Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 8,053	$ 13,345
Marketable securities	87,429	94,776
Prepaid expenses and other current assets	1,067	593
Total current assets	96,549	108,714
Property and Equipment, at cost:
Laboratory equipment	4,324	4,051
Office and computer equipment	855	824
Leasehold improvements	283	283
Furniture and fixtures	28	28
Property and Equipment, gross	5,490	5,186
Less-Accumulated depreciation	(2,048)	(1,781)
Property and Equipment, net	3,442	3,405
TOTAL ASSETS	99,991	112,119
Current Liabilities:
Accounts payable	2,081	3,652
Accrued expenses	3,345	3,327
Capital lease obligation, current portion	337	333
Deferred license fees, current portion	3,402	4,143
Total current liabilities	9,165	11,455
Long-term debt	1,000	1,000
Long-term accrued interest	68	63
Capital lease obligation, less current portion	625	711
Deferred license fees, less current portion		295
Commitments and contingencies
Stockholders' Equity:
Preferred stock, $0.01 par value Authorized-5,000,000 shares Issued and outstanding-no shares at March 31, 2013 and December 31, 2012
Common stock, $0.01 par value Authorized-100,000,000 shares Issued and outstanding-64,093,730 and 63,909,800 shares at March 31, 2013 and December 31, 2012	641	639
Additional paid-in capital	373,520	372,123
Other comprehensive income	71	78
Accumulated deficit	(285,099)	(274,245)
Total stockholders' equity	89,133	98,595
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 99,991	$ 112,119