Annual report pursuant to Section 13 and 15(d)

Capital Stock - Biotechnology Value Fund Financing 2017 - Additional Information (Details)

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Capital Stock - Biotechnology Value Fund Financing 2017 - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Dec. 31, 2018
Feb. 28, 2017
Dec. 31, 2018
Dec. 31, 2017
Class Of Warrant Or Right [Line Items]        
Cash proceeds from issuance of common stock and convertible preferred stock $ 19.7      
Preferred stock, stated value $ 0.05   $ 0.05 $ 0.05
BVF [Member]        
Class Of Warrant Or Right [Line Items]        
Cash proceeds from issuance of common stock and convertible preferred stock   $ 24.8    
Series X Convertible Preferred Stock [Member]        
Class Of Warrant Or Right [Line Items]        
Sale of shares   5,003    
Preferred stock, stated value   $ 4,030    
Conversion of preferred stock into registered common stock   1,000    
Preferred stock conversion price per share $ 4.03 $ 4.03 $ 4.03  
Total number of shares of common stock issued upon conversion   5,003,000    
Percentage of convertible preferred stock conversion blocker provision   19.99%    
Fair value of common stock amount exceeded purchase price of convertible preferred stock   $ 5.6    
Series X and Series Y Convertible Preferred Stock [Member]        
Class Of Warrant Or Right [Line Items]        
Conversion of preferred stock into registered common stock 1,000   1,000  
Series Y Convertible Preferred Stock [Member]        
Class Of Warrant Or Right [Line Items]        
Preferred stock, stated value $ 13,000   $ 13,000  
Conversion of preferred stock into registered common stock 1,000   1,000  
Preferred stock conversion price per share $ 13.00   $ 13.00  
Total number of shares of common stock issued upon conversion 1,252,772   1,252,772  
Percentage of convertible preferred stock conversion blocker provision 19.99%      
Common Stock [Member]        
Class Of Warrant Or Right [Line Items]        
Sale of shares 285,689 1,200,000 354,000 1,849,000
Common stock share price   $ 4.03