CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (44,215)	$ (28,748)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,817	1,577
Stock-based compensation expense	6,878	2,414
Non-cash interest and end of term accretion expense	540	511
Non-cash lease expense	829
Net amortization of premiums on marketable securities	1,356	634
Unrealized foreign currency transaction (gains) losses	928	(1,065)
Changes in operating assets and liabilities:
Accounts receivable	840	(218)
Inventory	(4,894)	(1,740)
Prepaid expenses and other current assets	(3,151)	(769)
Accounts payable	5,090	(5,802)
Accrued expenses and other current liabilities	4,875	1,948
Deferred revenue	7	60
Operating lease liabilities	236
Deferred rent		933
Net cash used in operating activities	(28,864)	(30,265)
Cash flows from investing activities:
Purchases of property and equipment	(3,519)	(455)
Purchases of marketable securities	(72,024)	(121,793)
Proceeds from sales and maturities of marketable securities	104,810	80,650
Net cash provided by (used) in investing activities	29,267	(41,598)
Cash flows from financing activities:
Proceeds from issuance of common stock in public offering, net of underwriting discounts and commissions		75,670
Payments of public offering and other financing costs		(705)
Proceeds from issuance of common stock upon exercise of stock options	974	227
Proceeds from issuance of common stock in connection with employee stock purchase plan	419	357
Proceeds from Paycheck Protection Program loan		2,249
Repayment of Paycheck Protection Program loan		(2,249)
Net cash provided by financing activities	1,393	75,549
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(797)	803
Net increase in cash, cash equivalents and restricted cash	999	4,489
Cash, cash equivalents and restricted cash, beginning of period	25,081	20,592
Cash, cash equivalents and restricted cash, end of period	26,080	25,081
Supplemental disclosure of cash flow information:
Cash paid for interest	3,334	3,475
Supplemental disclosure of non-cash investing and financing activities:
Transfers of inventory to property and equipment	1,823	1,191
Purchases of property and equipment included in accounts payable and accrued expenses	1,200
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	25,580	24,581
Restricted cash	500	500
Cash, cash equivalents and restricted cash, end of period	$ 26,080	$ 25,081