2seventy bio (TSVT) 10-Q 7 Nov 22 2022 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2022	Nov. 01, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	001-40791
Entity Registrant Name	2seventy bio, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	86-3658454
Entity Address, Address Line One	60 Binney Street
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	2142
City Area Code	339
Local Phone Number	499-9300
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	TSVT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		37,916,693
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001860782
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 127,021	$ 130,414
Marketable securities	196,089	134,643
Prepaid expenses	14,270	9,512
Receivables and other current assets	12,037	16,995
Total current assets	349,417	291,564
Property, plant and equipment, net	46,650	34,913
Marketable securities	1,407	97,124
Intangible assets, net	7,479	9,892
Goodwill	12,056	12,056
Operating lease right-of-use assets	253,458	275,534
Restricted cash and other non-current assets	38,277	38,592
Total assets	708,744	759,675
Current liabilities:
Accounts payable	7,983	6,024
Accrued expenses and other current liabilities	52,156	55,410
Operating lease liability, current portion	10,798	9,769
Deferred revenue, current portion	0	5,000
Collaboration research advancement, current portion	8,960	22,185
Total current liabilities	79,897	98,388
Deferred revenue, net of current portion	40,762	25,762
Collaboration research advancement, net of current portion	0	1,135
Operating lease liability, net of current portion	262,490	272,446
Other non-current liabilities	2,415	2,122
Total liabilities	385,564	399,853
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized, 0 shares issued and outstanding at September 30, 2022 and December 31, 2021	0	0
Common stock, $0.0001 par value; 200,000 shares authorized, 37,912 and 23,585 shares issued and outstanding at September 30, 2022 and December 31, 2021, respectively	4	2
Additional paid-in capital	597,566	400,026
Accumulated other comprehensive loss	(3,886)	(712)
Accumulated deficit	(270,504)	(39,494)
Total stockholders’ equity	323,180	359,822
Total liabilities and stockholders’ equity	$ 708,744	$ 759,675

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par value per share (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	37,912,000	23,585,000
Common stock, shares outstanding (in shares)	37,912,000	23,585,000

Condensed Consolidated and Comb

Condensed Consolidated and Combined Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenue:
Collaborative arrangement revenue	$ 7,903	$ 12,337	$ 18,425	$ 15,527
Total revenues	13,408	19,257	35,319	38,488
Operating expenses:
Research and development	61,739	61,131	199,423	202,394
Selling, general and administrative	19,610	22,996	60,749	69,025
Share of collaboration loss	0	0	9,642	10,071
Cost of royalty and other revenue	377	320	1,252	2,111
Change in fair value of contingent consideration	50	48	181	464
Total operating expenses	81,776	84,495	271,247	284,065
Loss from operations	(68,368)	(65,238)	(235,928)	(245,577)
Interest income, net	1,113	0	1,441	0
Other (loss) income, net	(624)	5,237	3,494	14,340
Loss before income taxes	(67,879)	(60,001)	(230,993)	(231,237)
Income tax (expense) benefit	0	0	(17)	0
Net loss	$ (67,879)	$ (60,001)	$ (231,010)	$ (231,237)
Net loss per share - basic (in dollars per share)	$ (1.76)	$ (2.57)	$ (6.67)	$ (9.90)
Net loss per share - diluted (in dollars per share)	$ (1.76)	$ (2.57)	$ (6.67)	$ (9.90)
Weighted-average number of common shares used in computing net loss per share - basic (in shares)	38,573,000	23,369,000	34,612,000	23,369,000
Weighted-average number of common shares used in computing net loss per share - diluted (in shares)	38,573,000	23,369,000	34,612,000	23,369,000
Other comprehensive loss:
Other comprehensive loss, net of tax benefit (expense) of $0.0 million and $0.0 million for the three and nine months ended September 30, 2022 and 2021, respectively.	$ (504)	$ 0	$ (3,174)	$ 0
Comprehensive loss	(68,383)	(60,001)	(234,184)	(231,237)
Service revenue
Revenue:
Revenue	4,642	6,312	14,363	17,544
Royalty and other revenue
Revenue:
Revenue	$ 863	$ 608	$ 2,531	$ 5,417

Condensed Consolidated and Co_2

Condensed Consolidated and Combined Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Tax benefit (expense)	$ 0	$ 0	$ 0	$ 0

Condensed Consolidated and Co_3

Condensed Consolidated and Combined Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Net parent investment	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2020		0
Beginning balance at Dec. 31, 2020	$ 74,629	$ 0	$ 74,629	$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	17,109		17,109
Transfers from bluebird bio, net	71,101		71,101
Net loss	(87,196)		(87,196)
Ending balance (in shares) at Mar. 31, 2021		0
Ending balance at Mar. 31, 2021	75,643	$ 0	75,643	0	0	0
Beginning balance (in shares) at Dec. 31, 2020		0
Beginning balance at Dec. 31, 2020	74,629	$ 0	74,629	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(231,237)
Ending balance (in shares) at Sep. 30, 2021		0
Ending balance at Sep. 30, 2021	(58,407)	$ 0	(58,407)	0	0	0
Beginning balance (in shares) at Mar. 31, 2021		0
Beginning balance at Mar. 31, 2021	75,643	$ 0	75,643	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	11,967		11,967
Transfers from bluebird bio, net	45,119		45,119
Net loss	(84,040)		(84,040)
Ending balance (in shares) at Jun. 30, 2021		0
Ending balance at Jun. 30, 2021	48,689	$ 0	48,689	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	11,230		11,230
Transfers from bluebird bio, net	(58,325)		(58,325)
Net loss	(60,001)		(60,001)
Ending balance (in shares) at Sep. 30, 2021		0
Ending balance at Sep. 30, 2021	$ (58,407)	$ 0	(58,407)	0	0	0
Beginning balance (in shares) at Dec. 31, 2021	23,585,000	23,585,000
Beginning balance at Dec. 31, 2021	$ 359,822	$ 2	0	400,026	(712)	(39,494)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		97,000
Exercise of stock options	1			1
Issuance of common stock in private placement, net of issuance costs (in shares)		13,934,000
Issuance of common stock in private placement, net of issuance costs	165,657	$ 2		165,655
Stock-based compensation	9,739			9,739
Other comprehensive loss	(2,092)				(2,092)
Net loss	(85,711)					(85,711)
Ending balance (in shares) at Mar. 31, 2022		37,616,000
Ending balance at Mar. 31, 2022	$ 447,416	$ 4	0	575,421	(2,804)	(125,205)
Beginning balance (in shares) at Dec. 31, 2021	23,585,000	23,585,000
Beginning balance at Dec. 31, 2021	$ 359,822	$ 2	0	400,026	(712)	(39,494)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (231,010)
Ending balance (in shares) at Sep. 30, 2022	37,912,000	37,912,000
Ending balance at Sep. 30, 2022	$ 323,180	$ 4	0	597,566	(3,886)	(270,504)
Beginning balance (in shares) at Mar. 31, 2022		37,616,000
Beginning balance at Mar. 31, 2022	447,416	$ 4	0	575,421	(2,804)	(125,205)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		18,000
Exercise of stock options	1			1
Additional issuance costs related to issuance of common stock in private placement	(124)			(124)
Stock-based compensation	9,689			9,689
Other comprehensive loss	(578)				(578)
Net loss	(77,420)					(77,420)
Ending balance (in shares) at Jun. 30, 2022		37,634,000
Ending balance at Jun. 30, 2022	378,984	$ 4	0	584,987	(3,382)	(202,625)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		245,000
Stock-based compensation	12,207			12,207
Purchase of common stock under ESPP (in shares)		33,000
Purchase of common stock under ESPP	372			372
Other comprehensive loss	(504)				(504)
Net loss	$ (67,879)					(67,879)
Ending balance (in shares) at Sep. 30, 2022	37,912,000	37,912,000
Ending balance at Sep. 30, 2022	$ 323,180	$ 4	$ 0	$ 597,566	$ (3,886)	$ (270,504)

Condensed Consolidated and Co_4

Condensed Consolidated and Combined Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net loss	$ (231,010)	$ (231,237)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of contingent consideration	181	464
Depreciation and amortization	9,208	12,815
Stock-based compensation expense	31,635	40,306
Other non-cash items	1,074	247
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(354)	3,036
Operating lease right-of-use assets	22,076	11,146
Accounts payable	422	607
Accrued expenses and other liabilities	(1,598)	32,066
Operating lease liabilities	(8,927)	(13,305)
Deferred revenue	10,000	(820)
Collaboration research advancement	(14,361)	(4,920)
Net cash used in operating activities	(181,654)	(149,595)
Cash flows from investing activities:
Purchases of property, plant and equipment	(19,676)	(10,600)
Purchases of marketable securities	(115,692)	0
Proceeds from maturities of marketable securities	147,597	0
Purchase of intangible assets	0	(8,000)
Net cash provided by (used in) investing activities	12,229	(18,600)
Cash flows from financing activities:
Transfers from bluebird bio	0	168,195
Proceeds from issuance of common stock in private placement, net of issuance costs	165,531	0
Proceeds from exercise of stock options and ESPP contributions	466	0
Net cash provided by financing activities	165,997	168,195
Decrease in cash, cash equivalents and restricted cash	(3,428)	0
Cash, cash equivalents and restricted cash at beginning of period	163,266	0
Cash, cash equivalents and restricted cash at end of period	159,838	0
Reconciliation of cash, cash equivalents, and restricted cash
Cash and cash equivalents	127,021	0
Restricted cash included in restricted cash and other non-current assets	32,817	0
Total cash, cash equivalents, and restricted cash	159,838	0
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	2,828	321
Non-cash return of bRT related assets to bluebird bio	$ 0	$ 110,300

