates. During construction, the Company paid $12.0 million upon the achievement of certain contractual milestones. Construction was completed in March 2018 and beginning in April 2018, the Company pays $5.1 million per year, subject to annual inflationary adjustments, in fixed suite fees, as well as certain fixed labor, raw materials, testing and shipping costs for manufacturing services. The Company may terminate this agreement at any time upon payment of a one-time termination fee and up to 24 months of fixed suite and labor fees. The Company concluded in prior periods that this agreement contained an embedded lease as the suites are designated for the Company’s exclusive use during the term of the agreement. The Company recorded a right-of-use asset and lease liability for this operating lease on the effective date of ASC 842 and is recognizing rent expense on a straight-line basis throughout the remaining term of the embedded lease.

In November 2016, the Company entered into an agreement for clinical and commercial production of the Company’s beti-cel, lovo-cel, and eli-cel drug products with a contract manufacturing organization at an existing facility. The Company concluded that this agreement contains an embedded operating lease as the clean rooms are designated for the Company’s exclusive use during the term of the agreement. The term of the agreement is five years with subsequent three-year renewals at the mutual option of each party. As a result, the Company recorded a right-of-use asset and lease liability for this operating lease on the effective date of ASC 842, and is recognizing rent expense on a straight-line basis throughout the estimated remaining term of the embedded lease. In March 2020, the Company amended its agreement with the contract manufacturing organization, resulting in a lease modification. Under the terms of the amended agreement, the Company may be required to pay annual maintenance and production fees of up to €16.5 million, depending on its production needs, and may terminate this agreement with twelve months’ notice and a one-time termination fee. In September 2021, the Company reassessed the term of this lease in light of the planned orderly wind down of its operations in Europe. As a result, the Company reduced the right-of-use asset and related lease liability to reflect a shortened expected term of the agreement. In November 2021, the Company exercised its right to terminate the lease agreement, and such termination will be effective in November 2022. Per the terms of the amended agreement, the Company was obligated to pay a one-time termination fee of €1.0 million upon termination, which was paid in December 2021. In connection with this termination, the Company will pay for services properly rendered through the date of termination in accordance with the contract manufacturing agreement, based on work completed and expenses incurred prior to the date of termination.

In July 2020, the Company entered into an agreement reserving manufacturing capacity with a contract manufacturing organization. The Company concluded that this agreement contains an embedded lease as a controlled environment room at the facility is designated for the Company's exclusive use during the term of the agreement, with the option to sublease the space if the Company provides notice that it will not utilize it for a specified duration of time. Under the terms of the agreement, the Company will be required to pay up to $5.4 million per year in maintenance fees in addition to the cost of any services provided and may terminate this agreement with eighteen months' notice. The agreement commenced in March 2021, and it has a term of five years with the option to extend. The Company classified the embedded lease as an operating lease and recognized a right-of-use asset and lease liability upon lease commencement in March 2021 and is recognizing rent expense on a straight-line basis throughout the remaining term of the embedded lease.

In February 2021, the Company entered into another agreement reserving manufacturing capacity with a contract manufacturing organization. The Company concluded that this agreement contains an embedded lease as a controlled

environment room at the facility is designated for the Company's exclusive use during the term of the agreement, with the option to sublease the space if the Company provides notice that it will not utilize it for a specified duration of time. Under the terms of the agreement, the Company will be required to pay up to $4.2 million per year in maintenance fees and an immaterial amount of other annual fees as well as per-batch fees for the cost of any services provided. Either party may terminate this agreement with eighteen months’ notice at any time or with eight months’ notice after stage 5 has commenced. The term of the agreement is five years, with the option to extend, and it commenced in November 2021. The Company classified the embedded lease as an operating lease and recognized a right-of-use asset and lease liability upon lease commencement in November 2021 and is recognizing rent expense on a straight-line basis throughout the remaining term of the embedded lease.

Summary of all lease costs recognized under ASC 842


	For the year ended December 31,
	2021			2020 (2)			2019 (2)
Lease cost (1)
Operating lease cost	$	25,067		$	18,660		$	20,005
Total lease cost	$	25,067		$	18,660		$	20,005

Other information
Operating cash flows used for operating leases	$	22,805		$	17,780		$	17,205
Weighted average remaining lease term	4.7 years			6.3 years			7.3 years
Weighted average discount rate	5.02		%	5.98		%	6.66		%

(1) Short-term lease costs and variable lease costs incurred by the Company for the twelve months ended December 31, 2021, 2020 and 2019 were immaterial.

(2) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Rent expense is calculated on a straight-line basis over the term of the lease. Rent expense recognized under all leases, including additional charges for utilities, parking, maintenance, and real estate taxes, was $36.2 million, $24.2 million, and $23.3 million for the years ended December 31, 2021, 2020 and 2019, respectively.

As of December 31, 2021, future minimum commitments under ASC 842 under the Company’s operating leases were as follows (in thousands):


	As of
Maturity of lease liabilities	December 31, 2021
2022	$	27,037
2023	21,460
2024	18,009
2025	14,639
2026	8,598
2027 and thereafter	12,356
Total lease payments	102,099
Less: imputed interest	(12,515)
Total operating lease liabilities	$	89,584

The above table excludes legally binding minimum lease payments for leases executed but not yet commenced as of December 31, 2021.

Income taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule Components of Loss Before Income Taxes

The components of loss before income taxes were as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
U.S.	$	(487,404)	$	(431,452)	$	(414,586)
Foreign	(74,976)		(128,918)		(140,981)
Total	$	(562,380)	$	(560,370)	$	(555,567)

Summary of Provision for (Benefit from) Income Taxes

The provision for (benefit from) income taxes were as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
Current:
Federal	$	—	$	—	$	—
State	—		2		7
Foreign	258		684		612
Deferred:
Federal	—		—		(966)
State	—		—		(198)
Foreign	—		—		—
Total income tax expense (benefit)	$	258	$	686	$	(545)

Reconciliation of Income Tax Provision (Benefit) Computed at the Statutory Federal Income Tax Rate to Effective Income Tax Rate (Provision) Benefit as Reflected in the Financial Statements

A reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate to the Company’s effective income tax rate as reflected in the financial statements is as follows:


	Year ended December 31,
	2021		2020		2019
Federal income tax expense at statutory rate	21.0	%	21.0	%	21.0	%
State income tax, net of federal benefit	3.9	%	3.1	%	3.7	%
Permanent differences	(0.6)	%	(0.6)	%	(0.8)	%
Stock-based compensation	(3.1)	%	(2.4)	%	(0.7)	%
Research and development credit	4.3	%	6.0	%	5.4	%
Foreign differential	(1.9)	%	(4.6)	%	(3.7)	%
Other	—	%	(0.3)	%	0.8	%
Change in valuation allowance	(23.6)	%	(22.3)	%	(25.6)	%
Effective income tax rate (expense) benefit	—	%	(0.1)	%	0.1	%

Components of Deferred Tax Assets and Liabilities

The significant components of the Company’s deferred tax assets and liabilities are composed of the following (in thousands):


	Year ended December 31,
	2021		2020 (1)
Deferred tax assets:
U.S. net operating loss carryforwards (federal and state)	$	703,125	$	546,098
Tax credit carryforwards (federal and state)	281,687		246,742
Capitalized license fees and research and development expenses	2,237		1,558
Deferred revenue	604		398
Stock-based compensation	25,181		37,164
Lease liabilities	22,916		14,787
Accruals and other	15,598		12,894
Total deferred tax assets	1,051,348		859,641
Right-of-use assets	(23,053)		(15,044)
Fixed assets	(1,546)		(1,212)
Less valuation allowance	(1,026,749)		(843,385)
Net deferred taxes	$	—	$	—

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):


	Unrecognized tax benefits
Balance as of December 31, 2019	$	15,945
Increases (decreases) for tax positions related to current period	3,149
Increases (decreases) for tax positions related to prior periods	(100)
Balance as of December 31, 2020	18,994
Increases (decreases) for tax positions related to current period	2,949
Increases (decreases) for tax positions related to prior periods	17
Balance as of December 31, 2021	21,960

Equity

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Equity

EquityThe Company is authorized to issue 125.0 million shares of common stock. Holders of common stock are entitled to one vote per share. Holders of common stock are entitled to receive dividends, if and when declared by the Company’s board of directors, and to share ratably in the Company’s assets legally available for distribution to the Company’s shareholders in the

event of liquidation. Holders of common stock have no preemptive, subscription, redemption or conversion rights. As of December 31, 2021 and 2020, the Company had 71.1 million and 66.4 million shares of common stock issued and outstanding, respectively.

