Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 14,188	$ 15,081
Marketable securities	120,265	146,302
Income tax receivable	749	664
Other receivables	1,019	926
Prepaid expenses	7,577	4,805
Restricted cash, current	361	361
Total current assets	144,159	168,139
Operating lease right-of-use asset	3,492
Marketable securities, non-current	21,687	21,396
Property and equipment, net	841	880
Restricted cash	408	408
Total assets	170,587	190,823
Current liabilities:
Accounts payable and accrued expenses	13,310	13,622
Operating lease liability, current	901
Current portion of deferred revenue	28,194	26,825
Total current liabilities	42,405	40,447
Operating lease liability, non-current	4,087
Deferred revenue, non-current	9,573	15,184
Deferred lease obligation		1,562
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at March 31, 2019 and December 31, 2018, zero shares issued and outstanding at March 31, 2019 and December 31, 2018
Common stock; $0.001 par value; 100,000,000 shares authorized at March 31, 2019 and December 31, 2018, 39,575,044 shares and 39,547,558 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	39	39
Additional paid-in capital	430,724	428,059
Accumulated deficit	(316,314)	(294,354)
Accumulated other comprehensive income (loss)	73	(114)
Total stockholders’ equity	114,522	133,630
Total liabilities and stockholders’ equity	$ 170,587	$ 190,823