Description of the business

Description of the business	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the business	Description of the business 2seventy bio, Inc. (the “Company” or “2seventy bio”) was incorporated in Delaware on April 26, 2021 and is a cell and gene therapy company focused on the research, development, and commercialization of transformative treatments for cancer. The Company’s approach combines its expertise in T cell engineering technology and lentiviral vector gene delivery approaches, experience in research, development, and manufacturing of cell therapies and a suite of technologies that can be selectively deployed to develop highly innovative, targeted cellular therapies for patients with cancer. The Company is advancing multiple preclinical and clinical programs in oncology and, together with Bristol-Myers Squibb (“BMS”), delivering the first U.S. Food and Drug Administration (“FDA”)-approved CAR T therapy in multiple myeloma, ABECMA (idecabtagene vicleucel, or ide-cel), to patients in the United States. Please refer to Note 9, Collaborative arrangements and strategic partnerships for further discussion of the collaboration with BMS . 2seventy bio Securities Corporation is a wholly-owned subsidiary of the Company which was incorporated in Massachusetts on December 13, 2021 and was granted securities corporation status in Massachusetts for the 2021 tax year. 2seventy bio Securities Corporation has no employees. The separation from bluebird bio, Inc. In January 2021, bluebird bio, Inc. (“bluebird bio”) announced its plans to separate its oncology portfolio and programs from its severe genetic disease portfolio and programs, and spin off its oncology portfolio and programs into a separate, publicly traded company. In furtherance of this plan, on September 30, 2021, bluebird bio’s board of directors approved the distribution of all of the issued and outstanding shares of 2seventy bio common stock on the basis of one share of 2seventy bio common stock for every three shares of bluebird bio common stock issued and outstanding on October 19, 2021, the record date for the distribution. As a result of the distribution, which occurred on November 4, 2021, 2seventy bio became an independent, publicly traded company. On November 3, 2021, the Company also entered into a separation agreement with bluebird bio, which is referred to in this quarterly report as the “Separation Agreement”, as well as various other agreements with bluebird bio, including a tax matters agreement, an employee matters agreement, an intellectual property license agreement, a transition services agreement under which 2seventy bio temporarily receives certain services from bluebird bio, and a second transition services agreement under which 2seventy bio temporarily provides certain services to bluebird bio. These agreements also govern certain of 2seventy bio’s relationships with bluebird bio after the separation. For additional information regarding the Separation Agreement and the other related agreements, refer to Note 13, Related-party transactions and the section captioned “Part III. Item 13. Certain Relationships and Related Transactions, and Director Independence,” included in our Annual Report on Form 10-K, which was filed with the SEC on March 22, 2022. Going concern In accordance with Accounting Standards Codification 205-40, Going Concern , the Company evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the date that the condensed consolidated and combined financial statements are issued. The Company has incurred losses and has experienced negative operating cash flows for all historical periods presented. During the nine months ended September 30, 2022, the Company incurred a net loss of $231.0 million and used $181.7 million of cash in operations. The Company expects to continue to generate operating losses and negative operating cash flows for the next few years. The Company's continued operations are dependent on its ability to raise additional funding.

Summary of significant accounti

Summary of significant accounting policies and basis of presentation	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of significant accounting policies and basis of presentation	Summary of significant accounting policies and basis of presentation Significant accounting policies The significant accounting policies used in preparation of these condensed consolidated and combined financial statements are consistent with those discussed in Note 2 to the consolidated and combined financial statements for the year ended December 31, 2021 included in the Company’s 2021 Annual Report on Form 10-K. Basis of presentation The Company did not operate as a separate, stand-alone entity prior to its separation from bluebird bio. Accordingly, the Company’s consolidated and combined statements of operations and comprehensive loss, stockholders’ equity and cash flows for the three and nine months ended September 30, 2021, have been prepared on a carve out basis, derived from bluebird bio’s consolidated financial statements and accounting records. The accompanying condensed consolidated and combined financial statements reflect the historical results of the operations, financial position and cash flows of the Company 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 GAAP as included in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”). The historical results of operations and cash flows of 2seventy bio presented in these condensed consolidated and combined financial statements for periods prior to the separation may not be indicative of what they would have been had 2seventy bio operated as an independent, stand-alone entity for those periods. The historical results of operations, financial position and cash flows of 2seventy bio presented in these condensed consolidated and combined financial statements for periods subsequent to the separation are not necessarily indicative of 2seventy bio's future results of operations, financial position and cash flows. In the opinion of management, the unaudited interim condensed consolidated and combined financial statements reflect all normal recurring adjustments considered necessary for a fair presentation of the Company’s financial position and the results of its operations for the interim periods presented. 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: allocations of revenue, expenses, assets and liabilities from bluebird bio's historical consolidated financial statements to the Company for periods prior to the separation, 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, the measurement of right-of-use assets and lease liabilities, contingent consideration, stock-based compensation expense, accrued expenses, income taxes, 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. In addition, estimates and judgments are used in the Company’s accounting for its revenue-generating arrangements, in particular as it relates to determining the stand-alone selling price of performance obligations, evaluating whether an option to acquire additional goods and services represents a material right, estimating the total transaction price, including estimating variable consideration and the probability of achieving future potential development and regulatory milestones, assessing the period of performance over which revenue may be recognized, and accounting for modifications to revenue-generating arrangements.

Marketable securities

Marketable securities	9 Months Ended
	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Marketable securities	Marketable securities The following table summarizes the marketable securities held at September 30, 2022 and December 31, 2021 (in thousands): Amortized Unrealized gains Unrealized losses Fair Value September 30, 2022 U.S. government agency securities and $ 124,212 $ — $ (2,700) $ 121,512 Corporate bonds 6,397 — (75) 6,322 Commercial paper 69,786 — (124) 69,662 Total $ 200,395 $ — $ (2,899) $ 197,496 December 31, 2021 U.S. government agency securities and $ 128,899 $ — $ (507) $ 128,392 Corporate bonds 49,368 — (58) 49,310 Commercial paper 54,065 — — 54,065 Total $ 232,332 $ — $ (565) $ 231,767 No available-for-sale debt securities held as of September 30, 2022 or December 31, 2021 had remaining maturities greater than five years. Accrued interest receivable on the Company's available-for-sale debt securities totaled $0.2 million and $0.4 million as of September 30, 2022 and December 31, 2021, respectively. No accrued interest receivable was written off during the three and nine months ended September 30, 2022 or 2021. The Company determined that there was no material change in the credit risk of the above investments during the nine months ended September 30, 2022. As such, an allowance for credit losses was not recognized. As of September 30, 2022, the Company does not intend to sell such securities and it is not more likely than not that the Company will be required to sell the securities before recovery of their amortized cost bases.

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 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 September 30, 2022 and December 31, 2021 (in thousands): Total Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) September 30, 2022 Assets: Cash and cash equivalents $ 127,021 $ 99,349 $ 27,672 $ — Marketable securities: U.S. government agency securities and treasuries 121,512 — 121,512 — Corporate bonds 6,322 — 6,322 — Commercial paper 69,662 — 69,662 — Total assets $ 324,517 $ 99,349 $ 225,168 $ — Liabilities: Contingent consideration $ 2,129 $ — $ — $ 2,129 Total liabilities $ 2,129 $ — $ — $ 2,129 December 31, 2021 Assets: Cash and cash equivalents $ 130,414 $ 130,414 $ — $ — Marketable securities: U.S. government agency securities and treasuries 128,392 — 128,392 — Corporate bonds 49,310 — 49,310 — Commercial paper 54,065 — 54,065 — Total assets $ 362,181 $ 130,414 $ 231,767 $ — Liabilities: Contingent consideration $ 1,948 $ — $ — $ 1,948 Total liabilities $ 1,948 $ — $ — $ 1,948 Contingent consideration In connection with bluebird bio's prior acquisition of Precision Genome Engineering, Inc. (“Pregenen”), the Company may be required to pay future consideration that is contingent upon the achievement of certain commercial milestone events. Contingent consideration is measured at fair value and is based on significant unobservable inputs, which represents a Level 3 measurement within the fair value hierarchy. The valuation of contingent consideration uses assumptions the Company believes would be made by a market participant. The Company assesses these estimates on an on-going basis as additional data impacting the assumptions is obtained. Future changes in the fair value of contingent consideration related to updated assumptions and estimates are recognized within the condensed consolidated and combined statements of operations and comprehensive loss. In the absence of new information related to the probability of milestone achievement, changes in fair value will reflect changing discount rates and the passage of time. Contingent consideration is included in other non-current liabilities on the condensed consolidated balance sheets. The table below provides a roll-forward of fair value of the Company’s contingent consideration obligations that include Level 3 inputs (in thousands): For the nine months ended September 30, 2022 Beginning balance $ 1,948 Additions — Changes in fair value 181 Payments — Ending balance $ 2,129 Please refer to Note 8, Commitments and contingencies , for further information.

Property, plant and equipment,

Property, plant and equipment, net	9 Months Ended
	Sep. 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 September 30, 2022 As of December 31, 2021 Laboratory equipment $ 35,238 $ 31,710 Leasehold improvements 26,709 28,479 Construction-in-progress 18,688 3,462 Office equipment 6,080 6,080 Computer equipment and software 5,625 5,260 Total property, plant and equipment 92,340 74,991 Less accumulated depreciation and amortization (45,690) (40,078) Property, plant and equipment, net $ 46,650 $ 34,913 Cambridge, Massachusetts drug product manufacturing facility In February 2022, the Company began construction of a drug product manufacturing facility within its Cambridge, Massachusetts headquarters. The facility will enable rapid translational research in clinical trials and the manufacture of drug product for use in Phase 1 clinical development activities. Construction-in-progress as of September 30, 2022 includes $16.8 million related to the ongoing build-out of the facility.

Accrued expenses and other curr

Accrued expenses and other current liabilities	9 Months Ended
	Sep. 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 September 30, 2022 As of December 31, 2021 Manufacturing costs $ 15,516 $ 5,459 Collaboration research costs 9,889 2,576 Employee compensation 9,657 24,655 Royalties 7,828 6,768 Clinical and contract research organization costs 2,285 3,229 Property, plant and equipment 683 2,241 Separation related costs 405 762 Professional fees 349 1,688 Other 5,544 8,032 Accrued expenses and other current liabilities $ 52,156 $ 55,410

Leases

Leases	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Leases	Leases The Company leases certain office and laboratory space, primarily located in Cambridge, Massachusetts and Seattle, Washington, that was assigned to it in connection with the separation. There have been no material changes to the lease obligations from those disclosed in Note 7, Leases , to the consolidated and combined financial statements included in the Company's 2021 Annual Report on Form 10-K.

