7. Leases

In October 2019, the Company entered into a noncancelable facility lease agreement (the “2019 Lease”) for 34,522 square feet of research and development and office space in Watertown, Massachusetts. The term of the 2019 Lease is 120 months and expires on March 31, 2030. The 2019 Lease has an option to be extended for an additional five years. The lease is not reasonably certain to be extended and as such the additional term is not included in the measurement of the lease. The 2019 Lease includes a rent escalation clause, and rent expense is being recorded on a straight-line basis. In accordance with the lease agreement, the Company is required to maintain a security deposit and provided a letter of credit to the landlord, which is recorded in restricted cash as of September 30, 2026 and December 31, 2025. The letter of credit totaled $1.3 million and $1.3 million as of September 30, 2026 and December 31, 2025, respectively.

In December 2021, the Company entered into a noncancelable lease (the “2021 Lease”) for 100,624 square feet of office and laboratory space in Watertown, Massachusetts, which the Company began occupying in February 2024. The 2021 Lease is subject to base rent of $0.8 million per month beginning two months after the commencement date, plus the Company’s ratable share of taxes, maintenance and other operating expenses. Base rent is subject to a 3% annual increase over the lease term of approximately 134 months following the commencement date. The Company also has two consecutive options to extend the term of the lease for five years each at then-market rates. The 2021 Lease also includes a tenant improvement allowance of approximately $20.1 million. In accordance with the lease agreement, the Company is required to maintain a security deposit and provided a letter of credit to the landlord, which is recorded in restricted cash as of September 30, 2026 and December 31, 2025. The letter of credit totaled $4.9 million and $4.5 million as of September 30, 2026 and December 31, 2025, respectively.

The 2021 Lease required the landlord to build-out the base building prior to the construction of the Company’s premises. The Company concluded the accounting commencement date occurred when the landlord completed the build-out of the base building and control passed to the Company, which occurred in early January 2023. The Company assessed the classification of the 2021 Lease at the accounting commencement date and concluded the lease should be accounted for as an operating lease. The Company recorded an operating lease liability of $48.9 million, measured as the present value of the remaining lease payments discounted using the incremental borrowing rate as of the accounting commencement date. The Company recorded an operating lease right-of-use asset of $48.9 million, measured as the present value of the remaining lease payments, net of the tenant incentives.

The Company concluded the improvements paid for by the landlord in connection with the tenant improvement allowance represent lessee assets and therefore recorded $20.1 million of leasehold improvements in property and equipment. The Company recorded an additional $17.9 million of leasehold improvements in excess of the tenant improvement allowance, all of which were placed in service in 2024.

Upon occupancy of the 2021 Lease facility in February of 2024, the Company exited the 2019 Lease facility and began looking to sublease the entire facility for the remaining noncancellable lease term through March 31, 2030. These actions resulted in impairment charges to date of $8.8 million.

The impairment charge reduces the carrying value of the associated ROU asset, leasehold improvements and certain furniture and fixture assets that remained in the facility to their estimated fair values. The fair values are estimated using a discounted cash flows approach based on forecasted future cash flows expected to be derived from the property based on current sublease market rent, which is considered a level 3 input in the fair value hierarchy, and other key assumptions such as future sublease market conditions and the discount rate.

In July 2026, the Company entered into a sublease for its 2019 Lease. The sublease commences on January 1, 2027 with rent commencement September 1, 2027, and terminates on March 31, 2030, which is concurrent with the termination of the Company's 2019 Lease. The Company was not relieved of its primary obligation under the 2019 Lease as a result of the sublease, and there was no incremental impairment recognized as a result of the sublease. The Company expects to begin recognizing sublease income on a straight-line basis over the term of the sublease agreement upon commencement of the lease.

The Company’s finance lease obligations consist of certain property and equipment financed through finance leases.