bluebird bio (BLUE) 10-Q 4 Aug 22 2022 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2022	Aug. 03, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
Document Transition Report	false
Entity File Number	001-35966
Entity Registrant Name	bluebird bio, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3680878
Entity Address, Address Line One	455 Grand Union Boulevard
Entity Address, City or Town	Somerville
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02145
City Area Code	339
Local Phone Number	499-9300
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	BLUE
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		77,121,751
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001293971
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 81,499	$ 161,160
Marketable securities	51,010	138,343
Prepaid expenses	24,473	25,628
Receivables and other current assets	10,476	11,389
Total current assets	167,458	336,520
Marketable securities	40,641	97,114
Property, plant and equipment, net	14,566	9,706
Goodwill	5,646	5,646
Operating lease right-of-use assets	292,731	91,532
Restricted cash and other non-current assets	52,550	53,277
Total assets	573,592	593,795
Current liabilities:
Accounts payable	24,865	25,883
Accrued expenses and other current liabilities	75,550	103,958
Operating lease liability, current portion	48,446	23,152
Total current liabilities	148,861	152,993
Operating lease liability, net of current portion	244,522	66,432
Other non-current liabilities	93	93
Total liabilities	393,476	219,518
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at June 30, 2022 and December 31, 2021	0	0
Common stock, $0.01 par value, 125,000 shares authorized; 73,551 and 71,115 shares issued and outstanding at June 30, 2022 and December 31, 2021, respectively	735	711
Additional paid-in capital	4,126,012	4,096,402
Accumulated other comprehensive loss	(4,416)	(2,911)
Accumulated deficit	(3,942,215)	(3,719,925)
Total stockholders’ equity	180,116	374,277
Total liabilities and stockholders’ equity	$ 573,592	$ 593,795

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2022	Dec. 31, 2021
Stockholders’ equity:
Preferred stock, par value (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)	73,551,000	71,115,000
Common stock, shares outstanding (in shares)	73,551,000	71,115,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue:
Total revenues	$ 1,519	$ 143	$ 3,464	$ 1,037
Operating expenses:
Research and development	63,841	84,645	141,716	167,488
Selling, general and administrative	36,694	54,984	72,800	118,553
Cost of product revenue	1,745	15,215	10,055	15,791
Restructuring expenses	6,639	0	6,639	0
Total operating expenses	108,919	154,844	231,210	301,832
Loss from operations	(107,400)	(154,701)	(227,746)	(300,795)
Interest income, net	174	218	280	573
Other (expense) income, net	7,088	(1,274)	5,176	23,027
Loss before income taxes	(100,138)	(155,757)	(222,290)	(277,195)
Income tax (expense) benefit	0	(216)	0	(282)
Net loss from continuing operations	(100,138)	(155,973)	(222,290)	(277,477)
Net loss from discontinued operations	0	(85,729)	0	(170,033)
Net loss	$ (100,138)	$ (241,702)	$ (222,290)	$ (447,510)
Net loss per share from continuing operations - basic (in dollars per share)	$ (1.36)	$ (2.31)	$ (3.02)	$ (4.13)
Net loss per share from continuing operations - diluted (in dollars per share)	(1.36)	(2.31)	(3.02)	(4.13)
Net loss per share from discontinued operations - basic (in dollars per share)	0	(1.27)	0	(2.53)
Net loss per share from discontinued operations - diluted (in dollars per share)	0	(1.27)	0	(2.53)
Net loss per share - basic (in dollars per share)	(1.36)	(3.58)	(3.02)	(6.66)
Net loss per share - diluted (in dollars per share)	$ (1.36)	$ (3.58)	$ (3.02)	$ (6.66)
Weighted-average number of common shares used in computing net loss per share - basic (in shares)	73,767	67,487	73,727	67,233
Weighted-average number of common shares used in computing net loss per share - diluted (in shares)	73,767	67,487	73,727	67,233
Other comprehensive (loss) income:
Other comprehensive income	$ 43	$ (328)	$ (1,505)	$ (272)
Comprehensive loss	(100,095)	(242,030)	(223,795)	(447,782)
Product revenue
Revenue:
Revenue	1,331	0	2,739	724
Other revenue
Revenue:
Revenue	$ 188	$ 143	$ 725	$ 313