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Contingent consideration related to business combinations On June 30, 2014, bluebird bio acquired Pregenen. All assets, liabilities and future obligations related to the Pregenen acquisition, including the resulting goodwill and contingent consideration, were assumed by the Company in connection with the separation. As of September 30, 2022, the Company may be required to make up to $99.9 million in contingent cash payments to the former equity holders of Pregenen upon the achievement of certain commercial milestones related to the Pregenen technology. In accordance with accounting guidance for business combinations, contingent consideration liabilities are required to be recognized on the condensed consolidated balance sheets at fair value. Estimating the fair value of contingent consideration requires the use of significant assumptions primarily relating to probabilities of successful achievement of certain clinical and commercial milestones, the expected timing in which these milestones will be achieved and discount rates. The use of different assumptions could result in materially different estimates of fair value. Please refer to Note 4, Fair value measurements, for further information. Other funding commitments Certain agreements that were assigned by bluebird bio to the Company in connection with the separation relate principally to licensed technology and may require future payments relating to milestones that may be met in subsequent periods or royalties on future sales of specified products. Additionally, to the extent an agreement relating to licensed technology was not assigned to the Company, bluebird bio entered into a sublicense with the Company, which may require the Company to make future milestone and/or royalty payments. Please refer to Note 9, Collaborative arrangements and strategic partnerships , for further information on the BMS, Regeneron Pharmaceuticals, Inc. (“Regeneron”), and Novo Nordisk A/S (“Novo”) agreements and to Note 10, Royalty and other revenue , for further information on license agreements. Based on the Company's development plans as of September 30, 2022, the Company may be obligated to make future development, regulatory and commercial milestone payments and royalty payments on future sales of specified products. Payments under these agreements generally become due and payable upon achievement of such milestones or sales. When the achievement of these milestones or sales has not occurred, such contingencies are not recorded in the Company’s financial statements. As further discussed in Note 9, Collaborative arrangements and strategic partnerships , BMS assumed responsibility for amounts due to licensors as a result of any future ex-U.S. sales of ABECMA. In July 2021, bluebird bio and National Resilience, Inc. (“Resilience”) announced a strategic manufacturing collaboration aimed to accelerate the early research, development, and delivery of cell therapies. Agreements related to the collaboration were executed in September 2021. As part of the agreement, Resilience acquired bluebird bio's North Carolina manufacturing facility and retained all staff employed at the site. Concurrent with the sale of the manufacturing facility in Durham, North Carolina, bluebird bio entered into certain ancillary agreements, including two manufacturing agreements and a license agreement (the “Resilience License Agreement”), among others (together referred to as the “Ancillary Agreements”). One manufacturing agreement will support the future manufacturing of lentiviral vector for the commercial product marketed in collaboration with BMS, ABECMA (the “Commercial Supply Agreement”), while the other will support ongoing manufacturing for lentiviral vector for development candidates (the “Development Manufacturing Supply Agreement”). Certain rights and obligations under these agreements were assigned by bluebird bio to 2seventy bio on November 4, 2021 upon the separation of 2seventy bio from bluebird bio. The assignments under the asset purchase agreement and the development manufacturing supply agreement commit the Company to reimburse Resilience for an amount equal to 50% of the net operating losses of and relating to the manufacturing facility’s business incurred during the twelve-month period ending on the first anniversary of the closing of the transaction, as calculated in accordance with the asset purchase agreement, subject to a cap of $15.0 million. In exchange, under the terms of the development manufacturing supply agreement, the Company was entitled to receive up to eight batches of lentiviral vector during the twelve-month period ending on the first anniversary of the closing of the transaction. The Company therefore committed to a minimum purchase of at least the Company's 50% share of the net operating losses during the twelve-month period ending on the first anniversary of the closing of the transaction, which occurred in September 2022. As of September 30, 2022, the Company has accrued $14.8 million representing our estimated share of the net operating losses of Resilience. The disposition of the net assets of the manufacturing facility previously assigned to 2seventy bio has been reflected as a transfer to bluebird bio via net parent investment as a result of bluebird bio’s sale of such facility. 2seventy bio is not a party to the sale of the manufacturing facility and, therefore, did not recognize any gain or loss arising from the transaction. Additionally, 2seventy bio 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. There have been no material changes in future minimum purchase commitments from those disclosed in Note 8, Commitments and Contingencies , to the consolidated and combined financial statements included in the Company's 2021 Annual Report on Form 10-K. Litigation From time to time, the Company expects to be party to various claims and complaints arising in the ordinary course of business. However, the Company is not currently a party to any litigation or legal proceedings that, in the opinion of its management, are probable of having a material adverse effect on its business. The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these 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. In addition, pursuant to the Separation Agreement, the Company indemnifies, holds harmless, and agrees to reimburse bluebird bio for its indemnification obligations with respect to the Company’s business partners, relating to the Company’s business or arising out of the Company’s activities, in the past or to be conducted in the future. 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 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 indemnifies each of its directors and officers 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 and indemnification agreements entered into with each of its directors and officers. The term of the indemnification period will last as long as a director or officer may be subject to any proceeding arising out of acts or omissions of such director or officer in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company holds director and officer liability insurance.

