As of December 31, 2019, 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 January 2020, we expanded our space in San Diego, with the addition of 21,180 square feet of office space. The lease of the additional space began on January 1, 2020 and expires on December 31, 2025. We have one 5-year option to renew this lease on expiration.

We leased 26,067 square feet of laboratory, office and warehouse space in Redwood City, California. The lease for the Redwood City space expired on May 31, 2019. On March 15, 2018, we entered into a sublease agreement for the Redwood City property. The sublease agreement expired on May 31, 2019. We also leased 1,898 square feet of office space in Jersey City, New Jersey. The lease for the Jersey City office space expired on December 31, 2019. We believe our facilities are adequate and suitable for our current needs and that we will be able to obtain new or additional leased space in the future when necessary.

On January 1, 2019, on the adoption of Topic 842, we recognized initial ROU lease assets of $13.7 million and initial lease liabilities of $14.5 million. Our weighted-average remaining lease term for our operating leases was 6 years. The option to extend our lease in San Diego was not recognized as part of our lease liability and ROU lease assets. During the year ended December 31, 2019, we recognized $3.0 million of operating lease expense and paid $3.4 million for our operating leases.

Annual future minimum lease payments as of December 31, 2019 are as follows (in thousands):

Year ended December 31:
2020	$	2,724
2021		2,804
2022		2,885
2023		2,969
2024		3,030
Thereafter		3,097
Total future minimum lease payments		17,509
Less: discount		(3,341	)
Total lease liabilities	$	14,168

On January 1, 2020, we recognized an initial ROU lease asset of $5.1 million, an unamortized lease incentive of $0.6 million and a lease liability of $5.7 million related to the additional space leased in San Diego, California. We have agreed to pay a basic annual rent for the additional office space that increases incrementally over the term of the lease from $0.9 million for the first 12 months of the lease (inclusive of certain rent abatements) to $1.3 million for the last 12 months of the lease, and such other amounts as set forth in the lease.

Rent expense under all operating leases totaled $3.1 million, $3.2 million and $3.1 million for the years ended December 31, 2019, 2018 and 2017, respectively.

We enter into agreements with clinical sites and clinical research organizations for the conduct of our clinical trials. We make payments to these sites and organizations based in part on the number of eligible patients enrolled and the length of their participation in the clinical trials. 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 and contract research organization 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.