Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 19,986	$ 36,392
Available-for-sale investments	27,444	4,925
Prepaid expenses and other current assets	554	1,438
Total current assets	47,984	42,755
Property and equipment, net	280	372
Other non-current assets	300	393
Total assets	48,564	43,520
Current liabilities:
Accounts payable	226	556
Accrued expenses	8,868	4,523
Total current liabilities	9,094	5,079
Total liabilities	9,094	5,079
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred Stock	0	0
Common stock, $0.001 par value, 100,000,000 shares authorized at September 30, 2017 and December 31, 2016; 17,619,418 and 16,603,559 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	18	17
Additional paid-in capital	202,113	198,201
Accumulated deficit	(184,190)	(159,777)
Accumulated other comprehensive loss	(7)
Total stockholders’ equity	39,470	38,441
Total liabilities and stockholders’ equity	48,564	43,520
Series A Convertible Preferred Stock [Member]
Stockholders’ equity:
Preferred Stock	$ 21,536