CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 112,629	$ 80,667
Short-term investments		28,347
Prepaid expenses and other current assets	3,992	2,030
Total current assets	116,621	111,044
Property and equipment, net	1,472	1,853
Restricted cash and other assets	324	334
Total assets	118,417	113,231
Current liabilities:
Accounts payable	1,334	556
Accrued expenses	8,000	7,394
Current portion of note payable	209	292
Current portion of deferred revenue	566	1,111
Total current liabilities	10,109	9,353
Deferred revenue, net of current portion		152
Note payable, net of current portion		209
Other liabilities	613	168
Total liabilities	10,722	9,882
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.001 par value, Authorized — 280,000 shares; Issued and outstanding — 195,625 and 149,065 shares at December 31, 2017 and December 31, 2016, respectively	196	149
Additional paid-in capital	711,993	641,687
Accumulated deficit	(604,494)	(538,470)
Accumulated other comprehensive loss		(17)
Total stockholders' equity	107,695	103,349
Total liabilities and stockholders' equity	118,417	113,231
Series A Preferred Stock
Stockholders' equity:
Preferred stock, $0.01 par value, Authorized — 5,000 shares: Series A convertible preferred stock; Designated — 1,500 shares, Issued and outstanding — 1 share