The Company has operating leases for its current corporate offices, laboratory space, manufacturing facility, and dedicated space in a vivarium in South San Francisco, California.

The components of lease expense were as follows (in thousands):


	Year Ended December 31,
	2024		2023
Operating lease expense	$	10,578	$	10,900
Variable lease expense (1)		1,247		1,018
Short-term lease expense		—		18
Total lease expense	$	11,825	$	11,936

Supplemental information related to operating leases were as follows (in thousands):


	Year Ended December 31,
	2024		2023
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$	14,680	$	11,540

The weighted-average remaining lease term was 9.0 years for the corporate office and laboratory space leases as of December 31, 2024. The corporate office lease includes an option to renew for an additional seven years. However, the renewal option was not included in the lease term for calculating the lease liability, as the renewal option allows the Company to maintain operational flexibility, and the Company was not reasonably certain that it would exercise the renewal option at the time of the lease commencement. The weighted-average discount rate was 9.8% as of December 31, 2024.

Maturities of operating lease liabilities under existing operating leases as of December 31, 2024 were as follows (in thousands):


Year ending December 31,	Amount
2025	$	12,537
2026		12,621
2027		13,041
2028		13,477
2029		13,927
2030 and thereafter		57,458
Total undiscounted future minimum lease payments		123,061
Less imputed interest		(42,788	)
Total operating lease liabilities	$	80,273
Operating lease liabilities:
Current		6,050
Non-current		74,223
Total lease liability	$	80,273

In May 2018, the Company entered into a lease agreement for corporate office and laboratory space located in South San Francisco, California with an expiration date in May 2025 (the "Initial Lease Agreement"). In April 2019, the Company executed the first amendment to the Initial Lease Agreement for additional corporate space, laboratory space and manufacturing capabilities. In May 2020, the Company executed the second amendment to the Initial Lease Agreement for additional corporate space and laboratory space in the same building. The lease for this additional space commenced in January 2021. In January 2021, the Company signed a third amendment to the Initial Lease Agreement for additional space in the same building. The lease amendment for this additional space commenced in April 2021 and expired in March 2024. In October 2021, the Company signed a fourth amendment to the Initial Lease Agreement for additional space in the same building, that commenced in April 2022. All space leased under the Initial Lease Agreement, together with the first amendment, second amendment, and fourth amendment to the Initial Lease Agreement, has a lease term through July 31, 2030, with an option to extend the lease for an additional seven-year term. This lease extension option was not considered in the right-of-use assets or the lease liability as the Company did not consider it reasonably certain the option would be exercised. In December 2024, the Company executed a sixth amendment to the Initial Lease Agreement, which updated the lease termination date for one of the spaces in the same building to July 31, 2025. In connection with the amendment, the Company agreed to pay the landlord a termination fee of $1.1 million, $0.6 million of which was paid in December

2024 and the remaining will be paid by July 2025. As a result of the modification, the Company decreased its right-of-use asset and lease liability each by $2.2 million.

In July 2021, the Company entered into an additional lease agreement for corporate office, manufacturing and laboratory space located in South San Francisco, California with an expiration date approximately twelve years after the lease commencement date (as amended from time to time, the "Additional Lease Agreement"). The lease for this additional space and the Company's obligation to pay rent commenced in January 2022. In addition to base rent, the Company is responsible for payment of direct expenses, which include operating, insurance and tax expenses. The Additional Lease Agreement provided for certain tenant improvement allowances that were fully utilized and reimbursed to the Company, and an additional tenant improvement allowance to be utilized at the option of the Company. In June 2023, the Company entered into an amendment to utilize the additional tenant improvement allowance of $4.4 million and under this amendment the Company is required to repay the tenant improvement costs in equal monthly payments at an annual rate of 8.5% over the remainder of the lease term starting in July 2023.

The Company tests long-lived assets for recoverability whenever events or changes in circumstances suggest that the carrying value of an asset or group of assets may not be recoverable. Beginning in the second quarter of 2023, the Company started to market for sublease portions of the Company's leased corporate office space in South San Francisco. As a result of these plans, the Company reviewed these spaces for impairment. As part of the impairment evaluation of the spaces being marketed for sublease, the Company compared the estimated undiscounted income for the marketed sublease spaces to the net book value of the related long-term assets, which include ROU assets and certain property, plant and equipment, primarily for leasehold improvements (collectively, "Sublease Asset Group"). The Company estimated potential sublease income using unobservable market participant assumptions, which the Company evaluated based on current real estate trends and market conditions. For the Sublease Asset Group, the Company determined that the respective ROU assets had net carrying values that exceeded their estimated undiscounted future cash flows. Accordingly, the Company then estimated the fair value of the Sublease Asset Group based on its discounted cash flows using the estimated borrowing rate of a market participant subtenant which we estimated to be 8%. The carrying value of the Sublease Asset Group exceeded its fair values and, as a result, the Company recorded an ROU asset impairment of $4.1 million for the year ended December 31, 2023. The impairment is recorded within general and administrative expenses in the statements of operations and comprehensive loss. No additional impairment has been recorded.

In September 2024 and November 2024, the Company entered into agreements to sublease a portion of the Company's leased corporate office space through November 2027 and July 2030, respectively. The sublease agreements both commenced during the fourth quarter of 2024 and rent payments will commence in 2025. The Company accounts for the sublease agreements in accordance with ASC 842, Leases. Sublease income during the year ended December 31, 2024, was not material.