Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (26,515)	$ (24,721)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization and write-off of property and equipment	1,051	1,112
Amortization and write-off of intangibles	525	612
Amortization of right of use assets under operating leases	364	352
Amortization of net premiums and (discounts) on marketable securities	605	(39)
Gain on extinguishment of note payable	(5,032)	0
Stock-based compensation	10,348	7,149
Changes in operating assets and liabilities:
Trade accounts receivable	(427)	999
Other current assets	(353)	60
Other assets	(54)	(45)
Accounts payable and other accrued liabilities	1,630	146
Deferred revenue	(847)	(1,092)
Lease liability and other long-term liabilities	242	236
Net cash used in operating activities	(18,463)	(15,231)
Cash flows from investing activities:
Purchase of property and equipment	(797)	(694)
Capitalized patent costs	(475)	(478)
Maturities of marketable securities	72,141	30,598
Purchases of marketable securities	(42,049)	(22,149)
Net cash provided by investing activities	28,820	7,277
Cash flows from financing activities:
Issuance of common stock, net of issuance costs	0	38,603
Proceeds from note payable	0	5,032
Exercise of stock options	0	135
Purchase of common stock	(4,898)	(1,568)
Net cash provided by (used in) financing activities	(4,898)	42,202
Net increase in cash and cash equivalents	5,459	34,248
Cash and cash equivalents at beginning of period	19,696	11,213
Cash and cash equivalents at end of period	25,155	45,461
Supplemental disclosure of cash flow information:
Cash received (paid) for income taxes, net	(35)	12
Supplemental schedule of non-cash investing and financing activities:
Property and equipment and patent costs in accounts payable	(115)	72
Common stock issuance costs in accounts payable	0	241
Stock-based compensation capitalized to software and patent costs	111	125
Cashless exercise of stock options	4,030	0
Gain on extinguishment of note payable	$ (5,094)	$ 0