Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.20.2
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
 12 Months Ended
May 31, 2020
May 31, 2019
May 31, 2018
Jan. 28, 2020
Apr. 30, 2010
Summary Of Significant Accounting Policies [Line Items]          
Net loss $ (124,403,402) $ (56,186,660) $ (50,149,681)    
Accumulated (deficit) (354,710,895) (229,363,407)      
Balance in excess of federally insured limits 14,000,000 3,300,000      
Impairment charges 0 0 0    
Pre-launch inventory qualified for capitalization $ 0 $ 0      
Estimated future unvested forfeitures 0.00%        
Common stock, shares authorized 700,000,000 700,000,000      
Common stock, shares outstanding 518,975,572 329,395,752      
Preferred Stock Shares authorized to be issued 5,000,000 5,000,000      
Treasury stock, par value $ 0.001        
Treasury stock, shares 286,008        
Amortization of discount on convertible notes $ 1,644,625 $ 1,707,068 1,666,017    
Amortization of debt issuance costs $ 404,340 $ 459,085 $ 435,609    
Federal statutory income tax rate, percent 21.00% 21.00% 28.60%    
Deferred income tax benefit   $ (2,826,919)      
Restricted cash $ 10,000 $ 853,599      
Common stock options and warrants to purchase 131,360,528 178,591,849 132,385,269    
Equity Securities          
Summary Of Significant Accounting Policies [Line Items]          
Deferred offering costs $ 2,300,000 $ 4,300,000 $ 3,500,000    
Short-Term Convertible Notes          
Summary Of Significant Accounting Policies [Line Items]          
Debt discount 0        
Direct costs associated with the convertible notes 0 1,000,000      
Amortization of debt issuance costs 400,000 500,000 400,000    
Short-Term Convertible Notes | Detachable Common Stock Warrants          
Summary Of Significant Accounting Policies [Line Items]          
Debt discount 2,100,000 4,200,000 1,500,000    
Amortization of discount on convertible notes $ 1,600,000 $ 1,700,000 $ 1,600,000    
Series B Convertible Preferred Stock          
Summary Of Significant Accounting Policies [Line Items]          
Common stock, shares authorized         100,000,000
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 outstanding 8,203        
Common Stock          
Summary Of Significant Accounting Policies [Line Items]          
Common shares issued upon conversion of debt securities 3,864,298 11,345,852      
Common shares issued upon conversion of preferred stock 30,129,860 7,973,911      
Series D Convertible Preferred Stock          
Summary Of Significant Accounting Policies [Line Items]          
Preferred Stock Shares authorized to be issued 11,737 11,737   11,737  
Preferred stock, shares outstanding 8,452 0      
Certificate of Incorporation, as amended          
Summary Of Significant Accounting Policies [Line Items]          
Common stock, shares authorized 800,000,000        
Maximum          
Summary Of Significant Accounting Policies [Line Items]          
Preferred Stock Shares authorized to be issued 5,000,000