Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 10,813	$ 19,371
Available-for-sale investments		2,496
Prepaid expenses and other current assets	614	1,369
Operating lease right-of-use asset	68
Total current assets	11,495	23,236
Property and equipment, net	83	263
Restricted cash	22	22
Total assets	11,600	23,521
Current liabilities:
Accounts payable	60	441
Accrued expenses	1,995	2,637
Operating lease liability	68
Total current liabilities	2,123	3,078
Total liabilities	2,123	3,078
Commitments and contingencies (Note 5)
Stockholders’ equity:
Common stock, $0.001 par value, 100,000,000 shares authorized at June 30, 2019 and December 31, 2018; 19,585,394 and 19,243,651 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	19	19
Additional paid-in capital	210,587	209,366
Accumulated deficit	(222,316)	(210,470)
Accumulated other comprehensive income	4	5
Total stockholders’ equity	9,477	20,443
Total liabilities and stockholders’ equity	11,600	23,521
Series A Convertible Preferred Stock [Member]
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized at June 30, 2019 and December 31, 2018: Series A convertible preferred stock 22,000 shares authorized at June 30, 2019 and December 31, 2018 authorized; 21,660 and 22,000 issued and outstanding at June 30, 2019 and at December 31, 2018, respectively	$ 21,183	$ 21,523