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Other comprehensive income (loss), tax	$ 0	$ 0	$ 0	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2020		66,432
Beginning balance at Dec. 31, 2020	$ 1,355,056	$ 665	$ 4,260,443	$ (5,505)	$ (2,900,547)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		294
Vesting of restricted stock units	0	$ 3	(3)
Exercise of stock options (in shares)		207
Exercise of stock options	1,219	$ 2	1,217
Purchase of common stock under ESPP (in shares)		67
Purchase of common stock under ESPP	1,707	$ 1	1,706
Stock-based compensation	36,090		36,090
Issuance of unrestricted stock awards to settle accrued employee compensation (in shares)		422
Issuance of unrestricted stock awards to settle accrued employee compensation	12,013	$ 4	12,009
Other comprehensive income	56			56
Net loss	(205,808)				(205,808)
Ending balance, shares (in shares) at Mar. 31, 2021		67,422
Ending balance at Mar. 31, 2021	1,200,333	$ 675	4,311,462	(5,449)	(3,106,355)
Beginning balance (in shares) at Dec. 31, 2020		66,432
Beginning balance at Dec. 31, 2020	1,355,056	$ 665	4,260,443	(5,505)	(2,900,547)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	(272)
Net loss	(447,510)
Ending balance, shares (in shares) at Jun. 30, 2021		67,551
Ending balance at Jun. 30, 2021	984,561	$ 676	4,337,719	(5,777)	(3,348,057)
Beginning balance (in shares) at Mar. 31, 2021		67,422
Beginning balance at Mar. 31, 2021	1,200,333	$ 675	4,311,462	(5,449)	(3,106,355)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		127
Vesting of restricted stock units	0	$ 1	(1)
Exercise of stock options (in shares)		2
Exercise of stock options	36		36
Stock-based compensation	26,222		26,222
Other comprehensive income	(328)			(328)
Net loss	(241,702)				(241,702)
Ending balance, shares (in shares) at Jun. 30, 2021		67,551
Ending balance at Jun. 30, 2021	$ 984,561	$ 676	4,337,719	(5,777)	(3,348,057)
Beginning balance (in shares) at Dec. 31, 2021	71,115	71,115
Beginning balance at Dec. 31, 2021	$ 374,277	$ 711	4,096,402	(2,911)	(3,719,925)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		310
Vesting of restricted stock units	0	$ 3	(3)
Exercise of stock options (in shares)		1
Exercise of stock options	1		1
Stock-based compensation	12,681		12,681
Issuance of unrestricted stock awards to settle accrued employee compensation (in shares)		12
Other comprehensive income	(1,548)			(1,548)
Net loss	(122,152)				(122,152)
Ending balance, shares (in shares) at Mar. 31, 2022		71,438
Ending balance at Mar. 31, 2022	$ 263,259	$ 714	4,109,081	(4,459)	(3,842,077)
Beginning balance (in shares) at Dec. 31, 2021	71,115	71,115
Beginning balance at Dec. 31, 2021	$ 374,277	$ 711	4,096,402	(2,911)	(3,719,925)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	2
Other comprehensive income	$ (1,505)
Net loss	$ (222,290)
Ending balance, shares (in shares) at Jun. 30, 2022	73,551	73,551
Ending balance at Jun. 30, 2022	$ 180,116	$ 735	4,126,012	(4,416)	(3,942,215)
Beginning balance (in shares) at Mar. 31, 2022		71,438
Beginning balance at Mar. 31, 2022	263,259	$ 714	4,109,081	(4,459)	(3,842,077)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		60
Vesting of restricted stock units	0	$ 1	(1)
Exercise of stock options (in shares)		1
Exercise of stock options	1		1
Stock-based compensation	8,908		8,908
Issuance of unrestricted stock awards to settle accrued employee compensation (in shares)		2,052
Issuance of unrestricted stock awards to settle accrued employee compensation	8,043	$ 20	8,023
Other comprehensive income	43			43
Net loss	$ (100,138)				(100,138)
Ending balance, shares (in shares) at Jun. 30, 2022	73,551	73,551
Ending balance at Jun. 30, 2022	$ 180,116	$ 735	$ 4,126,012	$ (4,416)	$ (3,942,215)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (222,290)	$ (447,510)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of contingent consideration	0	416
Depreciation and amortization	2,358	11,353
Stock-based compensation expense	21,298	73,687
Loss (gain) on equity securities	3,135	(28,286)
Excess inventory reserve	7,519	15,084
Other non-cash items	661	6,228
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(9,629)	(3,481)
Operating lease right-of-use assets	17,636	15,074
Accounts payable	(1,175)	7,475
Accrued expenses and other liabilities	(28,565)	17,453
Operating lease liabilities	(10,602)	(16,468)
Net cash used in operating activities	(219,654)	(348,975)
Cash flows from investing activities:
Purchase of property, plant and equipment	(6,836)	(9,204)
Purchases of marketable securities	0	(196,145)
Proceeds from maturities of marketable securities	108,225	557,751
Proceeds from sales of marketable securities	30,213	31,318
Purchase of intangible assets	0	(2,000)
Net cash provided by investing activities	131,602	381,720
Cash flows from financing activities:
Proceeds from exercise of stock options and ESPP contributions	0	4,192
Proceeds from the secondary public offering, net of issuance costs	8,043	0
Net cash provided by financing activities	8,043	4,192
(Decrease) increase in cash, cash equivalents and restricted cash	(80,009)	36,937
Cash, cash equivalents and restricted cash at beginning of period	206,693	373,728
Cash, cash equivalents and restricted cash at end of period	126,684	410,665
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	81,499	353,468
Restricted cash included in receivables and other current assets	1,635	2,687
Restricted cash included in restricted cash and other non-current assets	43,550	54,510
Total cash, cash equivalents and restricted cash	126,684	410,665
Supplemental cash flow disclosures from investing and financing activities:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	842	1,508
Right-of-use assets obtained in exchange for operating lease liabilities	218,836	22,049
Issuance of unrestricted stock awards to settle accrued employee compensation	0	12,013
Purchases of intangible assets included in accounts payable and accrued expenses, net of reimbursement receivable from collaboration partner	$ 0	$ 6,500

Description of the business

Description of the business	6 Months Ended
	Jun. 30, 2022
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. The Company’s programs in severe genetic diseases include betibeglogene autotemcel ("beti-cel", formerly "LentiGlobin for β-thalassemia gene therapy") being developed as a treatment for β-thalassemia; lovotibeglogene autotemcel ("lovo-cel", formerly "LentiGlobin for SCD") being developed as a treatment for sickle cell disease ("SCD"); and elivaldogene autotemcel ("eli-cel", formerly "Lenti-D gene therapy") being developed as a treatment for cerebral adrenoleukodystrophy ("CALD"). 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, SCD, and CALD. 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 sales forecasts and projected inventory consumption levels. 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 retained its severe genetic disease programs, including programs for β-thalassemia, SCD, and CALD, with a focus on the U.S. market. In April 2022, the Board of Directors approved a comprehensive restructuring plan intended to reduce operating expenses and enhance the Company’s focus on achieving U.S. Food and Drug Administration ("FDA") approval for its programs in the U.S. The Company intends to maintain targeted research efforts focused on in-vivo lentiviral vector ("LVV") gene therapy and to deprioritize direct investments in reduced toxicity conditioning and cryopreserved apheresis. As part of the restructuring, bluebird plans to reduce its workforce by approximately 30% across the second and third quarters of 2022. Refer to Note 14, Reduction in workforce, for more information on this restructuring. On June 22, 2022, the Company entered into an Equity Distribution Agreement (the “Equity Distribution Agreement”) with Goldman Sachs & Co. LLC (“Goldman”) to sell shares of the Company’s common stock up to $75.0 million, from time to time, through an “at the market” equity offering program under which Goldman will act as manager. The Equity Distribution Agreement also provides for the sale of shares to Goldman directly as principal, in which case the Company and Goldman will enter into a separate terms agreement. The Company will pay Goldman a commission equal to up to 3.0% of the gross proceeds of any Common Stock sold through Goldman under the Equity Distribution Agreement. In the three months ended June 30, 2022, the Company sold 2.1 million shares of common stock at-the-market under the Equity Distribution Agreement, resulting in gross proceeds of approximately $8.3 million ($8.0 million net of offering costs). Refer to Note 10, Equity , for more information. As of June 30, 2022, the Company had cash, cash equivalents and marketable securities of approximately $173.2 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 June 30, 2022, the Company had an accumulated deficit of $3.94 billion. During the six months ended June 30, 2022, the Company incurred a loss of $222.3 million and used $219.7 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 205-40, Going Concern ("ASC 205-40"), 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 condensed 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 condensed 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 lease, 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 condensed consolidated financial statements. The restructuring plan described above was approved by the Board of Directors in April 2022 and therefore was incorporated into the Company's assessment of its ability to continue as a going concern within one year after the date that these condensed consolidated financial statements are issued. 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 condensed consolidated financial statements are issued. Management's plans to alleviate the conditions that raise substantial doubt include implementing reduced 2022 spending, including projected savings through the move of the Company's headquarters to Assembly Row in Somerville, Massachusetts, the completion of its orderly wind down of European operations, the completion of its April 2022 restructuring plans, the potential sale of priority review vouchers that would be issued with the potential U.S. regulatory approvals of BLAs for beti-cel and/or 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. In accordance with ASC 205-40, 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 condensed consolidated financial statements.

