Warrants	12 Months Ended
Dec. 31, 2023
Warrants and Rights Note Disclosure [Abstract]
Warrants	8. Warrants Series A Warrant On August 15, 2022, the Company issued an aggregate of 3,000 shares of Series A Redeemable Convertible Preferred Stock with a par value of $0.001 per share and the Series A Warrant to purchase up to an aggregate of 428 shares of common stock of the Company at an exercise price of $750.00 per share (such number of shares and exercise price are adjusted for the reverse stock split described in Note 2) for an aggregate subscription amount equal to $0.3 million, before deducting estimated offering expenses payable by the Company. In the fourth quarter of 2022, the Series A Redeemable Convertible Preferred Stock was redeemed. The Series A Warrant became exercisable on February 15, 2023 and expires on February 15, 2028. The Series A Warrant contains certain anti-dilution provisions to protect the holder. On February 17, 2023, the Company issued and sold shares of common stock, pre-funded warrants to purchase common stock and warrants to purchase common stock to an underwriter pursuant to an underwriting agreement (see discussion below). The terms of that offering triggered an adjustment to the exercise price of the Series A Warrant to $54.00 effective as of February 17, 2023. The Company is required to measure the Series A Warrant at fair value at inception and in subsequent reporting periods with changes in fair value recognized in change in fair value of warrant liabilities in the period of change in the consolidated statements of operations and comprehensive loss. The fair value of the liability related to the Series A Warrant at inception was $0.4 million. The Series A Warrant was not exercised as of December 31, 2023 and remains outstanding. The change in fair value during the year ended December 31, 2023 was immaterial. Pre-Funded Warrants and Common Stock Warrants On February 17, 2023, the Company sold 90,185 shares of $0.001 par value common stock, 20,925 Pre-Funded Warrants and 222,222 Common Stock Warrants through an offering underwritten by Craig-Hallum Capital Group LLC. Each of the shares and Pre-Funded Warrants were sold in combination with an accompanying Common Stock Warrant to purchase two shares of the Company’s common stock. The combined purchase price for each share and accompanying Common Stock Warrant is $108.00, and for each Pre-Funded Warrant and accompanying Common Stock Warrant is $107.90, which was equal to the combined purchase price for each share and accompanying Common Stock Warrant sold in the offering, minus the Pre-Funded Warrant’s exercise price per share of $0.10. The total proceeds of $12.0 million from the February 17, 2023 offering were allocated between the common stock, Pre-Funded Warrants and Common Stock Warrants. Because the Common Stock Warrants are liability-classified, an amount of proceeds equal to the fair value of the liability were first allocated to the Common Stock Warrants. The remaining proceeds were allocated on a relative fair value basis to the common stock and the Pre-Funded Warrants and recognized in additional paid-in capital. Total issuance costs related to the offering of $1.1 million were allocated in a similar manner as the total proceeds. As a result, approximately $0.7 million of issuance costs were expensed at the issuance date and recognized as other, net in the consolidated statements of operations and comprehensive loss. The remaining issuance costs were recognized within additional paid-in-capital as a reduction to the proceeds received for the common stock and Pre-Funded Warrants. The Pre-Funded Warrants had (i) an exercise price per share of common stock equal to $0.10 or (ii) a cashless exercise option, with the number of shares received determined according to the formula set forth in the Pre-Funded Warrant. The Pre-Funded Warrants were exercisable upon issuance and did not expire. The exercise price and the number of shares of common stock issuable upon exercise of the Pre-Funded Warrants was subject to adjustment in the event of certain stock dividends and distributions, splits, combinations, reclassifications or similar events affecting the common stock. Holders of Pre-Funded Warrants participated in any distributions to common stockholders as if the holders had exercised the Pre-Funded Warrants. The Company determined that the Pre-Funded Warrants were indexed to the Company’s own stock and met the requirements for equity classification. Proceeds allocated to such warrants totaled $0.8 million. No Pre-Funded Warrants remain outstanding on December 31, 2023. The Common Stock Warrants have (i) an exercise price per share of common stock equal to $108.00 per share, (ii) a cashless exercise option if, at the time of exercise, there is no effective registration statement registering or the prospectus is not available for the issuance of the warrant shares to the holder, with the number of shares received determined according to the formula set forth in the Common Stock Warrant or (iii) an alternate cashless exercise option, which became exercisable on March 15, 2023, equal to the product of (x) the aggregate number of shares of common stock that would be issuable upon a cash exercise and (y) 0.5. The Common Stock Warrants are exercisable upon issuance and expire on February 17, 2028. The exercise price and the number of shares of common stock issuable upon exercise of the Common Stock Warrants is subject to adjustment in the event of certain stock dividends and distributions, splits, combinations, reclassifications or similar events affecting the common stock. Holders of the Common Stock Warrants will participate in any distributions to common stockholders as if the holders had exercised the Common Stock Warrants. The Common Stock Warrants are redeemable upon the occurrence of a Fundamental Transaction (as defined in the Common Stock Purchase Warrant Agreement). The Company determined that the Common Stock Warrants are not indexed to the Company’s own stock and therefore are precluded from equity classification. In addition, the Common Stock Warrant liability meets the definition of a derivative instrument. The Common Stock Warrants will be measured at fair value at inception and in subsequent reporting periods with changes in fair value recognized in income as change in fair value of warrant liabilities in the period of change in the consolidated statements of operations and comprehensive loss. The fair value of the Common Stock Warrant liability at inception was $7.6 million. During the year ended December 31, 2023, 155,557 Common Stock Warrants were exercised pursuant to the cashless exercise option resulting in the issuance of 77,776 shares of common stock. On December 31, 2023, 66,665 Common Stock Warrants remain outstanding. The change in fair value after issuance consisted of a reduction of expense of $5.9 million during the year ended December 31, 2023. The Company has also issued certain warrants in conjunction with its Term Loan Agreement. See Note 6.

