Short-Term Debt	9 Months Ended
Sep. 30, 2026
Short-Term Debt [Abstract]
Short-Term Debt	5. Short-Term Debt 2023 Term Loan and Warrants In February 2023, the Company entered into a term loan agreement with a principal amount of $5.5 million (the “2023 Term Loan”), bearing interest at 17% per annum with an existing investor of Legacy Ionetix who is a related party. See Note 16 for additional information regarding related party transactions. In connection with the issuance of the 2023 Term Loan, the Company issued 220,000 warrants to purchase shares of Legacy Ionetix Series F redeemable convertible preferred stock at an exercise price of $1.40 per share (the “Preferred Stock Warrants”). The Preferred Stock Warrants expire in February 2033. The Preferred Stock Warrants were classified as a liability and were remeasured at fair value at each reporting date, with changes in fair value recognized in other income (expense), net in the condensed consolidated statements of operations (see Note 3 Fair Value Measurement). The Company recognized a gain of $0 and $72 from the change in the fair value of the Preferred Stock Warrants for the three and nine months ended September 30, 2026, respectively, and a loss of $17 and $10 for the three and nine months ended September 30, 2025, respectively. In August 2025, the investor exercised 110,000 of the Preferred Stock Warrants. In connection with the Merger, all the remaining Legacy Ionetix Preferred Stock Warrants were assumed by the Company and converted into warrants to purchase 55,154 shares of the Company’s common stock, with the number of underlying shares and exercise price adjusted based on the Conversion Ratio. Upon conversion, the warrants met the criteria for equity classification, and the related liability of $99 was reclassified to additional paid-in capital as of the Merger date. As of September 30, 2026, warrants to purchase 55,154 shares of the Company’s common stock remained outstanding. In connection with subsequent amendments, the Company issued an aggregate of 1,250,000 common stock warrants to purchase Legacy Ionetix common stock, which were equity classified and were recorded as a debt discount amortized to interest expense over the remaining term of the loan at the time of each amendment. Of these warrants, 750,000 were exercised in August 2025, and the remaining 500,000 were exercised in March 2026. The shares issued upon exercise were converted into shares of the Company’s common stock in connection with the Merger based on the Conversion Ratio. No term loan-related common stock warrants were outstanding as of September 30, 2026. In connection with the Merger, the Company repaid the 2023 Term Loan in full, including all outstanding principal and accrued interest, and wrote off the remaining unamortized debt discount and issuance costs to other income (expense), net. Total interest expense and write-off of the debt discount related to the 2023 Term Loan were $0 and $376 for the three months ended September 30, 2026 and 2025, respectively, and $447 and $1,042 for the nine months ended September 30, 2026 and 2025, respectively. Promissory Notes In April 2025 and March 2026, the Company issued unsecured promissory notes with an aggregate principal amount of $1,495 to a board member of Legacy Ionetix and an existing investor, bearing interest at 11% to 15% per annum, of which $330 arose from the conversion of a related party advance. Certain of the notes issued in March 2026 included equity-classified warrants to purchase an aggregate of 420,000 shares of Legacy Ionetix common stock at an exercise price of $0.01 per share, with an aggregate fair value of $605 that was recorded as a debt discount. Warrants for 300,000 shares were exercised in March 2026, and the shares issued were converted into 150,420 shares of the Company’s common stock at the Merger. The remaining warrants for 120,000 shares were converted into warrants to purchase 60,168 shares of the Company’s common stock at an exercise price of $0.02 per share at the Merger and were exercised in May 2026. No such warrants were outstanding as of September 30, 2026. In connection with the Merger, the Company repaid all outstanding promissory notes in full, including all outstanding principal and accrued interest. As a result of the repayment, the Company wrote off the remaining unamortized debt discount and issuance costs to other income (expense), net. Total interest expense and write-off of the debt discount related to the promissory notes were $0 and $12 for the three months ended September 30, 2026 and 2025, respectively, and $668 and $23 for the nine months ended September 30, 2026 and 2025, respectively. Financing Agreements In March 2026, the Company entered into two insurance premium financing agreements with an unrelated third party with an aggregate principal amount of $106. The agreements were repaid in full in connection with the Merger. Related interest expense was not material.