In September 2021, the Company entered into an equity purchase agreement with certain investors, pursuant to which the Company agreed to sell and issue, in a private placement offering of securities, an aggregate of (i) 2.3 million shares of the Company’s common stock at a purchase price per share of $16.50 and (ii) pre-funded warrants to purchase up to 2.3 million shares of common stock (the “Pre-Funded Warrants”) at an effective price of $16.49 per share ($16.49 paid to the Company upon the closing of the offering and $0.01 to be paid upon exercise of such Pre-Funded Warrants). This resulted in aggregate gross proceeds to the Company of approximately $75.0 million. The Pre-Funded Warrants can be exercised at any time or times on or after September 7, 2021, until exercised in full. The Pre-Funded Warrants have been evaluated to determine the appropriate accounting and classification pursuant to ASC 480 and ASC 815. Based on the terms of the Pre-Funded Warrants, management concluded that they should be classified within stockholders' equity on its consolidated balance sheets, with no subsequent remeasurement as long as the underlying warrant agreements are not modified or amended.

The Company is authorized to issue 5.0 million shares of preferred stock in one or more series and to fix the powers, designations, preferences and relative participating option or other rights thereof, including dividend rights, conversion rights, voting rights, redemption terms, liquidation preferences and the number of shares constituting any series, without any further vote or action by the Company’s shareholders. As of December 31, 2021 and 2020, the Company had no shares of preferred stock issued or outstanding.

Reserved for future issuance

The Company has reserved for future issuance the following number of shares of common stock (in thousands):


	As of December 31,
	2021	2020
Options to purchase common stock (1)	5,534	6,262
Restricted stock units (1)	3,427	1,495
2013 Stock Option and Incentive Plan	2,250	2,545
Pre-funded warrants	2,273	—
2013 Employee Stock Purchase Plan	1,347	67
	14,831	10,369

(1) Stock options and restricted stock units that are reserved for future issuance include awards outstanding to employees of 2seventy bio.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI http://asc.fasb.org/topic&trid=2208762

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496171-112644

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123467817&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Inventory (Tables)

12 Months Ended

Dec. 31, 2021

Inventory Disclosure [Abstract]

Schedule of Inventory

Inventory consists of the following (in thousands):


	As of December 31, 2021		As of December 31, 2020
Raw materials	$	—	$	8,967
Finished goods	—		1,731
Inventory	$	—	$	10,698

Equity (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Summary of Future Issuance of Common Stock Shares

The Company has reserved for future issuance the following number of shares of common stock (in thousands):


	As of December 31,
	2021	2020
Options to purchase common stock (1)	5,534	6,262
Restricted stock units (1)	3,427	1,495
2013 Stock Option and Incentive Plan	2,250	2,545
Pre-funded warrants	2,273	—
2013 Employee Stock Purchase Plan	1,347	67
	14,831	10,369

(1) Stock options and restricted stock units that are reserved for future issuance include awards outstanding to employees of 2seventy bio.

Equity - Summary of Future Issuance of Common Stock Shares (Detail) - shares shares in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Capitalization [Line Items]
Common shares reserved for future issuance (in shares)	14,831	10,369
2013 Stock Option and Incentive Plan
Schedule of Capitalization [Line Items]
Common shares reserved for future issuance (in shares)	2,250	2,545
2013 Employee Stock Purchase Plan
Schedule of Capitalization [Line Items]
Common shares reserved for future issuance (in shares)	1,347	67
Options to purchase common stock
Schedule of Capitalization [Line Items]
Common shares reserved for future issuance (in shares)	5,534	6,262
Restricted stock units
Schedule of Capitalization [Line Items]
Common shares reserved for future issuance (in shares)	3,427	1,495
Pre-funded warrants
Schedule of Capitalization [Line Items]
Common shares reserved for future issuance (in shares)	2,273	0

Stock-based compensation - Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Expected volatility	66.70%	69.50%	70.70%
Expected term (in years)	6 years	6 years	6 years
Risk-free interest rate	0.80%	1.40%	2.30%
Expected dividend yield	0.00%	0.00%	0.00%

Reduction in workforce (Tables)

12 Months Ended

Dec. 31, 2021

Restructuring and Related Activities [Abstract]

Restructuring and Related Costs

The following table summarizes the accrued liabilities activity recorded in connection with the reduction in workforce for the year ended December 31, 2021 (in thousands):


	Charges		Amount paid		Amounts accrued at December 31, 2021
April 2021 reduction	$	4,625	$	(4,625)	$	—
July 2021 reduction	21,176		(16,503)		4,673
Total	$	25,801	$	(21,128)	$	4,673

Intangible assets - Narrative (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization expense		$ 0.4	$ 0.5	$ 0.3
In-licensed rights
Finite-Lived Intangible Assets [Line Items]
Intangible asset impairment	$ 4.0

Summary of significant accounting policies and basis of presentation - Narrative (Detail)	12 Months Ended
	Dec. 31, 2021 USD ($) target
Accounting Policies [Abstract]
Number of operating segments \| target	1
Goodwill, impaired, accumulated impairment loss \| $	$ 0

Intangible assets

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

Intangible assets, net of accumulated amortization, are summarized as follows (in thousands):


	As of December 31, 2021
	Cost		Accumulated amortization		Impairment		Net
In-licensed rights	$	5,224	(1,219)		(4,005)		—
Total	$	5,224	$	(1,219)	$	(4,005)	$	—


	As of December 31, 2020(1)
	Cost		Accumulated amortization		Impairment		Net
In-licensed rights	$	5,224	(827)		—		4,397
Total	$	5,224	$	(827)	$	—	$	4,397

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Amortization expense for intangible assets was $0.4 million, $0.5 million, and $0.3 million for the years ended December 31, 2021, 2020 and 2019, respectively.

In August 2021, the Company announced its decision to focus its efforts on the U.S. market and to execute an orderly wind down of its European operations. In connection with this, in September 2021, the Company recognized an impairment loss of $4.0 million for the remaining unamortized balance of the intangible asset associated with in-licensed rights for the ZYNTEGLO product, which is reflected within cost of product revenue in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2021.

Fair value measurements - Narrative (Detail) - USD ($)	1 Months Ended	12 Months Ended
Fair value measurements - Narrative (Detail) - USD ($)	Jan. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Realized gain (loss) recognized on sale		$ 0	$ 0
Interest receivable		300,000	1,500,000
Interest receivable, write-off		0	0
Investment at fair value		3,691,000	5,653,000
Proceeds from sale of equity securities	$ 31,300,000
Unrealized gain (loss) on equity securities		$ 29,400,000	$ (7,200,000)	$ (9,300,000)

Stock-based compensation

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Stock-based compensation

In June 2013, the Company’s board of directors adopted its 2013 Stock Option and Incentive Plan (“2013 Plan”), which was subsequently approved by its stockholders and became effective upon the closing of the Company’s IPO. The 2013 Plan replaces the 2010 Stock Option and Grant Plan (“2010 Plan”).

