Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.19.2
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
 12 Months Ended
May 31, 2019
May 31, 2018
May 31, 2017
May 22, 2019
Nov. 08, 2018
Jun. 07, 2018
Apr. 30, 2010
Summary Of Significant Accounting Policies [Line Items]              
Net loss $ (56,186,660) $ (50,149,681) $ (25,763,801)        
Accumulated (deficit) (229,363,407) (173,139,396)          
Balance in excess of federally insured limits 3,300,000 1,100,000          
Impairment charges 0 0 0        
Pre-launch inventory qualified for capitalization $ 0 $ 0          
Estimated future unvested forfeitures 0.00%            
Common stock, shares authorized 700,000,000 375,000,000         100,000,000
Preferred Stock Shares authorized to be issued 5,000,000            
Treasury stock, par value $ 0.001            
Treasury stock, shares 159,011            
Amortization of discount on convertible notes $ 1,707,068 $ 1,666,017 0        
Amortization of debt issuance costs $ 459,085 $ 435,609 $ 0        
Federal statutory income tax rate, percent 21.00% 28.60% 34.00%        
Deferred income tax benefit $ (2,826,919) $ 0 $ 0        
Restricted cash $ 853,599 $ 0          
Common stock options and warrants to purchase 178,591,849 132,385,269 77,859,626        
Equity Securities              
Summary Of Significant Accounting Policies [Line Items]              
Deferred offering costs $ 4,300,000 $ 3,500,000 $ 1,800,000        
Short-Term Convertible Notes              
Summary Of Significant Accounting Policies [Line Items]              
Debt discount 0            
Direct costs associated with the convertible notes 1,000,000 400,000          
Amortization of debt issuance costs 500,000 400,000 0        
Short-Term Convertible Notes | Detachable Common Stock Warrants              
Summary Of Significant Accounting Policies [Line Items]              
Debt discount 4,200,000 1,500,000 92,000        
Amortization of discount on convertible notes $ 1,700,000 $ 1,600,000 $ 0        
Series B Convertible Preferred Stock              
Summary Of Significant Accounting Policies [Line Items]              
Preferred Stock Shares authorized to be issued 400,000 400,000          
Preferred stock, shares outstanding 92,100 92,100          
Series C Convertible Preferred Stock              
Summary Of Significant Accounting Policies [Line Items]              
Preferred Stock Shares authorized to be issued 5,000            
Preferred stock, shares outstanding 3,246            
Common Stock              
Summary Of Significant Accounting Policies [Line Items]              
Common shares issued upon conversion of preferred stock 7,413,000            
Series C and B Preferred Stock              
Summary Of Significant Accounting Policies [Line Items]              
Preferred stock, shares outstanding 95,346            
Maximum              
Summary Of Significant Accounting Policies [Line Items]              
Common stock, shares authorized       700,000,000 600,000,000 450,000,000  
Preferred Stock Shares authorized to be issued 5,000,000            
Minimum              
Summary Of Significant Accounting Policies [Line Items]              
Common stock, shares authorized       600,000,000 450,000,000 375,000,000