Short-Term Debt

9 Months Ended

Sep. 30, 2026

5. Short-Term Debt

2023 Term Loan and Warrants

In February 2023, the Company entered into a term loan agreement with a principal amount of $5.5 million (the “2023 Term Loan”), bearing interest at 17% per annum with an existing investor of Legacy Ionetix who is a related party. See Note 16 for additional information regarding related party transactions.

In connection with the issuance of the 2023 Term Loan, the Company issued 220,000 warrants to purchase shares of Legacy Ionetix Series F redeemable convertible preferred stock at an exercise price of $1.40 per share (the “Preferred Stock Warrants”). The Preferred Stock Warrants expire in February 2033. The Preferred Stock Warrants were classified as a liability and were remeasured at fair value at each reporting date, with changes in fair value recognized in other income (expense), net in the condensed consolidated statements of operations (see Note 3 Fair Value Measurement). The Company recognized a gain of $0 and $72 from the change in the fair value of the Preferred Stock Warrants for the three and nine months ended September 30, 2026, respectively, and a loss of $17 and $10 for the three and nine months ended September 30, 2025, respectively. In August 2025, the investor exercised 110,000 of the Preferred Stock Warrants. In connection with the Merger, all the remaining Legacy Ionetix Preferred Stock Warrants were assumed by the Company and converted into warrants to purchase 55,154 shares of the Company’s common stock, with the number of underlying shares and exercise price adjusted based on the Conversion Ratio. Upon conversion, the warrants met the criteria for equity classification, and the related liability of $99 was reclassified to additional paid-in capital as of the Merger date. As of September 30, 2026, warrants to purchase 55,154 shares of the Company’s common stock remained outstanding.

In connection with subsequent amendments, the Company issued an aggregate of 1,250,000 common stock warrants to purchase Legacy Ionetix common stock, which were equity classified and were recorded as a debt discount amortized to interest expense over the remaining term of the loan at the time of each amendment. Of these warrants, 750,000 were exercised in August 2025, and the remaining 500,000 were exercised in March 2026. The shares issued upon exercise were converted into shares of the Company’s common stock in connection with the Merger based on the Conversion Ratio. No term loan-related common stock warrants were outstanding as of September 30, 2026.

In connection with the Merger, the Company repaid the 2023 Term Loan in full, including all outstanding principal and accrued interest, and wrote off the remaining unamortized debt discount and issuance costs to other income (expense), net. Total interest expense and write-off of the debt discount related to the 2023 Term Loan were $0 and $376 for the three months ended September 30, 2026 and 2025, respectively, and $447 and $1,042 for the nine months ended September 30, 2026 and 2025, respectively.

Promissory Notes

In April 2025 and March 2026, the Company issued unsecured promissory notes with an aggregate principal amount of $1,495 to a board member of Legacy Ionetix and an existing investor, bearing interest at 11% to 15% per annum, of which $330 arose from the conversion of a related party advance. Certain of the notes issued in March 2026 included equity-classified warrants to purchase an aggregate of 420,000 shares of Legacy Ionetix common stock at an exercise price of $0.01 per share, with an aggregate fair value of $605 that was recorded as a debt discount. Warrants for 300,000 shares were exercised in March 2026, and the shares issued were converted into 150,420 shares of the Company’s common stock at the Merger. The remaining warrants for 120,000 shares were converted into warrants to purchase 60,168 shares of the Company’s common stock at an exercise price of $0.02 per share at the Merger and were exercised in May 2026. No such warrants were outstanding as of September 30, 2026.

In connection with the Merger, the Company repaid all outstanding promissory notes in full, including all outstanding principal and accrued interest. As a result of the repayment, the Company wrote off the remaining unamortized debt discount and issuance costs to other income (expense), net. Total interest expense and write-off of the debt discount related to the promissory notes were $0 and $12 for the three months ended September 30, 2026 and 2025, respectively, and $668 and $23 for the nine months ended September 30, 2026 and 2025, respectively.

Financing Agreements

In March 2026, the Company entered into two insurance premium financing agreements with an unrelated third party with an aggregate principal amount of $106. The agreements were repaid in full in connection with the Merger. Related interest expense was not material.