BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 70,946	$ 81,053
Receivables	19	21
Prepaid expenses and other current assets	19,818	23,810
Total current assets	90,783	104,884
Property and equipment, net	1,211	843
Deposits	128	128
Other non-current assets	13,484	493
Total assets	105,606	106,348
Current liabilities:
Accounts payable	4,417	156
Accrued expenses	9,909	9,109
Deferred revenue - current portion	6,389	6,389
Deferred rent - current portion	141	155
Total current liabilities	20,856	15,809
Deferred revenue, net of current portion	35,139	41,528
Deferred rent, net of current portion	1	126
Derivative liabilities	2,424	862
Total liabilities	58,420	58,325
Commitments and contingencies (Note 7)
Preferred stock, $0.001 par value, 30,000,000 shares authorized
Stockholders' deficit:
Common stock, $0.001 par value; 250,000,000 shares authorized; 142,658,037 and 132,376,670 shares issued and outstanding at December 31, 2017 and 2016, respectively	143	132
Additional paid-in capital - common stock	615,493	580,567
Accumulated deficit	(712,442)	(657,997)
Total stockholders' deficit	(96,806)	(77,298)
Total liabilities and stockholders' deficit	105,606	106,348
Series 1 Preferred Stock
Current liabilities:
Series 1 preferred stock, $1,200 stated value; 250,000 designated; 119,644 and 106,184 shares issued and outstanding at December 31, 2017 and respectively; liquidation value of $143.6 million and $127.4 million at December 31, 2017 and 2016, respectively	$ 143,992	$ 125,321