Collaborative arrangements and

Collaborative arrangements and strategic partnerships	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborative arrangements and strategic partnerships	Collaborative arrangements and strategic partnerships To date, the Company’s service and collaborative arrangement revenue has been primarily generated from collaboration arrangements with BMS, Regeneron, and Novo, each as further described below. These agreements were assumed by the Company in connection with the separation. Bristol-Myers Squibb BMS Collaboration Agreement In March 2013, bluebird bio entered into a collaboration agreement with BMS. The details of the collaboration agreements and the payments the Company has received, and is entitled to receive, are further described in Note 10, Collaborative arrangements and strategic partnerships , to the consolidated and combined financial statements included in the Company's 2021 Annual Report on Form 10-K. During 2022, there have been no changes to the terms of the collaboration agreement with BMS. ABECMA Under the collaboration agreement with BMS, the Company shares equally in the profit and loss related to the development and commercialization of ide-cel in the United States (marketed as ABECMA). The Company has no remaining financial rights with respect to the development or commercialization of ide-cel outside of the United States. The Company accounts for its collaborative arrangement efforts with BMS in the United States within the scope of ASC 808 given that both parties are active participants in the activities and both parties are exposed to significant risks and rewards dependent on the commercial success of the activities. The calculation of collaborative activity to be recognized for joint ABECMA efforts in the United States is performed on a quarterly basis and is independent of previous quarterly activity. This may result in fluctuations between revenue and expense recognition period over period, depending on the varying extent of effort performed by each party during the period. The Company recognizes revenue related to the combined unit of accounting for the ex-U.S. license and lentiviral vector manufacturing services under Topic 606. Ide-cel U.S. Share of Collaboration Profit or Loss The U.S. commercial and development activities under the Amended Ide-Cel CCPS are within the scope of ASC 808. On a quarterly basis, the Company determines its share of collaboration profit or loss for commercial activities (i.e., commercial sales of ABECMA by BMS). The Company’s share of any collaboration profit for commercial activities is recognized as collaborative arrangement revenue and its share of any collaboration loss for commercial activity is recognized as an operating expense and classified as share of collaboration loss on the Company's condensed consolidated and combined statement of operations and comprehensive loss. The Company recognized the following on the 2022 and 2021 condensed consolidated and combined statements of operations and comprehensive loss, respectively, related to its share of collaboration profit or loss associated with ide-cel commercial activities following approval (in thousands). The amounts reported for these periods represent the Company’s share of BMS’ ABECMA product revenue, cost of goods sold, and selling costs, along with reimbursement by BMS of commercial costs incurred by the Company, and exclude expenses related to ongoing development, which are separately reflected in the condensed consolidated and combined statements of operations and comprehensive loss as described below. Three months ended Nine months ended March 31, 2022 June 30, 2022 September 30, 2022 September 30, 2022 Collaborative arrangement revenue from ide-cel commercial activities (1) $ — $ — $ 4,064 $ 4,064 Share of collaboration loss from ide-cel commercial activities (1) $ (5,352) $ (4,290) $ — $ (9,642) _________________ (1) As noted above, the calculation is performed on a quarterly basis. The calculation is independent of previous activity, which may result in fluctuations between revenue and expense recognition period over period. Three months ended Nine months ended March 31, 2021 June 30, 2021 September 30, 2021 September 30, 2021 Collaborative arrangement revenue from ide-cel commercial activities (1) $ — $ — $ 10,607 $ 10,607 Share of collaboration loss from ide-cel commercial activities (1) $ — $ (10,071) $ — $ (10,071) _________________ (1) As noted above, the calculation is performed on a quarterly basis. The calculation is independent of previous activity, which may result in fluctuations between revenue and expense recognition period over period. The Company is also responsible for equally sharing in the ongoing ide-cel research and development activities being conducted by BMS in the United States as BMS continues conducting ongoing clinical studies to support the use of ABECMA in earlier lines of therapy. The net amount owed to BMS for research and development activities determined on a quarterly basis is classified as research and development expense on the condensed consolidated and combined statement of operations and comprehensive loss. If BMS is obligated to reimburse the Company because the Company’s research and development costs exceeds BMS’ research and development costs in a particular quarterly period, the net amount is recorded as collaborative arrangement revenue. The following table summarizes the amounts associated with the research activities under the collaboration included in research and development expense or recognized as collaborative arrangement revenue for the three and nine months ended September 30, 2022 and 2021 (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 Net expense (included as a component of research and development expense) $ (9,252) $ (5,660) $ (21,608) $ (31,678) Ide-cel ex-U.S. Service Revenue The Company accounts for any ex-U.S. activities under the Amended Ide-cel CCPS pursuant to ASC 606. The following table summarizes the revenue recognized related to ide-cel ex-U.S. activities for the three and nine months ended September 30, 2022 and 2021 (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 ASC 606 ide-cel license and manufacturing revenue - ex-U.S. (included as a component of service revenue) $ 3,122 $ 5,314 $ 9,437 $ 14,698 bb21217 In addition to the activities related to ide-cel, BMS previously exercised its option to obtain an exclusive worldwide license to develop and commercialize bb21217, the second product candidate under the collaboration arrangement with BMS which is further described in Note 10, Collaborative arrangements and strategic partnerships , to the consolidated and combined financial statements included in the Company's 2021 Annual Report on Form 10-K. Under the collaboration arrangement with BMS, the Company had an option to co-develop and co-promote bb21217 within the United States. However, following completion of the CRB-402 clinical trial, in January 2022 the Company, along with BMS, evaluated its plans with respect to bb21217. Based in part on the strength of ABECMA clinical data and commercial sales to date, the Company and BMS elected to discontinue development of bb21217 and, as such, the Company did not exercise its option to co-develop and co-promote bb21217 within the United States. The Company is still eligible to receive U.S. milestones and royalties for U.S. sales of bb21217, if further developed by BMS. Additionally, pursuant to the terms of the collaboration agreement, because it did not exercise its option to co-develop and co-promote bb21217, the Company received an additional fee in the amount of $10.0 million from BMS during the second quarter of 2022. Pursuant to the variable consideration allocation exception, the $10.0 million of consideration received was allocated to the combined performance obligation for the bb21217 license and vector manufacturing services through development, described further below. As the Company has not yet commenced manufacturing, the entire $10.0 million payment received is included within deferred revenue, net of current portion on the September 30, 2022 condensed consolidated balance sheet. The transaction price associated with the collaboration arrangement consists of $31.0 million of upfront payments and option payments received from BMS, the $10.0 million bb21217 opt-out payment discussed above, and $1.8 million in variable consideration which represents reimbursement to be received from BMS for manufacturing vector and associated payloads through development which has not yet been received. The Company identified two performance obligations with respect to the arrangement with BMS. The initial performance obligation was for research and development services that were substantially completed in September 2019, associated with the initial phase 1 clinical trial of bb21217. The Company allocated $5.4 million of consideration to the research and development services performance obligation and fully recognized the consideration through September 2019. The other performance obligation relates to a combined performance obligation for the bb21217 license and vector manufacturing services through development, and the remaining $37.4 million in consideration was allocated to this combined performance obligation. The Company will satisfy this combined performance obligation as the bb21217 manufacturing services are performed. All of the remaining development, regulatory, and commercial milestones related to U.S. development, regulatory and commercialization activities are fully constrained and are therefore excluded from the transaction price. As of September 30, 2022, the Company has not commenced manufacturing and the full amount of the allocated transaction price remains unsatisfied. The Company had $35.8 million and $25.8 million of deferred revenue as of September 30, 2022 and December 31, 2021, respectively, associated with the combined performance obligation consisting of the bb21217 license and manufacturing services. The Company expects to recognize the remaining $35.8 million as these services are performed or upon BMS’s formal notification to the Company that these services will no longer be required. Contract assets and liabilities – ide-cel and bb21217 The Company receives payments from its collaborative partners based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until such time as the Company satisfies its performance obligations under these arrangements. A contract asset is a conditional right to consideration in exchange for goods or services that the Company has transferred to a customer. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The following table presents changes in the balances of the Company’s BMS receivables and contract liabilities during the nine months ended September 30, 2022 (in thousands): Balance at December 31, 2021 Additions Deductions Balance at September 30, 2022 Receivables $ 652 $ 10,000 $ (10,652) $ — Contract liabilities: Deferred revenue $ 25,762 $ 10,000 $ — $ 35,762 The decrease in the receivables balance for the nine months ended September 30, 2022 is driven by amounts paid to the Company from BMS in the period under the settlement terms of the collaboration agreement. The increase in the deferred revenue balance for the nine months ended September 30, 2022 is driven by the $10.0 million payment made to the Company by BMS upon the Company opting out of co-development and co-promotion of bb21217 in the United States. Regeneron Regeneron Collaboration Agreement In August 2018, bluebird bio entered into a Collaboration Agreement (the “Regeneron Collaboration Agreement”) with Regeneron pursuant to which the parties will apply their respective technology platforms to the discovery, development, and commercialization of novel immune cell therapies for cancer. In August 2018, following the completion of required regulatory reviews, the Regeneron Collaboration Agreement became effective. As noted above, the agreement was assumed by the Company in connection with the separation. Under the terms of the agreement, the parties will leverage Regeneron’s proprietary platform technologies for the discovery and characterization of fully human antibodies, as well as T cell receptors directed against tumor-specific proteins and peptides and the Company will contribute its field-leading expertise in gene therapy. In accordance with the Regeneron Collaboration Agreement, the parties jointly selected six initial targets and intend to equally share the costs of research up to the point of submitting an IND application for a potential gene therapy product directed to a particular target. Additional targets may be selected to add to or replace any of the initial targets during the five-year research collaboration term as agreed to by the parties. Regeneron will accrue a certain number of option rights exercisable against targets as the parties reach certain milestones under the terms of the agreement. Upon the acceptance of an IND for the first product candidate directed to a target, Regeneron will have the right to exercise an option for co-development/co-commercialization of product candidates directed to such target on a worldwide or applicable opt-in territory basis, with certain exceptions. Where Regeneron chooses to opt-in, the parties will share equally in the costs of development and commercialization and will share equally in any profits or losses therefrom in applicable opt-in territories. Outside of the applicable opt-in territories, the target becomes a licensed target and Regeneron would be eligible to receive, with respect to any resulting product, milestone payments of up to $130.0 million per product and royalties on net sales outside of the applicable opt-in territories at a rate ranging from the mid-single digits to low-double digits. A target would also become a licensed target in the event Regeneron does not have an option to such target, or Regeneron does not exercise its option with respect to such target. Either party may terminate a given research program directed to a particular target for convenience, and the other party may elect to continue such research program at its expense, receiving applicable cross-licenses. The terminating party will receive licensed product royalties and milestone payments on the potential applicable gene therapy products. Where the Company terminates a given research program for convenience, and Regeneron elects to continue such research program, the parties will enter into a transitional services agreement. Under certain conditions, following its opt-in, Regeneron may terminate a given collaboration program and the Company may elect to continue the development and commercialization of the applicable potential gene therapy products as licensed products. Regeneron Share Purchase Agreement A Share Purchase Agreement (“SPA”) was entered into by bluebird bio and Regeneron in August 2018. In August 2018, on the closing date of the transaction, bluebird bio issued Regeneron 0.4 million shares of bluebird bio’s common stock, subject to certain restrictions, for $238.10 per share, or $100.0 million in the aggregate. The purchase price represents $63.0 million worth of common stock plus a $37.0 million premium, which represents a collaboration research advancement, or credit to be applied to Regeneron’s initial 50 percent funding obligation for collaboration research, after which the collaborators will continue to fund ongoing research equally. The collaboration research advancement only applies to pre-IND research activities and is not refundable or creditable against post-IND research activities for any programs where Regeneron exercises its opt-in rights. Accounting analysis – Regeneron At the commencement of the arrangement, two units of accounting were identified, which are the issuance of 0.4 million shares of bluebird bio’s common stock and joint research activities during the five-year research collaboration term. The Company determined the total transaction price to be $100.0 million, which comprises $54.5 million attributed to the bluebird bio equity sold to Regeneron and $45.5 million attributed to the joint research activities. In determining the fair value of the bluebird bio common stock at closing, the Company considered the closing price of the bluebird bio common stock on the closing date of the transaction and included a lack of marketability discount because Regeneron received shares subject to certain restrictions. The Company analyzed the joint research activities to assess whether they fall within the scope of ASC 808, and will reassess this throughout the life of the arrangement based on changes in the roles and responsibilities of the parties. Based on the terms of the arrangement as outlined above, for the collaboration research performed prior to submission of an IND application for a potential gene therapy product, both parties are deemed to be active participants in the collaboration. Both parties are performing research and development activities and will share equally in these costs through IND submission. Additionally, Regeneron and the Company are exposed to significant risks and rewards dependent on the commercial success of any product candidates that may result from the collaboration. As such, the collaboration arrangement is deemed to be within the scope of ASC 808. The $45.5 million attributed to the joint research activities includes the $37.0 million creditable against amounts owed to the Company by Regeneron. The collaboration research advancement will be reduced over time for amounts due to the Company by Regeneron as a result of the parties agreeing to share in the costs of collaboration research equally. The remainder of the amount attributed to the joint research activities will be recognized over the five-year research collaboration term. Consistent with its collaboration accounting policy, the Company will recognize collaboration revenue or research and development expense related to the joint research activities in future periods depending on the amounts incurred by each party in a given reporting period. That is, if the Company’s research costs incurred exceed those research costs incurred by Regeneron in a given quarter, the Company will record collaboration revenue and reduce the original $37.0 million advance by the amount due from Regeneron until such advancement is fully utilized, after which the Company would record an amount due from Regeneron. If Regeneron’s research costs incurred exceed those research costs incurred by the Company in a given quarter, the Company will record research and development expense and record a liability for the amount due to Regeneron. As of September 30, 2022 and December 31, 2021, the Company has $9.0 million and $23.3 million, respectively, of the amount attributed to the joint research activities remaining to be recognized, which is classified as collaboration research advancement, current portion and collaboration research advancement, net of current portion on the condensed consolidated balance sheets. The Company recognized $3.8 million and $14.4 million of collaborative arrangement revenue from the Regeneron Collaboration Agreement during the three and nine months ended September 30, 2022, respectively. The Company recognized $1.7 million and $4.9 million of collaborative arrangement revenue from the Regeneron Collaboration Agreement during the three and nine months ended September 30, 2021, respectively. Novo Nordisk Novo Collaboration and License Agreement On December 23, 2021, the Company entered into a Collaboration and License Agreement (the “Novo Collaboration Agreement”) with Novo for the discovery, development, and commercialization of a potential new gene therapy in hemophilia A. The Company and Novo have agreed to develop an initial research program with the goal of researching and developing a lead candidate directed to hemophilia A. The Company will provide Novo with research licenses to support the companies’ activities during the initial research program and an option to enable Novo to obtain an exclusive license to commercialize the product derived from or containing compounds developed during the initial research program. Under the terms of the Novo Collaboration Agreement, Novo agreed to pay the Company: • a non-refundable, non-creditable upfront payment of $5.0 million; • $15.0 million upon achievement of certain scientific milestones during the initial research program, or $9.0 million should Novo decide to continue the initial research program without achieving the scientific milestones; • up to $26.0 million of exclusive license fees for the development, manufacture, and commercialization of the product should Novo exercise its option; and, • up to $72.0 million in development and commercialization milestones. Novo also agreed to reimburse the Company for research costs incurred in connection with the research program up to a mutually agreed upon amount, based on an updated budget of $13.2 million. If Novo exercises its option to obtain a license to commercialize the product developed during the initial research program, the Company is also eligible to receive mid-single digit royalties on product sales on a country-by-country and product-by-product basis, subject to certain royalty step-down provisions set forth in the agreement. Accounting Analysis - Novo The Company concluded that Novo is a customer, and as such, the arrangement falls within the scope of Topic 606. The Company identified two performance obligations consisting of (i) the research license and research and development services to be provided during the initial research program and (ii) a material right related to Novo’s option to obtain an exclusive license for the development, manufacture, and commercialization of the product developed during the initial research program. The Company determined that the research license and research and development services promises were not separately identifiable and were not distinct or distinct within the context of the contract due to the specialized nature of the services to be provided by 2seventy, specifically with respect to the Company’s expertise related to gene therapy and the interdependent relationship between the promises. The material right is considered a separate performance obligation pursuant to the provisions of Topic 606.

