CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 5,329	$ 3,423
Short-term investments	10,661	6,279
Accounts receivable	164	86
Unbilled receivables	34	27
Prepaid expenses and other current assets	436	527
Total current assets	16,624	10,342
Restricted cash	264	264
Property and equipment, net	890	921
Right-of-use assets	2,354	2,712
Other assets	283	283
Total assets	20,415	14,522
Current Liabilities:
Accounts payable	83	60
Accrued expenses	1,136	1,297
Lease liabilities	514	457
Total current liabilities	1,733	1,814
Lease liabilities, net of current portion	2,649	3,163
Other liabilities	7	13
Total liabilities	4,389	4,990
Commitments and contingencies (Note 7)
Stockholders' Equity:
Preferred stock ($0.01 par value per share); 5,000,000 shares authorized; no shares issued or outstanding	0	0
Common stock ($0.01 par value per share); 60,000,000 shares authorized at December 31, 2021 and 2020, and 4,881,851 and 3,334,048 shares issued and outstanding at December 31, 2021 and 2020, respectively	49	33
Additional paid-in capital	402,283	384,758
Accumulated other comprehensive loss	(175)	(159)
Accumulated deficit	(386,131)	(375,100)
Total stockholders' equity	16,026	9,532
Total liabilities and stockholders' equity	$ 20,415	$ 14,522