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Organization - Additional Information (Details) - USD ($)
 12 Months Ended
Apr. 10, 2019
Mar. 22, 2019
Feb. 01, 2019
Dec. 31, 2019
Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Entity incorporation date       Jul. 05, 2016  
Net proceeds received from offering       $ 49,747,000 $ 90,908,000
Accumulated deficit       154,132,000 71,393,000
Cash, cash equivalents and marketable securities       91,500,000  
Initial Public Offering          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Number of common stock shares sold 487,934 7,200,000      
Issuance price per shares $ 6.95 $ 6.95      
Net proceeds received from offering $ 3,200,000 $ 46,600,000      
Underwriting discounts and commissions and other offering expenses $ 200,000 $ 3,500,000      
Net proceeds received from offering       49,747,000 $ 89,370,000
Initial Public Offering | Maximum          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Option to purchase of common stock at public offering price   1,080,000      
At-the-Market Offering          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Net proceeds received from offering       $ 6,716,000  
At-the-Market Offering | Controlled Equity Offering Sales Agreement | SVB Leerink LLC and Cantor Fitzgerald and Co          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Number of common stock shares sold       688,000  
Issuance price per shares       $ 10.18  
Maximum aggregate value of common stock available for offering At-the-Market price     $ 50,000,000    
Sales commission percentage payable to sales agents in cash     3.00%    
Net proceeds received from offering       $ 6,700,000  
Issuance costs       75,000  
Common stock remained available for offering       $ 43,000,000