Lease obligation

12 Months Ended

Dec. 31, 2023

Lease obligation

Lease obligation

7. Lease obligation

Operating Leases

As of December 31, 2023, the Company has a lease for laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts through January 31, 2031 and a lease for additional office and laboratory space at 64 Sidney Street in Cambridge, Massachusetts through November 30, 2026.

In September 2021, the Company entered into an agreement with BioNTech US, Inc. (“BioNTech US”) to sublease part of the office and laboratory space leased by the Company at 75 Sidney Street in Cambridge, Massachusetts (the “Sublease Agreement”) at that time. The sublease term was for approximately 3.3 years. The sublease did not relieve the Company of its original obligation under the lease, and therefore the Company did not adjust the operating lease right-of-use asset as a result of the sublease and accounted for the sublease as a separate lease.

On June 22, 2022 the Company entered into a Lease Termination Agreement (the “Lease Termination Agreement”) and terminated the lease for office and laboratory space at 75 Sidney Street (the “75 Sidney Street Lease”), effective immediately. In connection with the Lease Termination Agreement, the Company also entered into a Sublease Termination Agreement (the “Sublease Termination Agreement”) and terminated the Sublease Agreement with BioNTech US. The Company did not incur any termination penalties in connection with the Lease Termination Agreement or Sublease Termination Agreement. The Company derecognized the related right-of-use asset of approximately $14.5 million and the operating lease liabilities of $17.0 million, accordingly, resulting in a gain of $2.5 million in the year ended December 31, 2022.

The Company’s lease agreements require the Company to maintain a cash deposit or irrevocable letter of credit in the aggregate amount of $1.5 million payable to its landlords as security for the performance of its obligations under the leases.

On August 11, 2023, the Company entered into a first amendment (the “First Amendment”) to its existing lease for laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts, pursuant to which the Company agreed to lease approximately 61,307 square feet of additional office and laboratory space. The term of the First Amendment commences on the date on which the landlord makes the space available for use by the Company, and expires on January 31, 2031, unless sooner terminated or extended. As of December 31, 2023, the Company did not have control of the space and therefore, the lease had not yet commenced. The commencement date for the First Amendment occurred on February 1, 2024. The expected contractual obligation under the First Amendment to the Company’s existing lease is approximately $37.8 million, to be paid over the 7 year term of the lease.

Total lease cost for operating leases of approximately $3.6 million, $4.6 million, and $6.8 million was incurred during the years ended December 31, 2023, 2022, and 2021, respectively. As of December 31, 2023, the weighted average remaining lease term was 5 years and the weighted average incremental borrowing rate used to determine the operating lease liability was 7.4%.

The following table summarizes the operating sublease income generated under the Sublease Agreement for the years ended December 31, 2023, 2022, and 2021:

	Years ended
	December 31,
	2023		2022		2021
	(in thousands)
Operating sublease income	$	—	$	1,380	$	838