As of December 31, 2023, we had an operating lease for 52,148 square feet of laboratory and office space in San Diego, California, with a lease term that expires on December 31, 2025. In October 2021, we entered into a sublease agreement to sublet 23,873 square feet of laboratory and office space. The space was delivered to the subtenant in March 2022. As a result of the sublease agreement, our one 5-year option to renew the lease on expiration applies only with respect to our remaining 28,275 square feet of laboratory and office space.

In September 2023, we also entered into a sublease agreement to sublet 5,840 square feet of office space in Cary, North Carolina, with a lease term that expires on April 30, 2025.

Annual future minimum lease payments as of December 31, 2023 are as follows (in thousands):


Year ended December 31:
2024	$	3,153
2025		3,138
2026		—
2027		—
2028		—
Thereafter		—
Total future minimum lease payments		6,291
Less: discount		(416	)
Total lease liabilities	$	5,875

Rent expense under all operating leases totaled $2.9 million and $2.8 million for the years ended December 31, 2023 and 2022, respectively. During the years ended December 31, 2023 and 2022, we paid $3.0 million and $2.9 million, respectively, for our operating leases.

We enter into agreements with clinical sites and clinical research organizations for the conduct of our clinical trials and contract manufacturing organizations for the manufacture and supply of preclinical, clinical and commercial materials and drug product. We make payments to these clinical sites and clinical research organizations based in part on the number of eligible patients enrolled and the length of their participation in the clinical trials. In some of our agreements with contract manufacturing organizations, we are required to meet minimum purchase obligations. Under certain of these agreements, we may be subject to penalties in the event that we prematurely terminate these agreements. At this time, due to the variability associated with clinical site agreements, contract research organization agreements and contract manufacturing agreements, we are unable to estimate with certainty the future costs we will incur. We intend to use our current financial resources to fund our obligations under these commitments.

At December 31, 2023, purchase obligations primarily consisted of non-cancellable commitments with third-party manufacturers in connection with the manufacturing of our commercial products. Total purchase obligations of $60.2 million were not included in our consolidated financial statements for the year ended December 31, 2023, with $39.0 million due in one year and $21.2 million due within two to three years.