CONDENSED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Balance at Dec. 31, 2018	$ (17,802)			$ 1	$ 411	$ (18,214)
Balance, Shares at Dec. 31, 2018				764,408
Balance at Dec. 31, 2018		$ 19,872
Balance, Shares at Dec. 31, 2018		20,000,000
Issuance of redeemable convertible preferred stock, net of issuance costs		$ 7,941
Issuance of redeemable convertible preferred stock, net of issuance costs, Shares		8,000,000
Stock-based compensation	15				15
Net loss	(4,119)					(4,119)
Balance at Mar. 31, 2019	(21,906)			$ 1	426	(22,333)
Balance, Shares at Mar. 31, 2019		28,000,000
Balance at Mar. 31, 2019		$ 27,813
Balance, Shares at Mar. 31, 2019				764,408
Balance at Dec. 31, 2018	(17,802)			$ 1	411	(18,214)
Balance, Shares at Dec. 31, 2018				764,408
Balance at Dec. 31, 2018		$ 19,872
Balance, Shares at Dec. 31, 2018		20,000,000
Net loss	(9,906)
Balance at Sep. 30, 2019	(27,517)			$ 1	602	(28,120)
Balance, Shares at Sep. 30, 2019		28,000,000
Balance at Sep. 30, 2019		$ 27,813
Balance, Shares at Sep. 30, 2019				764,408
Balance at Mar. 31, 2019	(21,906)			$ 1	426	(22,333)
Balance, Shares at Mar. 31, 2019				764,408
Balance at Mar. 31, 2019		$ 27,813
Balance, Shares at Mar. 31, 2019		28,000,000
Stock-based compensation	77				77
Net loss	(3,236)					(3,236)
Balance at Jun. 30, 2019	(25,065)			$ 1	503	(25,569)
Balance, Shares at Jun. 30, 2019		28,000,000
Balance at Jun. 30, 2019		$ 27,813
Balance, Shares at Jun. 30, 2019				764,408
Stock-based compensation	62				62
Issuance of warrant to purchase common stock	37				37
Net loss	(2,551)					(2,551)
Balance at Sep. 30, 2019	(27,517)			$ 1	602	(28,120)
Balance, Shares at Sep. 30, 2019		28,000,000
Balance at Sep. 30, 2019		$ 27,813
Balance, Shares at Sep. 30, 2019				764,408
Balance at Dec. 31, 2019	$ (30,637)			$ 1	664	(31,302)
Balance, Shares at Dec. 31, 2019	764,408			764,408
Balance at Dec. 31, 2019		$ 27,813
Balance, Shares at Dec. 31, 2019		28,000,000	0
Issuance of redeemable convertible preferred stock, net of issuance costs			$ 43,648
Issuance of redeemable convertible preferred stock, net of issuance costs, Shares			36,666,665
Stock-based compensation	$ 32				32
Net loss	(5,168)					(5,168)
Balance at Mar. 31, 2020	(35,773)			$ 1	696	(36,470)
Balance, Shares at Mar. 31, 2020		28,000,000	36,666,665
Balance at Mar. 31, 2020		$ 27,813	$ 43,648
Balance, Shares at Mar. 31, 2020				764,408
Balance at Dec. 31, 2019	$ (30,637)			$ 1	664	(31,302)
Balance, Shares at Dec. 31, 2019	764,408			764,408
Balance at Dec. 31, 2019		$ 27,813
Balance, Shares at Dec. 31, 2019		28,000,000	0
Net loss	$ (21,201)
Balance at Sep. 30, 2020	(51,441)			$ 1	1,061	(52,503)
Balance, Shares at Sep. 30, 2020		28,000,000	73,333,330
Balance at Sep. 30, 2020	$ 115,446	$ 27,813	$ 87,633
Balance, Shares at Sep. 30, 2020	822,022			822,022
Balance at Mar. 31, 2020	$ (35,773)			$ 1	696	(36,470)
Balance, Shares at Mar. 31, 2020				764,408
Balance at Mar. 31, 2020		$ 27,813	$ 43,648
Balance, Shares at Mar. 31, 2020		28,000,000	36,666,665
Exercise of stock options	8				8
Exercise of stock options, Shares				7,166
Stock-based compensation	96				96
Net loss	(6,446)					(6,446)
Balance at Jun. 30, 2020	(42,115)			$ 1	800	(42,916)
Balance, Shares at Jun. 30, 2020		28,000,000	36,666,665
Balance at Jun. 30, 2020		$ 27,813	$ 43,648
Balance, Shares at Jun. 30, 2020				771,574
Issuance of redeemable convertible preferred stock, net of issuance costs			$ 43,985
Issuance of redeemable convertible preferred stock, net of issuance costs, Shares			36,666,665
Exercise of stock options	43				43
Exercise of stock options, Shares				50,448
Stock-based compensation	218				218
Net loss	(9,587)					(9,587)
Balance at Sep. 30, 2020	(51,441)			$ 1	$ 1,061	$ (52,503)
Balance, Shares at Sep. 30, 2020		28,000,000	73,333,330
Balance at Sep. 30, 2020	$ 115,446	$ 27,813	$ 87,633
Balance, Shares at Sep. 30, 2020	822,022			822,022