Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 55,713	$ 36,088
Investments	17,177	113,895
Prepaid expenses and other current assets	6,556	5,095
Total current assets	79,446	155,078
Property and equipment, net	28,083	32,931
Restricted cash	1,513	1,513
Total assets	109,042	189,522
Current liabilities:
Accounts payable	6,475	7,033
Accrued expenses and other current liabilities	14,634	12,513
Deferred revenue - related party	17,901	12,079
Total current liabilities	39,010	31,625
Lease incentive obligation, net of current portion	7,685	8,989
Deferred rent	2,229	2,233
Deferred revenue, net of current portion - related party	89,554	84,847
Other long-term liabilities	1,129	1,129
Total liabilities	139,607	128,823
Commitments and contingencies (Note 10)
Stockholders’ equity/(deficit):
Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2018 and December 31, 2017; no shares issued and outstanding at September 30, 2018 and December 31, 2017
Common stock, $0.001 par value; 200,000,000 shares authorized at September 30, 2018 and December 31, 2017; 40,844,455 and 40,571,015 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	41	40
Additional paid-in capital	337,486	324,376
Accumulated other comprehensive loss	(9)	(146)
Accumulated deficit	(368,083)	(263,571)
Total stockholders’ equity/(deficit)	(30,565)	60,699
Total liabilities and stockholders’ equity	$ 109,042	$ 189,522