Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 70,718	$ 56,718
Short-term investment securities	27,024	27,999
Interest receivable	80	108
Prepaid research and development	11,389	8,056
Other current assets	526	437
Total current assets	109,737	93,318
Restricted cash	1,239	587
Leasehold interest, net	2,331	2,429
Equipment, net	268	248
Goodwill	799	799
Total assets	114,374	97,381
Current liabilities:
Accounts payable and accrued expenses	37,917	25,877
Accrued compensation	2,082	1,800
Current portion of deferred revenue	152	152
Notes payable	91	128
Total current liabilities	40,242	27,957
Deferred rent	1,436	1,364
Deferred revenue, net of current portion	952	1,067
Total liabilities	42,630	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 September 30, 2018 and December 31, 2017)	0	0
Common stock, $0.001 par value per share (150,000,000 shares authorized, 82,973,332 and 73,181,750 shares issued; 82,932,023 and 73,140,441 shares outstanding at September 30, 2018 and December 31, 2017, respectively)	83	73
Additional paid-in capital	546,380	422,017
Treasury stock, at cost, 41,309 shares at September 30, 2018 and December 31, 2017	(234)	(234)
Accumulated deficit	(474,485)	(354,863)
Total stockholders' equity	71,744	66,993
Total liabilities and stockholders' equity	$ 114,374	$ 97,381