Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.19.1
Stockholders' Equity - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended
Sep. 25, 2018
Feb. 27, 2018
Aug. 01, 2017
Jun. 23, 2017
Dec. 31, 2017
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock           3,521,735   3,521,735
Increase (decrease) in common stock warrants           $ (4,000) $ 614,000  
Issuance of warrant to purchase common stock in relation to term loan facility             1,521,000  
Term Loan Facility | Perceptive Credit Facility                
Class Of Warrant Or Right [Line Items]                
Warrant exercisable period   7 years            
Common stock exercise price   $ 9.5792            
Number of shares to be issued upon exercise of warrant   190,000            
2017 Warrants                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock           377,273   377,273
Common stock exercise price           $ 39.82    
Common Stock                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock           3,521,735    
Issuance of warrant to purchase common stock in relation to term loan facility             0  
Common Stock | Term Loan Facility | Perceptive Credit Facility                
Class Of Warrant Or Right [Line Items]                
Warrant exercisable period   7 years            
Common stock exercise price   $ 9.58            
Issuance of warrant to purchase common stock in relation to term loan facility   $ 1,500,000            
Expected dividend rate   0.00%            
Expected volatility   105.00%            
Risk free interest rate   2.83%            
Expected term   7 years            
Number of shares to be issued upon exercise of warrant   190,000            
Common Stock | 2017 Warrants                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock     377,273          
Common stock exercise price     $ 39.82          
Increase (decrease) in common stock warrants           $ 4,000 $ (614,000)  
Wedbush Agreement                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock         57,930      
Common stock exercise price         $ 6.84      
Issuance of warrant to purchase common stock in relation to term loan facility         $ 400,000      
Expected dividend rate         0.00%      
Expected volatility         108.00%      
Risk free interest rate         2.33%      
Expected term         7 years      
Takeda Pharmaceuticals Inc                
Class Of Warrant Or Right [Line Items]                
Aggregate purchase price       $ 20,000,000        
Each unit of shares transaction of common stock       2,922,993        
Purchase price per share       $ 6.84        
Private Placement                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock           2,954,462   2,954,462
Common stock exercise price           $ 6.84    
Private Placement | Common Stock                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock     2,896,532          
Common stock exercise price     $ 6.84          
Issuance of warrant to purchase common stock in relation to term loan facility     $ 16,300,000          
Expected dividend rate     0.00%          
Expected volatility     147.00%          
Risk free interest rate     2.07%          
Expected term     7 years          
Private Placement | Longitude Venture Partners III, L.P.                
Class Of Warrant Or Right [Line Items]                
Number of aggregate units sold     5,793,063          
Aggregate purchase price     $ 40,000,000          
Each unit of shares transaction of common stock     1          
Warrants to purchase shares of common stock     0.5     2,896,532    
Sale of units, description and its composition           the Company sold an aggregate of 5,793,063 units (the “Units”) accredited investors having an aggregate purchase price of $40.0 million, each such Unit consisting of (i) one (1) share (the “Shares”) of the Company’s common stock and (ii) a warrant (the “Private Placement Warrants”) to purchase 0.5 shares of the Company’s common stock (the “Private Placement”).    
Purchase price per unit     $ 6.9048          
Warrant exercisable period     7 years          
Common stock exercise price     $ 6.8423          
Private Placement | Wedbush Agreement | Common Stock                
Class Of Warrant Or Right [Line Items]                
Warrants to purchase shares of common stock         57,930 57,930    
Warrant exercisable period         7 years      
Common stock exercise price         $ 6.8423      
Underwritten Public Offering                
Class Of Warrant Or Right [Line Items]                
Shares issued under public offering 9,430,000              
Shares issued, price per share $ 5.50              
Proceeds from public offering $ 48,100,000              
Over-Allotment Option                
Class Of Warrant Or Right [Line Items]                
Shares issued under public offering 1,230,000