Basis of presentation, principl

Basis of presentation, principles of consolidation and significant accounting policies	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Basis of presentation, principles of consolidation and significant accounting policies	Basis of presentation, principles of consolidation and significant accounting policies Basis of presentation The accompanying condensed consolidated financial statements are unaudited and 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 Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended June 30, 2022 and 2021. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements as of and for the year ended December 31, 2021, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, filed with the Securities and Exchange Commission (the “SEC”) on March 4, 2022 (the "2021 Annual Report on Form 10-K"). Certain items in the prior year’s condensed 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 the three and six months ended June 30, 2021 (see Note 3, Discontinued operation s). 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. The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. 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. The Company views its operations and manages its business in one operating segment. 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 September 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 condensed consolidated financial statements for the three and six months ended June 30, 2021 have been updated to present 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 ). Significant accounting policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and six months ended June 30, 2022 are consistent with those discussed in Note 2 to the consolidated financial statements included in the Company’s 2021 Annual Report on Form 10-K, except as noted in the "Recent accounting pronouncements - Not yet adopted" section below. 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. Recent accounting pronouncements Not yet adopted ASU No. 2022-02, Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures In March 2022, the FASB issued ASU 2022-02, Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures (“ASU 2022-02”), which eliminates the recognition and measurement guidance on troubled debt restructurings for creditors that have adopted ASC 326 and requires enhanced disclosure of loan modifications for borrowers experiencing financial difficulty. ASU 2022-02 amends the guidance on vintage disclosures to require disclosure of current-period gross write-offs by year of origination. The new standard will be effective beginning January 1, 2023. The adoption of ASU 2022-02 is not expected to have a material impact on the Company's financial position or results of operations.

Discontinued operations

Discontinued operations	6 Months Ended
	Jun. 30, 2022
Discontinued Operations and Disposal Groups [Abstract]
Discontinued operations	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 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 associated with the Company's oncology programs. The Company recognized a loss on disposal of assets of $2.0 million during the year ended December 31, 2021. 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 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. bluebird and 2seventy bio also entered into a tax matters agreement, an employee matters agreement and an intellectual property agreement. 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. In addition, 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. During the three and six months ended June 30, 2022, the Company incurred $2.5 million and $5.5 million, respectively of net expense for transactions with 2seventy bio within research and development and selling, general and administrative expense in the condensed consolidated statements of operations and comprehensive loss, including $1.1 million and $2.3 million, respectively of net expense related to the 60 Binney Street Sublease. As of June 30, 2022, the Company had $0.4 million of accounts receivable due from and $2.9 million of accounts payable due to 2seventy bio. As of December 31, 2021, the Company had an immaterial amount of accounts receivable and accounts payable due from and due 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 three and six months ended June 30, 2021 (in thousands): Three months ended June 30, 2021 Six months ended June 30, 2021 Revenue: Service revenue $ 5,314 $ 11,232 Collaborative arrangement revenue 1,670 3,190 Royalty and other revenue 345 4,808 Total revenues 7,329 19,230 Operating expenses: Research and development 59,670 131,305 Selling, general and administrative 23,592 46,898 Share of collaboration loss 10,071 10,071 Cost of royalty and other revenue 86 1,791 Change in fair value of contingent consideration 47 416 Total operating expenses 93,466 190,481 Loss from operations (86,137) (171,251) Interest income, net 220 576 Other income, net 188 642 Loss before income taxes (85,729) (170,033) Income tax benefit (expense) — — Net loss $ (85,729) $ (170,033) There were no revenue and expenses of the discontinued operations for the three and six months ended June 30, 2022, as all operations were transferred to 2seventy bio upon the Separation. There were no assets and liabilities related to discontinued operations as of June 30, 2022 or December 31, 2021, as all balances were transferred to 2seventy bio upon the Separation. The following table summarizes the significant non-cash items and capital expenditures of the discontinued operations that are included in the condensed consolidated statements of cash flows for the six months ended June 30, 2021 (in thousands): Six months ended June 30, 2021 Operating activities: Change in fair value of contingent consideration $ 416 Depreciation and amortization 8,300 Stock-based compensation expense 19,104 Loss on fixed asset disposal 254 Investing activities: Purchase of property, plant and equipment $ (7,675) Purchase of intangible assets (2,000) Supplemental cash flow disclosures: Purchases of property, plant and equipment included in accounts payable and accrued expenses $ 1,345 Purchases of intangible assets included in accounts payable and accrued expenses, net of reimbursement receivable from collaboration partner 6,500

Marketable securities

Marketable securities	6 Months Ended
	Jun. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Marketable securities	Marketable securities The following table summarizes the marketable securities held at June 30, 2022 and December 31, 2021 (in thousands): Description Amortized cost / Cost Unrealized gains Unrealized losses Fair value June 30, 2022 U.S. government agency securities and treasuries $ 77,943 $ — $ (1,980) $ 75,963 Corporate bonds 13,294 (105) 13,189 Commercial paper 2,499 — — 2,499 Equity securities — — — — Total $ 93,736 $ — $ (2,085) $ 91,651 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 No available-for-sale debt securities held as of June 30, 2022 or December 31, 2021 had remaining maturities greater than five years.

Fair value measurements

Fair value measurements	6 Months Ended
	Jun. 30, 2022
Fair Value Disclosures [Abstract]
Fair value measurements	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 June 30, 2022 and December 31, 2021 (in thousands): Description Total Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) June 30, 2022 Assets: Cash and cash equivalents $ 81,499 $ 81,499 $ — $ — Marketable securities: U.S. government agency securities and treasuries 75,963 — 75,963 — Corporate bonds 13,189 — 13,189 — Commercial paper 2,499 — 2,499 — Equity securities — — — — Total $ 173,150 $ 81,499 $ 91,651 $ — 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 $ 396,617 $ 164,837 $ 231,780 $ — Cash and cash equivalents The Company considers all highly liquid securities with original final maturities of 90 days or less from the date of purchase to be cash equivalents. As of June 30, 2022 and December 31, 2021, 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 June 30, 2022 and December 31, 2021, 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 debt securities during the three and six months ended June 30, 2022 or 2021. Accrued interest receivable on the Company's available-for-sale debt securities totaled $0.1 million and $0.3 million as of June 30, 2022 and December 31, 2021, respectively. No accrued interest receivable was written off during the three and six months ended June 30, 2022 or 2021. 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 June 30, 2022 and December 31, 2021 (in thousands): Less than 12 months 12 months or greater Total Description Fair value Unrealized losses Fair value Unrealized losses Fair value Unrealized losses June 30, 2022 U.S. government agency securities $ 68,129 $ (1,814) $ 7,834 $ (166) $ 75,963 $ (1,980) Corporate bonds 6,672 (79) 6,517 (26) 13,189 (105) Total $ 74,801 $ (1,893) $ 14,351 $ (192) $ 89,152 $ (2,085) December 31, 2021 U.S. government agency securities $ 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) The Company determined that there was no material change in the credit risk of the above investments during the six months ended June 30, 2022. As such, an allowance for credit losses was not recognized. In April 2022, the Company sold securities with a carrying value of $29.7 million and realized net aggregate losses of $0.4 million. As of June 30, 2022, the Company does not intend to sell such securities before recovery of their amortized cost bases.

