Quarterly report pursuant to Section 13 or 15(d)

Going Concern - (Details)

v3.22.2
Going Concern - (Details) - USD ($)
$ in Thousands
 1 Months Ended 9 Months Ended
Jan. 26, 2022
Sep. 30, 2021
May 31, 2021
Oct. 31, 2020
Jul. 07, 2020
May 31, 2020
May 31, 2022
May 31, 2021
Aug. 31, 2021
Going Concern [Line Items]                  
Cash             $ 100    
Working capital deficit             23,100    
Net cash provided by (used in) operating activities             (13,380) $ (14,661)  
Retained earnings (accumulated deficit)             (179,767)   $ (149,338)
Proceeds from underwritten public offering, net of offering costs             0 10,701  
Proceeds from issuance of private placement, net of offering costs             4,183 11,063  
Proceeds from warrant exercises $ 5,900                
Proceeds from exercised warrants, net of offering costs $ 5,400           $ 5,410 $ 0  
Underwritten Public Offering                  
Going Concern [Line Items]                  
Proceeds from underwritten public offering, net of offering costs       $ 12,000   $ 12,000      
Proceeds from issuance of common stock, net of offering costs       $ 10,700   $ 10,300      
Overallotment                  
Going Concern [Line Items]                  
Proceeds from underwritten public offering, net of offering costs         $ 1,400        
Proceeds from issuance of common stock, net of offering costs         $ 1,200        
Private Placement                  
Going Concern [Line Items]                  
Proceeds from issuance of private placement   $ 12,000 $ 12,000            
Proceeds from issuance of private placement, net of offering costs   $ 11,100 $ 11,100