Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 22,460	$ 93,441
Marketable securities	37,544
Prepaid expenses and other current assets	1,727	1,605
Total current assets	61,731	95,046
Restricted cash	584	674
Property and equipment, net	4,143	6,467
Equity method investment	9,134	10,551
Other assets	4,634	4,588
Total assets	80,226	117,326
Current liabilities:
Accounts payable, accrued expenses and other	15,569	17,606
Deferred rent	2,325	2,171
Total current liabilities	17,894	19,777
Deferred rent, net of current portion		1,209
Other long-term liabilities	56	56
Total liabilities	17,950	21,042
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value: 10,000 shares authorized at June 30, 2018 and December 31, 2017; no shares issued or outstanding at June 30, 2018 or December 31, 2017
Common stock, $0.01 par value: 30,000 shares authorized at June 30, 2018 and 20,000 shares authorized at December 31, 2017; 13,343 shares issued and outstanding at June 30, 2018 and December 31, 2017	1,334	1,334
Additional paid-in capital	579,265	577,721
Accumulated deficit	(518,322)	(482,771)
Accumulated other comprehensive loss	(1)
Total stockholders’ equity	62,276	96,284
Total liabilities and stockholders’ equity	$ 80,226	$ 117,326