6. Commitments and Contingencies

Operating Leases

Corporate Headquarters Facility Lease

In May 2022, we entered into a lease (the Lease) with San Diego Creekside, LLC (Landlord), as lessor, pursuant to which we agreed to lease from Landlord approximately 23,696 rentable square feet (subject to increase pursuant to the terms of the Lease) of office and laboratory space. The term of the lease (the Lease Term) commenced on March 20, 2023 (the Lease Commencement Date) and will continue for 124 months from the Lease Commencement Date. We also have one option to extend the Lease Term for five years. Base rent during such extension period would be at the fair market rent for the Premises (as that term is defined in the Lease). Under the terms of the Lease, the base rent during the first 12 months of the Lease Term will be $5.75 per square foot of rentable area per month, subject to certain upward adjustments of approximately 3.0% annually. We are entitled to an allowance of up to $5.3 million for tenant improvements of which as of December 31, 2023 we had received $5.0 million, and we received the remaining $0.3 million in February 2024. We provided a $0.7 million security deposit in the form of a letter of credit which is included in restricted cash as of December 31, 2023. During the second quarter of 2023, additional common area amenities were completed by the Landlord which provided us with access to approximately 1,500 additional rentable square feet. As a result, our base rent increased for this additional rentable square feet at the same monthly base rent per rentable square foot as contemplated in the Lease.

Previous Corporate Headquarters Facility Lease

Our operating lease for our previous corporate headquarters was subject to base lease payments, additional charges for common area maintenance and other costs and it expired in May 2023.

Operating lease expense was $1.9 million, $1.5 million and $1.0 million for the years ended December 31, 2023, 2022 and 2021, respectively. As of December 31, 2023 and 2022, the weighted average remaining lease term was 9.4 years and 9.9 years, respectively. As of December 31, 2023 and 2022, the weighted average discount rate for each period was 8.8%.

Financing Leases

In April 2022, we entered into a master financing lease agreement to lease various research and development and information technology equipment over a 48-month term. Future minimum payments under the financing lease and reconciliation to the financing lease liability as of December 31, 2023 were as follows (in thousands):

As of December 31, 2023 and 2022, the weighted-average remaining lease term was 3.0 years and 3.7 years, respectively and the weighted-average discount rate was 8.3% and 7.9%, respectively. We provided a $2.7 million deposit to be held as collateral for the leased equipment, and this deposit is included in restricted cash as of December 31, 2023.