Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash	$ 38,687	$ 15,662
Prepaid expenses and other current assets	2,609	1,832
Total current assets	41,296	17,494
Operating lease right-of-use asset	74	0
Total assets	41,370	17,494
Current liabilities
Accounts payable	1,628	1,887
Accrued expenses	1,725	1,924
License payables	6,200	125
Convertible debt	2,296	2,431
Warrant liabilities, at fair value	1,440	1,062
Operating lease liability	49	0
Total current liabilities	13,338	7,429
License payables - long-term	0	200
Operating lease liability, long-term	25	0
Note payable	147	147
Convertible debt, long-term	3,100	7,146
Total liabilities	16,610	14,922
Commitments and contingencies (note 10)
Stockholders' equity (deficit)
Preferred stock, $.001 par value, 10,000,000 shares authorized, no shares issued or outstanding as of March 31, 20201and December 31, 2020	0	0
Common stock, $.001 par value, 120,000,000 shares authorized, 78,283,021 and 54,535,891 issued and outstanding as of March 31, 2021 and December 31, 2020, respectively	78	54
Additional paid-in-capital	118,960	77,680
Accumulated deficit	(94,278)	(75,162)
Total stockholders' equity (deficit)	24,760	2,572
Total liabilities and stockholders' equity (deficit)	$ 41,370	$ 17,494