Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common stock	Additional paid-in capital	Accumulated other comprehensive (loss) income	Accumulated deficit	Total
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
Vesting of common stock previously subject to repurchase		2			2
Vesting of common stock previously subject to repurchase (in shares)	236
Exercise of stock options		163			163
Exercise of stock options (in shares)	25,763
Foreign currency translation adjustment			2		2
Stock-based compensation expense		1,486			1,486
Issuance of common stock	$ 3	44,719			44,722
Issuance of common stock (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
Vesting of common stock previously subject to repurchase (in shares)	73
Exercise of stock options		119			119
Exercise of stock options (in shares)	19,457
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
Balance at Beginning of period at Dec. 31, 2020	$ 14	245,736	(71)	(196,653)	49,026
Balance at Beginning of period (in shares) at Dec. 31, 2020	14,437,107
Vesting of common stock previously subject to repurchase (in shares)	118
Exercise of stock options	$ 1	410			$ 411
Exercise of stock options (in shares)	54,293				54,293
Foreign currency translation adjustment			28		$ 28
Stock-based compensation expense		2,839			2,839
Stock-based compensation expense (in shares)	12,000
Reclassification of liability-classified stock-based compensation awards		82			82
Net loss				(24,657)	(24,657)
Balance at Ending period at Sep. 30, 2021	$ 15	249,067	(43)	(221,310)	27,729
Balance at Ending period (in shares) at Sep. 30, 2021	14,503,518
Balance at Beginning of period at Jun. 30, 2021	$ 14	248,076	(81)	(213,044)	34,965
Balance at Beginning of period (in shares) at Jun. 30, 2021	14,471,774
Vesting of common stock previously subject to repurchase (in shares)	36
Exercise of stock options	$ 1	258			259
Exercise of stock options (in shares)	31,708
Foreign currency translation adjustment			38		38
Stock-based compensation expense		733			733
Net loss				(8,266)	(8,266)
Balance at Ending period at Sep. 30, 2021	$ 15	$ 249,067	$ (43)	$ (221,310)	$ 27,729
Balance at Ending period (in shares) at Sep. 30, 2021	14,503,518