Condensed Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 18,305	$ 15,081
Marketable securities	136,701	146,302
Income tax receivable	816	664
Other receivables	971	926
Prepaid expenses	8,863	4,805
Restricted cash, current		361
Total current assets	165,656	168,139
Operating lease right-of-use asset	3,036
Marketable securities, non-current	63,159	21,396
Property and equipment, net	700	880
Restricted cash	408	408
Total assets	232,959	190,823
Current liabilities:
Accounts payable and accrued expenses	19,665	13,622
Operating lease liability, current	967
Current portion of deferred revenue	22,262	26,825
Total current liabilities	42,894	40,447
Operating lease liability, non-current	3,352
Deferred revenue, non-current		15,184
Deferred lease obligation		1,562
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at December 31, 2019 and December 31, 2018, zero shares issued and outstanding at December 31, 2019 and December 31, 2018
Common stock; $0.001 par value; 100,000,000 shares authorized at December 31, 2019 and December 31, 2018, 46,720,225 shares and 39,547,558 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	47	39
Additional paid-in capital	587,223	428,059
Accumulated deficit	(400,727)	(294,354)
Accumulated other comprehensive income (loss)	170	(114)
Total stockholders’ equity	186,713	133,630
Total liabilities and stockholders’ equity	$ 232,959	$ 190,823