8. Commitments and Contingencies Facility Leases In March 2014, the Company entered into an operating facility lease agreement to lease approximately 12,900 square feet in Menlo Park, California for its headquarters building for a period of thirty-nine months. The term of this lease ended in August 2017. In December 2015, the Company entered into an operating sublease agreement to lease approximately 10,900 square feet of additional office space in Menlo Park for a period of twenty-four months. The term of this lease ended in December 2017. In March 2017, the Company entered into an operating facility lease agreement for approximately 34,500 rentable square feet located at 1020 Marsh Road, Menlo Park, California. The lease commenced in August 2017 for a period of 86 months with one renewal option for a five-year term. The total obligation under this lease is approximately $19.4 million as of December 31, 2017. The Company is considered the "accounting owner" of the 1020 Space as a build-to-suit lease asset and has recorded a build-to-suit lease obligation on its consolidated balance sheet. Additional information regarding the build-to-suit lease is included in Note 7. "Build-To-Suit Lease." Rent expense was $1,510,000, $1,290,000, and $763,000, for the years ended December 31, 2017, 2016, and 2015, respectively. Future minimum payments under the Companys build-to-suit lease obligation as of December 31, 2017, are as follows (in thousands): Year Ended December 31, 2017 2018 $ 2,660 2019 2,732 2020 2,806 2021 2,882 2022 2,961 Thereafter 5,369 $ 19,410 Boehringer Ingelheim Commercial Supply Agreement In December 2016, through the Companys subsidiary, Versartis GmbH, entered into a Commercial Supply Agreement with Boehringer Ingelheim Biopharmaceuticals GmbH (BI), pursuant to which the Company engaged BI as a contract manufacturer to manufacture the bulk drug substance for our proprietary long-acting human growth hormone, somavaratan, fill it into the final container and closure and supply such drug product to us