Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Private Placement	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Common Stock	Common Stock Private Placement	Additional Paid in Capital	Additional Paid in Capital Private Placement	Other Comprehensive Income / (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ (32,626)				$ 3		$ 245		$ (49)	$ (32,825)
Beginning balance, shares at Dec. 31, 2018			9,008,919	9,152,108
Beginning balance at Dec. 31, 2018			$ 17,178	$ 86,868
Beginning balance, shares at Dec. 31, 2018					3,412,366
Exercise of stock options	69				$ 1		68
Exercise of stock options, shares					166,015
Stock based compensation	1,479						1,479
Vesting of Series B redeemable convertible preferred stock in lieu of rent				$ 948
Conversion of redeemable convertible preferred stock to common stock	104,994				$ 18		104,976
Conversion of redeemable convertible preferred stock to common stock, shares			(9,008,919)	(9,152,108)
Conversion of redeemable convertible preferred stock to common stock			$ (17,178)	$ (87,816)
Conversion of redeemable convertible preferred stock to common stock, shares					18,161,027
Issuance of common stock, net of issuance costs	77,827				$ 5		77,822
Issuance of common stock, net of issuance costs, shares					5,073,800
Exercise of stock warrant, shares					27,941
Other comprehensive income (loss)	145								145
Net loss	(24,601)									(24,601)
Ending balance at Sep. 30, 2019	127,287				$ 27		184,590		96	(57,426)
Ending balance, shares at Sep. 30, 2019					26,841,149
Beginning balance at Jun. 30, 2019	136,217				$ 27		183,678		80	(47,568)
Beginning balance, shares at Jun. 30, 2019					26,841,149
Stock based compensation	912						912
Other comprehensive income (loss)	16								16
Net loss	(9,858)									(9,858)
Ending balance at Sep. 30, 2019	127,287				$ 27		184,590		96	(57,426)
Ending balance, shares at Sep. 30, 2019					26,841,149
Beginning balance at Dec. 31, 2019	115,478				$ 27		185,196		60	(69,805)
Beginning balance, shares at Dec. 31, 2019					26,869,413
Exercise of stock options	1,235						1,235
Exercise of stock options, shares					124,836
Stock based compensation	9,511						9,511
Issuance of common stock, net of issuance costs		$ 117,628				$ 2		$ 117,626
Issuance of common stock, net of issuance costs, shares						2,500,000
Other comprehensive income (loss)	453								453
Net loss	(56,294)									(56,294)
Ending balance at Sep. 30, 2020	188,011				$ 29		313,568		513	(126,099)
Ending balance, shares at Sep. 30, 2020					29,494,249
Beginning balance at Jun. 30, 2020	205,467				$ 29		309,320		711	(104,593)
Beginning balance, shares at Jun. 30, 2020					29,486,269
Exercise of stock options	90						90
Exercise of stock options, shares					7,980
Stock based compensation	4,158						4,158
Other comprehensive income (loss)	(198)								(198)
Net loss	(21,506)									(21,506)
Ending balance at Sep. 30, 2020	$ 188,011				$ 29		$ 313,568		$ 513	$ (126,099)
Ending balance, shares at Sep. 30, 2020					29,494,249