Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 34,132	$ 36,392
Available-for-sale investments		4,925
Prepaid expenses and other current assets	1,255	1,438
Total current assets	35,387	42,755
Property and equipment, net	338	372
Other non-current assets	299	393
Total assets	36,024	43,520
Current liabilities:
Accounts payable	474	556
Accrued expenses	2,549	4,523
Total current liabilities	3,023	5,079
Total liabilities	3,023	5,079
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized, no shares issued and outstanding at March 31, 2017 and December 31, 2016	0	0
Common stock, $0.001 par value, 100,000,000 shares authorized at March 31, 2017 and December 31, 2016; 16,771,072 and 16,603,559 shares issued and outstanding at March 31, 2017 and December 31, 2016, respectively	17	17
Additional paid-in capital	199,259	198,201
Accumulated deficit	(166,275)	(159,777)
Total stockholders’ equity	33,001	38,441
Total liabilities and stockholders’ equity	$ 36,024	$ 43,520