BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 61,729	$ 70,946
Receivables	1,864	19
Prepaid expenses and other current assets	20,692	19,818
Total current assets	84,285	90,783
Property and equipment, net	1,097	1,211
Deposits	128	128
Other non-current assets	9,541	13,484
Total assets	95,051	105,606
Current liabilities:
Accounts payable	707	4,417
Accrued expenses	8,763	9,909
Deferred revenue - current portion		6,389
Deferred rent - current portion	13	141
Total current liabilities	9,483	20,856
Deferred revenue, net of current portion		35,139
Deferred rent, net of current portion	4	1
Derivative liabilities		2,424
Total liabilities	9,487	58,420
Commitments and contingencies (Note 8)
Preferred stock, $0.001 par value, 30,000,000 shares authorized
Stockholders' deficit:
Common stock, $0.001 par value; 250,000,000 shares authorized; 161,066,136 and 142,658,037 shares issued and outstanding at December 31, 2018 and 2017, respectively	161	143
Additional paid-in capital	651,732	615,493
Accumulated deficit	(566,329)	(712,442)
Total stockholders' equity (deficit)	85,564	(96,806)
Total liabilities and stockholders' equity (deficit)	$ 95,051	105,606
Series 1 Preferred Stock
Current liabilities:
Series 1 preferred stock, $1,200 stated value; 250,000 designated; 0 and 119,644 shares issued and outstanding at December 31, 2018 and 2017 respectively; liquidation value of $0 million and $143.6 at December 31, 2018 and 2017, respectively		$ 143,992