Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (unaudited) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock	Series C Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2018	$ (107,074)				$ 4,377	$ (111,451)
Temporary equity balance, Shares at Dec. 31, 2018		209,119,674
Temporary equity balance, Value at Dec. 31, 2018		$ 130,353
Balance, Shares at Dec. 31, 2018				170,156
Exercise of common stock options	109				109
Exercise of common stock options, Shares				60,474
Accretion of convertible preferred stock to redemption value	(234)				(234)
Temporary equity, Accretion of convertible preferred stock to redemption value		$ 234
Stock-based compensation	141				141
Net loss	(11,953)					(11,953)
Balance at Sep. 30, 2019	(119,011)				4,393	(123,404)
Temporary equity balance, Shares at Sep. 30, 2019		209,119,674
Temporary equity balance, Value at Sep. 30, 2019		$ 130,587
Balance, Shares at Sep. 30, 2019				230,630
Balance at Jun. 30, 2019	(114,840)				4,401	(119,241)
Temporary equity balance, Shares at Jun. 30, 2019		209,119,674
Temporary equity balance, Value at Jun. 30, 2019		$ 130,508
Balance, Shares at Jun. 30, 2019				220,618
Exercise of common stock options	22				22
Exercise of common stock options, Shares				10,012
Accretion of convertible preferred stock to redemption value	(79)				(79)
Temporary equity, Accretion of convertible preferred stock to redemption value		$ 79
Stock-based compensation	49				49
Net loss	(4,163)					(4,163)
Balance at Sep. 30, 2019	(119,011)				4,393	(123,404)
Temporary equity balance, Shares at Sep. 30, 2019		209,119,674
Temporary equity balance, Value at Sep. 30, 2019		$ 130,587
Balance, Shares at Sep. 30, 2019				230,630
Balance at Dec. 31, 2019	$ (123,338)				4,419	(127,757)
Temporary equity balance, Shares at Dec. 31, 2019	0	209,119,674
Temporary equity balance, Value at Dec. 31, 2019	$ 130,666	$ 130,666
Balance, Shares at Dec. 31, 2019				230,860
Exercise of common stock options	$ 1				1
Exercise of common stock options, Shares	254			254
Issuance of Series C redeemable convertible preferred stock, net of issuance costs			$ 29,446
Issuance of Series C redeemable convertible preferred stock, net of issuance costs, Shares			78,306,611
Accretion of convertible preferred stock to redemption value	$ (115)				(115)
Temporary equity, Accretion of convertible preferred stock to redemption value	115
Issuance of common stock warrants in conjunction with sale of Series C redeemable convertible preferred stock	740				740
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering	160,227		$ (160,227)	$ 8	160,219
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering, Shares			(287,426,285)	8,335,248
Issuance of common stock from initial public offering, net of issuance costs	57,284			$ 4	57,280
Issuance of common stock from initial public offering, net of issuance costs, Shares				4,025,000
Vesting of restricted common stock				19,661
Issuance of common stock upon exercise of warrants				$ 1	(1)
Issuance of common stock upon exercise of warrants, Shares				313,794
Stock-based compensation	1,221				1,221
Net loss	(15,106)					(15,106)
Balance at Sep. 30, 2020	$ 80,914			$ 13	223,764	(142,863)
Temporary equity balance, Shares at Sep. 30, 2020	0
Balance, Shares at Sep. 30, 2020				12,924,817
Balance at Jun. 30, 2020	$ 86,823			$ 13	223,339	(136,529)
Balance, Shares at Jun. 30, 2020				12,924,563
Exercise of common stock options	1				1
Exercise of common stock options, Shares				254
Issuance of common stock from initial public offering, net of issuance costs	(44)				(44)
Stock-based compensation	468				468
Net loss	(6,334)					(6,334)
Balance at Sep. 30, 2020	$ 80,914			$ 13	$ 223,764	$ (142,863)
Temporary equity balance, Shares at Sep. 30, 2020	0
Balance, Shares at Sep. 30, 2020				12,924,817