In December 2023, the Company entered into a royalty interest financing agreement, or the Royalty Interest Agreement, with United in Endeavour, LLC, or UiE, under which UiE acquired a portion of the Company's royalty interest in XACIATO. The Company received $5.0 million from UiE when the parties entered into the Royalty Interest Agreement (the "Initial Investment"), and until December 31, 2026, the Company may, in its sole discretion, but subject to XOMA's prior written consent (see Note 13, Royalty Purchase Agreements), elect to receive three additional payments (each a "Supplemental Investment") from UiE of up to an aggregate of $7.0 million, for a total of up to $12.0 million.

Under the Royalty Interest Agreement, the Company agreed to make the following payments to UiE, until such time when UiE has received aggregate payments equaling a 12% internal rate of return (the “IRR”) on the Initial Investment and each Supplemental Investment, if any: (i) from December 21, 2023 through December 31, 2025, 50% of the amount of royalty payments remaining after all amounts that are due and payable and actually paid by the Company to any licensor or sublicensee on the royalty payments generated and received by the Company on net sales of XACIATO by Organon have been deducted (the “Net Royalty Payments”), (ii) from January 1, 2026 through December 31, 2029, 75% of the Net Royalty Payments, and (iii) from December 21, 2023 through December 31, 2029, 10% of the amount of milestone payments remaining after all amounts that are due and payable and actually paid by the Company to any licensor or sublicensee on the milestone payments generated and received by the Company on net sales of XACIATO by Organon have been deducted. After December 31, 2029, the Company will be required to make certain additional payments to UiE to the extent UiE has not received payments equaling the IRR by December 31, 2029, December 31, 2033, and December 31, 2034, respectively. In addition, if UiE has not received payments equaling the IRR by December 31, 2035 and the Company has other sources of assets or income (besides XACIATO) sufficient to complete such payments, the Company has agreed to pay UiE quarterly payments evenly divided over a two-year term ("Catch-up Payments"), such that UiE will have obtained the IRR, taking into account all other payments received by UiE from the Company under the Royalty Interest Agreement. UiE’s right to receive payments will terminate when UiE has received payments in an amount equal to the IRR (such period of time is referred to as the "Financing Term"). Under the Royalty Interest Agreement, the Company has the right, at any time and from time to time, to make voluntary prepayments to UiE, and such payments will be credited against the IRR. In addition, the Company has the right at any time to pay in full and retire all of the Company's payment obligations to UiE by paying the full amount of the IRR (the "Call Payment"), calculated as of the date of the payment.

The Company evaluated the terms of the Royalty Interest Agreement and concluded that its features were similar to those of a debt instrument. As a result, the Company applied the debt recognition guidance under ASC 470, Debt, and recorded the Initial Investment as a liability related to the sale of future royalties, which will be amortized under the effective interest method over the estimated Financing Term. If the Company elects to receive additional Supplemental Investments, such additional Supplemental Investments will also be recorded as a liability related to the sale of future royalties when they are received and amortized under the interest method over the estimated remaining Financing Term. In addition, in accordance with ASC 470, Debt, any royalties and milestone payments received by or on behalf of the Company from Organon from and after the date of the Initial Investment are recorded as non-cash royalty revenue in the consolidated statements of operations as a reduction to the liability related to the sale of future royalties.

To determine the amortization of the liability related to the sale of future royalties, the Company is required to estimate the duration of the Financing Term and the total amount of future payments to UiE during the Financing Term. These estimates involve significant estimates and assumptions regarding future Net Royalty Payments that impact both the amount of the liability related to the sale of future royalties and the interest expense that will be recognized over the Financing Term. The Company will periodically reassess the estimated amounts due and payable to UiE and the duration of the Financing Term and to the extent the estimated amount or timing of such payments is materially different than the prior estimate, an adjustment will be recorded in future periods, prospectively to increase

or decrease interest expense. There are a number of factors that could materially affect XACIATO's commercial success, and therefore the amount and timing of the Company's payments to UiE, and correspondingly, the amount of interest expense and interest payable recorded by the Company, most of which are not within the Company’s control. Such factors include, but are not limited to, the capabilities of Organon and its commitment of sufficient resources to market, distribute and sell the product; timely and adequate commercial supply of XACIATO and its components; perceived superiority of XACIATO's cure rates compared to other available treatments; patient satisfaction and willingness to use XACIATO again and refer it to others; price pressure given the high level of generic treatments and changes in health care laws and regulations; adequate coverage, pricing and reimbursement from third-party payors; and approval of new entrants, including alternative, non-antibiotic treatment options. These factors could result in increases or decreases to the length of the Financing Term and the total amount owed to UiE. During the year ended December 31, 2025, based on Net Royalty Payments to date and other factors, the Company updated its forecast of Net Royalty Payments, resulting in an estimated Financing Term that is approximately 9.5 years longer than previously estimated, extending through 2037, and as of December 31, 2025, the effective interest rate on the liability related to the sale of future royalties is 12.8%. Under the current estimated Financing Term, the estimated total amount potentially owed to UiE would be approximately $22.0 million, substantially all of which would be paid as Catch-up Payments. However, as discussed above, the Company has the right to make voluntary prepayments to UiE that would be credited against the IRR, as well as the right to make the Call Payment, either of which actions could reduce the total amount owed to UiE, potentially materially.

In connection with entering into the Royalty Interest Agreement, the Company issued to UiE a warrant (the “Initial Royalty Warrant”) to purchase up to 422,804 shares of the Company’s common stock (see Note 9, Stockholders' Equity). In addition, for every $1.0 million of Supplemental Investment, the Company will issue to UiE a warrant to purchase 84,561 shares of common stock. If the Company elects to receive the maximum amount of Supplement Investments, the Company would issue to UiE warrants to purchase an aggregate of up to 591,927 shares of common stock (collectively the “Additional Royalty Warrants,” and together with the Initial Royalty Warrant, the “Royalty Interest Agreement Warrants”). As of December 31, 2025, the Company has only issued the Initial Royalty Warrant.