Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.2
Note 1 - The Company and Basis of Presentation (Details Textual) - USD ($)
 1 Months Ended 2 Months Ended 3 Months Ended 9 Months Ended
Jul. 02, 2021
May 04, 2021
Jan. 19, 2021
Jun. 09, 2020
Jun. 08, 2020
Apr. 20, 2020
Apr. 16, 2020
Feb. 28, 2021
Feb. 29, 2020
Mar. 31, 2021
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
May 03, 2021
Jan. 31, 2021
Jan. 18, 2021
Dec. 31, 2020
Dec. 16, 2020
Dec. 15, 2020
Apr. 15, 2020
Dec. 31, 2019
Fair Value Adjustment of Warrants                     $ (0) $ (0) $ 373,000 $ 1,838,000                
Proceeds from Warrant Exercises                         $ 179,000 8,407,000                
Preferred Stock, Shares Authorized (in shares)                     10,000,000   10,000,000         10,000,000 [1]        
Proceeds from Issuance of Common Stock                         $ 25,122,000 0                
Payments of Warrant Issuance Costs           $ 326,000             (0) 333,000                
Retained Earnings (Accumulated Deficit), Ending Balance                     $ (235,525,000)   (235,525,000)         $ (219,826,000) [1]        
Net Cash Provided by (Used in) Operating Activities, Total                         (9,651,000) (12,936,000)                
Net Cash Provided by (Used in) Financing Activities, Total                         25,955,000 9,231,000                
Proceeds from Stock Plans                         21,000 $ 0                
Cash and Cash Equivalents, at Carrying Value, Ending Balance                     22,665,000   22,665,000         $ 6,523,000 [1]        
Working Capital                     $ 23,563,000   $ 23,563,000                  
Series C Preferred Stock [Member]                                            
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)                     1   1                  
Preferred Stock, Shares Outstanding, Ending Balance (in shares)                   0 0   0         0        
Preferred Stock, Par or Stated Value Per Share (in dollars per share)                     $ 0.0001   $ 0.0001         $ 0.0001        
Series A Preferred Stock [Member]                                            
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)                     1   1                  
Preferred Stock, Shares Outstanding, Ending Balance (in shares)                     0   0           0      
Preferred Stock, Shares Authorized (in shares)                                       547,345    
Preferred Stock, Par or Stated Value Per Share (in dollars per share)                                       $ 0.0001    
Series B, A-2 and B-2 Common Stock Warrants [Member]                                            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)   $ 2.817                         $ 3.40              
Fair Value Adjustment of Warrants   $ 86,000                                        
Warrants Issued in Connection with Class A Units [Member] | Class A Units [Member]                                            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)     $ 3.40                                      
Warrants Per Unit (in shares)     1                                      
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)     1                                      
Warrants and Rights Outstanding, Term (Year)     5 years                                      
Warrants Issued in Connection with Class B Units [Member] | Class B Units [Member]                                            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)     $ 3.40                                      
Warrants Per Unit (in shares)     1                                      
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)     1                                      
Warrants and Rights Outstanding, Term (Year)     5 years                                      
Warrants Issued in Connection with January 2021 Offering [Member]                                            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)                               $ 3.40            
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)                               1            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)     8,117,640             8,104,880 8,104,880   8,104,880     8,117,640            
Stock Issued During Period, Shares, Warrant Exercises (in shares)                   12,760                        
Proceeds from Warrant Exercises                   $ 43,000                        
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 $ 15.50
Proceeds from Warrant Exercises             $ 3,089,000                              
Series B Warrants [Member]                                            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)     3.40                           $ 6.10          
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)                     285,632   285,632                  
Stock Issued During Period, Shares, Warrant Exercises (in shares)             24,279 40,000 4,548                          
Proceeds from Warrant Exercises               $ 136,000 $ 70,000                          
Series A-2 and Series B-2 Warrants [Member]                                            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)     $ 3.40     $ 6.371                     $ 6.371          
Fair Value Adjustment of Warrants     $ 287,000                                      
Warrants and Rights Outstanding, Term (Year)           5 years                                
