Annual report pursuant to Section 13 and 15(d)

Related Party Transactions - Additional Information (Details)

v3.8.0.1
Related Party Transactions - Additional Information (Details) - USD ($)
12 Months Ended
Aug. 01, 2017
Dec. 31, 2017
Dec. 31, 2016
Related Party Transaction [Line Items]      
Bridge note interest   $ 0 $ 201,000
Loss on conversion of notes   $ 4,619,000 0
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. | Concurrent Financing      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   15.30%  
Investments   $ 20,000,000  
CDK Associates, L.L.C. | Concurrent Financing      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   5.55%  
Investments   $ 7,000,000  
Excel Venture Fund II, L.P. | Concurrent Financing      
Related Party Transaction [Line Items]      
Investments   $ 333,000  
Excel Venture Fund II, L.P. | Concurrent Financing | Minimum      
Related Party Transaction [Line Items]      
Ownership percentage of merger company   5.00%  
Secured Convertible Promissory Notes      
Related Party Transaction [Line Items]      
Proceeds from stockholders $ 10,000,000   $ 7,300,000
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  
Bridge note interest   $ 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