Royalty and other revenue

Royalty and other revenue	9 Months Ended
	Sep. 30, 2022
License And Royalty Revenue [Abstract]
Royalty and other revenue	Royalty and other revenue bluebird bio has out-licensed intellectual property to various third parties. Under the terms of these agreements, some of which were assumed by the Company in connection with the separation, bluebird bio and the Company may be entitled to royalties and milestone payments. The Company recognized $0.9 million and $2.5 million of royalty and other revenue in the three and nine months ended September 30, 2022, respectively. The Company recognized $0.6 million and $5.4 million of royalty and other revenue in the three and nine months ended September 30, 2021, respectively. Novartis Pharma AG In April 2017, bluebird bio entered into a worldwide license agreement with Novartis. Under the terms of the agreement, Novartis non-exclusively licensed certain patent rights related to lentiviral vector technology to develop and commercialize CAR T cell therapies for oncology, including Kymriah (formerly known as CTL19), Novartis’s anti-CD19 CAR T therapy. The agreement was assumed by the Company in connection with the separation. Beginning in the fourth quarter of 2017, bluebird bio began receiving royalties from sales of tisagenlecleucel under the agreement. This license agreement was terminated effective March 2021, at which point in time Novartis was no longer required to make royalty or other payments on net sales of tisagenlecleucel or any future products. Royalty revenue recognized from sales of tisagenlecleucel is included within royalty and other revenue in the condensed consolidated and combined statement of operations and comprehensive loss. Juno Therapeutics In May 2020, bluebird bio entered into a non-exclusive license agreement with Juno Therapeutics, Inc. (“Juno”), a wholly-owned subsidiary of BMS, related to lentiviral vector technology to develop and commercialize CD-19-directed CAR T cell therapies. The agreement was assumed by the Company in connection with the separation. Upon regulatory approval of lisocabtagene maraleucel during the first quarter of 2021, bluebird bio received a $2.5 million milestone payment from Juno, which is included within royalty and other revenue in the Company’s condensed consolidated and combined financial statements. Royalty revenue recognized from sales of lisocabtagene maraleucel is also included within royalty and other revenue in the condensed consolidated and combined statement of operations and comprehensive loss. Resilience The Resilience License Agreement, entered into concurrently with the sale of bluebird bio’s North Carolina manufacturing facility, grants Resilience a worldwide, co-exclusive license to intellectual property controlled by the Company to perform Resilience’s obligations and exercise Resilience’s rights under the supply agreements, and a worldwide, nonexclusive right to offer certain manufacturing services to third-party customers under certain of the Company's intellectual property. Under the terms of the Resilience License Agreement, the Company may receive a high single-digit to low double-digit percentage tiered royalty based on Resilience’s gross margins for transactions entered into with parties other than the Company in which the Company's proprietary intellectual property is utilized as part of such transaction. Future royalty payments under the Resilience License Agreement are considered part of the consideration associated with the disposition of the manufacturing facility. In accordance with ASC 450, the Company will recognize future royalties received under the Resilience License Agreement in the period the contingencies are resolved as an adjustment to the consideration received as other (loss) income, net in the condensed consolidated and combined statements of operations and comprehensive loss. As of September 30, 2022, the Company has not recognized any royalties from Resilience under the Resilience License Agreement.

Equity

Equity	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Equity	EquityIn March 2022, the Company entered into stock purchase agreements with certain investors, pursuant to which the Company agreed to sell and issue, in a private placement, an aggregate of 13,934,427 shares of the Company’s common stock at a purchase price per share of $12.20. This resulted in aggregate net proceeds to the Company of $165.5 million, after deducting placement agent fees and other offering expenses payable by the Company.

Stock-based compensation

Stock-based compensation	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Stock-based compensation	Stock-based compensation In connection with 2seventy’s separation from bluebird bio on November 4, 2021, under the provisions of the existing plans, the outstanding bluebird bio equity awards were adjusted in accordance with the terms of the employee matters agreement (equitable adjustment) to preserve the intrinsic value of the awards immediately before and after distribution. Refer to Note 13, Stock-based compensation , to the consolidated and combined financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2021 for details on the conversion methodology of the equity awards. In October 2021, the Company’s board of directors adopted the 2021 Stock Option and Incentive Plan (“2021 Plan”) which allows for the granting of incentive stock options, non-qualified stock options, restricted stock units (“RSUs”), performance-based restricted stock units (“PRSUs”), and restricted stock awards to 2seventy bio’s employees, members of the board of directors, and consultants of 2seventy bio, including those who became employees of the Company in connection with the separation. Shares of the Company’s common stock underlie all awards granted under the 2021 Plan. Stock-based compensation expense For periods prior to the separation, stock-based compensation expense was allocated to the Company using a combination of specific identification and time spent on projects at various levels of the organization, which management believes are consistent and reasonable. Post separation, stock-based compensation expense includes compensation cost related to 2seventy equity awards held by its employees as well as bluebird bio equity awards issued upon separation to its employees. Stock-based compensation expense recognized by award type was as follows (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 Stock options $ 4,519 $ 5,090 $ 13,577 $ 19,140 Restricted stock units 7,615 4,659 17,901 15,578 Employee stock purchase plan and other 73 1,481 157 5,588 $ 12,207 $ 11,230 $ 31,635 $ 40,306 Stock-based compensation expense by classification included within the condensed consolidated and combined statements of operations and comprehensive loss was as follows (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 Research and development $ 5,314 $ 5,523 $ 14,263 $ 22,429 Selling, general and administrative 6,893 5,707 17,372 17,877 $ 12,207 $ 11,230 $ 31,635 $ 40,306 Employee Stock Purchase Plan During the three and nine months ended September 30, 2022, less than 0.1 million shares of common stock were issued under the Company’s 2021 Employee Stock Purchase Plan.