Series A Warrants [Member]                                            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)                     0   0                  
Stock Issued During Period, Shares, Warrant Exercises (in shares)             482,059   102,626                          
Proceeds from Warrant Exercises                 $ 1,591,000                          
Series A-2 Warrants [Member]                                            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)           482,059         392,830   392,830                  
Stock Issued During Period, Shares, Warrant Exercises (in shares)                         392,830                  
Series B-2 Warrants [Member]                                            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)           24,279         20,380   20,380                  
Stock Issued During Period, Shares, Warrant Exercises (in shares)                         20,380                  
Universal Shelf Registration Statement [Member]                                            
Universal Shelf Registration Statement, Proposed Maximum Securities Offering $ 75,000,000                                          
Universal Shelf Registration Statement, Maximum Capacity                     $ 75,000,000   $ 75,000,000                  
Stock Issued During Period, Shares, New Issues (in shares)                         0                  
Proceeds from Issuance or Sale of Equity, Total                         $ 0                  
Purchase Agreement with LPC [Member]                                            
Stock Issued During Period, Shares, New Issues (in shares)   250,000   52,500                                    
Shares Issued, Price Per Share (in dollars per share)   $ 2.817   $ 6.50                                    
Maximum Amount of Shares Issuable         $ 10,000,000                                  
Stock Purchase Agreement Duration Period (Month)         30 months                                  
Stock Purchase Agreement, Maximum Issuable Shares (in shares)         301,762                                  
Stock Purchase Agreement, Maximum Issuable Shares, Percent of Outstanding Stock         19.99%                                  
Stock Purchase Agreement, Share Price Covenant Trigger (in dollars per share)         $ 6.46                                  
Proceeds from Issuance of Common Stock   $ 704,000   $ 341,000                                    
Equity Facility, Remaining Financing Commitment                     $ 9,000,000   9,000,000                  
Proceeds From Issuance of Common Stock, Net                         633,000                  
January 2021 Offering [Member]                                            
Shares Issued, Price Per Share (in dollars per share)     $ 3.40                                      
Proceeds from Issuance or Sale of Equity, Total     $ 27,600,000                                      
Proceeds from Issuance or Sale of Equity, Net of Issuance Costs     $ 25,122,000                                      
Proceeds From Issuance of Common Stock, Net                         $ 25,122,000                  
January 2021 Offering [Member] | Class A Units [Member]                                            
Shares Issued, Price Per Share (in dollars per share)     $ 3.40                                      
Units Issued, Shares (in shares)     4,607,940                                      
Common Shares Per Unit (in shares)     1                                      
Warrants Per Unit (in shares)     1                                      
January 2021 Offering [Member] | Class B Units [Member]                                            
Shares Issued, Price Per Share (in dollars per share)     $ 3.40                                      
Units Issued, Shares (in shares)     2,450,880                                      
Common Shares Per Unit (in shares)     1                                      
Warrants Per Unit (in shares)     1                                      
Series C Convertible Preferred Stock Per Unit (in shares)     1                                      
January 2021 Offering [Member] | Series C Preferred Stock [Member]                                            
Stock Issued During Period, Shares, New Issues (in shares)     2,450,880                                      
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)     1             1                        
Over-Allotment Option [Member]                                            
Stock Issued During Period, Shares, New Issues (in shares)     1,058,820                                      
Over-Allotment Option [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                                      
First Amendment to the LPC Purchase Agreement [Member]                                            
Stock Issued During Period, Shares, New Issues (in shares)   250,000                                        
Shares Issued, Price Per Share (in dollars per share)   $ 2.817                                        
Stock Purchase Agreement, Maximum Issuable Shares (in shares)                   2,068,342                        
Stock Purchase Agreement, Maximum Issuable Shares, Percent of Outstanding Stock                   19.99%                        
Stock Purchase Agreement, Share Price Covenant Trigger (in dollars per share)                   $ 2.99                        
Proceeds from Issuance of Common Stock   $ 704,000                                        
[1] The condensed consolidated balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements as of that date.