Derivative Instruments	9 Months Ended
Sep. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	12. Derivative Instruments *Derivative Instrument in Connection with the 2020 Convertible Notes* One of the redemption features of the 2020 Convertible Notes met the requirements for separate accounting and was accounted for as a derivative instrument. The 2020 Derivative Instrument was recorded at fair value, which was $0.7 million at issuance. In August 2020, in connection with our issuance and sale of Series D Preferred Stock, all of the outstanding principal and accrued interest under the 2020 Convertible Notes was automatically converted into shares of Series D Preferred Stock and the derivative liability was extinguished. Prior to the extinguishment of derivative liability, the 2020 Derivative Instrument was marked to fair value and we recorded the change in the 2020 Derivative Instrument of ($29) thousand in the consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2020 (see Note 11). For the three and nine months ended September 30, 2020, we recorded the change in the 2020 Derivative Instrument of $15 thousand and $29 thousand, respectively, in the condensed consolidated statements of operations and comprehensive income (loss). Upon the closing of the Reverse Recapitalization (see Note 3), and pursuant to the Merger Agreement, all outstanding Clene Nanomedicine Preferred Stock was converted to Clene Inc. Common Stock. *Derivative Instruments in Connection with the Contingent Earn-Outs* The earn-out shares issued in connection with the Reverse Recapitalization met the requirements for separate accounting and are therefore accounted for as derivative instruments. Accordingly, upon the consummation of the Reverse Recapitalization, we recorded a liability in the condensed consolidated balance sheets and a debit to additional paid-in capital for the earn-out provision associated with the Initial Shareholders Contingent Earn-out and a debit to accumulated deficit for the earn-out provisions associated with the Clene Nanomedicine Contingent Earn-out. The contingent shares to be issued to the Clene Nanomedicine shareholders immediately prior to the Reverse Capitalization were treated as a deemed distribution. The Contingent Earn-outs were subsequently remeasured to fair value at each reporting date as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). Upon the closing of the Reverse Recapitalization, we recognized the Clene Nanomedicine Contingent Earn-out and Initial Shareholders Contingent Earn-out liabilities at their fair value of $64.7 million and $7.4 million, respectively, in the condensed consolidated balance sheets. As of December 31, 2020, the carrying values of the Clene Nanomedicine Contingent Earn-out and Initial Shareholders Contingent Earn-out were $52.1 million and $5.9 million, respectively. As of September 30, 2021, the carrying values of the Clene Nanomedicine Contingent Earn-out and Initial Shareholders Contingent Earn-out were $34.0 million and $4.2 million, respectively. For the three months ended September 30, 2021, we recognized gains of $35.0 million in change in fair value of the Clene Nanomedicine Contingent Earn-out and $3.4 million in change in fair value of the Initial Shareholders Contingent Earn-out as components of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). For the nine months ended September 30, 2021, we recognized gains of $18.1 million in change in fair value of the Clene Nanomedicine Contingent Earn-out and $1.7 million in change in fair value of the Initial Shareholders Contingent Earn-out as components of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). To date, none of the milestones have been achieved. *Derivative Instrument in Connection with the 2021 Avenue Loan* The Avenue Warrants issued pursuant to Tranche 1 of the 2021 Avenue Loan and the warrants issuable pursuant to the draw of Tranche 2 (see Note 8) met the requirements for separate accounting and are therefore accounted for as derivative instruments. The 2021 Avenue Loan has the following features: (i) prepayment provision, (ii) final payment provision, (iii) event of default redemption provision, and (iv) event of default interest provision. The provisions (i) to (iii) are related to the loan host and are not bifurcated pursuant to ASC 815. For the provision (iv), we have not experienced an event of default in the past and believe the probability of triggering one in the future is remote. Therefore, we determined the value of this feature to be de minimis on the remote probability of occurrence of a triggering event. Upon the closing of the 2021 Avenue Loan, we recognized the warrant liability as a debt discount based on its fair value of $1.5 million. The debt discount is being amortized over the contractual term using the effective interest method. Our determination of the fair value of the warrant utilized the Black-Scholes option-pricing valuation model. Additionally, a Monte Carlo simulation was used to simulate the exercise price as an input in the Black-Scholes valuation model (see Note 10). For the three and nine months ended September 30, 2021, we recognized income of $0.4 million and $0.5 million, respectively, in change in fair value of the warrant as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). To date, the warrants have not been exercised.

