Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 25,356	$ 21,170
Available-for-sale investments	11,462	20,971
Prepaid expenses and other current assets	1,215	1,339
Total current assets	38,033	43,480
Property and equipment, net	236	259
Other non-current assets	240	240
Total assets	38,509	43,979
Current liabilities:
Accounts payable	7,016	291
Accrued expenses	2,004	8,949
Total current liabilities	9,020	9,240
Total liabilities	9,020	9,240
Commitments and contingencies (Note 4)
Stockholders’ equity:
Preferred Stock	0	0
Common stock, $0.001 par value, 100,000,000 shares authorized at March 31, 2018 and December 31, 2017; 17,674,729 shares issued and outstanding at March 31, 2018 and December 31, 2017	18	18
Additional paid-in capital	203,774	202,953
Accumulated deficit	(195,822)	(189,741)
Accumulated other comprehensive loss	(4)	(14)
Total stockholders’ equity	29,489	34,739
Total liabilities and stockholders’ equity	38,509	43,979
Series A Convertible Preferred Stock [Member]
Stockholders’ equity:
Preferred Stock	$ 21,523	$ 21,523