The 2013 Plan allows for the granting of incentive stock options, non-qualified stock options, restricted stock units and restricted stock awards to the Company’s employees, members of the board of directors, and consultants of the Company. The Company initially reserved 1.0 million shares of its common stock for the issuance of awards under the 2013 Plan. The 2013 Plan provides that the number of shares reserved and available for issuance under the 2013 Plan will automatically increase each January 1, beginning on January 1, 2014, by four percent of the outstanding number of shares of common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee. In January 2021 and January 2022, the number of common stock available for issuance under the 2013 Plan was increased by approximately 2.7 million and 2.8 million shares, respectively, as a result of this automatic increase provision.

Any options or awards outstanding under the Company’s previous stock option plans, including both the 2010 Plan and the Second Amended and Restated 2002 Employee, Director and Consultant Stock Plan (“2002 Plan”), at the time of adoption of the 2013 Plan remain outstanding and effective. The shares of common stock underlying any awards that are forfeited, canceled, repurchased, expired or are otherwise terminated (other than by exercise) under the 2002 Plan and 2010 Plan are added to the shares of common stock available for issuance under the 2013 Plan. As of December 31, 2021, the total number of common stock that may be issued under all plans is 3.2 million.

The Company does not currently hold any treasury shares. Upon stock option exercise, the Company issues new shares and delivers them to the participant.

Conversion and modification of equity awards outstanding at the Separation

In connection with the Separation on November 4, 2021, under the provisions of the existing plans, the Company adjusted its outstanding equity awards in accordance with the terms of the Employee Matters Agreement (an equitable adjustment) to preserve the intrinsic value of the awards immediately before and after the Distribution. Upon the Distribution, employees holding stock options, restricted stock units (“RSUs”) and performance restricted stock units (“PRSUs”) denominated in pre-Distribution bluebird stock received a number of otherwise-similar awards either in post-Distribution bluebird stock or in a combination of post-Distribution bluebird stock and 2seventy bio stock based on conversion ratios outlined for each group of employees in the Employee Matters Agreement that the Company entered into in connection with the Distribution. The equity awards that were granted prior to 2021 were converted under the shareholder method, wherein employees holding outstanding equity awards received equity awards in both bluebird and 2seventy bio. The conversion ratio for the shareholder method took into consideration a distribution ratio of one share of 2seventy bio common stock for every three shares of bluebird common stock. For equity awards granted in 2021, the number of awards that were outstanding at the Separation were proportionately adjusted to maintain the aggregate intrinsic value of the awards at the date of the Separation. The conversion ratio was determined based on the volume weighted-average trading price for bluebird common stock for the five trading days before and after the Separation.

These modified awards otherwise retained substantially the same terms and conditions, including term and vesting provisions. Due to the modification of the equity awards as a result of the Distribution, the Company compared the fair value of the outstanding equity awards immediately before and after the Distribution. The modification resulted in an incremental fair value of $20.3 million, of which $4.5 million was immediately recognized as of the Distribution date.

Additionally, bluebird will not incur any future compensation cost related to equity awards held by 2seventy bio employees and directors. The Company will incur future compensation cost related to 2seventy bio equity awards held by bluebird employees.

Stock-based compensation expense

The Company recognized stock-based compensation expense totaling $98.7 million, $122.6 million, and $131.1 million during the years ended December 31, 2021, 2020 and 2019, respectively. Stock-based compensation expense recognized by award type is as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
Stock options	$	54,660	$	75,837	$	79,912
Restricted stock units	30,767		38,123		50,158
Employee stock purchase plan and other	13,313		8,636		1,013
	$	98,740	$	122,596	$	131,083

Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
Research and development	$	42,989	$	49,766	$	59,378
Selling, general and administrative	55,751		72,830		71,705
	$	98,740	$	122,596	$	131,083

Stock-based compensation of $1.0 million was capitalized into inventory during the year ended December 31, 2021. Stock-based compensation of $0.5 million was capitalized into inventory during the year ended December 31, 2020.

Unrestricted stock awards

During the first quarter of 2021, the Company granted 0.4 million unrestricted stock awards to employees as part of its 2020 annual incentive program. In addition, the Company implemented a retention program designed to incentivize and retain employees through the separation of its severe genetic disease and oncology programs. Under the retention program, employees are entitled to a one-time bonus payment, consisting of both a cash payment and unrestricted stock awards, with the condition that the employee remains employed at the end of 2021. For the twelve months ended December 31, 2021, the Company recognized $21.2 million in expense related to this program, which includes $10.6 million in stock compensation expense related to the anticipated grants of stock. During the third quarter of 2021, the Company granted 0.1 million unrestricted stock awards, related to the retention program, to those employees impacted by the orderly wind down of the Company's operations in Europe. During the fourth quarter of 2021, the Company granted 1.0 million unrestricted stock awards to employees as part of its retention program.

As of December 31, 2021, the Company had $34.2 million and $54.3 million of unrecognized compensation expense related to unvested stock options and restricted stock units (exclusive of those with service and performance conditions that have not yet been achieved), respectively, that is expected to be recognized over a weighted-average period of 2.19 years and 2.26 years, respectively.

Stock options

The fair value of each option issued to employees was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:


	Year ended December 31,
	2021		2020		2019
Expected volatility	66.7	%	69.5	%	70.7	%
Expected term (in years)	6.0		6.0		6.0
Risk-free interest rate	0.8	%	1.4	%	2.3	%
Expected dividend yield	0.0	%	0.0	%	0.0	%

The following table summarizes the stock option activity under the Company’s equity awards plans:


	Shares (in thousands)	Weighted- average exercise price per share		Weighted- average contractual life (in years)	Aggregate intrinsic value (a) (in thousands)
Outstanding at December 31, 2020	6,262	$	105.02
Granted	1,238	$	27.19
Exercised	(218)	$	6.82
Canceled or forfeited	(2,357)	$	81.20
Conversion and modification of awards	(1,339)	$	42.90
Outstanding at December 31, 2021	3,586	$	39.23	6.8	$	631
Exercisable at December 31, 2021	1,835	$	57.09	5.5	$	380
Vested and expected to vest at December 31, 2021	3,586	$	39.23	6.8	$	631

(a)The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for the options that were in the money at December 31, 2021.

(b)Pursuant to the terms of Employee Matters Agreement, the company granted 4,375 option conversion awards to bluebird employees which are reflected within the "Conversion and modification of awards" above. The weighted-average exercise price per share reflected above is related to these awards, rather than the number of awards reflected in the table.

The weighted-average fair values of options granted during the years ended December 31, 2021, 2020 and 2019 was $16.32, $43.24, and $83.44, respectively. The intrinsic value of options exercised during the years ended December 31, 2021, 2020 and 2019 was $5.1 million, $4.0 million and $29.0 million, respectively.

Restricted stock units

The following table summarizes the restricted stock unit activity under the Company’s equity award plans:


	Shares (in thousands)	Weighted-average grant date fair value
Unvested balance at December 31, 2020	1,495	$	102.34
Granted	3,359	26.43
Vested	(526)	112.21
Forfeited	(987)	53.58
Conversion and modification of awards	(148)	16.84
Unvested balance at December 31, 2021	3,193	$	16.21

(a)Pursuant to the terms of Employee Matters Agreement, the company granted 3,327 restricted stock unit conversion awards to bluebird employees which are reflected within the "Conversion and modification of awards" above. The weighted-average exercise price per share reflected above is related to these awards, rather than the number of awards reflected in the table.

