Annual report pursuant to Section 13 and 15(d)

Note 1 - The Company and Basis of Presentation (Details Textual)

v3.20.4
Note 1 - The Company and Basis of Presentation (Details Textual) - USD ($)
1 Months Ended 11 Months Ended 12 Months Ended
Jan. 19, 2021
Jun. 09, 2020
Jun. 08, 2020
Apr. 20, 2020
Apr. 16, 2020
Nov. 12, 2019
Sep. 30, 2020
Aug. 31, 2020
Jun. 30, 2020
May 31, 2020
Feb. 29, 2020
Nov. 30, 2019
Nov. 30, 2019
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Jan. 31, 2021
Jan. 18, 2021
Dec. 16, 2020
Apr. 15, 2020
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)                               2,473,785        
Preferred Stock, Shares Authorized (in shares)                             10,000,000 10,000,000        
Proceeds from Warrant Exercises                             $ 8,407,000        
Payments of Warrant Issuance Costs       $ 334,000                     334,000        
Debt Conversion, Converted Instrument, Amount                             35,529,000        
Retained Earnings (Accumulated Deficit), Ending Balance                             (219,826,000) (197,911,000)        
Cash and Cash Equivalents, at Carrying Value, Ending Balance                             6,523,000 13,308,000        
Working Capital                             8,628,000          
Net Cash Provided by (Used in) Operating Activities, Total                             (15,234,000) (31,236,000)        
Net Cash Provided by (Used in) Financing Activities, Total                             $ 9,230,000 $ 16,108,000        
Series B Convertible Preferred Stock Into Common Stock [Member] | Minimum [Member]                                        
Conversion of Stock, Conversion Rate (in dollars per share)           $ 15.30                            
Series B Convertible Preferred Stock Into Common Stock [Member] | Maximum [Member]                                        
Conversion of Stock, Conversion Rate (in dollars per share)           $ 18.36                            
Conversion of Term Loan with CRG Into Stock and Warrants [Member]                                        
Debt Conversion, Original Debt, Amount           $ 28,981,000                            
Debt Conversion, Converted Instrument, Amount           $ 31,300,000                            
Conversion of Term Loan with CRG Into Series B Convertible Preferred Stock [Member]                                        
Debt Conversion, Converted Instrument, Shares Issued (in shares)           31,300                            
Series A and Series B Warrants [Member]                                        
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                               $ 15.50       $ 6.10
Proceeds from Warrant Exercises         $ 3,089,000                              
Series A Warrants [Member]                                        
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                       1 1              
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                       $ 15.50 $ 15.50     $ 18.36        
Warrants and Rights Outstanding, Term (Year)                       1 year 1 year              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)                       741,939 741,939     989,379        
Stock Issued During Period, Shares, Warrant Exercises (in shares)         482,059     111,704 2,761 410 102,626                  
Proceeds from Warrant Exercises               $ 681,000 $ 17,000 $ 2,000 $ 1,591,000                  
Class of Warrant or Right, Outstanding (in shares)                             0          
Series B Warrants [Member]                                        
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                       1 1              
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                       $ 15.50 $ 15.50     $ 15.50        
Warrants and Rights Outstanding, Term (Year)                       5 years 5 years              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)                       741,939 741,939   325,632 741,940        
Stock Issued During Period, Shares, Warrant Exercises (in shares)         24,279   1,500 380,913 5,070   4,548                  
Proceeds from Warrant Exercises             $ 9,000 $ 2,324,000 $ 31,000   $ 70,000                  
Class of Warrant or Right, Outstanding (in shares)                             325,632          
Series A-2 Warrants [Member]                                        
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)       482,059                     392,830          
Stock Issued During Period, Shares, Warrant Exercises (in shares)               89,230             392,830          
Proceeds from Warrant Exercises               $ 568,000                        
Series B-2 Warrants [Member]                                        
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)       24,279                     20,380          
Stock Issued During Period, Shares, Warrant Exercises (in shares)               3,899             20,380          
Proceeds from Warrant Exercises               $ 25,000                        
Series A-2 and Series B-2 Warrants [Member]                                        
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)       $ 6.371                                
Warrants and Rights Outstanding, Term (Year)       5 years                                
Class of Warrant or Right, Outstanding (in shares)       1,838,000                                
Warrants Issued Upon Conversion of Term Loan with CRG [Member]                                        
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                               $ 15.50        
Warrants and Rights Outstanding, Term (Year)           5 years                            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)           989,379                   741,940        
Class of Warrants and Rights Outstanding, Exercise Price Percentage of Conversion Rate           120.00%                            
Class A Units [Member] | Series A Warrants [Member]                                        
Warrants Per Unit (in shares)                       1 1              
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                       1 1              
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                       $ 15.50 $ 15.50              
Warrants and Rights Outstanding, Term (Year)                       1 year 1 year              
Class A Units [Member] | Series B Warrants [Member]                                        
Warrants Per Unit (in shares)                       1 1              
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                       1 1              
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                       $ 15.50 $ 15.50              
Warrants and Rights Outstanding, Term (Year)                       5 years 5 years              
Class B Units [Member] | Series A Warrants [Member]                                        
Warrants Per Unit (in shares)                       1 1              
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                       1 1              
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                       $ 15.50 $ 15.50              
Warrants and Rights Outstanding, Term (Year)                       1 year 1 year              
Class B Units [Member] | Series B Warrants [Member]                                        
Warrants Per Unit (in shares)                       1 1              
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                       1 1              
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                       $ 15.50 $ 15.50              
