Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 9,784	$ 68,840
Available-for-sale investments	69,741	14,755
Prepaid expenses and other current assets	1,208	1,006
Total current assets	80,733	84,601
Property and equipment, net	80	83
Other non-current assets	114	114
Total assets	80,927	84,798
Current liabilities:
Accounts payable	1,205	917
Accrued expenses	1,429	1,421
Total current liabilities	2,634	2,338
Total liabilities	2,634	2,338
Commitments and contingencies (Note 5)
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized, no shares issued and outstanding at March 31, 2015 and December 31, 2014	0	0
Common stock, $0.001 par value, 100,000,000 shares authorized at March 31, 2015 and December 31, 2014; 16,448,691 and 16,448,455 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	16	16
Additional paid-in capital	192,731	192,324
Accumulated deficit	(114,454)	(109,874)
Accumulated other comprehensive loss		(6)
Total stockholders’ equity	78,293	82,460
Total liabilities and stockholders’ equity	$ 80,927	$ 84,798