Xenetic Biosciences, Inc.

Item 7.01. Regulation FD Disclosure. On September 23, 2026, Xenetic Biosciences, Inc. (“Xenetic”) released an updated investor presentation in connection with its pending share exchange transaction with Santersus AG (“Santersus”) as previously announced on September 16, 2026. Attached as Exhibit 99.1 is a copy of the updated investor presentation. The information in this Item 7.01, including Exhibit 99.1 attached hereto, is being furnished, shall not be deemed “filed” for any purpose, and shall not be deemed incorporated by reference in any filing under the Securities Act, or the Securities Exchange Act of 1934, as amended, except as expressly set forth by specific reference in such a filing. Additional Information and Where to Find It This communication relates to the proposed acquisition transaction (the “Acquisition”) involving Xenetic and Santersus and may be deemed to be solicitation material in respect of the Acquisition. In connection with the Acquisition, Xenetic will file with the Securities and Exchange Commission (“SEC”) a Proxy Statement on Schedule 14A and Registration Statement on Form S-1. Each party may also file other documents regarding the Acquisition with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ CAREFULLY THE PROXY STATEMENT, REGISTRATION STATEMENT ON FORM S-1, AND OTHER RELEVANT DOCUMENTS FILED OR WILL BE FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS THERETO AND ANY DOCUMENTS INCORPORATED BY REFERENCE THEREIN, IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE ACQUISITION, RELATED MATTERS AND THE PARTIES TO THE ACQUISITION. Investors and security holders may obtain a free copy of the Proxy Statement, the Registration Statement on Form S-1, and other relevant documents (if and when they become available) that are or will be filed with the SEC for free at the SEC’s website at www.sec.gov. Copies of the documents (when they become available) filed with the SEC by Xenetic will be available free of charge on Xenetic’s website at http://xeneticbio.com. Participants in the Solicitation Xenetic, and its directors and executive officers, and Santersus, and its directors and officers, may be deemed to be participants in the solicitation of proxies from the stockholders of Xenetic in connection with the Acquisition under the rules of the SEC. Information about the interests of these directors and executive officers and other persons who may be deemed to be participants in the solicitation of stockholders of Xenetic in connection with the Acquisition and a description of their direct and indirect interests, by security holdings or otherwise, will be included in the Proxy Statement related to the Acquisition, which will be filed with the SEC. Additional information about Xenetic, the directors and executive officers of Xenetic and their ownership of Xenetic common stock can also be found in its Annual Report on Form 10-K for the year ended December 31, 2025, as filed with the SEC on March 12, 2026, and amended on April 24, 2026, and its definitive proxy statement, as filed with the SEC on October 31, 2025, and other documents subsequently filed by Xenetic with the SEC. Free copies of these documents may be obtained as described above. To the extent holdings of Xenetic securities by its directors or executive officers have changed since the amounts set forth in such documents, such changes have been or are expected to be reflected on Initial Statements of Beneficial Ownership on Form 3 or Statements of Beneficial Ownership on Form 4 filed with the SEC. Additional information regarding the identity of potential participants, and their direct or indirect interests, by security holdings or otherwise, will be included in the Proxy Statement relating to the Acquisition when it is filed with the SEC. 2 No Offer or Solicitation This Current Report on Form 8-K is for informational purposes only. This communication shall not constitute an offer to subscribe for, buy or sell or the solicitation of an offer to subscribe for, buy or sell any securities, or a solicitation of any vote or approval, nor shall there be any sale of, or offer to sell or buy, securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. This communication is for informational purposes only. No offering of securities shall be made, except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act, and otherwise in accordance with applicable law.