Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 20,079	$ 93,441
Marketable securities	51,199
Restricted cash	584	102
Accounts receivable, net		100
Prepaid expenses and other current assets	4,240	1,403
Total current assets	76,102	95,046
Restricted cash		674
Property and equipment, net	2,269	6,467
Equity method investment	7,428	10,551
Other assets	2,744	4,588
Total assets	88,543	117,326
Current liabilities:
Accounts payable, accrued expenses and other	13,677	17,606
Deferred rent	1,118	2,171
Total current liabilities	14,795	19,777
Deferred rent, net of current portion		1,209
Note payable, net of discount	14,873
Other long-term liabilities	56	56
Total liabilities	29,724	21,042
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock, $0.01 par value: 10,000 shares authorized at December 31, 2018 and 2017; no shares issued or outstanding at December 31, 2018 or 2017
Common stock, $0.01 par value: 30,000 and 20,000 shares authorized at December 31, 2018 and 2017, respectively; 13,343 issued and outstanding at December 31, 2018 and 2017	1,334	1,334
Additional paid-in capital	580,771	577,721
Accumulated other comprehensive loss	(9)
Accumulated deficit	(523,277)	(482,771)
Total stockholders’ equity	58,819	96,284
Total liabilities and stockholders’ equity	$ 88,543	$ 117,326