Annual report pursuant to Section 13 and 15(d)

Organization and Description of Business - Additional Information (Detail)

v3.20.1
Organization and Description of Business - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 18, 2019
Dec. 12, 2019
Aug. 03, 2018
Jul. 25, 2017
Jul. 27, 2016
Jun. 12, 2015
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Organization And Description Of Business [Line Items]                  
Accumulated deficit             $ (212,114,385) $ (199,319,892)  
Net cash used in operating activities             $ (27,427,893) $ (26,258,849) $ (24,528,993)
Number of shares issued 2,565,000 3,715,000              
Public offering price, per unit $ 3.90 $ 2.70              
Net proceeds received $ 10,000,000                
Gross Proceed   $ 13,000,000              
Combined Net Proceeds   $ 21,300,000              
Follow-on Offering [Member]                  
Organization And Description Of Business [Line Items]                  
Number of shares issued     575,000 3,200,000 1,400,000        
Warrants to purchase shares of common stock       1,600,000          
Warrant exercise price per share       $ 15.50 $ 30.00        
Public offering price, per unit     $ 20.00 $ 12.50          
Net proceeds received     $ 10,400,000 $ 37,100,000 $ 32,000,000        
Private Placement [Member]                  
Organization And Description Of Business [Line Items]                  
Number of shares issued           472,812      
Warrants to purchase shares of common stock           236,406 18,903    
Warrant exercise price per share           $ 80.00 $ 46.50    
Public offering price, per unit   $ 2.70              
Net proceeds received           $ 18,300,000      
Issuance of securities in private placement, Shares   1,111,111