Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net loss	$ (27,720)	$ (21,560)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	911	962
Stock-based compensation expense	3,616	865
Gain on disposal of property and equipment		3
Net amortization of premiums and accretion discounts on investments	(4)	(143)
Change in fair value of redeemable convertible preferred stock tranche liability and TRDF liability		(2,024)
Change in fair value of redeemable convertible preferred stock warrant liability	897	(62)
Amortization of deferred debt issuance costs	84
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(5,000)	837
Other non-current assets	(1,560)	19
Accounts payable	1,442	244
Contract liabilities — related party	(2,493)	974
Deferred rent	(119)	(111)
Accrued and other current liabilities	1,738	(627)
Other liabilities	1
Net cash used in operating activities	(28,207)	(20,623)
Cash flows from investing activities
Cash and restricted cash acquired in connection with the Merger	64,114
Purchases of marketable debt securities	(5,700)	(60,056)
Proceeds from maturities of marketable debt securities	44,985	17,750
Purchases of property and equipment	(630)	(611)
Net cash provided by (used in) investing activities	102,769	(42,917)
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		77,044
Proceeds from exercise of stock options	193	24
Deferred debt issuance costs	(157)
Net cash provided by financing activities	36	77,068
Net change in cash, cash equivalents and restricted cash	74,598	13,528
Cash, cash equivalents and restricted cash, at the beginning of period	14,889	13,757
Cash, cash equivalents and restricted cash, at the end of period	89,487	27,285
Reconciliation of cash, cash equivalents and restricted cash to condensed consolidated balance sheets:
Cash, cash equivalents and restricted cash in condensed consolidated balance sheets	89,487	27,285
Supplemental cash flow information
Cash paid for income taxes	3	1
Supplemental disclosures of noncash investing and financing activities
Purchases of property and equipment included in accounts payable	76	58
Conversion of redeemable convertible preferred stock warrants to common stock warrants	114,083
Conversion of redeemable convertible preferred stock warrants into common stock warrants	2,922
Fair value of net assets acquired in Merger	84,142
Vesting of early exercised stock options		47
Issuance of redeemable convertible preferred stock warrants in connection with the Loan Agreement	$ 144
Termination of redeemable convertible preferred stock tranche liability		1,143
Settlement of TRDF liability		88
Series B Redeemable Convertible Preferred Stock
Supplemental disclosures of noncash investing and financing activities
Redeemable convertible preferred stock warrants issued in exchange for services in connection with issuance of Series B redeemable convertible preferred stock recorded as issuance costs		$ 2,131