Note 9 - Secured Promissory Note Payable to Oxford Finance	12 Months Ended
Dec. 31, 2021
Notes to Financial Statements
Secured Promissory Note Payable [Text Block]	NOTE 9. Secured Promissory Note Payable to Oxford Finance On December 22, 2016, the Company entered into a loan and security agreement (the “Loan Agreement”) with Oxford Finance, under which the Company borrowed $5.0 million. The $5.0 million loan, which bore interest at the 30-day U.S. LIBOR rate plus 6.17%, was evidenced by a secured promissory note and was repayable over four years, with interest only payable over the first 12 months and the balance fully amortized over the subsequent 36 months. The loan was secured by substantially all the Company’s assets, except for intellectual property. In conjunction with the execution of the Loan Agreement, all the holders of convertible promissory notes signed subordination agreements, under which they agreed to subordinate in favor of Oxford Finance all amounts due under their promissory notes and any security interest in the Company’s property. In addition, the holders of the notes agreed that they would not demand or receive any payment until all amounts owed to Oxford Finance under the Loan Agreement had been fully paid in cash. Upon repayment, an additional final payment equal to $325,000 would be due, which was accreted as interest expense over the term of the loan using the effective-interest method. In connection with the Loan Agreement, the Company issued a warrant to Oxford Finance to purchase 7,563 shares of its Series C convertible preferred stock at an exercise price of $33.11 per share (the “Warrant”). The fair value of the Warrant at the date of issuance was approximately $134,000 which, along with other initial costs, was recorded as debt discount and was amortized as interest expense over the term of the loan using the effective-interest method. Due to the antidilution protection, following the Merger, the Warrant was amended to allow the holder to purchase 10,914 shares of common stock at an exercise price of $22.99 per share. The annual effective interest rate of the note, including the accretion of the final payment and the amortization of the debt discount, was approximately 10.5%. The Company recorded interest expense related to the Loan Agreement of $311,000 during the year ended December 31, 2019, of which $223,000 was paid. The note was repaid in full on November 4, 2019. At that date, the unamortized deferred financing costs of $98,000 plus $2,000 reimbursed to Oxford Finance for legal fees were expensed as loss on debt extinguishment within other income and (expenses).

Note 9 - Secured Promissory Note Payable to Oxford Finance

12 Months Ended

Dec. 31, 2021

Secured Promissory Note Payable [Text Block]

NOTE 9. Secured Promissory Note Payable to Oxford Finance

On December 22, 2016, the Company entered into a loan and security agreement (the “Loan Agreement”) with Oxford Finance, under which the Company borrowed $5.0 million. The $5.0 million loan, which bore interest at the 30-day U.S. LIBOR rate plus 6.17%, was evidenced by a secured promissory note and was repayable over four years, with interest only payable over the first 12 months and the balance fully amortized over the subsequent 36 months. The loan was secured by substantially all the Company’s assets, except for intellectual property.

In conjunction with the execution of the Loan Agreement, all the holders of convertible promissory notes signed subordination agreements, under which they agreed to subordinate in favor of Oxford Finance all amounts due under their promissory notes and any security interest in the Company’s property. In addition, the holders of the notes agreed that they would not demand or receive any payment until all amounts owed to Oxford Finance under the Loan Agreement had been fully paid in cash. Upon repayment, an additional final payment equal to $325,000 would be due, which was accreted as interest expense over the term of the loan using the effective-interest method.

In connection with the Loan Agreement, the Company issued a warrant to Oxford Finance to purchase 7,563 shares of its Series C convertible preferred stock at an exercise price of $33.11 per share (the “Warrant”). The fair value of the Warrant at the date of issuance was approximately $134,000 which, along with other initial costs, was recorded as debt discount and was amortized as interest expense over the term of the loan using the effective-interest method. Due to the antidilution protection, following the Merger, the Warrant was amended to allow the holder to purchase 10,914 shares of common stock at an exercise price of $22.99 per share.

The annual effective interest rate of the note, including the accretion of the final payment and the amortization of the debt discount, was approximately 10.5%. The Company recorded interest expense related to the Loan Agreement of $311,000 during the year ended December 31, 2019, of which $223,000 was paid. The note was repaid in full on November 4, 2019. At that date, the unamortized deferred financing costs of $98,000 plus $2,000 reimbursed to Oxford Finance for legal fees were expensed as loss on debt extinguishment within other income and (expenses).