INCOME TAXES - Income Taxes by Jurisdiction (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
U.S. federal:
Current	$ 0	$ 0
Deferred	0	0
Total U.S. federal	0	0
U.S. state and local:
Current	1	1
Deferred	0	0
Total U.S. state and local	1	1
Foreign:
Current	0	0
Deferred	0	0
Total foreign	0	0
Provision for (benefit from) income taxes	1	1
Income taxes differ from the amounts computed by applying the U.S. federal income tax rate to pretax income (loss) before income taxes
Expected income tax benefit	(7,554)	(5,966)
State income tax (benefit), net of federal benefit	(2,812)	(1,961)
Valuation allowance	10,761	7,732
Permanent differences:
Stock options	255	353
Research & development credit	(617)	(560)
Adjustment to deferred taxes	(55)	400
Foreign rate differential	1	(1)
Other	22	4
Provision for (benefit from) income taxes	$ 1	$ 1