Results of Operations and Financial Condition. On August 12, 2026, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter ended June 30, 2026 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be furnished and…

Director — Daniel Curran, M.D.: Dr. Daniel Curran's re-appointment as a Class III director after his resignation from the Class II director position to achieve board balance.

Results of Operations and Financial Condition. On May 12, 2026, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter ended March 31, 2026 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be furnished and s…

Director — Cheryl R. Blanchard, Ph.D.: Dr. Cheryl R. Blanchard was elected as a Class III director and appointed to the Compensation Committee and Audit Committee, succeeding Christina Rossi.

Results of Operations and Financial Condition. On March 23, 2026, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter and year ended December 31, 2025 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be f…

Material Modification to Rights of Security Holders. To the extent required by

Entry into a Material Definitive Agreement. On February 11, 2026, Xilio Therapeutics, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Leerink Partners LLC, as representative of the underwriter named therein (the “Underwriter”), relating to an underwritten offering (the “Offering”) of pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 74,780,300 shares of common stock (the “Warrant Shares”) at a price to investors of $0.5349 per Pr…

Regulation FD Disclosure. The full text of the press release announcing the pricing of the Offering on February 11, 2026 is attached as Exhibit 99.1 hereto and is incorporated herein by reference. The information in this Current Report on Form 8-K under Item 7.01, including the information contained in Exhibit 99.1, is being furnished to the SEC and shall not be deemed to be “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or othe…

regarding the Company’s estimated cash balance above is based on preliminary, unaudited information and management estimates for the year ended December 31, 2025, is not a comprehensive statement of the Company’s financial results as of and for the fiscal year ended December 31, 2025 and may change. This estimate also does not present all information necessary for an understanding of the Company’s financial condition as of December 31, 2025 and its results of operations for the fourth quarter…

Chair of the Board — Paul Clancy: Paul Clancy retired from the Board and was succeeded by Sara M. Bonstein as Chair of the Board.

The filing describes stockholder approval of a new equity plan and repricing of existing options, which are administrative actions.

Results of Operations and Financial Condition. On November 13, 2025, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter ended September 30, 2025 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be furnis…

Other Events. ​ Initiation of Phase 2 Clinical Trial for Efarindodekin Alfa (XTX301) and Achievement of $17.5 Million Development Milestone ​ On September 9, 2025, the Xilio Therapeutics, Inc. (the “Company”) issued a press release announcing the initiation of patient dosing in Phase 2 of an ongoing Phase 1/2 clinical trial evaluating efarindodekin alfa (XTX301), a tumor-activated IL-12, as a monotherapy in patients with certain advanced solid tumors, the achievement of a $17.5 million develo…

Results of Operations and Financial Condition. ​ On August 14, 2025, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter ended June 30, 2025 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. ​ The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be furnished…

Director — Akintunde Bello, Ph.D.: Dr. Akintunde Bello was elected as a Class II director and appointed to the Nominating and Corporate Governance Committee.

Entry into a Material Definitive Agreement. On June 2, 2025, Xilio Therapeutics, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Leerink Partners LLC, as representative of the underwriter named therein (the “Underwriter”), relating to an underwritten public offering of pre-funded warrants (the “pre-funded warrants”) to purchase 66,676,000 shares of the Company’s common stock, par value $0.0001 per share (the “common stock”), Series A warrants to…

Other Events. Cash Runway Based on the Company’s current plans, the Company estimates that the Company’s existing cash and cash equivalents, together with the $46.6 million net proceeds from the underwritten public offering, but excluding any potential payments under the Company’s existing collaboration and partnership agreements with AbbVie Group Holdings Limited and Gilead Sciences, Inc., will enable the Company to fund its operating expenses and capital expenditure requirements through the…

Results of Operations and Financial Condition. ​ On May 8, 2025, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter ended March 31, 2025 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. ​ The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be furnished an…

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing. ​ On April 4, 2025, Xilio Therapeutics, Inc. (the “Company”) received a deficiency letter (the “Notice”) from the Listing Qualifications Department (the “Staff”) of the Nasdaq Stock Market, LLC (“Nasdaq”) notifying the Company that, for the last 30 consecutive business days, the bid price for the Company’s common stock had closed below $1.00 per share, which is the minimum bid price required t…

Results of Operations and Financial Condition. On March 11, 2025, Xilio Therapeutics, Inc. (the “Company”) announced its financial results for the quarter and year ended December 31, 2024 and other business highlights. The full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. The information in this Current Report on Form 8-K, including Exhibit 99.1, is intended to be f…

Entry into a Material Definitive Agreement. On March 11, 2025, Xilio Therapeutics, Inc. (the “Company”) entered into a Sales Agreement (the “Sales Agreement”) with Leerink Partners LLC (the “Agent”), under which the Company may, from time to time, sell shares of the Company’s common stock, par value $0.0001 per share. Pursuant to the prospectus supplement relating to the offering, the Company may sell up to $50.0 million of common stock through the Agent. Sales of the shares of common stock,…

Other Events. ​ Financial Guidance Based on its current operating plans, the Company anticipates that its cash and cash equivalents, together with the upfront payment under the Agreement and the proceeds from the AbbVie Private Placement, will be sufficient to fund its operating expenses and capital expenditure requirements into the first quarter of 2026. Cautionary Note Regarding Forward Looking Statements This Form 8-K contains forward-looking statements that involve estimates, assumptions,…

Entry into a Material Definitive Agreement. Collaboration, License and Option Agreement On February 10, 2025, Xilio Development, Inc. (“Xilio Development”), a wholly-owned subsidiary of Xilio Therapeutics, Inc. (the “Company”), entered into a collaboration, license and option agreement (the “Agreement”) with AbbVie Group Holdings Limited (“AbbVie”) for up to four programs leveraging the Company’s proprietary tumor-activation technology and platform, consisting of (i) an exclusive option for (…

The issuance and sale has not been registered under the Securities Act of 1933, as amended (the “Securities Act”) or any state securities laws. Based in part upon the representations of AbbVie in the Stock Purchase Agreement, the Company has relied on the exemption from the registration requirements of the Securities Act under Section 4(a)(2) thereof for a transaction by an issuer not involving any public offering. Neither this Current Report on Form 8-K nor any exhibit attached hereto is an…

Other Events. ​ On January 21, 2025, the Company issued a press release announcing initial data from its ongoing Phase 2 clinical trial evaluating vilastobart (XTX101) in combination with atezolizumab in patients with advanced solid tumors. These data will be presented in a poster presentation at the American Society of Clinical Oncology (ASCO) 2025 Gastrointestinal Cancer Symposium. The full text of the press release is filed as Exhibit 99.2 to this Current Report on Form 8-K and is incorpor…