Annual report pursuant to Section 13 and 15(d)

Related Party Transactions - Additional Information (Details)

v3.19.1
Related Party Transactions - Additional Information (Details) - USD ($)
12 Months Ended
Aug. 01, 2017
Dec. 31, 2018
Dec. 31, 2017
Related Party Transaction [Line Items]      
Loss on conversion of notes   $ 0 $ 4,619,000
Threshold Pharmaceuticals, Inc. Promissory Note      
Related Party Transaction [Line Items]      
Aggregate proceeds received from promissory note payable to Threshold Pharmaceuticals, Inc $ 4,000,000    
Longitude Venture Partners III, L.P. | Private Placement      
Related Party Transaction [Line Items]      
Ownership percentage of merger company 15.30%    
Investments $ 20,000,000    
CDK Associates, L.L.C. | Private Placement      
Related Party Transaction [Line Items]      
Ownership percentage of merger company 5.55%    
Investments $ 7,000,000    
BVF Partners L.P. | Public Offering      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   7.60%  
Investments   $ 15,300,000  
Perceptive Advisors LLC | Public Offering      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   5.90%  
Investments   $ 11,900,000  
Common Stock      
Related Party Transaction [Line Items]      
Stock issued   9,430,000 8,716,056
Common Stock | Longitude Venture Partners III, L.P. | Public Offering      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   12.33%  
Stock issued   365,000  
Common Stock | CDK Associates, L.L.C. | Public Offering      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   4.96%  
Stock issued   545,454  
Secured Convertible Promissory Notes      
Related Party Transaction [Line Items]      
Proceeds from stockholders     $ 10,000,000
Interest accrual rate     5.00%
Debt instrument maturity date     Sep. 07, 2017
Convertible notes price per share     $ 3.36
Debt principal amount     $ 10,000,000
Accrued interest on convertible notes payable     $ 486,900
Number of shares issued upon debt conversion     3,121,098
Loss on conversion of notes     $ 4,600,000
Secured Convertible Promissory Notes | Common Stock | Threshold      
Related Party Transaction [Line Items]      
Number of post split shares issued in merger     2,208,716