SAFE Liability	9 Months Ended
Sep. 30, 2026
SAFE Liability [Abstract]
SAFE Liability	7. SAFE Liability The Company issued Simple Agreements for Future Equity (“SAFEs”) for aggregate principal proceeds of $45.7 million that entitled holders to receive shares of Legacy Ionetix redeemable convertible preferred stock upon the occurrence of a qualifying equity financing event at a 15% discount to the price per share paid by other investors in such financing. The SAFEs were freestanding financial instruments and were classified as liabilities, as the SAFEs represented an obligation to issue a variable number of shares for a fixed monetary amount. The SAFEs were initially recorded at fair value upon issuance and subsequently remeasured to fair value at each reporting date, with changes in fair value recognized in the condensed consolidated statements of operations. During the three months ended March 31, 2026, the Company issued SAFEs with aggregate proceeds of $2.4 million, together with equity-classified common stock warrants. The SAFE liability and the warrants were recorded at their issuance-date fair values of $2.4 million and $2.2 million, respectively, and the excess of their aggregate fair value over the proceeds received was recognized as an upfront loss of $2.2 million in other income (expense), net. The Company recognized a loss on the change in fair value of the SAFE liability of $134 during the nine months ended September 30, 2026, all of which was recognized during the three months ended March 31, 2026, as all outstanding SAFEs were converted into shares of Legacy Ionetix Series F redeemable convertible preferred stock on March 31, 2026. During the three and nine months ended September 30, 2025, the Company issued SAFEs, without common stock warrant coverage, with aggregate proceeds of $1.5 million and $5.4 million, respectively. The Company recognized a loss on the change in fair value of the SAFE liability of $1.9 million and $2.9 million for the three and nine months ended September 30, 2025, respectively. Election to Convert SAFEs On October 31, 2025, holders of SAFEs with an aggregate carrying value of $50.7 million elected to settle their SAFEs into shares of Legacy Ionetix Series F redeemable convertible preferred stock at a conversion price of $1.40 per share. The Company accounted for the transaction as an extinguishment of the SAFE liability and, in connection with the conversion, recognized a freestanding make-whole derivative liability as described below. On March 31, 2026, all remaining outstanding SAFEs were converted into shares of Legacy Ionetix Series F redeemable convertible preferred stock at $1.40 per share. The SAFE liability was remeasured to fair value immediately prior to conversion, and the Legacy Ionetix Series F redeemable convertible preferred stock was recorded at an amount equal to that fair value. No additional gain or loss was recognized upon conversion. Make-Whole Provision In connection with the October 31, 2025 SAFE conversion, the Company recognized a freestanding derivative liability. The make-whole derivative liability was $71 as of December 31, 2025 and was derecognized upon termination of the make-whole right in connection with the Merger in April 2026, with no liability outstanding as of September 30, 2026. The Company recognized a change in fair value of $13 during the nine months ended September 30, 2026, substantially all of which was recognized during the three months ended March 31, 2026. No change in fair value was recognized during the three and nine months ended September 30, 2025, as the make-whole provision did not exist prior to October 31, 2025. Contingent Equity Arrangement Associated with a SAFE In connection with a SAFE issued in 2023, the Company entered into an arrangement that provided the investor with the right to receive a warrant upon the occurrence of certain future events, for which no amount had been recognized in the Company’s historical financial statements prior to the Merger. In connection with the Merger, the Company settled the arrangement by terminating the contingent right and related arrangements and issuing a new ten-year warrant to purchase 6,443,076 shares of Legacy Ionetix common stock at an exercise price of $0.01 per share. In connection with the Merger, such warrant was assumed by the Company and converted into a warrant to purchase 3,230,558 shares of the Company’s common stock at an exercise price of $0.02 per share, based on the Conversion Ratio. The new warrant is classified within stockholders’ equity. The Company determined the fair value of the new warrant at issuance to be $9.7 million, which was recognized as expense in other income (expense), net, with a corresponding increase to additional paid-in capital during the nine months ended September 30, 2026.

