BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 42,803	$ 68,204
Receivables	145	145
Prepaid expenses and other current assets	1,139	1,948
Total current assets	44,087	70,297
Property and equipment, net	531	801
Deposits	128	128
Other non current assets	491	528
Total assets	45,237	71,754
Current liabilities:
Accounts payable	2,004	422
Accrued expenses	7,182	6,357
Deferred revenue - current portion	1,360	800
Deferred rent - current portion	280	212
Total current liabilities	10,826	7,791
Deferred revenue		1,933
Deferred rent	570	851
Warrant liabilities		11,776
Other long term liabilities		20
Total liabilities	11,396	22,371
Commitments and contingencies (note 8)
Stockholders' equity:
Common stock, $0.001 par value; 250,000,000 shares authorized; 104,452,105 and 100,159,618 shares issued and outstanding at December 31, 2014 and 2013, respectively	104	100
Additional paid-in capital - common stock	406,349	386,511
Additional paid-in capital - warrants issued		3,603
Accumulated Deficit	(372,612)	(340,831)
Total stockholders' equity	33,841	49,383
Total liabilities and stockholders' equity	$ 45,237	$ 71,754