Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.7.0.1
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
 12 Months Ended
May 31, 2017
May 31, 2016
May 31, 2015
Aug. 24, 2016
Mar. 18, 2016
Mar. 17, 2016
Apr. 30, 2010
Summary Of Significant Accounting Policies [Line Items]              
Net loss $ (25,763,801) $ (25,703,612)          
Accumulated (deficit) (122,989,715) (97,225,914)          
Balance in excess of federally insured limits 1,500,000 9,400,000          
Impairment charges 0 0          
Pre-launch inventory qualified for capitalization $ 0 $ 0          
Estimated future unvested forfeitures 0.00%            
Common stock, shares authorized 350,000,000 250,000,000   350,000,000 250,000,000 200,000,000 100,000,000
Direct costs associated with the convertible notes $ 0   $ 709,000        
Amortization of debt issuance costs   $ 604,625          
Common stock options and warrants to purchase 77,859,626 63,307,150          
Convertible promissory notes $ 1,150,000            
Unrecognized benefits $ 0            
AVCP Convertible note payable              
Summary Of Significant Accounting Policies [Line Items]              
Number of shares issuable upon potentially debt conversion 1,533,333            
Equity Securities              
Summary Of Significant Accounting Policies [Line Items]              
Deferred offering costs $ 1,800,000 $ 3,900,000          
2015 Short-Term Convertible Notes              
Summary Of Significant Accounting Policies [Line Items]              
Amortization of debt issuance costs 0 $ 605,000          
Debt discount 0            
2017 Short Term Convertible Notes              
Summary Of Significant Accounting Policies [Line Items]              
Debt discount $ 92,000            
Series B Convertible Preferred Stock              
Summary Of Significant Accounting Policies [Line Items]              
Preferred Stock Shares authorized to be issued 400,000 400,000          
Common stock options and warrants to purchase 92,100 95,100          
Common shares issued upon conversion of preferred stock 921,000            
Maximum              
Summary Of Significant Accounting Policies [Line Items]              
Preferred Stock Shares authorized to be issued 5,000,000            
Minimum              
Summary Of Significant Accounting Policies [Line Items]              
Income tax examination, year under examination 2012