7. Commitments

In November 2010, the Company entered into a five-year, non-cancelable operating lease for office and laboratory space that provided for a five-year extension upon the completion of the lease term. In December 2011, the Company signed a lease amendment (the “2011 Lease Amendment”) that expanded the leased premises beginning in the second quarter of 2012. The 2011 Lease Amendment also extended the term of the existing lease through June 30, 2017. The 2011 Lease Amendment includes a free rent period for the expansion premises and escalating rent payments. In July 2015, the Company signed another lease amendment (the “2015 Lease Amendment”) that expanded the leased premises beginning in the third quarter of 2015. The 2015 Lease Amendment includes escalating rent payments and is effective through June 30, 2017. In November 2016, the Company signed a third lease amendment (the “2016 Lease Amendment”). The 2016 Lease Amendment includes escalating rent payments and is effective through June 30, 2018. In August 2017, the Company signed a fourth lease amendment (the “2017 Lease Amendment”). The 2017 Lease Amendment includes escalating rent payments and is effective through June 30, 2020. The Company is recognizing rent expense on a straight-line basis over the lease term.

Future minimum payments required under the non-cancelable operating lease as of September 30, 2017 are summarized as follows (in thousands):

Period Ending December 31,	Amount
Remainder 2017	$	340
2018	1,379
2019	1,421
2020	721

Total minimum lease payments	$	3,861

Rent expense for the three months ended September 30, 2017 and 2016 was $0.4 million and $0.2 million, respectively. Rent expense for the nine months ended September 30, 2017 and 2016 was $1.0 million and $0.7 million, respectively.