Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (24,657)	$ (21,004)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	170	158
Noncash interest expense	488	430
Amortization of intangible assets	228	228
Inventory excess and obsolescence charge	1,334	1,221
Stock-based compensation expense	2,839	1,486
Change in operating assets and liabilities:
Accounts receivable, net	(896)	190
Inventory	(3,701)	(664)
Prepaid expenses and other assets	180	1,440
Accounts payable	1,586	(1,675)
Accrued expenses and other current and long-term liabilities	1,561	831
Foreign currency remeasurement loss	24	7
Net cash used in operating activities	(20,844)	(17,352)
Cash flows from investing activities:
Proceeds from the sale and maturity of short-term investments		9,289
Purchase of property and equipment	(338)	(129)
Net cash (used in) provided by investing activities	(338)	9,160
Cash flows from financing activities:
Proceeds from follow-on offering, net of underwriting discounts, commissions and offering costs		44,722
Payment of initial public offering costs		(522)
Proceeds from exercise of stock options	411	163
Net cash provided by financing activities	411	44,363
Effect of exchange rate on cash and cash equivalents	13	(6)
Net (decrease) increase in cash and cash equivalents	(20,758)	36,165
Cash and cash equivalents, beginning of period	74,394	45,302
Cash and cash equivalents, end of period	53,636	81,467
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	2,187	2,231
Supplemental disclosures of noncash investing and financing activities:
Property and equipment in accounts payable	97	4
Issuance of common stock for early exercised stock options		$ 2
Reclassification of liability-classified stock-based compensation awards to equity-classified	$ 82