12. Commitments and Contingencies The Company leases office space in Waltham, Massachusetts under a non-cancelable operating lease agreement. In April 2015, the Company amended its lease to add an additional 17,700 square feet to its existing leased office space of 53,200 square feet, increasing the total to approximately 70,900 square feet. The term of the lease commenced April 1, 2013 and continues through June 30, 2017. The lease agreement provides for one month of free rent with respect to a portion of the leased premises and a tenant improvement allowance of $0.1 million. The Company recognizes rental expense on a straight-line basis over the respective lease term including any free rent periods and tenant allowances. The following table presents future minimum rental commitments, by fiscal year and in the aggregate, as of December 31, 2015 (in thousands): Operating Leases 2016 $ 2,345 2017 1,151 Thereafter  Total minimum lease payments $ 3,496 The Company recorded $647,000 , $1,525,000 and $2,091,000 in rent expense for the years ended December 31, 2013, 2014 and 2015, respectively. The Company has entered into agreements with certain vendors for the provision of services, including services related to data management clinical operation support services, that the Company is not contractually able to terminate for convenience and avoid any and all future obligations to the vendors. Under such agreements, the Company is contractually obligated to make certain minimum payments to the vendors, with the exact amounts in the event of termination to be based on the timing of the termination and the exact terms of the agreement. Litigation The Company may periodically become subject to legal proceedings and claims arising in connection with ongoing business activities, including claims or disputes related to patents that have been issued or that are pending in the field of research on which the Company is focused. The Company is not a party to any litigation and does not have contingency reserves established for a