Warrants

12 Months Ended

Dec. 31, 2023

Warrants and Rights Note Disclosure [Abstract]

8. Warrants

Series A Warrant

On August 15, 2022, the Company issued an aggregate of 3,000 shares of Series A Redeemable Convertible Preferred Stock with a par value of $0.001 per share and the Series A Warrant to purchase up to an aggregate of 428 shares of common stock of the Company at an exercise price of $750.00 per share (such number of shares and exercise price are adjusted for the reverse stock split described in Note 2) for an aggregate subscription amount equal to $0.3 million, before deducting estimated offering expenses payable by the Company. In the fourth quarter of 2022, the Series A Redeemable Convertible Preferred Stock was redeemed. The Series A Warrant became exercisable on February 15, 2023 and expires on February 15, 2028. The Series A Warrant contains certain anti-dilution provisions to protect the holder.

On February 17, 2023, the Company issued and sold shares of common stock, pre-funded warrants to purchase common stock and warrants to purchase common stock to an underwriter pursuant to an underwriting agreement (see discussion below). The terms of that offering triggered an adjustment to the exercise price of the Series A Warrant to $54.00 effective as of February 17, 2023.

The Company is required to measure the Series A Warrant at fair value at inception and in subsequent reporting periods with changes in fair value recognized in change in fair value of warrant liabilities in the period of change in the consolidated statements of operations and comprehensive loss. The fair value of the liability related to the Series A Warrant at inception was $0.4 million. The Series A Warrant was not exercised as of December 31, 2023 and remains outstanding. The change in fair value during the year ended December 31, 2023 was immaterial.

Pre-Funded Warrants and Common Stock Warrants

On February 17, 2023, the Company sold 90,185 shares of $0.001 par value common stock, 20,925 Pre-Funded Warrants and 222,222 Common Stock Warrants through an offering underwritten by Craig-Hallum Capital Group LLC. Each of the shares and Pre-Funded Warrants were sold in combination with an accompanying Common Stock Warrant to purchase two shares of the Company’s common stock. The combined purchase price for each share and accompanying Common Stock Warrant is $108.00, and for each Pre-Funded Warrant and accompanying Common Stock Warrant is $107.90, which was equal to the combined purchase price for each share and accompanying Common Stock Warrant sold in the offering, minus the Pre-Funded Warrant’s exercise price per share of $0.10.

