Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 18,385	$ 36,392
Available-for-sale investments	13,357	4,925
Prepaid expenses and other current assets	1,280	1,438
Total current assets	33,022	42,755
Property and equipment, net	309	372
Other non-current assets	300	393
Total assets	33,631	43,520
Current liabilities:
Accounts payable	1,193	556
Accrued expenses	2,944	4,523
Total current liabilities	4,137	5,079
Total liabilities	4,137	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 June 30, 2017 and December 31, 2016	0	0
Common stock, $0.001 par value, 100,000,000 shares authorized at June 30, 2017 and December 31, 2016; 17,619,418 and 16,603,559 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	18	17
Additional paid-in capital	201,366	198,201
Accumulated deficit	(171,883)	(159,777)
Accumulated other comprehensive loss	(7)
Total stockholders’ equity	29,494	38,441
Total liabilities and stockholders’ equity	$ 33,631	$ 43,520