Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 37,495	$ 60,033
Accounts receivable, net of allowance for doubtful accounts of $17 and $5, respectively	4	28
Inventory	571	597
Prepaid expenses and other current assets	1,278	1,202
Total current assets	39,348	61,860
Property and equipment, net	1,598	1,701
Intangible assets, net of accumulated amortization of $1,653 and $1,102, respectively	4,687	5,238
Other assets	1	215
Total assets	45,634	69,014
Current liabilities:
Accounts payable	1,124	2,958
Accrued expenses	1,675	487
Deferred revenue	416	148
Warrant liability, current	278	0
Total current liabilities	3,493	3,593
Warrant liability, long term	11,008	15,216
Other long term liabilities	724	539
Total liabilities	15,225	19,348
Commitments
Stockholders' equity:
Common stock, $0.001 par value; 100,000,000 shares authorized; 40,856,815 and 39,832,225 shares issued and outstanding, respectively	41	40
Additional paid-in capital	143,086	136,694
Accumulated deficit	(112,718)	(87,068)
Total stockholders’ equity	30,409	49,666
Total liabilities and stockholders’ equity	$ 45,634	$ 69,014