Condensed Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 5,267	$ 3,217
Accounts and other receivables	2,202	1,865
Prepaid expenses and other current assets	675	1,552
Total current assets	8,144	6,634
Property and equipment, net	1,079	1,471
Operating lease right-of-use assets	1,357	1,537
Restricted cash	186	338
Other long-term assets	438	527
Total assets	11,204	10,507
Liabilities and stockholders' deficit
Accounts payable and accrued expenses	4,347	4,911
Current portion of convertible notes	65,920
Current portion of operating lease liabilities	318	284
Other current liabilities	213	236
Total current liabilities	70,798	5,431
Convertible notes, less current portion, net		77,343
Derivative and warrant liability	184	120
Operating lease liabilities, less current portion	1,673	1,901
Loans payable	781
Other long-term liabilities	95	168
Total liabilities	73,531	84,963
Commitments and contingencies (Note D)
Stockholders’ deficit:
Common stock, $0.0001 par value, 250,000,000 shares authorized, 72,514,304 shares issued and outstanding as of September 30, 2020 (unaudited); 36,350,785 shares issued and outstanding as of December 31, 2019	7	4
Additional paid-in capital	191,284	171,254
Accumulated deficit	(253,618)	(245,714)
Total stockholders' deficit	(62,327)	(74,456)
Total liabilities and stockholders' deficit	11,204	10,507
Series A Convertible Preferred Stock [Member]
Stockholders’ deficit:
Preferred stock
Series B-1 Convertible Preferred Stock [Member]
Stockholders’ deficit:
Preferred stock
Series B-2 Convertible Preferred Stock [Member]
Stockholders’ deficit:
Preferred stock
Undesignated Preferred Stock [Member]
Stockholders’ deficit:
Preferred stock