Property, plant and equipment,

Property, plant and equipment, net	6 Months Ended
	Jun. 30, 2022
Property, Plant and Equipment [Abstract]
Property, plant and equipment, net	Property, plant and equipment, net Property, plant and equipment, net, consists of the following (in thousands): As of June 30, 2022 As of December 31, 2021 Laboratory equipment $ 28,838 $ 29,061 Computer equipment and software 1,733 421 Office equipment 5,679 117 Leasehold improvements — 12 Construction-in-progress 817 501 Total property, plant and equipment 37,067 30,112 Less accumulated depreciation and amortization (22,501) (20,406) Property, plant and equipment, net $ 14,566 $ 9,706

Accrued expenses and other curr

Accrued expenses and other current liabilities	6 Months Ended
	Jun. 30, 2022
Payables and Accruals [Abstract]
Accrued expenses and other current liabilities	Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following (in thousands): As of June 30, 2022 As of December 31, 2021 Accrued manufacturing costs $ 18,530 $ 15,722 Accrued goods and services 14,567 24,273 Accrued clinical and contract research organization costs 18,069 17,769 Accrued employee compensation 19,853 41,095 Accrued professional fees 1,226 1,665 Deferred revenue, current portion 1,635 2,282 Other 1,670 1,152 Total accrued expenses and other current liabilities $ 75,550 $ 103,958 Accrued employee compensation as of December 31, 2021 includes severance costs associated with the Company's orderly wind down of its European operations. In April 2022, the Company announced a restructuring which included a reduction in force. As of June 30, 2022, the Company had $2.7 million of accrued employee compensation related to the April 2022 restructuring. Please refer to Note 14, Reduction in workforce, for further information.

Leases

Leases	6 Months Ended
	Jun. 30, 2022
Leases [Abstract]
Leases	Leases The Company leases certain office and laboratory space, primarily located in Cambridge, Massachusetts and Somerville, Massachusetts. Additionally, the Company has embedded leases through its agreements with contract manufacturing organizations in both the United States and internationally. Except as described below, there have been no material changes in lease obligations from those disclosed in Note 10 to the consolidated financial statements included in the Company's 2021 Annual Report on Form 10-K. 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 (the “Assembly Row Lease”). Upon signing the Assembly Row Lease, the Company executed a $2.8 million letter of credit for the Landlord’s benefit, which is classified as restricted cash and other non-current assets on the Company’s condensed consolidated balance sheets. In March 2022, the Assembly Row Lease commenced upon the Landlord granting the Company control of the leased premises. The Assembly Row Lease will continue until December 31, 2032, with an option to extend for two additional five-year terms. The Company classified the Assembly Row Lease as an operating lease and recognized a right-of-use asset and lease liability upon lease commencement. The Company will recognize rent expense on a straight-line basis throughout the remaining term of the Assembly Row Lease. 50 Binney Street lease & sublease In April 2019, the Company entered into an agreement to lease office space located at 50 Binney Street in Cambridge, Massachusetts (the “50 Binney Street Lease”). In December 2021, the Company entered into an agreement to sublease the entire office space to Meta Platforms, Inc. (“Meta”) (the "Sublease"). In April 2022, both the 50 Binney Street Lease and the Sublease commenced upon the landlord granting access to the leased premises. In connection with the execution of the 50 Binney Street Lease, the Company also entered into a purchase agreement with the landlord 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. Upon lease commencement, the Company paid the remaining $7.25 million due under the Furniture Purchase Agreement. The fair value of the furniture is $2.4 million, and the remaining excess of the $7.25 million payment over fair value will be recognized as expense over the life of the lease. The Company classified the 50 Binney Street Lease as an operating lease and recognized the right-of-use asset and lease liability upon lease commencement. The Company will recognize rent expense on a straight-line basis throughout the remaining term of the 50 Binney Street Lease. The Sublease will continue until December 31, 2030. The Company classified the 50 Binney Street Sub-lease as an operating lease. The Company will earn rental income through its role as a lessor throughout the term of the Sublease. The

Commitments and contingencies

Commitments and contingencies	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies 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. Company may be obligated to make future development, regulatory, and commercial milestone payments, and royalty payments on future sales of specified products associated with its 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 occurred, the corresponding amounts are recognized in the Company’s financial statements. 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. As compared to the contractual obligations and commitments as disclosed in the Company's 2021 Annual Report on Form 10-K, the Company's future minimum purchase commitments as of the six months ended June 30, 2022 decreased by $23.0 million. While there are no material legal proceedings the Company is aware of, the Company may become 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.

Equity

Equity	6 Months Ended
	Jun. 30, 2022
Equity [Abstract]
Equity	Equity On June 22, 2022, the Company entered into the Equity Distribution Agreement with Goldman to sell shares of the Company’s common stock, with aggregate gross sales proceeds of up to $75.0 million, from time to time, through an “at the market” equity offering program under which Goldman will act as manager. The Equity Distribution Agreement also provides for the sale of shares to Goldman directly as principal, in which case the Company and Goldman will enter into a separate term agreement. Under the Equity Distribution Agreement, the Company will set the parameters for the sale of shares, including any price, time or size limits or other customary parameters or conditions. The Company intends to sell shares pursuant to the Equity Distribution Agreement from time to time in varying amounts, which may be limited, based upon factors including (among others) market conditions, trading liquidity, the trading price of the Company’s common stock, and determinations by the Company of its need for, and appropriate sources of, additional capital. Subject to the terms and conditions of the Equity Distribution Agreement, Goldman may sell the shares by any method permitted by law, including without limitation (i) by means of ordinary brokers’ transactions (whether or not solicited), (ii) to or through a market maker, (iii) directly on or through any national securities exchange or facility thereof, a trading facility of a national securities association, an alternative trading system, or any other market venue, (iv) in the over-the-counter market, (v) in privately negotiated transactions, or (vi) through a combination of any such methods. The Company will pay Goldman a commission equal to up to 3.0% of the gross proceeds of any common stock sold through Goldman under the Equity Distribution Agreement, and also has provided Goldman with customary representations, warranties, covenants and indemnification rights. The Equity Distribution Agreement may be terminated by the Company upon written notice to Goldman or by Goldman upon written notice to the Company. In the case of any purchase of shares by Goldman directly as principal pursuant to a Terms Agreement, such Terms Agreement may be terminated by Goldman upon notice to the Company under certain circumstances, including but not limited to the occurrence of a material adverse effect in the Company. In the three months ended June 30, 2022, the Company has sold 2.1 million shares of common stock for gross proceeds of $8.3 million ($8.0 million net of offering costs).

