Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 26,147	$ 17,287
Prepaid expenses	410	722
Other current assets	142	109
Total current assets	26,699	18,118
Property and equipment, net	371	416
Operating lease right-of-use asset	491	528
Restricted cash	260	260
Total assets	27,821	19,322
Current liabilities:
Accounts payable	2,343	1,997
Accrued liabilities	2,577	1,582
Current portion of long-term debt		991
Current portion of operating lease liabilities	377	373
Deferred revenue	5,000	5,000
Total current liabilities	10,297	9,943
Operating lease liabilities	539	616
Total liabilities	10,836	10,559
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized and no shares issued at March 31, 2021 and December 31, 2020
Common stock, $0.001 par value; 100,000,000 shares authorized at March 31, 2021 and December 31, 2020; 57,578,725 and 51,860,941 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	58	52
Additional paid-in capital	280,145	264,578
Accumulated deficit	(263,218)	(255,867)
Total stockholders’ equity	16,985	8,763
Total liabilities and stockholders’ equity	$ 27,821	$ 19,322