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

The Company has also entered into multiple contract research and contract manufacturing service agreements with third parties which contain embedded leases within the scope of ASC 842. The embedded leases are considered short term leases, as the contractual terms are twelve months or less. Accordingly, no lease liability or ROU asset has been recorded.

The components of operating lease cost were as follows:


(in thousands)	December 31, 2023		December 31, 2022
Operating lease costs	$	12,936	$	5,946
Variable lease costs		3,854		1,601
Short term lease costs		1,259		698
Total	$	18,049	$	8,245

Supplemental cash flow information related to operating leases was as follows:


(in thousands)	December 31, 2023		December 31, 2022
Cash paid for amounts included in the measurements of lease liabilities:
Operating cash flows related to operating leases	$	12,550	$	5,050

As of December 31, 2023, the Company’s operating leases were measured using a weighted-average incremental borrowing rate of 7.89% over a weighted-average remaining lease term of 9 years.

On August 19, 2021, the Company entered into a lease agreement with ARE-MA Region No. 87 Tenant, LLC, a Delaware limited liability company (the “Landlord”), pursuant to which the Company leased approximately 104,933 square feet of office and laboratory space located at 201 Brookline Avenue, Boston, Massachusetts (the “Boston Lease”), further amended in January 2022 to include an additional 249 square feet, for a total of 105,182 square feet (the “Premises”). In June 2022, the Company entered into a second amendment to specify separate target commencement dates for certain areas of the Premises.

The Premises were first made available to the Company in August 2022. Upon commencement of the lease, the Company recorded an operating lease ROU asset of $91.8 million and a total lease liability of $80.8 million.

The Company’s obligation for the payment of base rent for the Premises began in January 2023 (the “Rent Commencement Date”). Base rent is initially $0.8 million per month, and will increase by approximately 3% per annum.

The Boston Lease has a term of 10 years, measured from the Rent Commencement Date. The Company has the option to extend the term of the Boston Lease for a period of an additional five years. Under the terms of the Boston Lease, the Landlord made $21.0 million in certain tenant improvements to the Premises to suit the Company’s use (the “Tenant Improvement Allowance”), which amount is included in the base rent set forth in the Boston Lease.

In connection with its entry into the Boston Lease and as a security deposit, the Company has provided the Landlord a letter of credit in the amount of approximately $4.8 million, which may be reduced to approximately $3.5 million on the expiration of the 36-month anniversary of the Rent Commencement Date so long as there are, and have been, no defaults by the Company under the terms of the Boston Lease. The Company also paid a deposit in the amount of $0.8 million, which is equal to the first month of base rent. The Landlord has the right to terminate the Boston Lease upon customary events of default.

Future minimum commitments under non-cancellable leases as of December 31, 2023 were as follows:


Years ending December 31,	Amount
	(in thousands)
2024	$	10,563
2025		10,868
2026		11,183
2027		11,506
2028		11,839
Thereafter		50,075
Total lease payments	$	106,034
Less: interest		(31,127	)
Present value of operating lease liabilities	$	74,907