Derivative Instruments

9 Months Ended

Sep. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

12. Derivative Instruments

Derivative Instrument in Connection with the 2020 Convertible Notes

One of the redemption features of the 2020 Convertible Notes met the requirements for separate accounting and was accounted for as a derivative instrument. The 2020 Derivative Instrument was recorded at fair value, which was $0.7 million at issuance. In August 2020, in connection with our issuance and sale of Series D Preferred Stock, all of the outstanding principal and accrued interest under the 2020 Convertible Notes was automatically converted into shares of Series D Preferred Stock and the derivative liability was extinguished. Prior to the extinguishment of derivative liability, the 2020 Derivative Instrument was marked to fair value and we recorded the change in the 2020 Derivative Instrument of ($29) thousand in the consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2020 (see Note 11). For the three and nine months ended September 30, 2020, we recorded the change in the 2020 Derivative Instrument of $15 thousand and $29 thousand, respectively, in the condensed consolidated statements of operations and comprehensive income (loss). Upon the closing of the Reverse Recapitalization (see Note 3), and pursuant to the Merger Agreement, all outstanding Clene Nanomedicine Preferred Stock was converted to Clene Inc. Common Stock.

Derivative Instruments in Connection with the Contingent Earn-Outs

The earn-out shares issued in connection with the Reverse Recapitalization met the requirements for separate accounting and are therefore accounted for as derivative instruments. Accordingly, upon the consummation of the Reverse Recapitalization, we recorded a liability in the condensed consolidated balance sheets and a debit to additional paid-in capital for the earn-out provision associated with the Initial Shareholders Contingent Earn-out and a debit to accumulated deficit for the earn-out provisions associated with the Clene Nanomedicine Contingent Earn-out. The contingent shares to be issued to the Clene Nanomedicine shareholders immediately prior to the Reverse Capitalization were treated as a deemed distribution. The Contingent Earn-outs were subsequently remeasured to fair value at each reporting date as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss).

Upon the closing of the Reverse Recapitalization, we recognized the Clene Nanomedicine Contingent Earn-out and Initial Shareholders Contingent Earn-out liabilities at their fair value of $64.7 million and $7.4 million, respectively, in the condensed consolidated balance sheets. As of December 31, 2020, the carrying values of the Clene Nanomedicine Contingent Earn-out and Initial Shareholders Contingent Earn-out were $52.1 million and $5.9 million, respectively. As of September 30, 2021, the carrying values of the Clene Nanomedicine Contingent Earn-out and Initial Shareholders Contingent Earn-out were $34.0 million and $4.2 million, respectively. For the three months ended September 30, 2021, we recognized gains of $35.0 million in change in fair value of the Clene Nanomedicine Contingent Earn-out and $3.4 million in change in fair value of the Initial Shareholders Contingent Earn-out as components of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). For the nine months ended September 30, 2021, we recognized gains of $18.1 million in change in fair value of the Clene Nanomedicine Contingent Earn-out and $1.7 million in change in fair value of the Initial Shareholders Contingent Earn-out as components of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). To date, none of the milestones have been achieved.

Derivative Instrument in Connection with the 2021 Avenue Loan

The Avenue Warrants issued pursuant to Tranche 1 of the 2021 Avenue Loan and the warrants issuable pursuant to the draw of Tranche 2 (see Note 8) met the requirements for separate accounting and are therefore accounted for as derivative instruments. The 2021 Avenue Loan has the following features: (i) prepayment provision, (ii) final payment provision, (iii) event of default redemption provision, and (iv) event of default interest provision. The provisions (i) to (iii) are related to the loan host and are not bifurcated pursuant to ASC 815. For the provision (iv), we have not experienced an event of default in the past and believe the probability of triggering one in the future is remote. Therefore, we determined the value of this feature to be de minimis on the remote probability of occurrence of a triggering event.

Upon the closing of the 2021 Avenue Loan, we recognized the warrant liability as a debt discount based on its fair value of $1.5 million. The debt discount is being amortized over the contractual term using the effective interest method. Our determination of the fair value of the warrant utilized the Black-Scholes option-pricing valuation model. Additionally, a Monte Carlo simulation was used to simulate the exercise price as an input in the Black-Scholes valuation model (see Note 10). For the three and nine months ended September 30, 2021, we recognized income of $0.4 million and $0.5 million, respectively, in change in fair value of the warrant as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive income (loss). To date, the warrants have not been exercised.