Related-party transactions

Related-party transactions	9 Months Ended
	Sep. 30, 2022
Related Party Transactions [Abstract]
Related-party transactions	Related-party transactions Relationship with bluebird bio Following the separation, bluebird bio is considered a related party. In connection with the separation, the Company entered into the Separation Agreement with bluebird bio, dated as of November 3, 2021, that, among other things, set forth bluebird bio’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 identifies assets transferred to, liabilities assumed by and contracts assigned to 2seventy bio as part of the separation, and it provides for when and how these transfers, assumptions and assignments occur. The purpose of the Separation Agreement is to provide 2seventy bio and bluebird bio with assets to operate their respective businesses and retain or assume liabilities related to those assets. Each of 2seventy bio and bluebird bio agreed to releases, with respect to pre-separation claims, and cross indemnities with respect to post-separation claims, that are 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 bio under the Separation Agreement. bluebird bio and 2seventy bio are also each subject to mutual 12-month employee non-solicit and non-hire restrictions, subject to certain customary exceptions. In accordance with the Separation Agreement with bluebird bio, there were certain other transactions and adjustments post-Separation between the Company and bluebird bio. For the three and nine months ended September 30, 2022, the Company recorded an expense of $0.3 million and income of $2.8 million related to the Separation Agreement, respectively. The Company and bluebird bio also entered into a tax matters agreement, dated as of November 3, 2021, governing bluebird bio’s and 2seventy bio's respective rights, responsibilities and obligations with respect to taxes (including taxes arising in the ordinary course of business and taxes, if any, incurred as a result of any failure of the distribution and certain related transactions to qualify as tax-free for U.S. federal income tax purposes, tax attributes, the preparation and filing of tax returns, the control of audits and other tax proceedings, and assistance and cooperation in respect of tax matters). In connection with the separation, the Company also entered into an employee matters agreement with bluebird bio, dated as of November 3, 2021. The employee matters agreement allocates assets, liabilities and responsibilities relating to the employment, compensation and employee benefits of bluebird bio and 2seventy bio employees, and other related matters, in connection with the separation, including the treatment of outstanding bluebird bio incentive equity awards and certain retirement and welfare benefit obligations. The employee matters agreement generally provides that, unless otherwise specified, 2seventy bio is responsible for liabilities associated with employees who transfer to 2seventy bio and employees whose employment terminated prior to the distribution but who primarily supported the 2seventy bio business, and bluebird bio is responsible for liabilities associated with other employees, including employees retained by bluebird bio. Included in the agreement are also specific clauses relating to liabilities assumed by bluebird bio for the costs incurred prior to the separation. For the three and nine months ended September 30, 2022, the Company recorded a net charge to operating expense of $0.0 million and $0.2 million for costs stipulated by the employee matters agreement, respectively. The Company and bluebird bio also entered into an intellectual property license agreement on November 3, 2021, pursuant to which each party granted a license to certain intellectual property and technology to the other. bluebird bio granted 2seventy bio a perpetual, worldwide, non-exclusive, royalty-free, fully paid-up license (or, as the case may be, sublicense) to certain intellectual property to allow 2seventy bio to use such intellectual property in connection with 2seventy bio's ongoing and future research and development activities and product candidates. 2seventy bio granted bluebird bio a perpetual, worldwide, non-exclusive, royalty-free, fully paid-up license (or, as the case may be, sublicense) to certain intellectual property for use in bluebird bio’s existing products and product candidates. Such licenses between the parties generally allow current or future uses of the intellectual property in connection with each party's respective fields. Charges associated to the intellectual property license agreement commenced in 2022. As part of this agreement, the Company directly contacts and coordinates with bluebird bio’s third party licensors to make direct payments to the third parties. The Company and bluebird bio entered into two transition services agreements on November 3, 2021, pursuant to which bluebird bio will provide 2seventy bio with corporate and shared services and resources related to corporate functions such as finance, human resources, internal audit, research and development, financial reporting, and information technology, and to which 2seventy bio will provide certain services to bluebird bio, each for an initial term of two years, unless earlier terminated or extended according to the terms of the transition services agreement. For the three and nine months ended September 30, 2022, the Company recorded $1.9 million and $8.1 million, respectively, in other (loss) income, net reflecting services provided to bluebird bio and $0.1 million and $1.0 million, respectively, of operating expenses reflecting services received from bluebird bio, for activities related to the transition services agreement. Additionally, under the transition services agreements, 2seventy bio was subleasing 30% of its headquarters at 60 Binney Street in Cambridge, Massachusetts to bluebird bio through the first quarter of 2022. Beginning in the second quarter of 2022, this percentage decreased to 23% for the remainder of the year. The Company recorded $1.2 million and $3.6 million in other (loss) income, net related to sublease income from bluebird under this arrangement during the three and nine months ended September 30, 2022, respectively. As of September 30, 2022, amounts due to bluebird bio under the above agreements were $0.4 million and are included in accrued expenses. As of September 30, 2022, amounts due from bluebird bio under the above agreements were $1.9 million and are included in receivables and other current assets. Corporate allocations Prior to the separation, the Company did not operate as a separate, stand-alone entity, but rather was managed and operated in the normal course of business under bluebird bio. Accordingly, certain shared costs have been allocated to the Company and reflected as expenses in the Company's stand-alone condensed consolidated and combined financial statements for periods prior to the separation as described. The expenses reflected in the consolidated and combined financial statements may not be indicative of expenses that will be incurred by the Company in the future. For periods prior to the separation, the condensed consolidated and combined financial statements reflect allocations of certain expenses from bluebird bio, including, but not limited to, general corporate expenses, such as senior management, legal, human resources, accounting, other financial services (such as treasury, audit and purchasing), tax, information technology, and corporate employee benefits, incentives and stock-based compensation included within selling, general and administrative expense. These expenses have been allocated to the Company based on direct usage or benefit where specifically identifiable, with the remainder allocated based on employee time spent on projects, square footage or other measures that management believes are consistent and reasonable. Allocations for management costs and corporate support services provided to the Company totaled $14.5 million and $49.9 million for the three and nine months ended September 30, 2021. The financial information in these condensed consolidated and combined financial statements for periods prior to the separation does not necessarily include all the expenses that would have been incurred by the Company had it been a separate, stand-alone entity. Actual costs that may have been incurred if the Company had been a stand-alone company would depend on a number of factors, including the chosen organization structure and functions outsourced or performed by employees. See Note 2, Summary of significant accounting policies and basis of presentation , to the consolidated and combined financial statements included in the Company’s 2021 Annual Report on 10-K for additional information on the preparation and basis of presentation of these condensed consolidated and combined financial statements, including the treatment of certain research and development costs not directly attributable to individual programs. Usage of the Company's assets by bluebird bio and of bluebird bio's assets by the Company prior to separation Certain assets have been reflected in these condensed consolidated and combined financial statements as the underlying assets were assumed by the Company; however, bluebird bio has historically utilized a portion of the underlying asset as part of its operations. Accordingly, the expense related to the underlying asset has been reflected in the 2021 condensed consolidated and combined financial statements. The Company has also recorded an imputed charge to bluebird bio to reflect the cost of bluebird bio's proportional usage. In addition, the Company has recorded as an expense an imputed charge to reflect the cost of the Company's proportional usage of certain underlying assets not reflected in the condensed consolidated and combined financial statements but for which the Company has historically utilized a portion of the underlying asset as part of its operations. The income and expense recognized by the Company resulting from these imputed charges is recorded as other (loss) income, net in the 2021 condensed consolidated and combined financial statements and was as follows (in thousands): For the three months ended September 30, For the nine months ended September 30, 2021 2021 Imputed charge to bluebird bio for leases $ 4,519 $ 13,440 Imputed charge from bluebird bio for leases (209) (836) Imputed charge to bluebird bio for property, plant and equipment 507 1,714 Imputed charge from bluebird bio for property, plant and equipment (13) (1,125) Imputed charge to bluebird bio for intangible assets 9 82 Other — (1) $ 4,813 $ 13,274 Other components of other (loss) income, net, that are not shown in the table above primarily include immaterial rental income and gains and losses on disposals of fixed assets. There are no such imputed charges in 2022 as the Company recognized all post separation income and costs related pursuant to the terms of the various transition agreements between the Company and bluebird bio, as discussed in previous section. Stock-based compensation As discussed in Note 12, Stock-based compensation , 2seventy bio’s employees participated in bluebird bio's stock-based compensation plans, the costs of which have been allocated to 2seventy bio and recorded in research and development and selling, general and administrative expenses in the condensed consolidated and combined statements of operations and comprehensive loss. Retirement plans 2seventy bio’s employees participated in bluebird bio's 401(k) Savings plan, the costs of which have been allocated to 2seventy bio and recorded in research and development and selling, general and administrative expenses in the condensed consolidated and combined statements of operations and comprehensive loss. Transaction costs Prior to the separation, bluebird bio had incurred costs related to the separation of the Company. To the extent separation costs were incurred that directly benefited the Company as a stand-alone company, such costs were allocated to the Company. Centralized cash management Prior to separation, no separate cash accounts for 2seventy bio were maintained and, therefore, bluebird bio was presumed to have funded 2seventy bio’s operating, investing and financing activities as necessary. As cash was disbursed and received by bluebird bio, for purposes of the condensed consolidated and combined financial statements, funding of 2seventy bio’s expenditures was reflected in the condensed consolidated and combined financial statements as a component of net parent investment.

Income taxes

Income taxes	9 Months Ended
	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income taxes	Income taxesDeferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. 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.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 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 nine months ended September 30, 2022 2021 Outstanding stock options (1) 2,607 — Restricted stock units (1) 1,332 — ESPP shares and other 30 — 3,969 — (1) Outstanding stock options and restricted stock units include awards outstanding to employees of bluebird bio. As described further in Note 9, Stockholders’ equity

Subsequent events

Subsequent events	9 Months Ended
	Sep. 30, 2022
Subsequent Events [Abstract]
Subsequent events	Subsequent events In October 2022, the Company entered into a strategic alliance with JW (Cayman) Therapeutics Co., Ltd. (“JW”) to establish a translational and clinical cell therapy development platform designed to more rapidly explore T cell-based immunotherapy therapy products in the Chinese mainland, Hong Kong (China), and Macao (China). The initial focus of the collaboration is the Company’s MAGE-A4 TCR program in solid tumors which is being developed as part of its collaboration with Regeneron. Under the terms of the agreement, the Company will grant JW a license for the MAGE-A4 cell therapy in the Chinese mainland, Hong Kong (China), and Macao (China). JW will be responsible for development, manufacturing, and commercialization within China. The Company is eligible to receive milestones and royalties on product revenues in China. The Company and Regeneron will equally share all payments received from JW, including but not limited to all upfront, milestone and royalty payments made by JW to the Company. The Company and Regeneron will also equally share all costs for any eligible expenses incurred in accordance with the terms of the Regeneron Collaboration Agreement. Additionally, the Company may leverage the early clinical data generated under the collaboration to support development in other geographies. The closing of the transaction will be subject to the approval of the JW shareholders and other customary closing conditions.

Summary of significant accoun_2

Summary of significant accounting policies and basis of presentation (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The Company did not operate as a separate, stand-alone entity prior to its separation from bluebird bio. Accordingly, the Company’s consolidated and combined statements of operations and comprehensive loss, stockholders’ equity and cash flows for the three and nine months ended September 30, 2021, have been prepared on a carve out basis, derived from bluebird bio’s consolidated financial statements and accounting records. The accompanying condensed consolidated and combined financial statements reflect the historical results of the operations, financial position and cash flows of the Company 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 GAAP as included in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) of the Financial Accounting Standards Board (“FASB”). The historical results of operations and cash flows of 2seventy bio presented in these condensed consolidated and combined financial statements for periods prior to the separation may not be indicative of what they would have been had 2seventy bio operated as an independent, stand-alone entity for those periods. The historical results of operations, financial position and cash flows of 2seventy bio presented in these condensed consolidated and combined financial statements for periods subsequent to the separation are not necessarily indicative of 2seventy bio's future results of operations, financial position and cash flows.
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: allocations of revenue, expenses, assets and liabilities from bluebird bio's historical consolidated financial statements to the Company for periods prior to the separation, 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, the measurement of right-of-use assets and lease liabilities, contingent consideration, stock-based compensation expense, accrued expenses, income taxes, 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. In addition, estimates and judgments are used in the Company’s accounting for its revenue-generating arrangements, in particular as it relates to determining the stand-alone selling price of performance obligations, evaluating whether an option to acquire additional goods and services represents a material right, estimating the total transaction price, including estimating variable consideration and the probability of achieving future potential development and regulatory milestones, assessing the period of performance over which revenue may be recognized, and accounting for modifications to revenue-generating arrangements.