The intrinsic value of restricted stock units vested during the years ended December 31, 2021, 2020 and 2019 was $44.0 million, $30.9 million and $28.4 million, respectively.

Employee Stock Purchase Plan

In June 2013, the Company’s board of directors adopted its 2013 Employee Stock Purchase Plan (“2013 ESPP”), which was subsequently approved by its stockholders and became effective upon the closing of the Company’s IPO. The 2013 ESPP authorizes the initial issuance of up to a total of 0.2 million shares of the Company’s common stock to participating employees. In June 2021, the Company amended the 2013 ESPP to authorize an additional 1.4 million shares of the Company’s common stock available to participating employees. During each of the years ended December 31, 2021 and 2020, approximately 0.1 million shares of common stock were issued under the 2013 ESPP.

Selected quarterly financial data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2021

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information


	2021
	First quarter		Second quarter		Third quarter		Fourth quarter		Total
	(in thousands, except per share data)
Total revenues	$	894	$	143	$	1,019	$	1,606	$	3,662
Total operating expenses	146,988		154,844		155,468		137,273		594,573
Loss from operations	(146,094)		(154,701)		(154,449)		(135,667)		(590,911)
Net loss from continuing operations	(121,504)		(155,973)		(152,834)		(132,327)		(562,638)
Net loss from discontinued operations	(84,304)		(85,729)		(63,982)		(22,725)		(256,740)
Net loss	(205,808)		(241,702)		(216,816)		(155,052)		(819,378)
Net loss per share from continuing operations —basic and diluted	(1.81)		(2.31)		(2.23)		(1.83)		(8.16)
Net loss per share from discontinued operations—basic and diluted	(1.26)		(1.27)		(0.93)		(0.31)		(3.73)
Net loss per share—basic and diluted	$	(3.07)	$	(3.58)	$	(3.16)	$	(2.14)	$	(11.89)


	2020
	First quarter		Second quarter		Third quarter		Fourth quarter		Total
	(in thousands, except per share data)
Total revenues	$	—	$	—	$	—	$	—	$	—
Total operating expenses	144,479		143,650		131,743		139,387		559,259
Loss from operations	(144,479)		(143,650)		(131,743)		(139,387)		(559,259)
Net loss from continuing operations	(146,392)		(140,665)		(137,678)		(136,321)		(561,056)
Net income (loss) from discontinued operations	(56,219)		119,200		(57,067)		(63,553)		(57,639)
Net loss	(202,611)		(21,465)		(194,745)		(199,874)		(618,695)
Net loss per share from continuing operations —basic and diluted	(2.63)		(2.33)		(2.08)		(2.05)		(9.02)
Net income (loss) per share from discontinued operations—basic and diluted	(1.01)		1.97		(0.86)		(0.96)		(0.93)
Net loss per share—basic and diluted	$	(3.64)	$	(0.36)	$	(2.94)	$	(3.01)	$	(9.95)

Property, plant and equipment, net

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Property, plant and equipment, net

Property, plant and equipment, net, consists of the following (in thousands):


	As of December 31,
	2021		2020 (1)
Laboratory equipment	$	29,061	$	27,146
Computer equipment and software	421		447
Office equipment	117		1,077
Leasehold improvements	12		5,949
Construction-in-progress	501		895
Total property, plant and equipment	30,112		35,514
Less accumulated depreciation and amortization	(20,406)		(18,141)
Property, plant and equipment, net	$	9,706	$	17,373

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Depreciation and amortization expense related to property, plant and equipment was $4.9 million, $5.1 million, and $4.1 million for the years ended December 31, 2021, 2020, and 2019, respectively.

Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock-Based Compensation Expense by Award Type

Stock-based compensation expense recognized by award type is as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
Stock options	$	54,660	$	75,837	$	79,912
Restricted stock units	30,767		38,123		50,158
Employee stock purchase plan and other	13,313		8,636		1,013
	$	98,740	$	122,596	$	131,083

Schedule of Stock-Based Compensation Expense by Classification

Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Year ended December 31,
	2021		2020		2019
Research and development	$	42,989	$	49,766	$	59,378
Selling, general and administrative	55,751		72,830		71,705
	$	98,740	$	122,596	$	131,083

Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted

The fair value of each option issued to employees was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:


	Year ended December 31,
	2021		2020		2019
Expected volatility	66.7	%	69.5	%	70.7	%
Expected term (in years)	6.0		6.0		6.0
Risk-free interest rate	0.8	%	1.4	%	2.3	%
Expected dividend yield	0.0	%	0.0	%	0.0	%

Summary of Stock Option Activity Under Plan

The following table summarizes the stock option activity under the Company’s equity awards plans:


	Shares (in thousands)	Weighted- average exercise price per share		Weighted- average contractual life (in years)	Aggregate intrinsic value (a) (in thousands)
Outstanding at December 31, 2020	6,262	$	105.02
Granted	1,238	$	27.19
Exercised	(218)	$	6.82
Canceled or forfeited	(2,357)	$	81.20
Conversion and modification of awards	(1,339)	$	42.90
Outstanding at December 31, 2021	3,586	$	39.23	6.8	$	631
Exercisable at December 31, 2021	1,835	$	57.09	5.5	$	380
Vested and expected to vest at December 31, 2021	3,586	$	39.23	6.8	$	631

Summary of Restricted Common Stock Awards

The following table summarizes the restricted stock unit activity under the Company’s equity award plans:


	Shares (in thousands)	Weighted-average grant date fair value
Unvested balance at December 31, 2020	1,495	$	102.34
Granted	3,359	26.43
Vested	(526)	112.21
Forfeited	(987)	53.58
Conversion and modification of awards	(148)	16.84
Unvested balance at December 31, 2021	3,193	$	16.21

Discontinued operations (Tables)

12 Months Ended

Dec. 31, 2021

Discontinued Operations and Disposal Groups [Abstract]

Distribution of Assets, Liabilities and Stockholders' Equity

The transfer of assets and liabilities to 2seventy bio was effected through a contribution in accordance with the Separation Agreement, as summarized below (in thousands):


	As of November 4, 2021
Assets
Current assets:
Cash and cash equivalents	$	174,284
Marketable securities	160,447
Prepaid expenses	8,732
Receivables and other current assets	21,637
Total current assets	365,100
Marketable securities	106,826
Property, plant and equipment, net	33,972
Intangible assets, net	10,664
Goodwill	6,410
Operating lease right-of-use assets	255,556
Restricted cash and other non-current assets	5,650
Total assets	$	784,178
Liabilities
Current liabilities:
Accounts payable	$	2,982
Accrued expenses and other current liabilities	85,659
Operating lease liability, current portion	6,938
Collaboration research advancement, current portion	8,957
Total current liabilities	104,536
Deferred revenue, net of current portion	25,762
Collaboration research advancement, net of current portion	16,264
Operating lease liability, net of current portion	257,575
Other non-current liabilities	1,896
Total liabilities	$	406,033
Net assets transferred to 2seventy bio	$	378,145

The following table summarizes the assets and liabilities of the discontinued operations as of December 31, 2020 (in thousands):