Stock-based compensation

Stock-based compensation	6 Months Ended
	Jun. 30, 2022
Share-Based Payment Arrangement [Abstract]
Stock-based compensation	Stock-based compensation In January 2022 and 2021, the number of shares of common stock available for issuance under the 2013 Stock Option and Incentive Plan (“2013 Plan”) was increased by approximately 2.8 million and 2.7 million shares, respectively, as a result of the automatic increase provision of the 2013 Plan. As of June 30, 2022, the total number of shares of common stock available for issuance under the 2013 Plan was approximately 4.7 million. Stock-based compensation expense The Company recognized stock-based compensation expense totaling $8.9 million and $23.1 million during the three months ended June 30, 2022 and 2021, respectively. The Company recognized stock based compensation expense totaling $21.3 million and $54.4 million on for the six months ended June 30, 2022 and 2021, respectively. Stock-based compensation expense recognized by award type is included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): For the three months ended June 30, For six months ended June 30, 2022 2021 (1) 2022 2021 (1) Stock options $ 3,685 $ 13,863 $ 8,945 $ 30,289 Restricted stock units 4,850 5,956 11,884 16,173 Employee stock purchase plan and other 372 3,307 469 7,958 $ 8,907 $ 23,126 $ 21,298 $ 54,420 (1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation. Stock-based compensation expense by classification included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): For the three months ended June 30, For six months ended June 30, 2022 2021 (1) 2022 2021 (1) Research and development $ 5,255 $ 10,336 $ 11,810 $ 22,726 Selling, general and administrative 3,652 12,790 9,488 31,694 $ 8,907 $ 23,126 $ 21,298 $ 54,420 (1) Prior period amounts have been retrospectively adjusted to reflect the effects of the Separation. Stock options The following table summarizes the stock option activity under the Company’s equity award plans and have been adjusted to reflect the effects of the Separation: Shares (in thousands) Weighted- average exercise price per share Outstanding at December 31, 2021 3,586 $ 39.23 Granted 967 $ 7.48 Exercised (2) $ 1.04 Canceled or forfeited (1,482) $ 41.11 Outstanding at June 30, 2022 3,069 $ 29.48 Exercisable at June 30, 2022 1,296 $ 51.24 Vested and expected to vest at June 30, 2022 3,069 $ 29.48 During the six months ended June 30, 2022, less than 0.1 million stock options were exercised, resulting in total proceeds to the Company of less than $0.1 million. Restricted stock units The following table summarizes the restricted stock unit activity under the Company’s equity award plans and have been adjusted to reflect the effects of the Separation: Shares Weighted- Unvested at December 31, 2021 3,193 $ 16.21 Granted 1,451 $ 7.51 Vested (293) $ 25.65 Forfeited (1,076) $ 12.67 Unvested at June 30, 2022 3,275 $ 12.70 Employee stock purchase plan In June 2013, the Company adopted its 2013 Employee Stock Purchase Plan (“2013 ESPP”), which authorized 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 six months ended June 30, 2022 and 2021, no shares and less than 0.1 million shares, respectively, of common stock were issued under the 2013 ESPP.

Income taxes

Income taxes	6 Months Ended
	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. 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 tax expense recognized during the three and six months ended June 30, 2022 is immaterial due to the wind down of our operations in Europe. 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.

Net loss per share

Net loss per share	6 Months Ended
	Jun. 30, 2022
Earnings Per Share [Abstract]
Net loss per share	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): For the three and six months ended June 30, 2022 2021 Outstanding stock options (1) 4,958 6,099 Restricted stock units (1) 3,408 1,865 ESPP shares and other 264 746 8,630 8,710

Restructuring

Restructuring	6 Months Ended
	Jun. 30, 2022
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In April 2022, the Board of Directors of the Company approved a comprehensive restructuring plan intended to reduce operating expenses. The Company intends to maintain targeted research efforts focused on in-vivo LVV gene therapy and to deprioritize direct investments in reduced toxicity conditioning and cryopreserved apheresis. As part of the restructuring, the Company plans to reduce its workforce by 30% across the second and third quarters of 2022. The Company estimates that it will incur approximately $6.6 million in costs to implement the restructuring, comprised primarily of severance payments and continuing health care coverage over the severance period. The restructuring actions associated with these charges commenced in April 2022, and are expected to be substantially completed by the end of 2022. The following table summarizes the accrued liabilities activity recorded in connection with the restructuring for the three and six months ended June 30, 2022: As of June 30, 2022 Beginning balance $ — Total expense $ 6,639 Payments made from inception through June 30, 2022 $ 3,989 Remaining accrual at June 30, 2022 $ 2,650

Subsequent events

Subsequent events	6 Months Ended
	Jun. 30, 2022
Subsequent Events [Abstract]
Subsequent events	Subsequent events The Company has raised approximately additional gross proceeds of $24.7 million and issued 5.5 million shares of common stock under the Equity Distribution Agreement through the date of this report. Of this $24.7 million, $8.0 million in net proceeds were realized in the second quarter of 2022 and are reflected in the restricted cash, cash and cash equivalents and marketable securities balances as of June 30, 2022. Please refer to Note 10, Equity, for further information.

Basis of presentation, princi_2

Basis of presentation, principles of consolidation and significant accounting policies (Policies)	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying condensed consolidated financial statements are unaudited and 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 Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended June 30, 2022 and 2021.
Consolidation	The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. 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. The Company views its operations and manages its business in one operating segment.
Discontinued operations	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 September 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 condensed consolidated financial statements for the three and six months ended June 30, 2021 have been updated to present 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	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.
Recent accounting pronouncements	Recent accounting pronouncements Not yet adopted ASU No. 2022-02, Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures In March 2022, the FASB issued ASU 2022-02, Financial Instruments – Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures (“ASU 2022-02”), which eliminates the recognition and measurement guidance on troubled debt restructurings for creditors that have adopted ASC 326 and requires enhanced disclosure of loan modifications for borrowers experiencing financial difficulty. ASU 2022-02 amends the guidance on vintage disclosures to require disclosure of current-period gross write-offs by year of origination. The new standard will be effective beginning January 1, 2023. The adoption of ASU 2022-02 is not expected to have a material impact on the Company's financial position or results of operations.

Discontinued operations (Tables

Discontinued operations (Tables)	6 Months Ended
	Jun. 30, 2022
Discontinued Operations and Disposal Groups [Abstract]
Summary of Revenues , Expenses, Non-cash Items and Capital Expenditures for Discontinued Operations	The following table summarizes revenue and expenses of the discontinued operations for the three and six months ended June 30, 2021 (in thousands): Three months ended June 30, 2021 Six months ended June 30, 2021 Revenue: Service revenue $ 5,314 $ 11,232 Collaborative arrangement revenue 1,670 3,190 Royalty and other revenue 345 4,808 Total revenues 7,329 19,230 Operating expenses: Research and development 59,670 131,305 Selling, general and administrative 23,592 46,898 Share of collaboration loss 10,071 10,071 Cost of royalty and other revenue 86 1,791 Change in fair value of contingent consideration 47 416 Total operating expenses 93,466 190,481 Loss from operations (86,137) (171,251) Interest income, net 220 576 Other income, net 188 642 Loss before income taxes (85,729) (170,033) Income tax benefit (expense) — — Net loss $ (85,729) $ (170,033) Six months ended June 30, 2021 Operating activities: Change in fair value of contingent consideration $ 416 Depreciation and amortization 8,300 Stock-based compensation expense 19,104 Loss on fixed asset disposal 254 Investing activities: Purchase of property, plant and equipment $ (7,675) Purchase of intangible assets (2,000) Supplemental cash flow disclosures: Purchases of property, plant and equipment included in accounts payable and accrued expenses $ 1,345 Purchases of intangible assets included in accounts payable and accrued expenses, net of reimbursement receivable from collaboration partner 6,500

