Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities:
Net loss	$ (6,456)	$ (8,167)
Adjustments to reconcile net loss to net cash used in operating activities:
Write-off of inventory	0	3
Depreciation	30	36
Reduction in the carrying amount of right-of-use assets	274	241
Non-cash board compensation expense	0	115
Share-based compensation	800	1,596
Changes in operating assets and liabilities:
Accounts receivable	3	(67)
Inventory	0	1
Prepaid expenses and other current assets	48	365
Other receivable due from related party	56	(519)
Accounts payable	210	610
Accrued liabilities and other current liabilities	(149)	708
Deferred revenue	734	(2)
Operating lease liability - current	(298)	42
Operating lease liability - noncurrent	0	(298)
Net cash used in operating activities	(4,748)	(5,336)
Investing activities:
Purchase of property and equipment	(55)	(9)
Net cash used in investing activities	(55)	(9)
Financing activities:
Proceeds from sales of common stock	2,001	11,500
Issuance costs of sale of common stock	(67)	(1,160)
Proceeds from note payable	0	506
Proceeds from exercise of common stock options	5	0
Net cash provided by financing activities	1,939	10,846
Net change in cash and cash equivalents	(2,864)	5,501
Cash and cash equivalents at beginning of period	21,407	5,585
Cash and cash equivalents at end of period	18,543	11,086
Supplemental disclosure for noncash investing and financing activities:
Unpaid issuance costs of common stock	66	0
Issuance of restricted stock units in lieu of cash bonus obligations	393	391
Issuance of restricted stock units in lieu of board cash compensation obligations	0	613
Issuance of common stock in lieu of board cash compensation obligations	0	148
Non-cash interest expense accretion to loan payable	$ 0	$ 1