Marketable securities (Tables)

Marketable securities (Tables)	9 Months Ended
	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Summary of Marketable Securities	The following table summarizes the marketable securities held at September 30, 2022 and December 31, 2021 (in thousands): Amortized Unrealized gains Unrealized losses Fair Value September 30, 2022 U.S. government agency securities and $ 124,212 $ — $ (2,700) $ 121,512 Corporate bonds 6,397 — (75) 6,322 Commercial paper 69,786 — (124) 69,662 Total $ 200,395 $ — $ (2,899) $ 197,496 December 31, 2021 U.S. government agency securities and $ 128,899 $ — $ (507) $ 128,392 Corporate bonds 49,368 — (58) 49,310 Commercial paper 54,065 — — 54,065 Total $ 232,332 $ — $ (565) $ 231,767

Fair value measurements (Tables

Fair value measurements (Tables)	9 Months Ended
	Sep. 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 September 30, 2022 and December 31, 2021 (in thousands): Total Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) September 30, 2022 Assets: Cash and cash equivalents $ 127,021 $ 99,349 $ 27,672 $ — Marketable securities: U.S. government agency securities and treasuries 121,512 — 121,512 — Corporate bonds 6,322 — 6,322 — Commercial paper 69,662 — 69,662 — Total assets $ 324,517 $ 99,349 $ 225,168 $ — Liabilities: Contingent consideration $ 2,129 $ — $ — $ 2,129 Total liabilities $ 2,129 $ — $ — $ 2,129 December 31, 2021 Assets: Cash and cash equivalents $ 130,414 $ 130,414 $ — $ — Marketable securities: U.S. government agency securities and treasuries 128,392 — 128,392 — Corporate bonds 49,310 — 49,310 — Commercial paper 54,065 — 54,065 — Total assets $ 362,181 $ 130,414 $ 231,767 $ — Liabilities: Contingent consideration $ 1,948 $ — $ — $ 1,948 Total liabilities $ 1,948 $ — $ — $ 1,948
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	The table below provides a roll-forward of fair value of the Company’s contingent consideration obligations that include Level 3 inputs (in thousands): For the nine months ended September 30, 2022 Beginning balance $ 1,948 Additions — Changes in fair value 181 Payments — Ending balance $ 2,129

Property, plant and equipment_2

Property, plant and equipment, net (Tables)	9 Months Ended
	Sep. 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 September 30, 2022 As of December 31, 2021 Laboratory equipment $ 35,238 $ 31,710 Leasehold improvements 26,709 28,479 Construction-in-progress 18,688 3,462 Office equipment 6,080 6,080 Computer equipment and software 5,625 5,260 Total property, plant and equipment 92,340 74,991 Less accumulated depreciation and amortization (45,690) (40,078) Property, plant and equipment, net $ 46,650 $ 34,913

Accrued expenses and other cu_2

Accrued expenses and other current liabilities (Tables)	9 Months Ended
	Sep. 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 September 30, 2022 As of December 31, 2021 Manufacturing costs $ 15,516 $ 5,459 Collaboration research costs 9,889 2,576 Employee compensation 9,657 24,655 Royalties 7,828 6,768 Clinical and contract research organization costs 2,285 3,229 Property, plant and equipment 683 2,241 Separation related costs 405 762 Professional fees 349 1,688 Other 5,544 8,032 Accrued expenses and other current liabilities $ 52,156 $ 55,410

Collaborative arrangements an_2

Collaborative arrangements and strategic partnerships (Tables)	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Total Transaction Price, Allocation of Total Transaction Price to Identified Performance Obligations Under Arrangement and Amount of Transaction Price Unsatisfied	The amounts reported for these periods represent the Company’s share of BMS’ ABECMA product revenue, cost of goods sold, and selling costs, along with reimbursement by BMS of commercial costs incurred by the Company, and exclude expenses related to ongoing development, which are separately reflected in the condensed consolidated and combined statements of operations and comprehensive loss as described below. Three months ended Nine months ended March 31, 2022 June 30, 2022 September 30, 2022 September 30, 2022 Collaborative arrangement revenue from ide-cel commercial activities (1) $ — $ — $ 4,064 $ 4,064 Share of collaboration loss from ide-cel commercial activities (1) $ (5,352) $ (4,290) $ — $ (9,642) _________________ (1) As noted above, the calculation is performed on a quarterly basis. The calculation is independent of previous activity, which may result in fluctuations between revenue and expense recognition period over period. Three months ended Nine months ended March 31, 2021 June 30, 2021 September 30, 2021 September 30, 2021 Collaborative arrangement revenue from ide-cel commercial activities (1) $ — $ — $ 10,607 $ 10,607 Share of collaboration loss from ide-cel commercial activities (1) $ — $ (10,071) $ — $ (10,071) _________________ (1) As noted above, the calculation is performed on a quarterly basis. The calculation is independent of previous activity, which may result in fluctuations between revenue and expense recognition period over period. The following table summarizes the amounts associated with the research activities under the collaboration included in research and development expense or recognized as collaborative arrangement revenue for the three and nine months ended September 30, 2022 and 2021 (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 Net expense (included as a component of research and development expense) $ (9,252) $ (5,660) $ (21,608) $ (31,678) For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 ASC 606 ide-cel license and manufacturing revenue - ex-U.S. (included as a component of service revenue) $ 3,122 $ 5,314 $ 9,437 $ 14,698
Changes in Balances of Company's Receivables and Contract Liabilities	The following table presents changes in the balances of the Company’s BMS receivables and contract liabilities during the nine months ended September 30, 2022 (in thousands): Balance at December 31, 2021 Additions Deductions Balance at September 30, 2022 Receivables $ 652 $ 10,000 $ (10,652) $ — Contract liabilities: Deferred revenue $ 25,762 $ 10,000 $ — $ 35,762

Stock-based compensation (Table

Stock-based compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Summary of Stock-Based Compensation Expense by Award Type	Stock-based compensation expense recognized by award type was as follows (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 Stock options $ 4,519 $ 5,090 $ 13,577 $ 19,140 Restricted stock units 7,615 4,659 17,901 15,578 Employee stock purchase plan and other 73 1,481 157 5,588 $ 12,207 $ 11,230 $ 31,635 $ 40,306
Schedule of Stock-Based Compensation Expense by Classification	Stock-based compensation expense by classification included within the condensed consolidated and combined statements of operations and comprehensive loss was as follows (in thousands): For the three months ended September 30, For the nine months ended September 30, 2022 2021 2022 2021 Research and development $ 5,314 $ 5,523 $ 14,263 $ 22,429 Selling, general and administrative 6,893 5,707 17,372 17,877 $ 12,207 $ 11,230 $ 31,635 $ 40,306

Related-party transactions (Tab

Related-party transactions (Tables)	9 Months Ended
	Sep. 30, 2022
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	The income and expense recognized by the Company resulting from these imputed charges is recorded as other (loss) income, net in the 2021 condensed consolidated and combined financial statements and was as follows (in thousands): For the three months ended September 30, For the nine months ended September 30, 2021 2021 Imputed charge to bluebird bio for leases $ 4,519 $ 13,440 Imputed charge from bluebird bio for leases (209) (836) Imputed charge to bluebird bio for property, plant and equipment 507 1,714 Imputed charge from bluebird bio for property, plant and equipment (13) (1,125) Imputed charge to bluebird bio for intangible assets 9 82 Other — (1) $ 4,813 $ 13,274

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2022 2021 Outstanding stock options (1) 2,607 — Restricted stock units (1) 1,332 — ESPP shares and other 30 — 3,969 —

Description of the business - N

Description of the business - Narrative (Detail) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022 USD ($) employee	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2022 USD ($) employee	Sep. 30, 2021 USD ($)
Subsequent Event [Line Items]
Conversion ratio				0.3333				0.3333
Net loss	$ 67,879	$ 77,420	$ 85,711	$ 60,001	$ 84,040	$ 87,196	$ 231,010	$ 231,237
Net cash used in operating activities							181,654	$ 149,595
Cash, cash equivalents, and marketable securities	$ 324,500						$ 324,500
2seventy bio Securities Corporation
Subsequent Event [Line Items]
Number of employees | employee	0						0

Marketable securities - Summary

Marketable securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Amortized cost/ cost	$ 200,395	$ 232,332
Unrealized gains	0	0
Unrealized losses	(2,899)	(565)
Fair Value	197,496	231,767
U.S. government agency securities and treasuries
Marketable Securities [Line Items]
Amortized cost/ cost	124,212	128,899
Unrealized gains	0	0
Unrealized losses	(2,700)	(507)
Fair Value	121,512	128,392
Corporate bonds
Marketable Securities [Line Items]
Amortized cost/ cost	6,397	49,368
Unrealized gains	0	0
Unrealized losses	(75)	(58)
Fair Value	6,322	49,310
Commercial paper
Marketable Securities [Line Items]
Amortized cost/ cost	69,786	54,065
Unrealized gains	0	0
Unrealized losses	(124)	0
Fair Value	$ 69,662	$ 54,065

Marketable securities - Narrati

Marketable securities - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Interest receivable	$ 0.2		$ 0.2		$ 0.4
Interest receivable, write-off	$ 0	$ 0	$ 0	$ 0

Fair value measurements - Recor

Fair value measurements - Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets:
Marketable securities:	$ 197,496	$ 231,767
U.S. government agency securities and treasuries
Assets:
Marketable securities:	121,512	128,392
Corporate bonds
Assets:
Marketable securities:	6,322	49,310
Commercial paper
Assets:
Marketable securities:	69,662	54,065
Fair value, measurements, recurring
Assets:
Cash and cash equivalents	127,021	130,414
Total assets	324,517	362,181
Liabilities:
Contingent consideration	2,129	1,948
Total liabilities	2,129	1,948
Fair value, measurements, recurring | U.S. government agency securities and treasuries
Assets:
Marketable securities:	121,512	128,392
Fair value, measurements, recurring | Corporate bonds
Assets:
Marketable securities:	6,322	49,310
Fair value, measurements, recurring | Commercial paper
Assets:
Marketable securities:	69,662	54,065
Fair value, measurements, recurring | Quoted prices in active markets (Level 1)
Assets:
Cash and cash equivalents	99,349	130,414
Total assets	99,349	130,414
Liabilities:
Contingent consideration	0	0
Total liabilities	0	0
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	27,672	0
Total assets	225,168	231,767
Liabilities:
Contingent consideration	0	0
Total liabilities	0	0
Fair value, measurements, recurring | Significant other observable inputs (Level 2) | U.S. government agency securities and treasuries
Assets:
Marketable securities:	121,512	128,392
Fair value, measurements, recurring | Significant other observable inputs (Level 2) | Corporate bonds
Assets:
Marketable securities:	6,322	49,310
Fair value, measurements, recurring | Significant other observable inputs (Level 2) | Commercial paper
Assets:
Marketable securities:	69,662	54,065
Fair value, measurements, recurring | Significant unobservable inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Total assets	0	0
Liabilities:
Contingent consideration	2,129	1,948
Total liabilities	2,129	1,948
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 - Roll-

Fair value measurements - Roll-Forward of Fair Value of the Company's Contingent Consideration Obligations (Detail) - Significant unobservable inputs (Level 3) - Contingent consideration obligations $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 1,948
Additions	0
Changes in fair value	181
Payments	0
Ending balance	$ 2,129

Property, plant and equipment_3

Property, plant and equipment, net - Summary of Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 92,340	$ 74,991
Less accumulated depreciation and amortization	(45,690)	(40,078)
Property, plant and equipment, net	46,650	34,913
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	35,238	31,710
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	26,709	28,479
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	18,688	3,462
Office equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	6,080	6,080
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 5,625	$ 5,260

