Unaudited Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (13,234)	$ (8,630)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	392	480
Amortization of debt discount and debt issuance costs	202	575
Non-cash interest expense	397	484
Revaluation of warrant liabilities	0	(267)
Deferred income taxes	(117)	0
Loss on disposal of assets	0	20
Stock-based compensation	1,877	85
Changes in assets and liabilities:
Accounts receivable, net	(3,582)	(286)
Prepaid expenses and other current assets	1,627	510
Other assets	0	(24)
Accounts payable	781	174
Accrued and other liabilities	1,472	1,095
Net cash used in operating activities	(10,185)	(5,784)
Cash flows from investing activities:
Purchases of property and equipment	(450)	(377)
Proceeds from sale of property and equipment	0	300
Net cash used in investing activities	(450)	(77)
Cash flows from financing activities:
Proceeds from exercise of stock options	12	0
Proceeds from common stock issued under Employee Stock Purchase Pan	142	0
Proceeds from exercise of common stock warrants	18	0
Principal payment on capital lease obligations	(187)	(94)
Proceeds from Paycheck Protection Program loan	2,865	0
Repayment of Paycheck Protection Program loan	(2,865)	0
Proceeds from initial public offering, net of issuance costs and offering costs	0	52,195
Net cash (used in) provided by financing activities	(15)	70,525
Net change in cash, cash equivalents and restricted cash	(10,650)	64,664
Cash, cash equivalents and restricted cash, beginning of period	72,184	13,264
Cash, cash equivalents and restricted cash, end of period	61,534	77,928
Supplemental disclosure of cash flow information:
Cash paid for interest expense	1,312	1,661
Supplemental disclosure of non-cash items:
Accretion to redemption value of redeemable convertible preferred stock	0	4,640
Equipment purchased under capital lease obligations	123	412
Costs incurred, but not paid, in connection with capital expenditures	197	71
Conversion of redeemable convertible preferred stock	0	138,906
Net exercise of common and preferred stock warrants	0	511
Issuance costs included in accounts payable and accrued liabilities	0	1,677
Reclassification of redeemable convertible preferred stock warrant liabilities as equity	0	726
Series G redeemable convertible preferred stock
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	0	7,742
Supplemental disclosure of non-cash items:
Deemed dividend from conversion of Series G to Series H redeemable convertible preferred stock	0	6,860
Conversion of Series G to Series H redeemable convertible preferred stock	0	11,875
Series H redeemable convertible preferred stock
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	0	10,682
Supplemental disclosure of non-cash items:
Deemed dividend recognized for beneficial conversion features of Series H redeemable convertible preferred stock	$ 0	$ 6,741