The Company’s operating lease activity is comprised of non-cancelable facility leases for office and laboratory space in Boston, Massachusetts.

On March 16, 2022, the Company and IDB 17-19 Drydock Limited Partnership, as landlord (Landlord), entered into a lease agreement (IDB Lease) with respect to approximately 81,229 square feet of office and laboratory space (Premises) in Boston, Massachusetts. The initial fixed rental rate is $0.5 million per month, which is for a 12 month period during which the base rent is payable for 65,000 square feet, and will increase 3% per annum thereafter for the entire 81,229 square feet leased.

The accounting commencement date occurred in April 2023 when both the Landlord's build-out and the tenant improvements were substantially completed. On the accounting commencement date, the Company recorded an operating lease right-of-use (ROU) asset of $77.6 million and a total lease liability of $63.6 million.

The IDB Lease has a term of approximately 10 years, unless earlier terminated in accordance with the terms of the IDB Lease. The Company has (i) the option to extend the IDB Lease for an additional period of five (5) years, and (ii) a right of first offer on adjacent space to the Premises, subject to the terms and conditions of the IDB Lease. As these options are not reasonably certain of occurring, they have not been included in the initial calculation of the Company's ROU asset upon lease commencement.

Under the terms of the IDB Lease, the Landlord provided an allowance of $19.5 million toward the cost of completing tenant improvements for the Premises. In addition, the Landlord provided an additional contribution of $1.6 million toward the cost of tenant improvements to the Premises, which amount shall be repaid by the Company over the term of the IDB Lease. Such repayments are included in the maturity of the lease liability table below. As of December 31, 2023, the Company had received the full tenant improvement allowance from the Landlord.

The Company concluded that the improvements resulting from both the Landlord's build-out and the tenant improvements are the Landlord's assets for accounting purposes. Accordingly, the $13.9 million of costs incurred by the Company related to the tenant improvements in excess of the Landlord's allowance were reclassified from other non-current assets to right-of-use assets upon commencement of the IDB lease and will be recognized as rent expense over the remaining lease term.

In connection with the execution of the IDB Lease, the Company executed a cash-collateralized letter of credit, which may be reduced in the future subject to reduction requirements specified in the IDB Lease therein. The $4.0 million of cash collateralizing the letter of credit is classified as restricted cash on the Company's consolidated balance sheets.

The Company entered into an operating lease for office and laboratory space at 6 Tide Street in Boston, Massachusetts in February 2020, and entered into subsequent amendments through 2021 to lease additional space (6 Tide Street Lease). Such amendments run co-terminus with the original lease.

During 2023, the Company entered into amendments to the 6 Tide Street lease pursuant to which the Company surrendered portions of the leased space in exchange for being relieved of its obligation to make lease payments. Upon the lease modification, the Company reassessed its incremental borrowing rate and remeasured the lease liability and right-of-use asset. Subsequent to the amendment, the Company continues to classify the 6 Tide Street Lease as an operating lease.

As of December 31, 2023, the Company had a total of 23,189 square feet licensed at this facility. The term for the remaining leased space will end on November 30, 2025. The fixed rental payment will be approximately $0.5 million per month for the remainder of the lease term. The Company has the option to extend the remaining leased space for a period of 3 years, or terminate such remaining space leased without penalty provided sufficient notice is given. At the adoption of ASC 842, the Company concluded that it is not reasonably certain that it will exercise its option to terminate the lease early or exercise its option to extend the leased space.

As of December 31, 2023, the Company's security deposit for the 6 Tide Street Lease was $0.7 million, of which, $0.3 million is recorded as a component of other current assets as it is expected to be received with one year of the balance sheet date. The remaining $0.4 million is recorded as a component of other non-current assets.


Other information	Year ended December 31, 2023
Operating cash flows used for operating leases (in thousands)	$	16,268
Weighted average remaining lease term	8.2 years
Weighted average discount rate	8.13%


Maturity of lease liabilities	Amount
2024	13,084
2025	13,161
2026	8,826
2027	9,083
2028	9,349
Thereafter	41,091
Total lease payments	$	94,594
Less: imputed interest	(26,364)
Present value of operating lease liabilities	$	68,230

In December 2022, the Company entered into a sublease agreement to sublease a portion of the office and laboratory space leased under the IDB Lease to a third-party (subtenant). The sublease term is 3 years and the subtenant has an option to extend the lease term for 6 months. The initial fixed rental rate is $0.2 million per month, and will increase 3% per annum thereafter. The sublessee is obligated to pay its ratable portion of operating expenses during the sublease term. The Company received a letter of credit of $0.5 million in place of a security deposit. As of December 31, 2023, no amounts have been drawn on the letter of credit.

The sublease accounting commencement date occurred in April 2023. During the year ended December 31, 2023, the Company recognized $1.5 million of sublease income. Such amount is recorded as a reduction to rent expense.