Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 57,960	$ 36,088
Investments	38,106	113,895
Prepaid expenses and other current assets	5,471	5,095
Total current assets	101,537	155,078
Property and equipment, net	29,904	32,931
Restricted cash	1,513	1,513
Total assets	132,954	189,522
Current liabilities:
Accounts payable	5,158	7,033
Accrued expenses and other current liabilities	13,651	12,513
Deferred revenue - related party	17,962	12,079
Total current liabilities	36,771	31,625
Lease incentive obligation, net of current portion	8,119	8,989
Deferred Rent	2,231	2,233
Deferred revenue, net of current portion - related party	97,959	84,847
Other long-term liabilities	1,129	1,129
Total liabilities	146,209	128,823
Commitments and contingencies (Note 10)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2018 and December 31, 2017; no shares issued and outstanding at June 30, 2018 and December 31, 2017
Common stock, $0.001 par value; 200,000,000 shares authorized at June 30, 2018 and December 31, 2017; 40,754,681 and 40,571,015 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	40	40
Additional paid-in capital	332,870	324,376
Accumulated other comprehensive loss	(29)	(146)
Accumulated deficit	(346,136)	(263,571)
Total stockholders’ equity/(deficit)	(13,255)	60,699
Total liabilities and stockholders’ equity	$ 132,954	$ 189,522