Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 17,802	$ 9,388
Marketable securities	114,159	83,181
Income tax receivable	473	731
Other receivables	116	123
Prepaid expenses	5,615	1,635
Restricted cash, current	361
Total current assets	138,526	95,058
Property and equipment, net	959	1,177
Restricted cash	408	769
Total assets	139,893	97,004
Current liabilities:
Accounts payable and accrued expenses	12,553	8,506
Current portion of deferred revenue	22,270
Total current liabilities	34,823	8,506
Deferred revenue, non-current	30,299
Deferred lease obligation	1,695	1,718
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at June 30, 2018 and December 31, 2017, zero shares issued and outstanding at June 30, 2018 and December 31, 2017
Common stock; $0.001 par value; 100,000,000 shares authorized at June 30, 2018 and December 31, 2017, 34,059,214 shares and 32,662,255 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	34	33
Additional paid-in capital	327,401	307,158
Accumulated deficit	(254,302)	(220,341)
Accumulated other comprehensive loss	(57)	(70)
Total stockholders’ equity	73,076	86,780
Total liabilities and stockholders’ equity	$ 139,893	$ 97,004