5. Commitments and Contingencies Leases We lease 28,275 square feet of laboratory and office space in San Diego, California under a lease which began on December 1, 2016 and expires on April 15, 2024. We have one 5 -year option to renew this lease. We also lease 26,067 square feet of laboratory, office and warehouse space in Redwood City, California and 1,898 square feet of office space in Jersey City, New Jersey. The lease for the Redwood City space expires on May 31, 2019. The lease for the Jersey City office space expires on June 30, 2018. 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. We also lease certain office equipment under operating lease arrangements. Annual future minimum lease payments as of December 31, 2017 are as follows (in thousands): Year ended December 31: 2018 $ 2,418 2019 1,906 2020 1,503 2021 1,546 2022 1,590 Thereafter 2,124 Total future minimum lease payments $ 11,087 Rent expense under all operating leases totaled $3.1 million, $2.1 million and $1.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. Clinical Development Agreements We have entered into agreements with various vendors for the research and development of product candidates, which are generally cancellable anytime at our option. Under the terms of these agreements, the vendors provide a variety of services including conducting preclinical development, conducting research, manufacturing clinical compounds, enrolling and recruiting patients, monitoring studies, data analysis and regulatory filing assistance. Payments under these agreements typically include fees for services and reimbursement of expenses. In addition, under certain agreements, we are subject to penalties in the event we permanently discontinue performance under these agreements. Purchase Obligations At December 31, 2017, our purchase obligations of $39.7 million primarily consisted of commitments with third -party