Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability - Additional Information (Details) $ / shares in Units, $ in Thousands										2 Months Ended	3 Months Ended	5 Months Ended	9 Months Ended
	Sep. 29, 2020 shares	Sep. 28, 2020 USD ($) $ / shares shares	Sep. 16, 2020	Jul. 28, 2020 $ / shares shares	Jul. 02, 2020 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares	Mar. 05, 2020 shares	Mar. 04, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Aug. 31, 2020 USD ($)	Sep. 30, 2020 $ / shares shares	Jul. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 shares
Class Of Stock [Line Items]
Share issue price per share | $ / shares						$ 7.52
Common stock, shares authorized		200,000,000		32,685,000							200,000,000		200,000,000	10,895,000
Convertible preferred stock, shares authorized				15,647,052
Convertible preferred stock, shares authorized		10,000,000									10,000,000		10,000,000	0
Preferred stock, shares issued											0		0	0
Preferred stock, shares outstanding											0		0	0
Preferred stock tranche liability | $								$ 1,100
Non cash expenses due to remeasured fair value of tranche liability | $						$ 17,000			$ 0				$ (17,030)
Mile stone shares issued during the period					4,000,000	200,000
Amount reclassified to convertible preferred stock | $					$ 18,100
Common Stock
Class Of Stock [Line Items]
Shares issued during period											9,050,000		9,050,000
Conversion of stock, shares issued		17,047,378									17,047,378		17,047,378
Conversion ratio		1.0895	1.0895
Series A Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of convertible preferred stock to common stock, shares		10,000,000									10,000,000		10,000,000
Convertible preferred stock, shares authorized				10,000,000
Number of share options exercised					3,800,000	200,000
Clinical milestones for gross proceeds | $					$ 11,400	$ 600
Proceeds from issuances of convertible preferred stock, net of issuance costs | $									0			$ 30,000	$ 29,569
Convertible preferred stock tranche liability, offering price | $ / shares								$ 3.00
Convertible preferred stock tranche liability, term								1 year
Mile stone pro-rate shares issued during the period						200,000
Series A Convertible Preferred Stock | Risk Free Rate
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input								0.0059
Series A Convertible Preferred Stock | Expected Volatility
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input								0.80
Series A Convertible Preferred Stock | Probability of Achieving Clinical Milestones and Timing
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input								0.60
Series A Convertible Preferred Stock | PBM TGT Holdings, LLC
Class Of Stock [Line Items]
Shares issued during period						3,266,667
Series A Convertible Preferred Stock | Nolan Capital, LLC
Class Of Stock [Line Items]
Shares issued during period						400,000
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of convertible preferred stock to common stock, shares		5,647,048									5,647,048		5,647,048
Convertible preferred stock, shares authorized				5,647,052
Proceeds from issuances of convertible preferred stock, net of issuance costs | $									$ 0	$ 96,000			$ 95,815
Convertible preferred stock tranche liability, offering price | $ / shares						$ 17.00
Convertible preferred stock tranche liability, term						6 months
Series B Convertible Preferred Stock | Risk Free Rate
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input						0.0017
Series B Convertible Preferred Stock | Expected Volatility
Class Of Stock [Line Items]
Convertible preferred stock tranche liability, measurement input						0.80
Series B Convertible Preferred Stock | Series B Purchase Agreement
Class Of Stock [Line Items]
Share issue price per share | $ / shares					$ 17.00
IPO
Class Of Stock [Line Items]
Shares issued during period		7,869,566											9,050,000
Share issue price per share | $ / shares		$ 20.00									$ 20.00		$ 20.00
Gross proceeds from issuance of common stock | $		$ 181,000
Stock issuance costs, including underwriters’ discounts and commissions | $		$ 15,100
Increase in outstanding shares		26,097,378
Underwriters’ Option to Purchase Additional Shares
Class Of Stock [Line Items]
Shares issued during period	1,180,434
Private Placement | Series A Convertible Preferred Stock | Series A Purchase Agreement
Class Of Stock [Line Items]
Share issue price per share | $ / shares								$ 3.00
Private Placement | Series A Convertible Preferred Stock | Series A Purchase Agreement | Maximum
Class Of Stock [Line Items]
Shares issued during period								10,000,000
Private Placement | Series A Convertible Preferred Stock | Initial Closing
Class Of Stock [Line Items]
Shares issued during period								6,000,000
Private Placement | Series A Convertible Preferred Stock | Achievement of Specific Clinical Milestone One
Class Of Stock [Line Items]
Shares issued during period							2,000,000
Private Placement | Series A Convertible Preferred Stock | Achievement of Specific Clinical Milestone Two
Class Of Stock [Line Items]
Shares issued during period							2,000,000
Private Placement | Series A Convertible Preferred Stock | Upon Achievement of Certain Defined Clinical Milestones
Class Of Stock [Line Items]
Shares issued during period								4,000,000
Private Placement | Series B Convertible Preferred Stock | Series B Purchase Agreement
Class Of Stock [Line Items]
Shares issued during period				5,647,048
Share issue price per share | $ / shares				$ 17.00
Proceeds from issuances of convertible preferred stock, net of issuance costs | $										$ 96,000
Private Placement | Series B Convertible Preferred Stock | Series B Purchase Agreement | Maximum
Class Of Stock [Line Items]
Shares issued during period				5,647,052