	As of December 31, 2020
Assets
Current assets:
Cash and cash equivalents	$	57,076
Marketable securities	413,947
Prepaid expenses	11,754
Receivables and other current assets	12,244
Total current assets of discontinued operations	495,021
Marketable securities	61,446
Property, plant and equipment, net	145,458
Intangible assets, net	5,644
Goodwill	7,482
Operating lease right-of-use assets	116,456
Restricted cash and other non-current assets	7,078
Total non-current assets of discontinued operations	343,564
Total assets of discontinued operations	$	838,585
Liabilities
Current liabilities:
Accounts payable	$	7,791
Accrued expenses and other current liabilities	48,716
Operating lease liability, current portion	15,313
Collaboration research advancement, current portion	9,236
Deferred revenue, current portion	820
Total current liabilities of discontinued operations	81,876
Deferred revenue, net of current portion	25,762
Collaboration research advancement, net of current portion	21,581
Operating lease liability, net of current portion	112,290
Other non-current liabilities	1,509
Total non-current liabilities of discontinued operations	161,142
Total liabilities of discontinued operations	$	243,018

Summary of Revenue and Expenses for Discontinued Operations

The following table summarizes revenue and expenses of the discontinued operations for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	Year ended December 31,
	2021		2020		2019
Revenue:
Service revenue	$	18,130	$	114,064	$	30,729
Collaborative arrangement revenue	18,602		115,594		5,740
Royalty and other revenue	5,762		21,076		8,205
Total revenues	42,494		250,734		44,674
Operating expenses:
Research and development	204,287		268,647		255,294
Selling, general and administrative	82,078		46,945		35,518
Share of collaboration loss	10,071		—		—
Cost of royalty and other revenue	2,292		5,396		2,978
Change in fair value of contingent consideration	387		(6,468)		2,747
Total operating expenses	299,115		314,520		296,537
Loss from operations	(256,621)		(63,786)		(251,863)
Interest income, net	791		5,770		17,380
Other income (expense), net	(910)		377		(103)
Loss before income taxes	(256,740)		(57,639)		(234,586)
Net loss	$	(256,740)	$	(57,639)	$	(234,586)

The following table summarizes the significant non-cash items and capital expenditures of the discontinued operations that are included in the consolidated statements of cash flows for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	Year ended December 31,
	2021		2020		2019
Operating activities:
Change in fair value of contingent consideration	$	387	$	(6,468)	$	2,747
Depreciation and amortization	14,195		13,730		12,995
Stock-based compensation expense	29,175		34,036		29,545
Loss on fixed assets disposal	569		146		108
Loss on sale of Durham, North Carolina manufacturing facility	1,986		—		—

Investing activities:
Purchase of property, plant and equipment	$	(11,256)	$	(23,159)	$	(57,196)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300		—		—
Purchase of intangible assets	(8,500)		—		—

Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	$	778	$	2,039	$	3,064
Right-of-use assets obtained in exchange for operating lease liabilities	151,520		4,989		9,745

Summary of Significant Non-Cash Items and Capital Expenditures for Discontinued Operations

The following table summarizes revenue and expenses of the discontinued operations for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	Year ended December 31,
	2021		2020		2019
Revenue:
Service revenue	$	18,130	$	114,064	$	30,729
Collaborative arrangement revenue	18,602		115,594		5,740
Royalty and other revenue	5,762		21,076		8,205
Total revenues	42,494		250,734		44,674
Operating expenses:
Research and development	204,287		268,647		255,294
Selling, general and administrative	82,078		46,945		35,518
Share of collaboration loss	10,071		—		—
Cost of royalty and other revenue	2,292		5,396		2,978
Change in fair value of contingent consideration	387		(6,468)		2,747
Total operating expenses	299,115		314,520		296,537
Loss from operations	(256,621)		(63,786)		(251,863)
Interest income, net	791		5,770		17,380
Other income (expense), net	(910)		377		(103)
Loss before income taxes	(256,740)		(57,639)		(234,586)
Net loss	$	(256,740)	$	(57,639)	$	(234,586)


	Year ended December 31,
	2021		2020		2019
Operating activities:
Change in fair value of contingent consideration	$	387	$	(6,468)	$	2,747
Depreciation and amortization	14,195		13,730		12,995
Stock-based compensation expense	29,175		34,036		29,545
Loss on fixed assets disposal	569		146		108
Loss on sale of Durham, North Carolina manufacturing facility	1,986		—		—

Investing activities:
Purchase of property, plant and equipment	$	(11,256)	$	(23,159)	$	(57,196)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300		—		—
Purchase of intangible assets	(8,500)		—		—

Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	$	778	$	2,039	$	3,064
Right-of-use assets obtained in exchange for operating lease liabilities	151,520		4,989		9,745

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 205
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=109222160&loc=SL51721533-107759

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721659-107760

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721665-107760

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
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-URI http://asc.fasb.org/extlink&oid=109222650&loc=d3e1361-107760

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
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-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721671-107760

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
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-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
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-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721663-107760

+ Details

Restricted cash - Narrative (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Restricted cash balance	$ 45,500	$ 56,023
Letter of Credit
Debt and Equity Securities, FV-NI [Line Items]
Restricted cash balance	$ 43,200	$ 54,500

Accrued expenses and other current liabilities (Tables)

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Summary of accrued expenses and other current liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	As of December 31,
	2021		2020 (1)
Employee compensation	$	41,095	$	41,192
Accrued goods and services	24,273		14,855
Accrued clinical and contract research organization costs	17,769		20,912
Accrued manufacturing costs	15,722		15,763
Accrued professional fees	1,665		1,541
Deferred revenue, current portion	2,282		1,500
Other	1,152		2,427
Total accrued expenses and other current liabilities	$	103,958	$	98,190

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Accrued expenses and other current liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Employee compensation	$ 41,095	$ 41,192
Accrued goods and services	24,273	14,855
Accrued clinical and contract research organization costs	17,769	20,912
Accrued manufacturing costs	15,722	15,763
Accrued professional fees	1,665	1,541
Deferred revenue, current portion	2,282	1,500
Other	1,152	2,427
Total accrued expenses and other current liabilities	$ 103,958	$ 98,190

Discontinued operations

12 Months Ended

Dec. 31, 2021

Discontinued Operations and Disposal Groups [Abstract]

Discontinued operations

Sale of bluebird Research Triangle manufacturing facility

In November 2017, the Company acquired a manufacturing facility in Durham, North Carolina ("bRT") for the future manufacture of LVV for the Company’s therapies related to its oncology programs. In July 2021, the Company and Resilience US, Inc., an affiliate of National Resilience, Inc. ("Resilience"), signed an Asset Purchase Agreement (the “Agreement”). As part of the Agreement, and upon the closing of the transaction which occurred in September 2021, Resilience acquired the Company's LVV manufacturing facility located in Durham, North Carolina and retained staff currently employed at the site. As a result of the transaction, the Company disposed of $111.2 million of net assets, primarily consisting of the building and laboratory equipment, that were associated with the Company's oncology programs. The Company recognized a loss on disposal of assets of $2.0 million. As the sale of the bRT manufacturing facility and the separation of 2seventy bio (as described below) were deemed to represent multiple components of a single disposal plan, the assets, liabilities and results of operations related to bRT have been included as a component of discontinued operations.

2seventy bio Separation

On November 4, 2021, the Company completed the previously announced separation of its oncology programs and portfolio, and the certain related assets and liabilities, into a separate, independent publicly traded company (the “Separation”). The Separation was effected by means of a distribution of all of the outstanding shares of common stock of 2seventy bio in which each bluebird stockholder received one share of common stock, par value $0.0001 per share, of 2seventy bio for every three shares of common stock, par value $0.01 per share, of bluebird held as of the close of business on October 19, 2021 (the “Distribution”).

