Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (16,679)	$ (10,694)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	420	239
Stock-based compensation expense	4,978	3,533
Amortization of premiums on investments, net		186
Amortization of debt discount and debt issuance costs	39	41
Amortization of right-of-use asset	242	158
Loss on disposal of property and equipment	120
Change in provision for doubtful accounts receivable	(6)
Provision for excess and obsolete inventories	(8)	24
Changes in assets and liabilities:
Accounts receivable	(2,038)	(2,036)
Inventories	134	(1,790)
Prepaid expenses and other current assets	847	583
Other assets	(5)	(6)
Accounts payable	19	218
Accrued liabilities	(3,168)	(2,423)
Other liabilities	380	(5)
Net cash used in operating activities	(14,725)	(11,972)
Cash flows from investing activities
Purchases of property and equipment	(2,072)	(67)
Proceeds from maturity of investments		36,300
Net cash provided by (used in) investing activities	(2,072)	36,233
Cash flows from financing activities
Proceeds from issuance of common stock	168	848
Net cash provided by financing activities	168	848
Net change in cash, cash equivalents and restricted cash	(16,629)	25,109
Cash, cash equivalents and restricted cash, beginning of period	110,463	69,776
Cash, cash equivalents and restricted cash, end of period	93,834	94,885
Supplemental disclosure of cash flow information
Cash paid for interest	582	582
Noncash investing and financing activities:
Accounts payable and accrued liabilities for purchases of property and equipment	$ 638	$ 106