Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (58,505)	$ (63,660)	$ (49,851)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	690	480	430
Amortization of intangible assets	665	666	665
Stock-based compensation	5,191	14,601	10,075
Write-off of excessive and obsolete inventory	8,477	0	0
Net premium amortization and discount on available-for-sale securities	0	13	5
Loss on disposal of fixed assets	185	0	119
Gain on U.S. Treasury securities	0	0	(8)
Changes in operating assets and liabilities:
Accounts receivable	61	(61)	0
Inventory	(2,653)	(5,824)	0
Prepaid expenses and other current assets	1,164	(1,374)	194
Other receivables	(41)	54	0
Right-of-use assets	723	653	509
Other long-term assets	0	0	129
Accounts payable	(1,304)	1,160	(266)
Accrued expenses	(1,794)	(937)	2,830
Deferred revenue	(16)	16	0
Lease liabilities	(774)	(542)	(196)
Accrued interest on related party note payable	917	0	0
Accrued interest on note payable	1	658	0
Net cash used in operating activities	(47,013)	(54,097)	(35,365)
Cash flows from investing activities:
Purchases of property and equipment	(401)	(437)	(441)
Purchases of investments	0	0	(29,025)
Maturities of investments	0	8,000	35,000
Sales of investments	0	0	4,510
Net cash provided by (used in) investing activities	(401)	7,563	10,044
Cash flows from financing activities:
Proceeds from issuance of common stock under employee stock purchase plan	486	810	490
Proceeds from exercises of warrants	26	4,217	244
Proceeds from exercises of stock options	0	786	717
Proceeds from issuance of common stock	14,864	56,697	29,434
Proceeds from issuance of related party note	65,000	0	0
Proceeds from insurance loan agreement	0	1,939	0
Payments made on insurance loan agreement	(437)	(1,532)	0
Tax payments related to shares withheld for vested restricted stock units	0	(232)	0
Net cash provided by financing activities	79,939	62,685	30,885
Net increase in cash and cash equivalents	32,525	16,151	5,564
Cash and cash equivalents at beginning of period	28,614	12,463	6,899
Cash and cash equivalents at end of period	61,139	28,614	12,463
Supplemental disclosure of noncash investing and financing activities:
Other receivable from exercise of warrants and stock options	0	0	1,053
Change in unrealized gains on available-for-sale securities	0	1	(5)
Equipment purchases included in accounts payable and accrued expenses	(27)	(27)	(20)
Equipment purchases included in accounts payable and accrued expenses	27	27	20
Accrued interest settled via issuance of common stock from private placement equity offering	$ 0	$ 629	$ 0