CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Series B Preferred Stock	Series A Preferred Stock
Balance at Dec. 31, 2019	$ (51,503)		$ 3,748	$ 68	$ (55,319)
Temporary equity, Balance, Shares at Dec. 31, 2019						14,877,697	44,520,653
Temporary equity, Balance at Dec. 31, 2019						$ 120,923	$ 52,204
Balance, Shares at Dec. 31, 2019		2,099,740
Issuance of common stock, upon vesting of restricted stock, Shares		292,644
Unrealized (loss) gain on available-for-sale securities	176			176
Stock-based compensation	646		646
Net loss	(9,339)				(9,339)
Balance at Mar. 31, 2020	(60,020)		4,394	244	(64,658)
Temporary equity, Balance, Shares at Mar. 31, 2020						14,877,697	44,520,653
Temporary equity, Balance at Mar. 31, 2020						$ 120,923	$ 52,204
Balance, Shares at Mar. 31, 2020		2,392,384
Balance at Dec. 31, 2019	(51,503)		3,748	68	(55,319)
Temporary equity, Balance, Shares at Dec. 31, 2019						14,877,697	44,520,653
Temporary equity, Balance at Dec. 31, 2019						$ 120,923	$ 52,204
Balance, Shares at Dec. 31, 2019		2,099,740
Unrealized (loss) gain on available-for-sale securities	(83)
Unrealized loss on foreign currency translation adjustment	(26)
Net loss	(44,585)
Balance at Sep. 30, 2020	373,903	$ 7	473,841	(41)	(99,904)
Balance, Shares at Sep. 30, 2020		61,659,533
Balance at Mar. 31, 2020	(60,020)		4,394	244	(64,658)
Temporary equity, Balance, Shares at Mar. 31, 2020						14,877,697	44,520,653
Temporary equity, Balance at Mar. 31, 2020						$ 120,923	$ 52,204
Balance, Shares at Mar. 31, 2020		2,392,384
Issuance of common stock, upon vesting of restricted stock, Shares		409,475
Unrealized (loss) gain on available-for-sale securities	(134)			(134)
Stock-based compensation	492		492
Net loss	(11,632)				(11,632)
Balance at Jun. 30, 2020	(71,294)		4,886	110	(76,290)
Temporary equity, Balance, Shares at Jun. 30, 2020						14,877,697	44,520,653
Temporary equity, Balance at Jun. 30, 2020						$ 120,923	$ 52,204
Balance, Shares at Jun. 30, 2020		2,801,859
Issuance of common stock, upon vesting of restricted stock, Shares		311,035
Initial public offering, net of underwriting discounts, commissions and offering costs	291,975	$ 2	291,973
Initial public offering, net of underwriting discounts, commissions and offering costs, Shares		18,687,500
Conversion of convertible preferred stock into common stock upon initial public offering	173,127	$ 5	173,122
Conversion of convertible preferred stock into common stock upon initial public offering, Shares		39,859,139
Temporary equity conversion of convertible preferred stock into common stock upon initial public offering						$ (120,923)	$ (52,204)
Temporary equity conversion of convertible preferred stock into common stock upon initial public offering, Shares						(14,877,697)	(44,520,653)
Unrealized (loss) gain on available-for-sale securities	(125)			(125)
Unrealized loss on foreign currency translation adjustment	(26)			(26)
Stock-based compensation	3,860		3,860
Net loss	(23,614)				(23,614)
Balance at Sep. 30, 2020	373,903	$ 7	473,841	(41)	(99,904)
Balance, Shares at Sep. 30, 2020		61,659,533
Balance at Dec. 31, 2020	353,064	$ 7	478,272	(112)	(125,103)
Balance, Shares at Dec. 31, 2020		61,931,255
Issuance of common stock, upon vesting of restricted stock, Shares		519,839
Unrealized (loss) gain on available-for-sale securities	42			42
Unrealized loss on foreign currency translation adjustment	83			83
Stock-based compensation	8,103		8,103
Net loss	(30,923)				(30,923)
Balance at Mar. 31, 2021	330,369	$ 7	486,375	13	(156,026)
Balance, Shares at Mar. 31, 2021		62,451,094
Balance at Dec. 31, 2020	$ 353,064	$ 7	478,272	(112)	(125,103)
Balance, Shares at Dec. 31, 2020		61,931,255
Issuance of common stock, upon exercise of stock options, Shares	9,425
Unrealized (loss) gain on available-for-sale securities	$ 23
Unrealized loss on foreign currency translation adjustment	(44)
Net loss	(114,021)
Balance at Sep. 30, 2021	267,304	$ 7	506,554	(133)	(239,124)
Balance, Shares at Sep. 30, 2021		63,177,928
Balance at Mar. 31, 2021	330,369	$ 7	486,375	13	(156,026)
Balance, Shares at Mar. 31, 2021		62,451,094
Issuance of common stock, upon vesting of restricted stock, Shares		340,949
Unrealized (loss) gain on available-for-sale securities	(16)			(16)
Unrealized loss on foreign currency translation adjustment	(22)			(22)
Stock-based compensation	9,726		9,726
Net loss	(37,588)				(37,588)
Balance at Jun. 30, 2021	302,469	$ 7	496,101	(25)	(193,614)
Balance, Shares at Jun. 30, 2021		62,792,043
Issuance of common stock, upon vesting of restricted stock, Shares		376,460
Issuance of common stock, upon exercise of stock options	167		167
Issuance of common stock, upon exercise of stock options, Shares		9,425
Unrealized (loss) gain on available-for-sale securities	(3)			(3)
Unrealized loss on foreign currency translation adjustment	(105)			(105)
Stock-based compensation	10,286		10,286
Net loss	(45,510)				(45,510)
Balance at Sep. 30, 2021	$ 267,304	$ 7	$ 506,554	$ (133)	$ (239,124)
Balance, Shares at Sep. 30, 2021		63,177,928