Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 47,906	$ 23,559
Short-term investments	141,968	212,093
Prepaid expenses and other current assets	2,335	19,945
Total current assets	192,209	255,597
Property and equipment, net	13,540	16,151
Long-term investments	5,990	22,199
Other non-current assets	2,713	2,713
Total assets	214,452	296,660
Current liabilities:
Accounts payable	3,272	2,849
Accrued expenses	6,952	8,454
Deferred rent and lease incentive, current	61	61
Deferred revenue, current—related party	55,157	51,142
Other current liabilities	104	45
Total current liabilities	65,546	62,551
Deferred rent and lease incentive, net of current portion	2,062	1,955
Deferred revenue, net of current portion—related party	42,715	65,018
Other non-current liabilities	0	27
Total liabilities	110,323	129,551
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock, $0.001 par value: 5,000 shares authorized at December 31, 2018 and 2017; no shares issued or outstanding at December 31, 2018 or 2017	0	0
Common stock, $0.001 par value: 160,000 shares authorized at December 31, 2018 and 2017; 32,948 and 32,265 shares issued at December 31, 2018 and 2017, respectively; 32,941 and 32,249 shares outstanding at December 31, 2018 and 2017, respectively	33	32
Additional paid-in capital	268,081	257,101
Accumulated other comprehensive loss	(78)	(409)
Accumulated deficit	(163,907)	(89,615)
Total stockholders’ equity	104,129	167,109
Total liabilities and stockholders’ equity	$ 214,452	$ 296,660