CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 11,908	$ 14,572
Short-term investments	19,770	29,201
Accounts receivable	336	839
Due from related parties		75
Unbilled receivables	819	372
Inventory	3,196	3,204
Prepaid expenses and other current assets	884	692
Total current assets	36,913	48,955
Restricted cash	619	594
Property and equipment, net	1,087	1,358
Long-term investments		2,508
Other assets	95	95
Total assets	38,714	53,510
Current Liabilities:
Accounts payable	102	1,233
Accrued expenses	3,211	3,519
Current portion of deferred rent	138	165
Short-term deferred revenue	529	1,067
Total current liabilities	3,980	5,984
Deferred rent, net of current portion		55
Other long-term liabilities	137	131
Total liabilities	4,117	6,170
Commitments and contingencies (Note 10)
Stockholders' Equity:
Preferred stock ($0.01 par value per share); 5,000,000 shares authorized; no shares issued or outstanding
Common stock ($0.01 par value per share); 100,000,000 shares authorized at June 30, 2013 and December 31, 2012, 34,451,328 and 34,306,570 shares issued and outstanding at June 30, 2013 and December 31, 2012, respectively	345	343
Additional paid-in capital	290,971	289,050
Accumulated other comprehensive loss	(59)	(21)
Accumulated deficit	(256,660)	(242,032)
Total stockholders' equity	34,597	47,340
Total liabilities and stockholders' equity	$ 38,714	$ 53,510