In connection with the Separation, bluebird entered into a separation agreement (the “Separation Agreement”) with 2seventy bio, dated as of November 3, 2021, that, among other things, set forth bluebird’s agreements with 2seventy bio regarding the principal actions to be taken in connection with the Separation, including the Distribution. The effective time of the Distribution was 12:01 a.m. on November 4, 2021. The Separation Agreement identified assets transferred to, liabilities assumed by and contracts assigned to 2seventy bio as part of the Separation, and it provided for when and how these transfers, assumptions and assignments occurred. The purpose of the Separation Agreement was to provide 2seventy bio and bluebird with assets to operate their respective businesses and retain or assume liabilities related to those assets. Each of 2seventy bio and bluebird agreed to releases, with respect to pre-Separation claims, and cross indemnities, with respect to post-Separation claims, that were principally designed to place financial responsibility for the obligations and liabilities allocated to 2seventy bio under the Separation Agreement with 2seventy bio and financial responsibility for the obligations and liabilities allocated to bluebird under the Separation Agreement with bluebird. bluebird and 2seventy bio are also each subject to mutual 12-month employee non-solicit and non-hire restrictions, subject to certain customary exceptions.

The transfer of assets and liabilities to 2seventy bio was effected through a contribution in accordance with the Separation Agreement, as summarized below (in thousands):


	As of November 4, 2021
Assets
Current assets:
Cash and cash equivalents	$	174,284
Marketable securities	160,447
Prepaid expenses	8,732
Receivables and other current assets	21,637
Total current assets	365,100
Marketable securities	106,826
Property, plant and equipment, net	33,972
Intangible assets, net	10,664
Goodwill	6,410
Operating lease right-of-use assets	255,556
Restricted cash and other non-current assets	5,650
Total assets	$	784,178
Liabilities
Current liabilities:
Accounts payable	$	2,982
Accrued expenses and other current liabilities	85,659
Operating lease liability, current portion	6,938
Collaboration research advancement, current portion	8,957
Total current liabilities	104,536
Deferred revenue, net of current portion	25,762
Collaboration research advancement, net of current portion	16,264
Operating lease liability, net of current portion	257,575
Other non-current liabilities	1,896
Total liabilities	$	406,033
Net assets transferred to 2seventy bio	$	378,145

bluebird and 2seventy bio also entered into a tax matters agreement, dated as of November 3, 2021, governing bluebird’s and 2seventy bio's respective rights, responsibilities and obligations with respect to taxes (including taxes arising in the ordinary course of business and taxes, if any, incurred as a result of any failure of the distribution and certain related transactions to qualify as tax-free for U.S. federal income tax purposes), tax attributes, the preparation and filing of tax returns, the control of audits and other tax proceedings, and assistance and cooperation in respect of tax matters.

In connection with the Separation, bluebird also entered into an employee matters agreement with 2seventy bio, dated as of November 3, 2021. The employee matters agreement allocates assets, liabilities and responsibilities relating to the employment, compensation and employee benefits of bluebird and 2seventy bio employees, and other related matters, in connection with the Separation, including the treatment of outstanding bluebird incentive equity awards and certain retirement and welfare benefit obligations. The employee matters agreement generally provides that, unless otherwise specified, 2seventy bio is responsible for liabilities associated with employees who transfer to 2seventy bio and employees whose employment terminated prior to the distribution but who primarily supported the 2seventy bio business, and bluebird is responsible for liabilities associated with other employees, including employees retained by bluebird. Pursuant to the employee matters agreement, the outstanding bluebird equity awards held by 2seventy bio and bluebird employees were adjusted immediately prior to the distribution, with the intent to maintain, immediately following the distribution, the economic value of the awards immediately before the distribution date.

bluebird and 2seventy bio also entered into an intellectual property license agreement on November 3, 2021, pursuant to which each party granted a license to certain intellectual property and technology to the other. bluebird granted 2seventy bio a perpetual, worldwide, non-exclusive, royalty-free, fully paid-up license (or, as the case may be, sublicense) to certain intellectual property to allow 2seventy bio to use such intellectual property in connection with 2seventy bio's ongoing and future research and development activities and product candidates. 2seventy bio granted bluebird a perpetual, worldwide, non-

exclusive, royalty-free, fully paid-up license (or, as the case may be, sublicense) to certain intellectual property for use in bluebird’s existing products and product candidates. Such licenses between the parties generally allow current or future uses of the intellectual property in connection with each party's respective fields.

Additionally, bluebird entered into two transition services agreements with 2seventy bio, whose President is a member of the Company’s Board of Directors. . Pursuant to the transition service agreements, bluebird is obligated to provide and is entitled to receive certain transition services related to corporate functions, such as finance, human resources, internal audit, research and development, financial reporting, and information technology. Services provided by bluebird to 2seventy bio will continue for an initial term of up to two years, unless earlier terminated or extended according to the terms of the transition services agreement. Services received and performed are paid at a mutually agreed upon rate. Amounts received for services provided to 2seventy bio are recorded as other income and amounts paid for services provided by 2seventy bio are recorded as selling, general and administrative expense and research and development expense, as applicable. During the year ended December 31, 2021, the Company incurred $0.7 million of net expense for services provided by 2seventy bio within Research and development and Selling, general and administrative expense in the Consolidated Statements of Operations and Comprehensive Loss. As of December 31, 2021, the Company had an immaterial amount of accounts receivable and accounts payable due from and to 2seventy bio.

Discontinued operations

In connection with the Separation, the Company determined its oncology business, together with the bRT manufacturing facility, qualified for discontinued operations accounting treatment in accordance with ASC 205-20. The following table summarizes revenue and expenses of the discontinued operations for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	Year ended December 31,
	2021		2020		2019
Revenue:
Service revenue	$	18,130	$	114,064	$	30,729
Collaborative arrangement revenue	18,602		115,594		5,740
Royalty and other revenue	5,762		21,076		8,205
Total revenues	42,494		250,734		44,674
Operating expenses:
Research and development	204,287		268,647		255,294
Selling, general and administrative	82,078		46,945		35,518
Share of collaboration loss	10,071		—		—
Cost of royalty and other revenue	2,292		5,396		2,978
Change in fair value of contingent consideration	387		(6,468)		2,747
Total operating expenses	299,115		314,520		296,537
Loss from operations	(256,621)		(63,786)		(251,863)
Interest income, net	791		5,770		17,380
Other income (expense), net	(910)		377		(103)
Loss before income taxes	(256,740)		(57,639)		(234,586)
Net loss	$	(256,740)	$	(57,639)	$	(234,586)

There were no assets and liabilities related to discontinued operations as of December 31, 2021, as all balances were transferred to 2seventy bio upon Separation. The following table summarizes the assets and liabilities of the discontinued operations as of December 31, 2020 (in thousands):


	As of December 31, 2020
Assets
Current assets:
Cash and cash equivalents	$	57,076
Marketable securities	413,947
Prepaid expenses	11,754
Receivables and other current assets	12,244
Total current assets of discontinued operations	495,021
Marketable securities	61,446
Property, plant and equipment, net	145,458
Intangible assets, net	5,644
Goodwill	7,482
Operating lease right-of-use assets	116,456
Restricted cash and other non-current assets	7,078
Total non-current assets of discontinued operations	343,564
Total assets of discontinued operations	$	838,585
Liabilities
Current liabilities:
Accounts payable	$	7,791
Accrued expenses and other current liabilities	48,716
Operating lease liability, current portion	15,313
Collaboration research advancement, current portion	9,236
Deferred revenue, current portion	820
Total current liabilities of discontinued operations	81,876
Deferred revenue, net of current portion	25,762
Collaboration research advancement, net of current portion	21,581
Operating lease liability, net of current portion	112,290
Other non-current liabilities	1,509
Total non-current liabilities of discontinued operations	161,142
Total liabilities of discontinued operations	$	243,018