The total proceeds of $12.0 million from the February 17, 2023 offering were allocated between the common stock, Pre-Funded Warrants and Common Stock Warrants. Because the Common Stock Warrants are liability-classified, an amount of proceeds equal to the fair value of the liability were first allocated to the Common Stock Warrants. The remaining proceeds were allocated on a relative fair value basis to the common stock and the Pre-Funded Warrants and recognized in additional paid-in capital. Total issuance costs related to the offering of $1.1 million were allocated in a similar manner as the total proceeds. As a result, approximately $0.7 million of issuance costs were expensed at the issuance date and recognized as other, net in the consolidated statements of operations and comprehensive loss. The remaining issuance costs were recognized within additional paid-in-capital as a reduction to the proceeds received for the common stock and Pre-Funded Warrants.

The Pre-Funded Warrants had (i) an exercise price per share of common stock equal to $0.10 or (ii) a cashless exercise option, with the number of shares received determined according to the formula set forth in the Pre-Funded Warrant. The Pre-Funded Warrants were exercisable upon issuance and did not expire. The exercise price and the number of shares of common stock issuable upon exercise of the Pre-Funded Warrants was subject to adjustment in the event of certain stock dividends and distributions, splits, combinations, reclassifications or similar events affecting the common stock. Holders of Pre-Funded Warrants participated in any distributions to common stockholders as if the holders had exercised the Pre-Funded Warrants.

The Company determined that the Pre-Funded Warrants were indexed to the Company’s own stock and met the requirements for equity classification. Proceeds allocated to such warrants totaled $0.8 million. No Pre-Funded Warrants remain outstanding on December 31, 2023.

The Common Stock Warrants have (i) an exercise price per share of common stock equal to $108.00 per share, (ii) a cashless exercise option if, at the time of exercise, there is no effective registration statement registering or the prospectus is not available for the issuance of the warrant shares to the holder, with the number of shares received determined according to the formula set forth in the Common Stock Warrant or (iii) an alternate cashless exercise option, which became exercisable on March 15, 2023, equal to the product of (x) the aggregate number of shares of common stock that would be issuable upon a cash exercise and (y) 0.5. The Common Stock Warrants are exercisable upon issuance and expire on February 17, 2028. The exercise price and the number of shares of common stock issuable upon exercise of the Common Stock Warrants is subject to adjustment in the event of certain stock dividends and distributions, splits, combinations, reclassifications or similar events affecting the common stock. Holders of the Common Stock Warrants will participate in any distributions to common stockholders as if the holders had exercised the Common Stock Warrants. The Common Stock Warrants are redeemable upon the occurrence of a Fundamental Transaction (as defined in the Common Stock Purchase Warrant Agreement).

The Company determined that the Common Stock Warrants are not indexed to the Company’s own stock and therefore are precluded from equity classification. In addition, the Common Stock Warrant liability meets the definition of a derivative instrument. The Common Stock Warrants will be measured at fair value at inception and in subsequent reporting periods with changes in fair value recognized in income as change in fair value of warrant liabilities in the period of change in the consolidated statements of operations and comprehensive loss. The fair value of the Common Stock Warrant liability at inception was $7.6 million. During the year ended December 31, 2023, 155,557 Common Stock Warrants were exercised pursuant to the cashless exercise option resulting in the issuance of 77,776 shares of common stock. On December 31, 2023, 66,665 Common Stock Warrants remain outstanding. The change in fair value after issuance consisted of a reduction of expense of $5.9 million during the year ended December 31, 2023.

The Company has also issued certain warrants in conjunction with its Term Loan Agreement. See Note 6.