Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 189,863	$ 205,912
Accounts receivable	3,844	4,151
Prepaid expenses and other current assets	7,042	3,705
Total current assets	200,749	213,768
Property and equipment, net	948	943
Restricted cash	199	199
Other assets		7
Total assets	201,896	214,917
Current liabilities:
Accounts payable	1,490	2,857
Accrued expenses	7,372	6,931
Deferred revenue	1,378	909
Total current liabilities	10,240	10,697
Deferred rent, net of current portion	$ 151	$ 165
Commitments and contingencies
Stockholders’ equity:
Preferred stock, par value $0.001 per share; 5,000 shares authorized; no shares issued and outstanding
Common stock, par value $0.001 per share; 125,000 shares authorized; 36,599 and 36,585 shares issued and outstanding at March 31, 2016 and December 31, 2015, respectively	$ 37	$ 37
Additional paid-in capital	477,861	473,670
Accumulated deficit	(286,393)	(269,652)
Total stockholders’ equity	191,505	204,055
Total liabilities and stockholders’ equity	$ 201,896	$ 214,917