9. 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. 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 December 31, 2016 are summarized as follows (in thousands):

Period Ending December 31,	Amount
2017	$	1,288
2018		680

Total minimum lease payments	$	1,968

Rent expense for the years ended December 31, 2016, 2015 and 2014 was $0.9 million, $0.8 million and $0.7 million, respectively.