Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Series A Redeemable convertible preferred stock Preferred Stock [Member]	Series B Redeemable convertible preferred stock Preferred Stock [Member]	Common stock	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit	Total
Balance at Beginning of period at Dec. 31, 2018	$ 33,112	$ 91,038
Balance at Beginning of period (in shares) at Dec. 31, 2018	22,501,174	63,032,500
Increase (Decrease) in Temporary Equity [Roll Forward]
Sale of Series B redeemable convertible preferred stock, net of stock issue costs		12,527,956
Sale of Series B redeemable convertible preferred stock, net of stock issue costs		$ 14,391
Accretion of redeemable convertible preferred stock to redemption value	$ 1,346	5,497
Balance at Ending period at Sep. 30, 2019	$ 34,458	$ 110,926
Balance at Ending period (in shares) at Sep. 30, 2019	22,501,174	75,560,456
Balance at Beginning of period at Dec. 31, 2018						$ (137,860)	$ (137,860)
Balance at Beginning of period (in shares) at Dec. 31, 2018			295,717
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			508
Vesting of common stock previously subject to repurchase				$ 3			3
Exercise of stock options (in shares)			1,892
Exercise of stock options				12			12
Foreign currency translation adjustment					$ (2)		(2)
Stock-based compensation expense				183			183
Accretion of redeemable convertible preferred stock to redemption value				(198)		(6,645)	(6,843)
Net loss						(15,893)	(15,893)
Balance at Ending period at Sep. 30, 2019					(2)	(160,398)	(160,400)
Balance at Ending period (in shares) at Sep. 30, 2019			298,117
Balance at Beginning of period at Jun. 30, 2019	$ 34,005	$ 107,058
Balance at Beginning of period (in shares) at Jun. 30, 2019	22,501,174	73,587,014
Increase (Decrease) in Temporary Equity [Roll Forward]
Sale of Series B redeemable convertible preferred stock, net of stock issue costs		1,973,442
Sale of Series B redeemable convertible preferred stock, net of stock issue costs		$ 2,263
Accretion of redeemable convertible preferred stock to redemption value	$ 453	1,605
Balance at Ending period at Sep. 30, 2019	$ 34,458	$ 110,926
Balance at Ending period (in shares) at Sep. 30, 2019	22,501,174	75,560,456
Balance at Beginning of period at Jun. 30, 2019					(3)	(153,744)	(153,747)
Balance at Beginning of period (in shares) at Jun. 30, 2019			297,502
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			202
Vesting of common stock previously subject to repurchase				2			2
Exercise of stock options (in shares)			413
Exercise of stock options				4			4
Foreign currency translation adjustment					1		1
Stock-based compensation expense				64			64
Accretion of redeemable convertible preferred stock to redemption value				(70)		(1,988)	(2,058)
Net loss						(4,666)	(4,666)
Balance at Ending period at Sep. 30, 2019					(2)	(160,398)	(160,400)
Balance at Ending period (in shares) at Sep. 30, 2019			298,117
Balance at Beginning of period at Dec. 31, 2019			$ 11	198,829	(19)	(167,859)	30,962
Balance at Beginning of period (in shares) at Dec. 31, 2019			11,406,221
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			236
Vesting of common stock previously subject to repurchase				2			$ 2
Exercise of stock options (in shares)			25,763				25,763
Exercise of stock options				163			$ 163
Foreign currency translation adjustment					2		2
Stock-based compensation expense				1,486			1,486
Issuance of common stock upon follow-on offering, net of underwriting discounts, commissions and offering costs			$ 3	44,719			44,722
Issuance of common stock upon follow-on offering, net of underwriting discounts, commissions and offering costs (in shares)			3,000,000
Net loss						(21,004)	(21,004)
Balance at Ending period at Sep. 30, 2020			$ 14	245,199	(17)	(188,863)	56,333
Balance at Ending period (in shares) at Sep. 30, 2020			14,432,220
Balance at Beginning of period at Jun. 30, 2020			$ 14	244,537	12	(181,160)	63,403
Balance at Beginning of period (in shares) at Jun. 30, 2020			14,412,690
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			73
Exercise of stock options (in shares)			19,457
Exercise of stock options				119			119
Foreign currency translation adjustment					(29)		(29)
Stock-based compensation expense				543			543
Net loss						(7,703)	(7,703)
Balance at Ending period at Sep. 30, 2020			$ 14	$ 245,199	$ (17)	$ (188,863)	$ 56,333
Balance at Ending period (in shares) at Sep. 30, 2020			14,432,220