Warrants and Rights Outstanding, Term (Year)                       5 years 5 years              
Common Stock [Member]                                        
Stock Issued During Period, Shares, New Issues (in shares)                             52,500          
Common Stock [Member] | Series A and Series B Warrants [Member]                                        
Stock Issued During Period, Shares, Warrant Exercises (in shares)                             1,115,863          
Common Stock [Member] | Series A-2 and Series B-2 Warrants [Member]                                        
Stock Issued During Period, Shares, Warrant Exercises (in shares)                             93,129          
Series A Preferred Stock [Member]                                        
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)                       1 1   1 1        
Stock Issued During Period, Shares, New Issues (in shares)                       547,345                
Preferred Stock, Shares Outstanding, Ending Balance (in shares)                             0 185,218     0  
Preferred Stock, Shares Authorized (in shares)                             547,345       547,345  
Preferred Stock, Par or Stated Value Per Share (in dollars per share)                             $ 0.0001 $ 0.0001     $ 0.0001  
Subsequent Event [Member] | Series A and Series B Warrants [Member]                                        
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) $ 3.40                                 $ 6.10    
Subsequent Event [Member] | Series A-2 and Series B-2 Warrants [Member]                                        
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) 1                                      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) $ 3.40                                 $ 6.371    
Subsequent Event [Member] | Class A Units [Member] | Warrants Issued in Connection with Class A Units [Member]                                        
Warrants Per Unit (in shares) 1                                      
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) 1                                      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) $ 3.40                                      
Warrants and Rights Outstanding, Term (Year) 5 years                                      
Subsequent Event [Member] | Class B Units [Member] | Warrants Issued in Connection with Class B Units [Member]                                        
Warrants Per Unit (in shares) 1                                      
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) 1                                      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) $ 3.40                                      
Warrants and Rights Outstanding, Term (Year) 5 years                                      
Subsequent Event [Member] | Series C Preferred Stock [Member]                                        
Preferred Stock, Shares Outstanding, Ending Balance (in shares)                                 0      
January 2021 Offering [Member] | Subsequent Event [Member]                                        
Proceeds from Issuance or Sale of Equity, Total $ 27,600,000                                      
Shares Issued, Price Per Share (in dollars per share) $ 3.40                                      
Proceeds from Issuance or Sale of Equity, Net of Issuance Costs $ 25,223,000                                      
January 2021 Offering [Member] | Subsequent Event [Member] | Class A Units [Member]                                        
Units Issued, Shares (in shares) 4,607,940                                      
Shares Issued, Price Per Share (in dollars per share) $ 3.40                                      
Common Shares Per Unit (in shares) 1                                      
January 2021 Offering [Member] | Subsequent Event [Member] | Class B Units [Member]                                        
Units Issued, Shares (in shares) 2,450,880                                      
Shares Issued, Price Per Share (in dollars per share) $ 3.40                                      
Series C Convertible Preferred Stock Per Unit (in shares) 1                                      
January 2021 Offering [Member] | Subsequent Event [Member] | Series C Preferred Stock [Member]                                        
Convertible Preferred Stock, Shares Issued upon Conversion (in shares) 1                                      
Stock Issued During Period, Shares, New Issues (in shares) 2,450,880                                      
Over-Allotment Option [Member] | Subsequent Event [Member]                                        
Stock Issued During Period, Shares, New Issues (in shares) 1,058,820                                      
Over-Allotment Option [Member] | Subsequent Event [Member] | Warrants Issued in Connection with January 2021 Offering [Member]                                        
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 1,058,820                                      
Purchase Agreement with LPC [Member]                                        
Shares Issued, Price Per Share (in dollars per share)   $ 6.50                                    
Stock Issued During Period, Shares, New Issues (in shares)   52,500                                    
Maximum Amount of Shares Issuable     $ 10,000,000                                  
Stock Purchase Agreement Duration Period (Month)     2 years 180 days                                  
Maximum Number of Shares Issuable on Any Business Day Selected by The Company (in shares)   25,000                                    
Maximum Number of Shares Issuable on Any Business Day Selected by The Company in Certain Circumstances (in shares)   50,000                                    
Purchase Agreement with LPC [Member] | Forecast [Member]                                        
Proceeds from Issuance or Sale of Equity, Total                           $ 9,700,000            
November 2019 Offering [Member]                                        
Proceeds from Issuance or Sale of Equity, Total                       $ 11,500,000                
Shares Issued, Price Per Share (in dollars per share)                       $ 15.50 $ 15.50              
Common Shares Per Unit (in shares)                       1 1              
Proceeds From Issuance of Common Stock, Net                       $ 9,922,000                
November 2019 Offering [Member] | Class A Units [Member]                                        
Shares Issued, Price Per Share (in dollars per share)                       $ 15.50 $ 15.50              
Common Shares Per Unit (in shares)                       1 1              
November 2019 Offering [Member] | Class B Units [Member]                                        
Shares Issued, Price Per Share (in dollars per share)                       $ 15.50 $ 15.50              
Series A Convertible Preferred Stock Per Unit (in shares)                       1 1              
November 2019 Offering [Member] | Common Stock [Member]                                        
Stock Issued During Period, Shares, New Issues (in shares)                       194,595 194,595     194,595        
November 2019 Offering [Member] | Series A Preferred Stock [Member]                                        
Stock Issued During Period, Shares, New Issues (in shares)                       547,345 547,341              
November 2019 Offering [Member] | Series A Preferred Stock [Member] | Class B Units [Member]                                        
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)                       1 1