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Leases | 9 Months Ended
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Sep. 30, 2025
Leases [Abstract] |
Leases | 7. Leases The Company’s only lease as of September 30, 2025 and December 31, 2024 was an operating lease for approximately 180,000 square feet of corporate office space, administrative areas and laboratories at 850 and 852 Winter Street in Waltham, Massachusetts, which includes 34,000 square feet of laboratory space (as amended, the “Winter Street Lease”). Under the terms of the Winter Street Lease, the Company also has the ability to sub-lease its corporate office and laboratory space. The original lease commenced in 2010 and was extended, at the Former Parent’s option, for approximately five years in 2020. The lease extension commenced in March 2021 for approximately 163,000 square feet of space and in September 2021 for the remaining approximately 17,000 square feet of space. The Winter Street Lease expires in 2026 and includes a tenant option to extend the term of the lease for an additional five-year period, which the Company is not reasonably certain to exercise. The Winter Street Lease was assigned to the Company in connection with the Separation and is used solely for operations of the Company. The Former Parent has been primarily obligated to the landlord for the Winter Street Lease, and, following the Separation, the Former Parent is jointly and severally liable with the Company for, and continues to guarantee, all obligations under the Winter Street Lease. As of December 31, 2023, the Former Parent was the applicant with respect to a letter of credit security deposit that secured the obligations of the tenant under the Winter Street Lease. The Former Parent maintained a $1.9 million collateralized letter of credit (the “Former Parent Letter of Credit”) related to such security deposit as of December 31, 2023. On January 3, 2024, the Company entered into a $1.7 million collateralized letter of credit that secures the obligations of the tenant under the Winter Street Lease. This letter of credit replaced the $1.9 million Former Parent Letter of Credit. On August 16, 2024, the Company entered into a sub-lease pursuant to which the Company sub-leased to a third party approximately 5,155 square feet of office space and approximately 3,739 square feet of laboratory space that the Company leases under the Winter Street Lease and the Company also entered into a separate sub-lease pursuant to which the Company sub-leased to another third party (both sub-lessees together, the “August Sub-lessees”) approximately 3,387 square feet of office space and approximately 2,690 square feet of laboratory space that the Company leases under the Winter Street Lease (both sub-leases together, the “August Sub-leases”). The August Sub-leases commenced on August 20, 2024 and are expected to terminate on April 18, 2026. Under the August Sub-leases, the August Sub-lessees will pay to the Company a total annualized fixed base rent of $0.5 million beginning 30 days after the commencement date of the August Sub-leases, as well as compensate the Company for the August Sub-lessees’ proportionate share of operating and other expenses related to the August Sub-leases. The August Sub-lessees’ base rent and proportionate share of operating and other expenses are included as contra-expense in the Company’s unaudited condensed consolidated statements of operations and comprehensive loss. On October 10, 2024, the Company entered into a sub-lease (the “October Sub-lease”) pursuant to which the Company sub-leased to an additional third party (the “October Sub-lessee”) approximately 30,102 square feet of office space that the Company leases under the Winter Street Lease. Under the October Sub-lease, the October Sub-lessee will pay the Company an annualized fixed base rent of $0.7 million beginning on January 1, 2025, as well as compensate the Company for a proportionate share of operating and other expenses related to the October Sub-lease beginning with the commencement date of the October Sub-lease. The October Sub-lease commenced on November 1, 2024 and is expected to terminate on April 30, 2026. As of the nine months ended September 30, 2025 and 2024, the incremental borrowing rate for the Winter Street Lease was 3.52%. As of September 30, 2025, the remaining term for the Winter Street Lease was 1.1 years. Cash paid for amounts included in the measurement of lease liabilities is included within cash flows from operating activities. During the three and nine months ended September 30, 2025, cash paid by the Company for amounts included for the measurement of lease liabilities was $1.7 million and $5.0 million. During the three and nine months ended September 30, 2024, cash paid by the Company for amounts previously included in the measurement of lease liabilities was $1.6 million and $4.9 million, respectively. The following table summarizes the effect of lease costs in the Company’s unaudited condensed consolidated statements of operations and comprehensive loss:
|  | Three Months Ended |  |  | Nine Months Ended |
|  | September 30, |  |  | September 30, |
(in thousands) |  | 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |
Operating lease cost |  | $ | 1,272 |  |  | $ | 1,398 |  |  | $ | 3,828 |  |  | $ | 4,211 |
Variable lease cost |  |  | 642 |  |  |  | 1,111 |  |  |  | 1,956 |  |  |  | 3,410 |
Total lease cost |  | $ | 1,914 |  |  | $ | 2,509 |  |  | $ | 5,784 |  |  | $ | 7,621 |
Future lease payments under non-cancelable leases as of September 30, 2025 consisted of the following:
(in thousands) |  | September 30, 2025 |
Remainder of 2025 |  | $ | 1,116 |
2026 |  |  | 2,484 |
Total operating lease payments |  | $ | 3,600 |
Less: imputed interest |  |  | (53 | )
Total operating lease liabilities |  | $ | 3,547 |

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- Definition The entire disclosure for operating leases of lessee. Includes, but is not limited to, description of operating lease and maturity analysis of operating lease liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/842-20/tableOfContent + Details
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