CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 94,046	$ 112,629
Prepaid expenses and other current assets	3,923	3,992
Total current assets	97,969	116,621
Property and equipment, net	1,225	1,472
Restricted cash and other assets	320	324
Total assets	99,514	118,417
Current liabilities:
Accounts payable	1,118	1,334
Accrued expenses	12,721	8,000
Note payable		209
Deferred revenue	235	566
Total current liabilities	14,074	10,109
Other liabilities	374	613
Total liabilities	14,448	10,722
Commitments and contingencies
Stockholders' equity:
Common stock, $0.001 par value, Authorized — 70,000 shares; Issued and outstanding — 27,171 and 24,453 shares at June 30, 2018 and December 31, 2017, respectively	27	24
Additional paid-in capital	725,659	712,165
Accumulated deficit	(640,620)	(604,494)
Total stockholders' equity	85,066	107,695
Total liabilities and stockholders' equity	99,514	118,417
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