Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 34,268	$ 93,441
Marketable securities	41,998
Prepaid expenses and other current assets	844	1,605
Total current assets	77,110	95,046
Restricted cash	674	674
Property and equipment, net	5,358	6,467
Equity method investment	9,805	10,551
Other assets	4,548	4,588
Total assets	97,495	117,326
Current liabilities:
Accounts payable, accrued expenses and other	15,323	17,606
Deferred rent	2,211	2,171
Total current liabilities	17,534	19,777
Deferred rent, net of current portion	651	1,209
Other long-term liabilities	56	56
Total liabilities	18,241	21,042
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value: 10,000 shares authorized at March 31, 2018 and December 31, 2017; no shares issued or outstanding at March 31, 2018 or December 31, 2017
Common stock, $0.01 par value: 20,000 shares authorized at March 31, 2018 and December 31, 2017; 13,343 shares issued and outstanding at March 31, 2018 and December 31, 2017	1,334	1,334
Additional paid-in capital	578,485	577,721
Accumulated deficit	(500,553)	(482,771)
Accumulated other comprehensive loss	(12)
Total stockholders’ equity	79,254	96,284
Total liabilities and stockholders’ equity	$ 97,495	$ 117,326