Marketable securities (Tables)

Marketable securities (Tables)	6 Months Ended
	Jun. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Summary of Marketable Securities Held	The following table summarizes the marketable securities held at June 30, 2022 and December 31, 2021 (in thousands): Description Amortized cost / Cost Unrealized gains Unrealized losses Fair value June 30, 2022 U.S. government agency securities and treasuries $ 77,943 $ — $ (1,980) $ 75,963 Corporate bonds 13,294 (105) 13,189 Commercial paper 2,499 — — 2,499 Equity securities — — — — Total $ 93,736 $ — $ (2,085) $ 91,651 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

Fair value measurements (Tables

Fair value measurements (Tables)	6 Months Ended
	Jun. 30, 2022
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 June 30, 2022 and December 31, 2021 (in thousands): Description Total Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) June 30, 2022 Assets: Cash and cash equivalents $ 81,499 $ 81,499 $ — $ — Marketable securities: U.S. government agency securities and treasuries 75,963 — 75,963 — Corporate bonds 13,189 — 13,189 — Commercial paper 2,499 — 2,499 — Equity securities — — — — Total $ 173,150 $ 81,499 $ 91,651 $ — 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 $ 396,617 $ 164,837 $ 231,780 $ —
Summary of Available-for-sale Debt Securities in Continuous Unrealized Loss Position	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 June 30, 2022 and December 31, 2021 (in thousands): Less than 12 months 12 months or greater Total Description Fair value Unrealized losses Fair value Unrealized losses Fair value Unrealized losses June 30, 2022 U.S. government agency securities $ 68,129 $ (1,814) $ 7,834 $ (166) $ 75,963 $ (1,980) Corporate bonds 6,672 (79) 6,517 (26) 13,189 (105) Total $ 74,801 $ (1,893) $ 14,351 $ (192) $ 89,152 $ (2,085) December 31, 2021 U.S. government agency securities $ 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)

Property, plant and equipment_2

Property, plant and equipment, net (Tables)	6 Months Ended
	Jun. 30, 2022
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 June 30, 2022 As of December 31, 2021 Laboratory equipment $ 28,838 $ 29,061 Computer equipment and software 1,733 421 Office equipment 5,679 117 Leasehold improvements — 12 Construction-in-progress 817 501 Total property, plant and equipment 37,067 30,112 Less accumulated depreciation and amortization (22,501) (20,406) Property, plant and equipment, net $ 14,566 $ 9,706

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	6 Months Ended
	Jun. 30, 2022
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 June 30, 2022 As of December 31, 2021 Accrued manufacturing costs $ 18,530 $ 15,722 Accrued goods and services 14,567 24,273 Accrued clinical and contract research organization costs 18,069 17,769 Accrued employee compensation 19,853 41,095 Accrued professional fees 1,226 1,665 Deferred revenue, current portion 1,635 2,282 Other 1,670 1,152 Total accrued expenses and other current liabilities $ 75,550 $ 103,958

Stock-based compensation (Table

Stock-based compensation (Tables)	6 Months Ended
	Jun. 30, 2022
Share-Based Payment Arrangement [Abstract]
Summary of Stock-Based Compensation Expense by Award Type	Stock-based compensation expense recognized by award type is included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): For the three months ended June 30, For six months ended June 30, 2022 2021 (1) 2022 2021 (1) Stock options $ 3,685 $ 13,863 $ 8,945 $ 30,289 Restricted stock units 4,850 5,956 11,884 16,173 Employee stock purchase plan and other 372 3,307 469 7,958 $ 8,907 $ 23,126 $ 21,298 $ 54,420
Schedule of Stock-Based Compensation Expense by Classification	Stock-based compensation expense by classification included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): For the three months ended June 30, For six months ended June 30, 2022 2021 (1) 2022 2021 (1) Research and development $ 5,255 $ 10,336 $ 11,810 $ 22,726 Selling, general and administrative 3,652 12,790 9,488 31,694 $ 8,907 $ 23,126 $ 21,298 $ 54,420
Summary of Stock Option Activity Under Plan	The following table summarizes the stock option activity under the Company’s equity award plans and have been adjusted to reflect the effects of the Separation: Shares (in thousands) Weighted- average exercise price per share Outstanding at December 31, 2021 3,586 $ 39.23 Granted 967 $ 7.48 Exercised (2) $ 1.04 Canceled or forfeited (1,482) $ 41.11 Outstanding at June 30, 2022 3,069 $ 29.48 Exercisable at June 30, 2022 1,296 $ 51.24 Vested and expected to vest at June 30, 2022 3,069 $ 29.48
Summary of Restricted Common Stock Awards	The following table summarizes the restricted stock unit activity under the Company’s equity award plans and have been adjusted to reflect the effects of the Separation: Shares Weighted- Unvested at December 31, 2021 3,193 $ 16.21 Granted 1,451 $ 7.51 Vested (293) $ 25.65 Forfeited (1,076) $ 12.67 Unvested at June 30, 2022 3,275 $ 12.70

Net loss per share (Tables)

Net loss per share (Tables)	6 Months Ended
	Jun. 30, 2022
Earnings Per Share [Abstract]
Common Stock Equivalents Excluded from Calculation of Diluted 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): For the three and six months ended June 30, 2022 2021 Outstanding stock options (1) 4,958 6,099 Restricted stock units (1) 3,408 1,865 ESPP shares and other 264 746 8,630 8,710

Restructuring (Tables)

Restructuring (Tables)	6 Months Ended
	Jun. 30, 2022
Restructuring and Related Activities [Abstract]
Summary of Accrued Liability Activity Recorded in Connection with Reduction in Workforce	The following table summarizes the accrued liabilities activity recorded in connection with the restructuring for the three and six months ended June 30, 2022: As of June 30, 2022 Beginning balance $ — Total expense $ 6,639 Payments made from inception through June 30, 2022 $ 3,989 Remaining accrual at June 30, 2022 $ 2,650

Description of the business (De

Description of the business (Detail) - USD ($) $ in Thousands, shares in Millions			1 Months Ended	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Jun. 22, 2022	Apr. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Subsequent Event [Line Items]
Cash, cash equivalents and marketable securities	$ 173,200			$ 173,200				$ 173,200
Accumulated deficit	3,942,215			3,942,215				3,942,215		$ 3,719,925
Net loss				100,138	$ 122,152	$ 241,702	$ 205,808	222,290	$ 447,510
Net cash used in operating activities								$ (219,654)	$ (348,975)
Private Placement
Subsequent Event [Line Items]
Proceeds from stock offering	$ 8,300			$ 8,300
Commission fee, percentage of gross proceeds (up to)		3%
Shares of common stock sold (in shares)	2.1			2.1
Offering costs	$ 8,000			$ 8,000
Maximum | Private Placement
Subsequent Event [Line Items]
Proceeds from stock offering		$ 75,000
April 2022 Reduction
Subsequent Event [Line Items]
Plans to reduce workforce, as a percent			30%

