Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 16,763,000	$ 19,371,000
Available-for-sale investments		2,496,000
Prepaid expenses and other current assets	1,035,000	1,369,000
Operating lease right-of-use asset	135,000
Total current assets	17,933,000	23,236,000
Property and equipment, net	105,000	263,000
Restricted cash	22,000	22,000
Total assets	18,060,000	23,521,000
Current liabilities:
Accounts payable	1,676,000	441,000
Accrued expenses	1,559,000	2,637,000
Operating lease liability	135,000
Total current liabilities	3,370,000	3,078,000
Total liabilities	3,370,000	3,078,000
Commitments and contingencies (Note 5)
Stockholders’ equity:
Common stock, $0.001 par value, 100,000,000 shares authorized at March 31, 2019 and December 31, 2018; 19,585,394 and 19,243,651 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	19,000	19,000
Additional paid-in capital	210,486,000	209,366,000
Accumulated deficit	(217,001,000)	(210,470,000)
Accumulated other comprehensive income	3,000	5,000
Total stockholders’ equity	14,690,000	20,443,000
Total liabilities and stockholders’ equity	18,060,000	23,521,000
Series A Convertible Preferred Stock [Member]
Stockholders’ equity:
Series A convertible preferred stock 22,000 shares authorized at March 31, 2019 and December 31, 2018 authorized; 21,660 and 22,000 issued and outstanding at March 31, 2019 and at December 31, 2018 , respectively	$ 21,183,000	$ 21,523,000