Quarterly report pursuant to Section 13 or 15(d)

Note 6 - Note Payable (Details Textual)

v3.21.1
Note 6 - Note Payable (Details Textual) - USD ($)
3 Months Ended
Nov. 12, 2019
Dec. 29, 2017
May 22, 2017
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)       9,793,605    
Notes Payable, Noncurrent, Total       $ 4,660,000   $ 4,518,000 [1]
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          
Warrants Issued Upon Conversion of Term Loan with CRG [Member]            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 989,379          
Warrants and Rights Outstanding, Term (Year) 5 years          
Class of Warrants and Rights Outstanding, Exercise Price Percentage of Conversion Rate 120.00%          
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          
The 2017 Loan Agreement [Member]            
Notes Payable, Noncurrent, Total       4,660,000    
The 2017 Loan Agreement [Member] | CRG LP [Member]            
Debt Instrument, Face Amount     $ 20,000,000      
Debt Agreement, Covenant, Additional Funding     10,000,000      
Debt Agreement, Maximum Borrowing Capacity     $ 30,000,000      
Proceeds from Lines of Credit, Total   $ 10,000,000        
Debt Instrument, Back-end Facility Fee Percentage of Principal 25.00%   5.00%      
Paid-in-Kind Interest       141,000 $ 126,000  
Notes Payable, Noncurrent, Total       $ 4,660,000   $ 4,518,000
[1] The condensed consolidated balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements as of that date.