Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 105,672	$ 56,718
Short-term investment securities	20,573	27,999
Interest receivable	87	108
Prepaid research and development	8,890	8,056
Other current assets	816	437
Total current assets	136,038	93,318
Restricted cash	1,237	587
Leasehold interest, net	2,376	2,429
Equipment, net	265	248
Goodwill	799	799
Total assets	140,715	97,381
Current liabilities:
Accounts payable and accrued expenses	35,394	25,877
Accrued compensation	1,182	1,800
Current portion of deferred revenue	152	152
Notes payable	210	128
Total current liabilities	36,938	27,957
Deferred rent	1,411	1,364
Deferred revenue, net of current portion	990	1,067
Total liabilities	39,339	30,388
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value per share (10,000,000 shares authorized, none issued and outstanding as of June 30, 2018 and December 31, 2017)	0	0
Common stock, $0.001 par value per share (150,000,000 shares authorized, 82,539,417 and 73,181,750 shares issued, 82,498,108 and 73,140,441 shares outstanding at June 30, 2018 and December 31, 2017, respectively)	82	73
Additional paid-in capital	542,062	422,017
Treasury stock, at cost, 41,309 shares at June 30, 2018 and December 31, 2017	(234)	(234)
Accumulated deficit	(440,534)	(354,863)
Total stockholders’ equity	101,376	66,993
Total liabilities and stockholders’ equity	$ 140,715	$ 97,381