Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities
Net loss	$ (67,484)	$ (37,940)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,697	1,409
Loss on disposal of property and equipment	122	1
Stock-based compensation	6,056	1,419
Preferred stock warrant liability revaluation	123	33
Accretion of discount on investments	(800)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,394)	(1,370)
Accounts payable	826	698
Accrued expenses	2,465	1,085
Other current liabilities	160
Deferred rent	691	(35)
Net cash used in operating activities	(58,538)	(34,700)
Cash Flows from Investing Activities
Purchase of property and equipment	(3,447)	(1,764)
Purchase of investments	(99,646)
Proceeds from maturities of investments	75,000	22,398
Change in deposits	189	24
Net cash provided by (used in) investing activities	(27,904)	20,658
Cash Flows from Financing Activities
Proceeds from issuance of convertible preferred stock, net		120,306
Proceeds from the issuance of common stock under the Employee Stock Purchase Plan	133
Proceeds from exercise of stock options	303	46
Proceeds from initial public offering, net	133,633
Principal payments on capital lease obligations	(47)	(48)
Payments of initial offering costs	(2,848)
Net cash provided by financing activities	131,174	120,304
Net change in cash, cash equivalents and restricted cash	44,732	106,262
Cash, cash equivalents and restricted cash, beginning of period	114,504	8,242
Cash, cash equivalents and restricted cash, end of period	159,236	114,504
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	6	9
Cash paid for income taxes	1	$ (1)
Supplemental Schedule of Non-Cash Investing and Financing Activities
Conversion of redeemable convertible preferred stock to common stock	209,668
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	503
Vesting of early exercised common stock options	$ 15