Commitments and Contingencies Operating Leases The Company has a non-cancellable operating lease for its laboratory and office space located in Watertown, Massachusetts. As part of the lease agreement, the landlord provided the Company a tenant improvement allowance of up to $0.7 million , which the Company fully utilized during 2012. The tenant improvement allowance is accounted for as a lease incentive obligation and is being amortized as a reduction to rent expense over the lease term. The leasehold improvements are capitalized as a component of property and equipment. In connection with the lease, the Company secured a letter of credit for $0.3 million which renews automatically each year and is classified in restricted cash and other deposits in the accompanying consolidated balance sheets. In August 2016, the Company signed an amendment to the operating lease, which extends the lease term of the Company's laboratory and office space through March 31, 2020. The lease agreement includes a rent escalation clause, and accordingly, rent expense is being recognized on a straight-line basis over the lease term. Deferred rent and lease incentive liability totaled $0.3 million and $0.3 million as of June 30, 2017 and December 31, 2016 , respectively. Included in that amount, the current portion of deferred rent and lease incentive liability is classified as accrued expenses and was less than $0.1 million at June 30, 2017 and December 31, 2016 , respectively. The Company has a month-to-month facility agreement for its Moscow, Russia facility. Rent expense is recognized as incurred. Rent expense, net of sublease payments, for the three months ended June 30, 2017 and 2016 was $0.4 million and $0.3 million , respectively. For the six months ended June 30, 2017 and 2016, the rent expense, net of sublease payments was 0.9 million and $0.7 million , respectively. As of December 31, 2016, the future minimum lease payments under the lease agreement, as amended by the lease amendments are as follows (in thousands): Year ended