Annual report pursuant to Section 13 and 15(d)

Stock Options and Warrants - Additional Information (Detail)

v3.20.2
Stock Options and Warrants - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Oct. 07, 2019
Sep. 12, 2019
Apr. 16, 2019
May 31, 2020
May 31, 2019
May 31, 2018
Mar. 13, 2020
Feb. 04, 2020
Nov. 30, 2019
May 22, 2019
Apr. 15, 2019
Apr. 05, 2019
Feb. 13, 2019
Jun. 15, 2018
Aug. 24, 2017
May 31, 2017
Mar. 31, 2016
Feb. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, Shares     150,000                              
Stock options, term 10 years 10 years                                
Warrants to purchase common shares, shares               833,332                    
Term of warrants                       5 years            
Exercise price of warrants, per share                 $ 0.45                  
Common Stock issued       519,261,580 329,554,763                          
Compensation expense       $ 6,547,803 $ 3,388,095 $ 1,290,777                        
Director                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         500,000                          
Term of warrants         10 years                          
Exercise price of warrants, per share         $ 0.51                          
Warrants grant date fair value         $ 0.28                          
Placement Agent                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares                 655,305     938,790 965,563 133,600        
Term of warrants           5 years     5 years       5 years 5 years        
Exercise price of warrants, per share                       $ 0.50 $ 0.50 $ 0.55        
Placement Agent | Minimum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Exercise price of warrants, per share                 $ 0.40                  
Placement Agent | Maximum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Exercise price of warrants, per share                 $ 0.444                  
Consultant                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         300,000                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.56                          
Warrants grant date fair value         $ 0.30                          
Investor                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares             275,625                      
Investor | Series C Convertible Preferred Stock [Member]                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         3,895,000                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.50                          
Two lead investor [Member] | Series C Convertible Preferred Stock [Member]                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         1,000,000                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.50                          
Private Equity Offering                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares           35,286,904                        
Term of warrants         5 years 5 years                        
Exercise price of warrants, per share         $ 0.75 $ 0.75                   $ 1.00    
Proceeds from Issuance of Common Stock         $ 23,500,000                          
Private Equity Offering | Placement Agent                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         4,446,917 2,813,491                        
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.50 $ 0.55                        
Private Equity Offering | Investor                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         23,487,585                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.75                          
Subscription Agreements | Investor                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Term of warrants             5 years                      
Exercise price of warrants, per share             $ 1.00                      
Convertible notes payable offering | Placement Agent                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         972,000                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.50                          
Convertible notes payable offering | Investor                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         5,460,000                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.30                          
Direct equity offering | Placement Agent                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares                       938,790 965,563 133,600        
Term of warrants                     5 years   5 years 5 years        
Exercise price of warrants, per share                     $ 0.50   $ 0.50 $ 0.55        
Direct equity offering | Investor                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares                     5,465,500   5,364,240 1,970,000        
Term of warrants                     5 years   5 years 5 years        
Exercise price of warrants, per share                     $ 0.50   $ 0.50 $ 0.75        
Secured convertible promissory note [Member] | Investor                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares         5,000,000                          
Term of warrants         5 years                          
Exercise price of warrants, per share         $ 0.30                          
Warrants [Member]                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Warrants to purchase common shares, shares       45,305,642                            
Common Stock issued       42,029,203                            
Proceeds from Issuance of Common Stock       $ 20,500,000                            
Warrants [Member] | Minimum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Exercise price of warrants, per share       $ 0.30                            
Warrants [Member] | Maximum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Exercise price of warrants, per share       $ 1.35                            
2012 Equity Incentive Plan                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Compensation expense       $ 6,500,000 $ 3,400,000 $ 1,300,000                        
Grant date fair value of options and warrants       3,300,000 $ 2,100,000 $ 1,400,000                        
Unrecognized compensation expense       $ 800,000                            
Weighted average period over which unrecognized compensation expense is expected to be recognized       8 years 14 days                            
2012 Equity Incentive Plan | Executive Management and Employees                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Vesting period         3 years                          
Stock options, term         10 years                          
2012 Equity Incentive Plan | Employee Stock Option One                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, Shares       8,753,828                            
Stock options, term       10 years                            
Common Stock issued       8,723,070                            
Proceeds from Issuance of Common Stock       $ 5,600,000                            
2012 Equity Incentive Plan | Employee Stock Option One | Range One                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, Shares       3,236,815                            
Stock option granted, exerices price       $ 0.39                            
2012 Equity Incentive Plan | Employee Stock Option One | Range Two                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price       2.25                            
2012 Equity Incentive Plan | Employee Stock Option One | Minimum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price       0.39                            
2012 Equity Incentive Plan | Employee Stock Option One | Maximum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price       $ 1.09                            
2012 Equity Incentive Plan | Employee Stock Option One | Director | Range One                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Shares available for future stock-based grants       724,486                            
Stock option granted, Shares         1,219,726                          
Stock option granted, exerices price         $ 0.49                          
Stock option vested, Shares       2,512,329                            
Vesting period         1 year                          
Stock options, term         10 years                          
2012 Equity Incentive Plan | Employee Stock Option One | Director | Range Two                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price         $ 0.57                          
2012 Equity Incentive Plan | Employee Stock Option One | Director | Minimum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock options grant date fair value       $ 0.19                            
2012 Equity Incentive Plan | Employee Stock Option One | Director | Maximum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock options grant date fair value       $ 1.65                            
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Shares available for future stock-based grants       1,650,000                            
Stock option granted, Shares       8,690,000                            
Stock option vested, Shares       4,600,000                            
Stock options, term       10 years                            
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Tranche One                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option vested, Shares       437,500                            
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Tranche Two                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option vested, Shares       890,000                            
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Tranche Three                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option vested, Shares       1,112,500                            
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Minimum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price       $ 0.30                            
Stock options grant date fair value       0.12 0.26                          
2012 Equity Incentive Plan | Employee Stock Option One | Executive Management and Employees | Maximum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price       1.10                            
Stock options grant date fair value       $ 0.79 0.41                          
2012 Equity Incentive Plan | Employee Stock Option One | Managing Director | Range One                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock options grant date fair value         0.29                          
2012 Equity Incentive Plan | Employee Stock Option One | Managing Director | Range Two                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock options grant date fair value         $ 0.31                          
2012 Equity Incentive Plan | Stock Options                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Shares available for future stock-based grants       1,162,511                            
2012 Equity Incentive Plan | Stock Options | Before Amendment                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Shares available for future issuance                   15,000,000         7,000,000   5,000,000 3,000,000
2012 Equity Incentive Plan | Stock Options | After Amendment                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Shares available for future issuance                   25,000,000         15,000,000   7,000,000 5,000,000
2012 Equity Incentive Plan | Stock Options | Executive Management and Employees                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, Shares         3,715,000                          
Warrants to purchase common shares, shares         950,000                          
2012 Equity Incentive Plan | Stock Options | Executive Management and Employees | Range One                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price         $ 0.48                          
2012 Equity Incentive Plan | Stock Options | Executive Management and Employees | Range Two                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock option granted, exerices price         $ 0.57