Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 54,001	$ 60,033
Accounts receivable, net of allowance for doubtful accounts of $10 and $5, respectively	58	28
Inventory	506	597
Prepaid expenses and other current assets	885	1,202
Total current assets	55,450	61,860
Property and equipment, net of accumulated depreciation of $819 and $735, respectively	1,696	1,701
Intangible assets, net of accumulated amortization of $1,240 and $1,102, respectively	5,100	5,238
Other assets	143	215
Total assets	62,389	69,014
Current liabilities:
Accounts payable	903	2,958
Accrued expenses	1,371	487
Deferred revenue	149	148
Total current liabilities	2,423	3,593
Warrant liability	18,266	15,216
Other long term liabilities	586	539
Total liabilities	21,275	19,348
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares outstanding
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	142,150	136,694
Accumulated deficit	(101,077)	(87,068)
Total stockholders' equity	41,114	49,666
Total liabilities and stockholders' equity	$ 62,389	$ 69,014