Property, plant and equipment_4

Property, plant and equipment, net - Narrative (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 92,340	$ 74,991
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	18,688	$ 3,462
Cambridge, Massachusetts | Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 16,800

Accrued expenses and other cu_3

Accrued expenses and other current liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Manufacturing costs	$ 15,516	$ 5,459
Collaboration research costs	9,889	2,576
Employee compensation	9,657	24,655
Royalties	7,828	6,768
Clinical and contract research organization costs	2,285	3,229
Property, plant and equipment	683	2,241
Separation related costs	405	762
Professional fees	349	1,688
Other	5,544	8,032
Accrued expenses and other current liabilities	$ 52,156	$ 55,410

Commitments and contingencies -

Commitments and contingencies - Narrative (Detail) $ in Millions	1 Months Ended
	Jul. 31, 2021 USD ($) batch	Sep. 30, 2022 USD ($)
Resilience
Commitments And Contingencies Disclosure [Line Items]
Net operating losses, percentage of reimbursement	50%
Reimbursement cap	$ 15
Net operating losses, percentage of minimum purchase amount	50%
Accrued Liabilities		$ 14.8
Maximum | Resilience
Commitments And Contingencies Disclosure [Line Items]
Number of lentiviral vector batches | batch	8
Pregenen
Commitments And Contingencies Disclosure [Line Items]
Contingent future cash payments		$ 99.9

Collaborative arrangements an_3

Collaborative arrangements and strategic partnerships - Collaborative Arrangement Revenue (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement revenue	$ 7,903			$ 12,337			$ 18,425	$ 15,527
Share of collaboration loss	0			0			(9,642)	(10,071)
Ide Cel Commercial Activities | Bristol-Myers Squibb
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement revenue	4,064	$ 0	$ 0	10,607	$ 0	$ 0	4,064	10,607
Share of collaboration loss	$ 0	$ (4,290)	$ (5,352)	$ 0	$ (10,071)	$ 0	$ (9,642)	$ (10,071)

Collaborative arrangements an_4

Collaborative arrangements and strategic partnerships - Narrative (Detail) $ / shares in Units, $ in Thousands, shares in Millions		1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 24, 2018 USD ($) accounting_unit $ / shares shares	Aug. 31, 2018 target	Sep. 30, 2022 USD ($) performance_obligation	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) performance_obligation	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 23, 2021 USD ($) performance_obligation	Sep. 30, 2020 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Income (loss) from collaborative arrangements			$ 0	$ 0	$ (9,642)	$ (10,071)
Number of performance obligations | performance_obligation			2		2
Number of accounting units | accounting_unit	2
Bristol-Myers Squibb
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement, transaction price			$ 31,000		$ 31,000
Estimated variable consideration			1,800		1,800
Contract with customer liability			35,762		35,762		$ 25,762
Bristol-Myers Squibb | Phase I, Additional Obligation
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Estimated variable consideration									$ 37,400
Bristol-Myers Squibb | Research and development services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Estimated variable consideration									$ 5,400
Bristol-Myers Squibb | bb21217 license agreement | U.S.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional fee receivable if option to co-develop and co-promote is not exercised			10,000		10,000
Bristol-Myers Squibb | Bb Two One Two One Seven License And Manufacturing Services | License and manufacturing services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract with customer liability			35,800		35,800		25,800
Regeneron Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of initial collaboration targets | target		6
Research collaboration term		5 years
Joint research activities remaining to be recognized			9,000		9,000		$ 23,300
Regeneron Collaboration Agreement | Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue balance recognized as gross revenues			3,800	$ 1,700	14,400	$ 4,900
Regeneron Collaboration Agreement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	$ 130,000
Regeneron Collaboration Agreement | Research and development services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement, transaction price	100,000
Purchase price premium	$ 37,000
Collaborative arrangement amortization period	5 years
Collaborative arrangement amount attributed to joint research activities	$ 45,500
Regeneron Collaboration Agreement | Research and development services | Bluebird Bio
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement amount attributed to equity sold	$ 54,500
Regeneron Collaboration Agreement | Share purchase agreement | Bluebird Bio
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Common stock price per share (in dollars per share) | $ / shares	$ 238.10
Investment in common stock	$ 100,000
Purchase price premium	$ 37,000
Collaborative arrangement research initial funding obligation, percentage	50%
Regeneron Collaboration Agreement | Share purchase agreement | Common stock | Bluebird Bio
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock to Regeneron (in shares) | shares	0.4
Investment in common stock	$ 63,000
Novo Nordisk A/S | Novo Collaboration and License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Estimated variable consideration			18,200		18,200
Number of performance obligations | performance_obligation								2
Contract with customer liability								$ 5,000
Estimated variable consideration, research reimbursement			13,200		13,200
Estimated variable consideration, upfront payment			5,000		5,000
Revenue			$ 1,500		$ 4,900
Novo Nordisk A/S | Novo Collaboration and License Agreement | License and manufacturing services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable								26,000
Novo Nordisk A/S | Novo Collaboration and License Agreement | Development and Commercialization Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable								72,000
Novo Nordisk A/S | Novo Collaboration and License Agreement | Scientific Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable								15,000
Novo Nordisk A/S | Novo Collaboration and License Agreement | Extension of Research Plan without Achieving Scientific Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable								$ 9,000

Collaborative arrangements an_5

Collaborative arrangements and strategic partnerships - Summary of Revenue Recognized or Expense Incurred for Joint Ide-cel Development Efforts Related to Combined Unit of Accounting for its License and Vector Manufacturing of Ide-cel (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	$ (61,739)	$ (61,131)	$ (199,423)	$ (202,394)
Bristol-Myers Squibb | U.S. | Ide-cel Research And Development Services | License and manufacturing services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	(9,252)	(5,660)	(21,608)	(31,678)
Bristol-Myers Squibb | Outside of U.S. | Ide-cel license and manufacturing services | License and manufacturing services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue	$ 3,122	$ 5,314	$ 9,437	$ 14,698

Collaborative arrangements an_6

Collaborative arrangements and strategic partnerships - Changes in Balances of Company's Receivables and Contract Liabilities (Detail) - Bristol-Myers Squibb $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Receivables
Balance at December 31, 2021	$ 652
Additions	10,000
Deductions	(10,652)
Balance at September 30, 2022	0
Contract liabilities:
Balance at December 31, 2021	25,762
Additions	10,000
Deductions	0
Balance at September 30, 2022	$ 35,762

Royalty and other revenue - Add

Royalty and other revenue - Additional Information (Detail) - Royalty and other revenue - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
License And Royalty Revenue [Line Items]
Revenue	$ 863	$ 608		$ 2,531	$ 5,417
Juno Therapeutics
License And Royalty Revenue [Line Items]
Revenue			$ 2,500

Equity - Narrative (Details)

Equity - Narrative (Details) - Private Placement $ / shares in Units, $ in Millions	1 Months Ended
	Mar. 31, 2022 USD ($) $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in transaction (in shares) | shares	13,934,427
Common stock price per share (in dollars per share) | $ / shares	$ 12.20
Proceeds from issuance of common stock | $	$ 165.5

Stock-based compensation - Summ

Stock-based compensation - Summary of Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 12,207	$ 11,230	$ 31,635	$ 40,306
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	4,519	5,090	13,577	19,140
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	7,615	4,659	17,901	15,578
Employee stock purchase plan and other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 73	$ 1,481	$ 157	$ 5,588

Stock-based compensation - Sche

Stock-based compensation - Schedule of Stock-Based Compensation Expense by Classification (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 12,207	$ 11,230	$ 31,635	$ 40,306
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5,314	5,523	14,263	22,429
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,893	$ 5,707	$ 17,372	$ 17,877

Stock-based compensation - Narr

Stock-based compensation - Narrative (Detail) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
2021 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, shares issued in period (less than) (in shares)	100,000	100,000

Related-party transactions - Na

Related-party transactions - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2022	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Nov. 03, 2021 agreement
Related Party Transaction [Line Items]
Operating income (loss)	$ (68,368)	$ (65,238)		$ (235,928)	$ (245,577)
Costs and expenses	81,776	84,495		271,247	284,065
Number of transition services agreements | agreement						2
Transition services agreement, initial term						2 years
Other (loss) income, net	(624)	5,237		3,494	14,340
Bluebird Bio | Management Costs and Corporate Support Services
Related Party Transaction [Line Items]
Allocations for management costs and corporate support services provided to the Company		$ 14,500			$ 49,900
Bluebird Bio | Separation Agreement
Related Party Transaction [Line Items]
Operating income (loss)	(300)			2,800
Costs and expenses	0			200
Bluebird Bio | Transition Services Agreement
Related Party Transaction [Line Items]
Costs and expenses	100			1,000
Other (loss) income, net	1,900			$ 8,100
Area of sublease, percent				30%
Sublease income	1,200			$ 3,600
Due to related parties	400			400
Due from related parties	$ 1,900			$ 1,900
Bluebird Bio | Transition Services Agreement | Scenario, Forecast
Related Party Transaction [Line Items]
Area of sublease, percent			23%

Related Party Disclosures - Imp

Related Party Disclosures - Imputed Charges (Details) - Bluebird Bio - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 4,813	$ 13,274
Imputed charge to bluebird bio for leases
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	4,519	13,440
Imputed charge from bluebird bio for leases
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	(209)	(836)
Imputed charge to bluebird bio for property, plant and equipment
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	507	1,714
Imputed charge from bluebird bio for property, plant and equipment
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	(13)	(1,125)
Imputed charge to bluebird bio for intangible assets
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	9	82
Other
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 0	$ (1)

Net Loss Per Share - Common Sto

Net Loss Per Share - Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 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)	3,969,000	0	3,969,000	0
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)	2,607,000	0	2,607,000	0
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)	1,332,000	0	1,332,000	0
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)	30,000	0	30,000	0

Net Loss Per Share - Narrative

Net Loss Per Share - Narrative (Details) - Pre-funded Warrants - Private Placement	Nov. 30, 2021 $ / shares shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Pre-funded warrants issued (in shares) | shares	757,575
Exercise price of warrants (in dollars per share) | $ / shares	$ 0.0001