In August 2007, the Company entered into an operating lease, as amended, for office and laboratory space in Watertown, Massachusetts. The lease includes certain rent escalations. In July 2023, the Company amended the lease to extend the expiration of the lease term from April 2024 to April 2027. Under the terms of the amended lease, the Company no longer has the right to terminate the lease after January 1, 2024.

The Company maintains a letter of credit of approximately $0.3 million securing its obligations under the operating lease which is secured by approximately $0.3 million, which are included as restricted cash in the consolidated balance sheets. Rent expense is recognized on a straight-line basis over the terms of occupancy.

In May 2022, the Company executed a lease agreement located at 880 Winter Street in Waltham, Massachusetts. The leased premises comprises approximately 29,000 square feet of office and lab space, and the lease initially provides for base rent of $2.2 million per year, which will increase 3% per year over the noncancellable term ending on June 30, 2033. The Company has the option to extend the lease for one additional five-year term and is responsible for its share of real estate taxes, maintenance, and other operating expenses applicable to the leased premises. The Company did not include the option to extend the lease for the additional five-year term in its measurement of the right-of-use asset and lease liability.

In connection with the lease, a security deposit was delivered to the landlord in the form of an irrevocable standby letter of credit collateralized by $1.1 million of deposits with the financial institution which is recorded as restricted cash.

In December 2023, the Company executed a sublease agreement for additional lab and office space located at 880 Winter Street in Waltham, Massachusetts. The subleased premises comprise approximately 24,000 square feet, and the sublease provides for base rent of $1.8 million per year, which will increase 3% per year over the noncancellable term ending on November 30, 2032. The Company is also responsible for its share of real estate taxes, maintenance, and other operating expenses applicable to the subleased premises.

Upon sublease commencement on January 3, 2024, the Company recorded the sublease as a component of its operating lease right-of-use asset and operating lease liabilities. In connection with the sublease, a security deposit was delivered to the sublandlord in the form of an irrevocable standby letter of credit collateralized by $0.6 million of deposits with the financial institution which is recorded as restricted cash.

The components of lease cost recorded in the Company’s condensed consolidated financial statements were as follows (in thousands):


	Three Months Ended March 31,
	2024		2023
Lease Cost:
Operating lease cost	$	1,859	$	444
Variable lease cost		672		246
Total lease cost	$	2,531	$	690

Variable lease payments include the Company’s allocated share of costs incurred and expenditures made by the landlord in the operation and management of the building.

The weighted-average remaining lease term and discount rate related to the Company’s operating leases were as follows:


	As of March 31, 2024
Weighted-average remaining lease term (in years)		8.1
Weighted-average discount rate		6.25	%