CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (10,562)	$ (7,917)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	507	445
Stock-based compensation expense	2,310	1,112
Non-cash interest expense and end of term accretion expense	137	130
Non-cash lease expense	178
Net amortization of premiums on marketable securities	228	391
Unrealized foreign currency transaction losses	214	484
Changes in operating assets and liabilities:
Accounts receivable	(5,804)	(583)
Inventory	(2,926)	(381)
Prepaid expenses and other current assets	88	(908)
Accounts payable	(4,013)	(82)
Accrued expenses and other current liabilities	(4)	(180)
Deferred revenue		182
Operating lease liabilities	1,241
Deferred rent		(23)
Net cash used in operating activities	(18,406)	(7,330)
Cash flows from investing activities:
Purchases of property and equipment	(1,953)	(20)
Purchases of marketable securities	(2,033)	(11,708)
Proceeds from sales and maturities of marketable securities	14,500	21,000
Net cash provided by investing activities	10,514	9,272
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of stock options	202	372
Proceeds from issuance of common stock in connection with employee stock purchase plan	203	211
Net cash provided by financing activities	405	583
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(196)	(379)
Net increase (decrease) in cash, cash equivalents and restricted cash	(7,683)	2,146
Cash, cash equivalents and restricted cash, beginning of period	26,080	25,081
Cash, cash equivalents and restricted cash, end of period	18,397	27,227
Supplemental disclosure of non-cash investing and financing activities:
Transfers of inventory to property and equipment	1,030	429
Purchases of property and equipment included in accounts payable and accrued expenses	939	7
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	17,897	26,727
Restricted cash	500	500
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 18,397	$ 27,227