Basis of presentation, princi_3

Basis of presentation, principles of consolidation and significant accounting policies (Detail)	6 Months Ended
	Jun. 30, 2022 segment
Accounting Policies [Abstract]
Number of operating segments	1

Discontinued operations - Narra

Discontinued operations - Narrative (Details) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2022 USD ($) $ / shares	Jun. 30, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($) $ / shares	Nov. 04, 2021 $ / shares	Nov. 03, 2021 agreement	Sep. 30, 2021 USD ($)
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	$ 0.01	$ 0.01
Number of transition services agreements | agreement					2
Initial term of transition services agreement					2 years
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
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
Selling, general and administrative expense related to transition services agreement	$ 2.5	$ 5.5
Accounts receivable due from related party	0.4	0.4
Accounts payable to related party	2.9	2.9
2seventy bio | 60 Binney Street Lease
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Related party expense	$ 1.1	$ 2.3

Discontinued operations - Reven

Discontinued operations - Revenue and Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net loss	$ 0	$ (85,729)	$ 0	$ (170,033)
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		7,329		19,230
Research and development		59,670		131,305
Selling, general and administrative		23,592		46,898
Share of collaboration loss		10,071		10,071
Change in fair value of contingent consideration		47		416
Total operating expenses		93,466		190,481
Loss from operations		(86,137)		(171,251)
Interest income, net		220		576
Other income, net		188		642
Loss before income taxes		(85,729)		(170,033)
Income tax benefit (expense)		0		0
Net loss		(85,729)		(170,033)
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		5,314		11,232
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		1,670		3,190
2seventy bio | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Other revenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues		345		4,808
Cost of royalty and other revenue		$ 86		$ 1,791

Discontinued operations - Signi

Discontinued operations - Significant Non-Cash Items and Capital Expenditures (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities:
Change in fair value of contingent consideration	$ 0	$ 416
Stock-based compensation expense	21,298	73,687
Investing activities:
Purchase of property, plant and equipment	(6,836)	(9,204)
Purchase of intangible assets	0	(2,000)
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	$ 842	1,508
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | 2seventy bio
Operating activities:
Change in fair value of contingent consideration		416
Depreciation and amortization		8,300
Stock-based compensation expense		19,104
Loss on fixed assets disposal		254
Investing activities:
Purchase of property, plant and equipment		(7,675)
Purchase of intangible assets		(2,000)
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses		1,345
Purchases of intangible assets included in accounts payable and accrued expenses, net of reimbursement receivable from collaboration partner		$ 6,500

Marketable securities (Detail)

Marketable securities (Detail) - USD ($)	Jun. 30, 2022	Apr. 30, 2022	Dec. 31, 2021
Amortized cost / Cost
Equity securities	$ 0		$ 4,305,000
Marketable securities	93,736,000		236,638,000
Unrealized gains
Equity securities	0		0
Marketable securities	0		0
Unrealized losses
Equity securities	0		(614,000)
Marketable securities	(2,085,000)		(1,182,000)
Fair value
Debt securities		$ 29,700,000
Equity securities	0		3,691,000
Marketable securities	91,651,000		235,456,000
Debt securities, available-for-sale, noncurrent	0		0
U.S. government agency securities and treasuries
Amortized cost / Cost
Debt securities	77,943,000		128,902,000
Unrealized gains
Debt securities	0		0
Unrealized losses
Debt securities	(1,980,000)		(509,000)
Fair value
Debt securities	75,963,000		128,393,000
Corporate bonds
Amortized cost / Cost
Debt securities	13,294,000		49,366,000
Unrealized gains
Debt securities			0
Unrealized losses
Debt securities	(105,000)		(59,000)
Fair value
Debt securities	13,189,000		49,307,000
Commercial paper
Amortized cost / Cost
Debt securities	2,499,000		54,065,000
Unrealized gains
Debt securities	0		0
Unrealized losses
Debt securities	0		0
Fair value
Debt securities	$ 2,499,000		$ 54,065,000

Fair value measurements - Recor

Fair value measurements - Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets:
Marketable securities:	$ 91,651	$ 235,456
Equity securities	0	3,691
Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	81,499	161,160
Equity securities	0	3,691
Total	173,150	396,617
Fair Value, Measurements, Recurring | U.S. government agency securities and treasuries
Assets:
Marketable securities:	75,963	128,393
Fair Value, Measurements, Recurring | Corporate bonds
Assets:
Marketable securities:	13,189	49,308
Fair Value, Measurements, Recurring | Commercial paper
Assets:
Marketable securities:	2,499	54,065
Fair Value, Measurements, Recurring | Quoted prices in active markets (Level 1)
Assets:
Cash and cash equivalents	81,499	161,146
Equity securities	0	3,691
Total	81,499	164,837
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	0	14
Equity securities	0	0
Total	91,651	231,780
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | U.S. government agency securities and treasuries
Assets:
Marketable securities:	75,963	128,393
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Corporate bonds
Assets:
Marketable securities:	13,189	49,308
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Commercial paper
Assets:
Marketable securities:	2,499	54,065
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Equity securities	0	0
Total	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

Fair value measurements - Narra

Fair value measurements - Narrative (Detail) - USD ($)	1 Months Ended			3 Months Ended		6 Months Ended
	May 31, 2022	Apr. 30, 2022	Jan. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized gain (loss) on available-for-sale securities		$ 400,000		$ 0	$ 0	$ 0	$ 0
Interest receivable				100,000		100,000		$ 300,000
Interest receivable, write-offs				0	0	0	0
Debt securities		$ 29,700,000
Investment at fair value				0		0		$ 3,691,000
Proceeds from sale of equity securities	$ 600,000		$ 31,300,000
Equity securities, gain (loss)						(3,135,000)	28,286,000
Other (Expense) Income, Net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, gain (loss)				$ (600,000)	$ (100,000)	$ (3,100,000)	$ (28,300,000)

Fair value measurements - Sched

Fair value measurements - Schedule of Unrealized Loss on Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair value
Less than 12 months	$ 74,801	$ 153,737
12 months or greater	14,351	6,392
Total	89,152	160,129
Unrealized losses
Less than 12 months	(1,893)	(561)
12 months or greater	(192)	(6)
Total	(2,085)	(567)
U.S. government agency securities and treasuries
Fair value
Less than 12 months	68,129	108,695
12 months or greater	7,834	2,496
Total	75,963	111,191
Unrealized losses
Less than 12 months	(1,814)	(505)
12 months or greater	(166)	(4)
Total	(1,980)	(509)
Corporate bonds
Fair value
Less than 12 months	6,672	45,042
12 months or greater	6,517	3,896
Total	13,189	48,938
Unrealized losses
Less than 12 months	(79)	(56)
12 months or greater	(26)	(2)
Total	$ (105)	$ (58)

