CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net loss	$ (34,718)	$ (29,305)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	8,757	5,596
Depreciation and amortization	786	570
Bad debt expense	235	0
Accretion on marketable securities	(16)	(1,288)
Realized gain on marketable securities	(43)	0
Amortization of debt issuance costs	204	194
Loss on extinguishment of debt	1,534	0
Loss on sale and disposal of property and equipment	248	152
Changes in operating assets and liabilities:
Accounts receivable	63	(1,383)
Inventory	337	(1,575)
Prepaid expenses and other assets	1,489	394
Accounts payable	416	526
Accrued liabilities and other	(2,072)	3,525
Net cash used in operating activities	(22,780)	(22,594)
Cash flows from investing activities
Maturities of marketable securities	63,200	117,100
Sales of marketable securities	12,592	0
Purchases of marketable securities	(69,145)	(107,545)
Purchases of property and equipment	(1,744)	(1,639)
Net cash provided by investing activities	4,903	7,916
Cash flows from financing activities
Proceeds from follow-on public offering, net of underwriting discounts, commissions and offering costs	62,978	0
Proceeds from debt financing	45,297	0
Principal repayments of debt financing	(45,297)	0
Payments of debt issuance costs	(750)	0
Payments of prepayment penalty and lender fees	(843)	0
Proceeds from issuance of common stock under employee stock purchase plan	991	1,263
Proceeds from the exercise of stock options	987	1,178
Repurchase of Unvested Stock Options	0	(38)
Payments of additional initial public offering related costs	0	(167)
Net cash provided by financing activities	63,363	2,236
Effect of exchange rate changes on cash and cash equivalents	75	(64)
Net increase (decrease) in cash and cash equivalents	45,561	(12,506)
Cash and cash equivalents at
Beginning of period	10,435	25,120
End of period	55,996	12,614
Supplemental disclosure of non-cash information
Vesting of early exercised stock options	62	161
Unpaid purchases of property and equipment	$ 256	$ 31