	Year ended December 31,
	2021		2020		2019
Operating activities:
Change in fair value of contingent consideration	$	387	$	(6,468)	$	2,747
Depreciation and amortization	14,195		13,730		12,995
Stock-based compensation expense	29,175		34,036		29,545
Loss on fixed assets disposal	569		146		108
Loss on sale of Durham, North Carolina manufacturing facility	1,986		—		—

Investing activities:
Purchase of property, plant and equipment	$	(11,256)	$	(23,159)	$	(57,196)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300		—		—
Purchase of intangible assets	(8,500)		—		—

Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	$	778	$	2,039	$	3,064
Right-of-use assets obtained in exchange for operating lease liabilities	151,520		4,989		9,745

Equity - Narrative (Detail) $ / shares in Units, $ in Millions	1 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2021 vote shares	Dec. 31, 2020 shares
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized (in shares)		125,000,000	125,000,000
Common stock, number of votes (in votes per share) \| vote		1
Common stock, shares issued (in shares)		71,115,000	66,432,000
Common stock, shares outstanding (in shares)		71,115,000	66,432,000
Preferred stock, shares authorized (in shares)		5,000,000	5,000,000
Preferred Stock, shares issued (in shares)		0	0
Preferred stock, shares outstanding (in shares)		0	0
Private Placement
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares)	2,300,000
Common stock price per share (in dollars per share) \| $ / shares	$ 16.50
Proceeds from stock offering \| $	$ 75.0
Private Placement \| Pre-funded warrants
Subsidiary, Sale of Stock [Line Items]
Number of securities called by warrants	2,300,000
Warrant price per share (in dollars per share) \| $ / shares	$ 16.49
Exercise price of warrants (in dollars per share) \| $ / shares	$ 0.01

Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table sets forth the Company’s assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2021 and 2020 (in thousands):


	Total		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
December 31, 2021
Assets:
Cash and cash equivalents	$	161,160	$	161,146	$	14	$	—
Marketable securities:
U.S. government agency securities and treasuries	128,393		—		128,393		—
Corporate bonds	49,308		—		49,308		—
Commercial paper	54,065		—		54,065		—
Equity securities	3,691		3,691		—		—
Total assets	$	396,617	$	164,837	$	231,780	$	—
December 31, 2020 (1)
Assets:
Cash and cash equivalents	$	260,629	$	260,629	$	—	$	—
Marketable securities:
U.S. government agency securities and treasuries	337,635		—		337,635		—
Corporate bonds	98,781		—		98,781		—
Commercial paper	38,975		—		38,975		—
Equity securities	5,653		5,653		—		—
Total assets	$	741,673	$	266,282	$	475,391	$	—

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value


	Less than 12 months				12 months or greater				Total
Description	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
December 31, 2021
U.S. government agency securities and treasuries	$	108,695	$	(505)	$	2,496	$	(4)	$	111,191	$	(509)
Corporate bonds	45,042		(56)		3,896		(2)		48,938		(58)
Total	$	153,737	$	(561)	$	6,392	$	(6)	$	160,129	$	(567)
December 31, 2020 (1)
U.S. government agency securities and treasuries	$	105,692	$	(37)	$	—	$	—	$	105,692	$	(37)
Corporate bonds	38,299		(20)		603		—		38,902		(20)
Total	$	143,991	$	(57)	$	603	$	—	$	144,594	$	(57)

(1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation.

Description of the business - Additional Information (Detail) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 04, 2021 company
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of companies \| company												2
Cash, cash equivalents and marketable securities	$ 396,600								$ 396,600
Accumulated deficit	3,719,925				$ 2,900,547				3,719,925	$ 2,900,547
Net loss from continuing operations	$ 132,327	$ 152,834	$ 155,973	$ 121,504	$ 136,321	$ 137,678	$ 140,665	$ 146,392	562,638	561,056	$ 555,022
Net cash used in operating activities									$ 635,639	$ 470,351	$ 564,384

- Definition

Amount after tax of income (loss) from continuing operations attributable to the parent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4613673-111683

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=125511455&loc=SL5780133-109256

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.13)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

+ Details

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details

Reduction in workforce - Accrued Liabilities Activity (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jul. 31, 2021	Apr. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Charges			$ 25,801,000	$ 0	$ 0
Amount paid			(21,128,000)
Amounts accrued at December 31, 2021			4,673,000
April 2021 reduction
Restructuring Cost and Reserve [Line Items]
Charges		$ 4,600,000	4,625,000
Amount paid			(4,625,000)
Amounts accrued at December 31, 2021			0
July 2021 reduction
Restructuring Cost and Reserve [Line Items]
Charges	$ 21,200,000		21,176,000
Amount paid			(16,503,000)
Amounts accrued at December 31, 2021			$ 4,673,000

Discontinued operations - Assets, Liabilities and Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Nov. 04, 2021	Dec. 31, 2020
Current assets:
Total current assets of discontinued operations	$ 0		$ 495,021
Non-current assets of discontinued operations	0		343,564
Current liabilities:
Total current liabilities	0		81,876
Non-current liabilities of discontinued operations	$ 0		161,142
2seventy bio \| Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Current assets:
Cash and cash equivalents		$ 174,284	57,076
Marketable securities		160,447	413,947
Prepaid expenses		8,732	11,754
Receivables and other current assets		21,637	12,244
Total current assets of discontinued operations		365,100	495,021
Marketable securities		106,826	61,446
Property, plant and equipment, net		33,972	145,458
Intangible assets, net		10,664	5,644
Goodwill		6,410	7,482
Operating lease right-of-use assets		255,556	116,456
Restricted cash and other non-current assets		5,650	7,078
Non-current assets of discontinued operations			343,564
Total assets		784,178	838,585
Current liabilities:
Accounts payable		2,982	7,791
Accrued expenses and other current liabilities		85,659	48,716
Operating lease liability, current portion		6,938	15,313
Collaboration research advancement, current portion		8,957	9,236
Deferred revenue, current portion			820
Total current liabilities		104,536	81,876
Deferred revenue, net of current portion		25,762	25,762
Collaboration research advancement, net of current portion		16,264	21,581
Operating lease liability, net of current portion		257,575	112,290
Other non-current liabilities		1,896	1,509
Non-current liabilities of discontinued operations			161,142
Total liabilities		406,033	$ 243,018
Net assets transferred to 2seventy bio		$ 378,145

Fair value measurements - Schedule of Unrealized Loss on Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair value
Less than 12 months	$ 153,737	$ 143,991
12 months or greater	6,392	603
Total	160,129	144,594
Unrealized losses
Less than 12 months	(561)	(57)
12 months or greater	(6)	0
Total	(567)	(57)
U.S. government agency securities and treasuries
Fair value
Less than 12 months	108,695	105,692
12 months or greater	2,496	0
Total	111,191	105,692
Unrealized losses
Less than 12 months	(505)	(37)
12 months or greater	(4)	0
Total	(509)	(37)
Corporate bonds
Fair value
Less than 12 months	45,042	38,299
12 months or greater	3,896	603
Total	48,938	38,902
Unrealized losses
Less than 12 months	(56)	(20)
12 months or greater	(2)	0
Total	$ (58)	$ (20)

Income taxes - Reconciliation of Income Tax Provision (Benefit) (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	21.00%	21.00%	21.00%
State income tax, net of federal benefit	3.90%	3.10%	3.70%
Permanent differences	(0.60%)	(0.60%)	(0.80%)
Stock-based compensation	(3.10%)	(2.40%)	(0.70%)
Research and development credit	4.30%	6.00%	5.40%
Foreign differential	(1.90%)	(4.60%)	(3.70%)
Other	0.00%	(0.30%)	0.80%
Change in valuation allowance	(23.60%)	(22.30%)	(25.60%)
Effective income tax rate (expense) benefit	0.00%	(0.10%)	0.10%