SAFE Liability

9 Months Ended

Sep. 30, 2026

7. SAFE Liability

The Company issued Simple Agreements for Future Equity (“SAFEs”) for aggregate principal proceeds of $45.7 million that entitled holders to receive shares of Legacy Ionetix redeemable convertible preferred stock upon the occurrence of a qualifying equity financing event at a 15% discount to the price per share paid by other investors in such financing.

The SAFEs were freestanding financial instruments and were classified as liabilities, as the SAFEs represented an obligation to issue a variable number of shares for a fixed monetary amount. The SAFEs were initially recorded at fair value upon issuance and subsequently remeasured to fair value at each reporting date, with changes in fair value recognized in the condensed consolidated statements of operations.

During the three months ended March 31, 2026, the Company issued SAFEs with aggregate proceeds of $2.4 million, together with equity-classified common stock warrants. The SAFE liability and the warrants were recorded at their issuance-date fair values of $2.4 million and $2.2 million, respectively, and the excess of their aggregate fair value over the proceeds received was recognized as an upfront loss of $2.2 million in other income (expense), net. The Company recognized a loss on the change in fair value of the SAFE liability of $134 during the nine months ended September 30, 2026, all of which was recognized during the three months ended March 31, 2026, as all outstanding SAFEs were converted into shares of Legacy Ionetix Series F redeemable convertible preferred stock on March 31, 2026. During the three and nine months ended September 30, 2025, the Company issued SAFEs, without common stock warrant coverage, with aggregate proceeds of $1.5 million and $5.4 million, respectively. The Company recognized a loss on the change in fair value of the SAFE liability of $1.9 million and $2.9 million for the three and nine months ended September 30, 2025, respectively.

Election to Convert SAFEs

On October 31, 2025, holders of SAFEs with an aggregate carrying value of $50.7 million elected to settle their SAFEs into shares of Legacy Ionetix Series F redeemable convertible preferred stock at a conversion price of $1.40 per share. The Company accounted for the transaction as an extinguishment of the SAFE liability and, in connection with the conversion, recognized a freestanding make-whole derivative liability as described below.

On March 31, 2026, all remaining outstanding SAFEs were converted into shares of Legacy Ionetix Series F redeemable convertible preferred stock at $1.40 per share. The SAFE liability was remeasured to fair value immediately prior to conversion, and the Legacy Ionetix Series F redeemable convertible preferred stock was recorded at an amount equal to that fair value. No additional gain or loss was recognized upon conversion.

Make-Whole Provision

In connection with the October 31, 2025 SAFE conversion, the Company recognized a freestanding derivative liability. The make-whole derivative liability was $71 as of December 31, 2025 and was derecognized upon termination of the make-whole right in connection with the Merger in April 2026, with no liability outstanding as of September 30, 2026. The Company recognized a change in fair value of $13 during the nine months ended September 30, 2026, substantially all of which was recognized during the three months ended March 31, 2026. No change in fair value was recognized during the three and nine months ended September 30, 2025, as the make-whole provision did not exist prior to October 31, 2025.

Contingent Equity Arrangement Associated with a SAFE

In connection with a SAFE issued in 2023, the Company entered into an arrangement that provided the investor with the right to receive a warrant upon the occurrence of certain future events, for which no amount had been recognized in the Company’s historical financial statements prior to the Merger.

In connection with the Merger, the Company settled the arrangement by terminating the contingent right and related arrangements and issuing a new ten-year warrant to purchase 6,443,076 shares of Legacy Ionetix common stock at an exercise price of $0.01 per share. In connection with the Merger, such warrant was assumed by the Company and converted into a warrant to purchase 3,230,558 shares of the Company’s common stock at an exercise price of $0.02 per share, based on the Conversion Ratio. The new warrant is classified within stockholders’ equity. The Company determined the fair value of the new warrant at issuance to be $9.7 million, which was recognized as expense in other income (expense), net, with a corresponding increase to additional paid-in capital during the nine months ended September 30, 2026.