Related-party transactions

12 Months Ended

Dec. 31, 2023

Related Party Transactions [Abstract]

Related-party transactions

Related-party transactions

Relationship with Bluebird Bio

In connection with the separation, the Company entered into a separation agreement (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. 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. Following the completion of the separation and distribution, the Company and bluebird bio have operated separately, each as an independent public company and bluebird bio no longer owns any shares of the Company’s common stock. Therefore, starting in 2023, transactions under those agreements are no longer accounted for as related party transactions. The Company recorded other income of $2.8 million for the year ended December 31, 2022 and an expense of $0.2 million for the two months since separation through December 31, 2021, related to the Separation Agreement.

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 Company recorded a reduction to operating expense of $0.2 million for the year ended December 31, 2022 and $1.8 million for the two months since separation through to December 31, 2021 for costs stipulated by the employee matters agreement.

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. 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, 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 year ended December 31, 2022, the Company recorded $10.0 million in other income, net, reflecting services provided to bluebird bio and $1.0 million of operating expenses for services received from bluebird bio. For the two months since separation through December 31, 2021, the Company recorded $1.4 million in other income, net and $0.7 million of operating expenses for services provided and received from bluebird bio, respectively.

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 $4.9 million for the year ended December 31, 2022 and $0.8 million for the year ended December 31, 2021 in other income, net related to sublease income from bluebird under this arrangement.

As of December 31, 2022, amounts due to bluebird bio under the above agreements were $0.1 million and are included in accrued expenses. As of December 31, 2022, amounts due from bluebird bio under the above agreements were $1.9 million and were included in receivables and other current assets.

On February 23, 2023, the Company entered into a Partial Assignment and Assumption Agreement (the “Assignment and Assumption Agreement”) with Institut Pasteur (“Institut Pasteur”) and bluebird bio. Pursuant to the Assignment and Assumption Agreement, bluebird bio assigned to the Company bluebird bio’s rights, obligations and interests under a license agreement with Institut Pasteur that were previously licensed to the Company by bluebird bio under the License Agreement. The Company will pay Institut Pasteur an annual maintenance payment, a percentage of income received in the event of sublicensing arrangements and, upon commercialization of certain products, a percentage of net sales as a royalty, which varies depending on the indication of the product.

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 consolidated and combined financial statements for periods prior to the separation. 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 the year ended December 31, 2021, the 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 $55.3 million, for the year ended December 31, 2021.

The financial information in these 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, for additional information on the preparation and basis of presentation of these 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 the separation

Certain assets have been reflected in these consolidated and combined financial statements as the underlying assets were attributed to 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 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 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 for periods prior to the separation resulting from these imputed charges was recorded as other income, net in the combined financial statements and was as follows:

	Year ended December 31,
	2021
Imputed charge to bluebird bio for leases	$	14,833
Imputed charge from bluebird bio for leases	(908)
Imputed charge to bluebird bio for property, plant and equipment	1,891
Imputed charge from bluebird bio for property, plant and equipment	(1,130)
Imputed charge to bluebird bio for intangible assets	82
Other	(1)
	$	14,767

Other components of other income, net, that are not shown in the table above include immaterial gains and losses on disposals of fixed assets.

Stock-based compensation

As discussed in Note 13, Stock-based compensation, prior to the separation, 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 consolidated and combined statements of operations and comprehensive loss.

Retirement plans

As discussed in Note 15, 401(k) Savings plan, prior to the separation, 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 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 are incurred that will directly benefit the Company as a stand-alone company, such costs were allocated to the Company.

Centralized cash management

Prior to the 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 consolidated and combined financial statements, funding

of 2seventy bio’s expenditures was reflected in the consolidated and combined financial statements as a component of net parent investment.