Restricted cash - Schedule of Collateralized Bank Account of Financial Institution (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Total restricted cash	$ 45,500	$ 56,023
50 Binney Street lease
Debt and Equity Securities, FV-NI [Line Items]
Total restricted cash	40,072	40,072
Assembly Row lease
Debt and Equity Securities, FV-NI [Line Items]
Total restricted cash	2,753	0
60 Binney Street lease
Debt and Equity Securities, FV-NI [Line Items]
Total restricted cash	0	13,763
Other
Debt and Equity Securities, FV-NI [Line Items]
Total restricted cash	$ 2,675	$ 2,188

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 0	$ 8,967
Finished goods	0	1,731
Inventory, Total	0	10,698
Reserve for excess inventory	$ 29,900	$ 0

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 31, 2018			54,738,000
Beginning balance at Dec. 31, 2018	$ 1,885,070	$ 6,564	$ 547	$ 3,386,958	$ (3,627)	$ (1,498,808)	$ 6,564
Vesting of restricted stock units (in shares)			251,000
Vesting of restricted stock units	0		$ 3	(3)
Exercise of stock options (in shares)			354,000
Exercise of stock options	17,838		$ 4	17,834
Purchase of common stock under ESPP (in shares)			25,000
Purchase of common stock under ESPP	2,766			2,766
Stock-based compensation	160,629			160,629
Other comprehensive income (loss)	1,734				1,734
Net loss	(789,608)					(789,608)
Ending balance (in shares) at Dec. 31, 2019			55,368,000
Ending balance at Dec. 31, 2019	$ 1,284,993		$ 554	3,568,184	(1,893)	(2,281,852)
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2016-02 [Member]
Issuance of common stock (in shares)			10,455,000
Issuance of common stock	$ 541,536		$ 105	541,431
Vesting of restricted stock units (in shares)			434,000
Vesting of restricted stock units	0		$ 4	(4)
Exercise of stock options (in shares)			95,000
Exercise of stock options	1,847		$ 1	1,846
Purchase of common stock under ESPP (in shares)			80,000
Purchase of common stock under ESPP	3,775		$ 1	3,774
Stock-based compensation	145,212			145,212
Other comprehensive income (loss)	(3,612)				(3,612)
Net loss	$ (618,695)					(618,695)
Ending balance (in shares) at Dec. 31, 2020	66,432,000		66,432,000
Ending balance at Dec. 31, 2020	$ 1,355,056		$ 665	4,260,443	(5,505)	(2,900,547)
Issuance of common stock (in shares)			2,273,000
Issuance of common stock	37,500		$ 23	37,477
Vesting of restricted stock units (in shares)			534,000
Vesting of restricted stock units	$ 0		$ 5	(5)
Exercise of stock options (in shares)	218,000		218,000
Exercise of stock options	$ 1,488		$ 2	1,486
Purchase of common stock under ESPP (in shares)			120,000
Purchase of common stock under ESPP	2,581		$ 1	2,580
Issuance of pre-funded warrants	37,477			37,477
Issuance of unrestricted stock awards to settle accrued employee compensation (in shares)			1,538,000
Issuance of unrestricted stock awards to settle accrued employee compensation	25,074		$ 15	25,059
Stock-based compensation	110,260			110,260
Distribution of 2seventy bio	378,145			378,375	(230)
Other comprehensive income (loss)	2,364				2,364
Net loss	$ (819,378)					(819,378)
Ending balance (in shares) at Dec. 31, 2021	71,115,000		71,115,000
Ending balance at Dec. 31, 2021	$ 374,277		$ 711	$ 4,096,402	$ (2,911)	$ (3,719,925)

Leases - Schedule of Future Minimum Commitments Under Operating Leases (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Leases [Abstract]
2022	$ 27,037
2023	21,460
2024	18,009
2025	14,639
2026	8,598
2027 and thereafter	12,356
Total lease payments	102,099
Less: imputed interest	(12,515)
Total operating lease liabilities	$ 89,584

Selected quarterly financial data (unaudited) - Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 1,606	$ 1,019	$ 143	$ 894	$ 0	$ 0	$ 0	$ 0	$ 3,662	$ 0	$ 0
Total operating expenses	137,273	155,468	154,844	146,988	139,387	131,743	143,650	144,479	594,573	559,259	562,963
Loss from operations	(135,667)	(154,449)	(154,701)	(146,094)	(139,387)	(131,743)	(143,650)	(144,479)	(590,911)	(559,259)	(562,963)
Net loss from continuing operations	(132,327)	(152,834)	(155,973)	(121,504)	(136,321)	(137,678)	(140,665)	(146,392)	(562,638)	(561,056)	(555,022)
Net income (loss) from discontinued operations	(22,725)	(63,982)	(85,729)	(84,304)	(63,553)	(57,067)	119,200	(56,219)	(256,740)	(57,639)	(234,586)
Net loss	$ (155,052)	$ (216,816)	$ (241,702)	$ (205,808)	$ (199,874)	$ (194,745)	$ (21,465)	$ (202,611)	$ (819,378)	$ (618,695)	$ (789,608)
Net loss per share from continuing operations - basic (in dollars per share)	$ (1.83)	$ (2.23)	$ (2.31)	$ (1.81)	$ (2.05)	$ (2.08)	$ (2.33)	$ (2.63)	$ (8.16)	$ (9.02)	$ (10.06)
Net loss per share from continuing operations - diluted (in dollars per share)	(1.83)	(2.23)	(2.31)	(1.81)	(2.05)	(2.08)	(2.33)	(2.63)	(8.16)	(9.02)	(10.06)
Net income (loss) per share from discontinued operations - basic	(0.31)	(0.93)	(1.27)	(1.26)	(0.96)	(0.86)	1.97	(1.01)	(3.73)	(0.93)
Net income (loss) per share from discontinued operations - diluted	(0.31)	(0.93)	(1.27)	(1.26)	(0.96)	(0.86)	1.97	(1.01)	(3.73)	(0.93)
Net loss per share - basic (in dollars per share)	(2.14)	(3.16)	(3.58)	(3.07)	(3.01)	(2.94)	(0.36)	(3.64)	(11.89)	(9.95)	(14.31)
Net loss per share - diluted (in dollars per share)	$ (2.14)	$ (3.16)	$ (3.58)	$ (3.07)	$ (3.01)	$ (2.94)	$ (0.36)	$ (3.64)	$ (11.89)	$ (9.95)	$ (14.31)

Income taxes - Summary of Provision for (Benefit from) Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ 0	$ 0	$ 0
State	0	2	7
Foreign	258	684	612
Deferred:
Federal	0	0	(966)
State	0	0	(198)
Foreign	0	0	0
Total income tax expense (benefit)	$ 258	$ 686	$ (545)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Restricted cash

12 Months Ended

Dec. 31, 2021

Other Assets, Noncurrent [Abstract]

Restricted cash

As of December 31, 2021 and 2020, the Company maintained letters of credit of $43.2 million and $54.5 million, respectively, which are collateralized with bank accounts at financial institutions in accordance with the agreements. Total restricted cash as of December 31, 2021 and 2020 consisted of the following (in thousands):


	As of December 31,
	2021		2020
50 Binney Street lease	$	40,072	$	40,072
Assembly Row lease	2,753		—
60 Binney Street lease	—		13,763
Other	2,675		2,188
Total restricted cash	$	45,500	$	56,023

Refer to Note 10, Leases, for further information on the Company's letters of credit.