CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (4,775)	$ (14,376)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,538	1,145
Stock-based compensation	3,195	795
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(543)	(2,815)
Accounts payable	574	(493)
Accrued liabilities	(753)	(182)
Deferred rent	139
Deferred revenue	(22,378)	(1,759)
Net cash used in operating activities	(23,003)	(17,685)
Cash flows from investing activities:
Maturities of marketable securities	71,565
Purchase of marketable securities	(53,364)
Purchase of property and equipment	(4,279)	(2,067)
Net cash provided by (used in) investing activities	13,922	(2,067)
Cash flows from financing activities:
Proceeds from initial public offering, net of issuance costs		77,264
Proceeds from issuances of common stock	40	43
Proceeds from the term loan		4,540
Payments of the term loan	(694)
Net cash (used in) provided by financing activities	(654)	81,847
Net (decrease) increase in cash, cash equivalents and restricted cash	(9,735)	62,095
Cash, cash equivalents and restricted cash—beginning of period	39,130	135,633
Cash, cash equivalents and restricted cash—end of period	29,395	197,728
Supplemental disclosures of cash flow information:
Cash paid for interest	85	80
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment included in accrued liabilities	$ 809	75
Deferred financing costs included in accrued liabilities		154
Conversion of convertible preferred stock into common stock		$ 162,223