CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash	$ 466
Restricted cash	50	$ 50
Grant receivable	22	77
Prepaid expenses and other current assets	388	524
Total current assets	926	1,677
Property, plant and equipment, net	174	217
Right-of-use assets	156	182
Total assets	1,256	2,076
Current liabilities:
Accounts payable	81	31
Accrued and other current liabilities	220	317
Current portion of notes payable	346	284
Warrant liability	14	17
Current portion of operating lease liability	110	107
Total current liabilities	771	756
Notes payable, net of current portion	58	120
Operating lease liability, net of current portion	46	75
Total liabilities	875	951
Commitments and contingencies (Note)
Stockholders' equity:
Preferred stock, $0.01 par value; 2,000,000 shares authorized as of March 31, 2021 and December 31, 2020, 0 issued and outstanding	0	0
Common stock, par value $0.01 per share, 60,000,000 shares authorized as of March 31, 2021 and December 31, 2020; 9,388,407 issued and outstanding at March 31, 2021 and December 31, 2020	94	94
Additional paid-in capital	70,121	69,991
Accumulated deficit	(69,834)	(68,960)
Total stockholders' equity	381	1,125
Total liabilities and stockholders' equity	$ 1,256	$ 2,076