Property, plant and equipment_3

Property, plant and equipment, net - Summary of Property, Plant and Equipment Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 37,067	$ 30,112
Less accumulated depreciation and amortization	(22,501)	(20,406)
Property, plant and equipment, net	14,566	9,706
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	28,838	29,061
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	1,733	421
Office equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	5,679	117
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	0	12
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 817	$ 501

Accrued expenses and other cu_3

Accrued expenses and other current liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued manufacturing costs	$ 18,530	$ 15,722
Accrued goods and services	14,567	24,273
Accrued clinical and contract research organization costs	18,069	17,769
Accrued employee compensation	19,853	41,095
Accrued professional fees	1,226	1,665
Deferred revenue, current portion	1,635	2,282
Other	1,670	1,152
Total accrued expenses and other current liabilities	$ 75,550	$ 103,958

Accrued expenses and other cu_4

Accrued expenses and other current liabilities - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Accrued employee compensation	$ 19,853	$ 41,095
April 2022 Restructuring
Restructuring Cost and Reserve [Line Items]
Accrued employee compensation	$ 2,700

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands	1 Months Ended		6 Months Ended
	Mar. 31, 2022 renewalOption	Nov. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Apr. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Fair value of furniture			$ 14,566		$ 9,706
Sublease income			$ 7,500
Assembly Row Lease
Lessee, Lease, Description [Line Items]
Number of lease renewal options | renewalOption	2
Lease renewal term			5 years
Collateralized letter of credit		$ 2,800
50 Binney Street Sublease
Lessee, Lease, Description [Line Items]
Upfront payment for purchase of furniture and equipment				$ 7,500
Payment for purchase of furniture and equipment, upon lease commencement				7,250
Fair value of furniture				$ 2,400

Commitments and contingencies (

Commitments and contingencies (Detail) $ in Millions	Jun. 30, 2022 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Decrease in purchase commitments	$ 23

Equity (Details)

Equity (Details) - Private Placement - USD ($) shares in Millions, $ in Millions			3 Months Ended
	Jun. 30, 2022	Jun. 22, 2022	Jun. 30, 2022
Subsidiary, Sale of Stock [Line Items]
Proceeds from stock offering (up to)	$ 8.3		$ 8.3
Commission fee, percentage of gross proceeds (up to)		3%
Shares of common stock sold (in shares)	2.1		2.1
Offering costs	$ 8		$ 8
Maximum
Subsidiary, Sale of Stock [Line Items]
Proceeds from stock offering (up to)		$ 75

Stock-based compensation - Narr

Stock-based compensation - Narrative (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Jan. 31, 2022	Jan. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increased number of issuance of awards under the 2013 Plan (in shares)	2,800,000	2,700,000
Number of shares available for issuance (in shares)			4,700,000		4,700,000
Stock-based compensation expense			$ 8,907	$ 23,126	$ 21,298	$ 54,420
Stock option share exercised (in shares)					2,000
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option share exercised (in shares)					100,000
Proceed from option share exercised					$ 100
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			3,685	13,863	8,945	30,289
ESPP shares and other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 372	$ 3,307	$ 469	$ 7,958
Common shares reserved for future issuance (in shares)							200,000
Increase in shares authorized (in shares)				1,400,000		1,400,000
ESPP shares and other | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued under plan (in shares)					0	100,000

Stock-based compensation - Summ

Stock-based compensation - Summary of Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 8,907	$ 23,126	$ 21,298	$ 54,420
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	3,685	13,863	8,945	30,289
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	4,850	5,956	11,884	16,173
Employee stock purchase plan and other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 372	$ 3,307	$ 469	$ 7,958

Stock-based compensation - Sche

Stock-based compensation - Schedule of Stock-Based Compensation Expense by Classification (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 8,907	$ 23,126	$ 21,298	$ 54,420
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5,255	10,336	11,810	22,726
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,652	$ 12,790	$ 9,488	$ 31,694

Stock-based compensation - Su_2

Stock-based compensation - Summary of Stock Option Activity Under Plan (Detail) - $ / shares shares in Thousands	6 Months Ended
	Jun. 30, 2022
Shares (in thousands)
Outstanding at beginning of period (in shares)	3,586
Granted (in shares)	967
Exercised (in shares)	(2)
Canceled or forfeited (in shares)	(1,482)
Outstanding at end of period (in shares)	3,069
Exercisable at end of period (in shares)	1,296
Vested and expected to vest at end of period (in shares)	3,069
Weighted- average exercise price per share
Outstanding at beginning of period (in dollars per share)	$ 39.23
Granted (in dollars per share)	7.48
Exercised (in dollars per share)	1.04
Canceled or forfeited (in dollars per share)	41.11
Outstanding at end of period (in dollars per share)	29.48
Exercisable at end of period (in dollars per share)	51.24
Vested and expected to vest at end of period (in dollars per share)	$ 29.48

Stock-based compensation - Su_3

Stock-based compensation - Summary of Restricted Stock Units (Detail) - Restricted stock units shares in Thousands	6 Months Ended
	Jun. 30, 2022 $ / shares shares
Shares (in thousands)
Unvested balance at beginning of period (in shares) | shares	3,193
Granted (in shares) | shares	1,451
Vested (in shares) | shares	(293)
Forfeited (in shares) | shares	(1,076)
Unvested balance at end of period (in shares) | shares	3,275
Weighted- average grant date fair value
Unvested balance at beginning of period (in dollars per share) | $ / shares	$ 16.21
Granted (in dollars per share) | $ / shares	7.51
Vested (in dollars per share) | $ / shares	25.65
Forfeited (in dollars per share) | $ / shares	12.67
Unvested balance at end of period (in dollars per share) | $ / shares	$ 12.70

Net loss per share (Detail)

Net loss per share (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
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)	8,630	8,710
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)	4,958	6,099
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)	3,408	1,865
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)	264	746

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - April 2022 Reduction $ in Millions	1 Months Ended
	Apr. 30, 2022 USD ($)
Restructuring Cost and Reserve [Line Items]
Plans to reduce workforce, as a percent	30%
Anticipated cost savings associated with restructuring	$ 6.6

Restructuring - Accrued Liabili

Restructuring - Accrued Liabilities Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Restructuring Reserve [Roll Forward]
Total expense	$ 6,639	$ 0	$ 6,639	$ 0
April 2022 Reduction
Restructuring Reserve [Roll Forward]
Beginning balance	0		0
Total expense	6,639		6,639
Expenses paid from inception through current period	3,989		3,989
Remaining accrual at June 30, 2022	$ 2,650		$ 2,650

Subsequent Events (Details)

Subsequent Events (Details) - Private Placement - USD ($) shares in Millions, $ in Millions		1 Months Ended	3 Months Ended
	Jun. 30, 2022	Aug. 04, 2022	Jun. 30, 2022
Subsequent Event [Line Items]
Proceeds from stock offering	$ 8.3		$ 8.3
Shares of common stock sold (in shares)	2.1		2.1
Offering costs	$ 8		$ 8
Subsequent Event
Subsequent Event [Line Items]
Proceeds from stock offering		$ 24.7
Shares of common stock sold (in shares)		5.5