CONDENSED STATEMENTS OF PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Preferred Stock Series A Preferred Stock	Preferred Stock Series A-3 preferred stock	Preferred Stock Series B Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Series A Preferred Stock	Series B Preferred Stock	Total
Balance at the beginning at Dec. 31, 2017				$ 1	$ 84		$ (24,498)			$ (24,413)
Balance at the beginning (in shares) at Dec. 31, 2017				1,369,212
Balance at the beginning at Dec. 31, 2017	$ 40,000
Balance at the beginning (in shares) at Dec. 31, 2017	40,000,000
Increase (Decrease) in Stockholders' Deficit
Stock based compensation					24					24
Net loss							(4,996)			(4,996)
Balance at the end at Mar. 31, 2018				$ 1	108		(29,494)			(29,385)
Balance at the end (in shares) at Mar. 31, 2018				1,369,212
Balance at the end at Mar. 31, 2018	$ 40,000
Balance at the end (in shares) at Mar. 31, 2018	40,000,000
Balance at the beginning at Dec. 31, 2017				$ 1	84		(24,498)			(24,413)
Balance at the beginning (in shares) at Dec. 31, 2017				1,369,212
Balance at the beginning at Dec. 31, 2017	$ 40,000
Balance at the beginning (in shares) at Dec. 31, 2017	40,000,000
Increase (Decrease) in Stockholders' Deficit
Net loss										(15,937)
Balance at the end at Sep. 30, 2018				$ 1	222		(40,435)			(40,212)
Balance at the end (in shares) at Sep. 30, 2018				1,369,212
Balance at the end at Sep. 30, 2018	$ 71,000
Balance at the end (in shares) at Sep. 30, 2018	68,181,819
Balance at the beginning at Mar. 31, 2018				$ 1	108		(29,494)			(29,385)
Balance at the beginning (in shares) at Mar. 31, 2018				1,369,212
Balance at the beginning at Mar. 31, 2018	$ 40,000
Balance at the beginning (in shares) at Mar. 31, 2018	40,000,000
Increase (Decrease) in Stockholders' Deficit
Initial public offering, net of issuance costs of $9.4 million		$ 31,000
Initial public offering, net of issuance costs of $9.4 million (in shares)		28,181,819
Stock based compensation					24					24
Net loss							(5,231)			(5,231)
Balance at the end at Jun. 30, 2018				$ 1	132		(34,725)			(34,592)
Balance at the end (in shares) at Jun. 30, 2018				1,369,212
Balance at the end at Jun. 30, 2018	$ 71,000
Balance at the end (in shares) at Jun. 30, 2018	68,181,819
Increase (Decrease) in Stockholders' Deficit
Stock based compensation					90					90
Net loss							(5,710)			(5,710)
Balance at the end at Sep. 30, 2018				$ 1	222		(40,435)			(40,212)
Balance at the end (in shares) at Sep. 30, 2018				1,369,212
Balance at the end at Sep. 30, 2018	$ 71,000
Balance at the end (in shares) at Sep. 30, 2018	68,181,819
Balance at the beginning at Dec. 31, 2018				$ 1	352		(47,297)			$ (46,944)
Balance at the beginning (in shares) at Dec. 31, 2018				1,374,812						1,374,812
Balance at the beginning at Dec. 31, 2018	$ 71,000		$ 91,223					$ 71,000	$ 91,223	$ 162,223
Balance at the beginning (in shares) at Dec. 31, 2018	68,181,819		56,828,851
Increase (Decrease) in Stockholders' Deficit
Stock based compensation					383					383
Issuance of stock					4					4
Issuance of stock (in shares)				4,697
Net loss							(6,155)			(6,155)
Balance at the end at Mar. 31, 2019				$ 1	739		(53,452)			(52,712)
Balance at the end (in shares) at Mar. 31, 2019				1,379,509
Balance at the end at Mar. 31, 2019	$ 71,000		$ 91,223
Balance at the end (in shares) at Mar. 31, 2019	68,181,819		56,828,851
Balance at the beginning at Dec. 31, 2018				$ 1	352		(47,297)			$ (46,944)
Balance at the beginning (in shares) at Dec. 31, 2018				1,374,812						1,374,812
Balance at the beginning at Dec. 31, 2018	$ 71,000		$ 91,223					$ 71,000	$ 91,223	$ 162,223
Balance at the beginning (in shares) at Dec. 31, 2018	68,181,819		56,828,851
Increase (Decrease) in Stockholders' Deficit
Unrealized loss on marketable securities										(58)
Net loss										(22,810)
Balance at the end at Sep. 30, 2019				$ 23	240,791	$ (58)	(70,107)			$ 170,649
Balance at the end (in shares) at Sep. 30, 2019				22,739,345						22,739,345
Balance at the beginning at Mar. 31, 2019				$ 1	739		(53,452)			$ (52,712)
Balance at the beginning (in shares) at Mar. 31, 2019				1,379,509
Balance at the beginning at Mar. 31, 2019	$ 71,000		$ 91,223
Balance at the beginning (in shares) at Mar. 31, 2019	68,181,819		56,828,851
Increase (Decrease) in Stockholders' Deficit
Initial public offering, net of issuance costs of $9.4 million				$ 6	76,848					76,854
Initial public offering, net of issuance costs of $9.4 million (in shares)				5,750,000
Conversion of preferred stock to common stock	$ (71,000)		$ (91,223)	$ 15	162,208					162,223
Conversion of preferred stock to common stock (in shares)	(68,181,819)		(56,828,851)	15,560,569
Stock based compensation					412					412
Issuance of stock				$ 1	38					39
Issuance of stock (in shares)				24,687
Net loss							(8,221)			(8,221)
Balance at the end at Jun. 30, 2019				$ 23	240,245		(61,673)			178,595
Balance at the end (in shares) at Jun. 30, 2019				22,714,765
Increase (Decrease) in Stockholders' Deficit
Stock based compensation					524					524
Issuance of stock					22					22
Issuance of stock (in shares)				24,580
Unrealized loss on marketable securities						(58)				(58)
Net loss							(8,434)			(8,434)
Balance at the end at Sep. 30, 2019				$ 23	$ 240,791	$ (58)	$ (70,107)			$ 170,649
Balance at the end (in shares) at Sep. 30, 2019				22,739,345						22,739,345