CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (8,210)	$ (36,052)	$ (16,123)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	100	1,433	172
Net amortization of premiums and accretion of discounts on marketable securities		(10)
Amortization of operating lease right-of-use assets		179	254
Change in fair value of preferred stock tranche liability	3,013		2,260
Stock-based compensation expense		2,677	57
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(1,093)	(36)
Accounts payable		348	290
Operating lease liabilities		(392)	351
Accrued expenses and other current liabilities		2,582	1,282
Other long-term liabilities			(62)
Net cash used in operating activities		(30,328)	(11,555)
Cash flows from investing activities:
Purchases of property and equipment		(3,234)	(929)
Purchases of marketable securities		(141,434)
Net cash used in investing activities		(144,668)	(929)
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs paid		104,837	25,016
Proceeds from initial public offering of common stock		227,269
Payments of finance lease obligations		(189)	(74)
Proceeds from exercise of stock options and sale of restricted common stock		42	56
Payments of initial public offering costs	(34)	(3,419)
Net cash provided by financing activities		328,540	24,998
Net increase in cash, cash equivalents and restricted cash		153,544	12,514
Cash, cash equivalents and restricted cash at beginning of period		26,395	24,340
Cash, cash equivalents and restricted cash at end of period	36,854	179,939	36,854
Supplemental cash flow information:
Cash paid for interest		5	8
Supplemental disclosure of non‑cash investing and financing information:
Purchases of property and equipment included in accounts payable and accrued expenses		157
Settlement of preferred stock tranche liability			6,027
Operating lease liabilities arising from obtaining right-of-use assets			6,550
Leasehold improvements paid by lessor			4,922
Vesting of common stock subject to repurchase		73	(38)
Reconciliation of cash, cash equivalents and restricted cash:
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 36,854	$ 179,939	$ 36,854