Quarterly report pursuant to sections 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended 112 Months Ended
Feb. 28, 2013
Feb. 29, 2012
Feb. 28, 2013
Feb. 29, 2012
Feb. 28, 2013
May 31, 2012
Class of Stock [Line Items]            
Net loss $ 2,359,107 $ 1,417,847 $ 7,082,759 $ 4,082,037 $ 29,915,365  
Accumulated deficit 31,517,277   31,517,277   31,517,277  
Working capital deficit 2,989,559   2,989,559   2,989,559  
Estimated future unvested option forfeitures     0.00%      
Deferred offering costs 423,486   423,486   423,486 677,327
Common stock options and warrants to purchase     18,038,297 8,331,576    
Convertible preferred stock, shares outstanding 95,100   95,100   95,100 98,900
Face amount of notes 5,908,250   5,908,250   5,908,250  
Unrecognized benefits 0   0   0  
Convertible Debt
            
Class of Stock [Line Items]            
Face amount of notes $ 5,341,250   $ 5,341,250   $ 5,341,250  
Investor
            
Class of Stock [Line Items]            
Warrants to purchase common shares, shares 7,877,343   7,877,343   7,877,343  
Series B convertible preferred stock
            
Class of Stock [Line Items]            
Convertible preferred stock, shares outstanding 95,100   95,100   95,100  
Common stock shares issued up on conversion of preferred stock     951,000      
Common Stock | Investor
            
Class of Stock [Line Items]            
Warrants to purchase common shares, shares 7,121,667   7,121,667   7,121,667