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Stockholders' Equity - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Dec. 23, 2020
Mar. 31, 2021
Dec. 31, 2020
Jul. 23, 2018
Class Of Stock [Line Items]        
Common stock, shares outstanding   14,306,614 15,160,397  
Series X1 Preferred Stock [Member]        
Class Of Stock [Line Items]        
Warrants available for exercise   55,853.875    
Shares of common stock issued upon conversion of each share of preferred stock   55.5556    
Series X Preferred Stock [Member]        
Class Of Stock [Line Items]        
Preferred shares outstanding   6,204 0  
Common Stock Warrants [Member]        
Class Of Stock [Line Items]        
Warrants available for exercise   846,939 337,822  
Common Stock [Member]        
Class Of Stock [Line Items]        
Common stock number of shares issued 1,004,111      
Warrant Exchange Agreement and Exchange Agreements [Member] | Series X Preferred Stock [Member]        
Class Of Stock [Line Items]        
Preferred shares outstanding     6,203.98  
Warrant Exchange Agreement and Exchange Agreements [Member] | Common Stock [Member]        
Class Of Stock [Line Items]        
Common stock, shares outstanding     14,306,614  
Warrant Exchange Agreement and Exchange Agreements [Member] | Common Stock [Member] | Series X Preferred Stock [Member]        
Class Of Stock [Line Items]        
Shares of common stock issued upon conversion of each share of preferred stock     344,663  
Exchange Agreement [Member]        
Class Of Stock [Line Items]        
Warrants available for exercise   509,117    
Piper Jaffray & Co. [Member] | Equity Distribution Agreement [Member]        
Class Of Stock [Line Items]        
Equity distribution agreement maximum value of common shares issuable       $ 9,800,000
Common stock number of shares issued   0 0  
BVF Exchanging Stockholders, Series X Exchanging Stockholders [Member] | Series X Exchange Agreement [Member] | Series X Preferred Stock [Member]        
Class Of Stock [Line Items]        
Conversion of stock, shares issued     6,203.98  
BVF Exchanging Stockholders, Series X Exchanging Stockholders [Member] | Series X Exchange Agreement [Member] | Common Stock [Member]        
Class Of Stock [Line Items]        
Conversion of stock, shares converted     344,666  
BVF Exchanging Stockholders | Warrant Exchange Agreement and Exchange Agreements [Member] | Common Stock [Member]        
Class Of Stock [Line Items]        
Warrants to issue shares of common stock     509,117