Item 9.01. Financial Statements and Exhibits.

CERTIFICATE OF AMENDMENT OF

RESTATED CERTIFICATE OF INCORPORATION

OF XILIO THERAPEUTICS, INC.

(Pursuant to Section 242 of the

General Corporation Law of the State of Delaware)

Xilio Therapeutics, Inc. (the “Corporation”), a corporation organized and existing under and by virtue of the provisions of the General Corporation Law of the State of Delaware, does hereby certify as follows:

FIRST: A resolution was duly adopted by the Board of Directors of the Corporation pursuant to Section 242 of the General Corporation Law of the State of Delaware setting forth a proposed amendment to the Restated Certificate of Incorporation of the Corporation and declaring said amendment to be advisable. The stockholders of the Corporation duly approved said proposed amendment in accordance with Section 242 of the General Corporation Law of the State of Delaware. The resolution setting forth the amendment is as follows:

RESOLVED: That the first sentence of Article FOURTH of the Restated Certificate of Incorporation of the Corporation be and hereby is deleted in its entirety and the following is inserted in lieu thereof:

“FOURTH: The total number of shares of all classes of stock that the Corporation shall have authority to issue is 605,000,000 shares, consisting of (i) 600,000,000 shares of common stock, $0.0001 par value per share (“Common Stock”), and (ii) 5,000,000 shares of Preferred Stock, $0.0001 par value per share (“Preferred Stock”).

Effective upon the effective time (the “Effective Time”) of this Certificate of Amendment (the “Certificate of Amendment”) to the Restated Certificate of Incorporation, a one-for-fourteen reverse stock split of the Common Stock shall become effective, pursuant to which each fourteen (14) (the “Reverse Stock Split Number”) shares of Common Stock issued and outstanding and held of record by each stockholder of the Corporation or issued and held by the Corporation in treasury immediately prior to the Effective Time shall be reclassified and combined into one (1) validly issued, fully paid and nonassessable share of Common Stock automatically and without any action by the holder thereof and shall represent one share of Common Stock from and after the Effective Time (such reclassification and combination of shares, the “Reverse Stock Split”). The par value of the Common Stock following the Reverse Stock Split shall remain at $0.0001 par value per share. No fractional shares of Common Stock shall be issued as a result of or in connection with the Reverse Stock Split. Stockholders of record who otherwise would be entitled to receive a fractional share of Common Stock as a result of the Reverse Stock Split, following the Effective Time, shall be entitled to receive a cash payment (without interest) in lieu of such fractional share equal to the fraction of a share of Common Stock to which such holder would otherwise be entitled multiplied by (i) the closing price per share of the Common Stock on the Nasdaq Capital Market at the close of business on the trading day preceding the date of the Effective Time multiplied by (ii) the Reverse Stock Split Number.

Each stock certificate or book entry position that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares formerly represented by such certificate or book entry position have been reclassified as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time; provided, however, that each stockholder of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new book entry position evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been reclassified.”

SECOND: This Certificate of Amendment shall be effective at 5:00 p.m. Eastern Time, on March 13, 2026.

***

IN WITNESS WHEREOF, this Certificate of Amendment has been executed by a duly authorized officer of the Corporation on this 12th day of March, 2026.

Xilio Therapeutics, Inc.

By: /s/ René Russo

René Russo

Title: President and Chief Executive Officer

Xilio Therapeutics Announces 1-for-14 Reverse Stock Split

WALTHAM, Mass., March 12, 2026 -- Xilio Therapeutics, Inc. (Nasdaq: XLO), a clinical-stage biotechnology company discovering and developing masked immuno-oncology therapies for people living with cancer, today announced that it will implement a 1-for-14 reverse stock split of the issued shares of the company’s common stock, effective at 5:00 p.m. Eastern Time on March 13, 2026.

The reverse stock split was approved by the company’s stockholders at the company’s Special Meeting of Stockholders held on February 23, 2026, with the final ratio subsequently determined by the company’s Board of Directors. One of the primary goals of the reverse stock split is to increase the per-share market price of the company’s common stock to enable the company to regain compliance with the minimum bid price requirement for continued listing on the Nasdaq Capital Market.

The company’s common stock is expected to begin trading on a split-adjusted basis when the markets open on March 16, 2026 under the company’s existing ticker “XLO” with the new CUSIP number 98422T209.

At the effective time of the reverse stock split, every 14 shares of the company’s issued and outstanding common stock will be automatically reclassified and combined into one share of common stock. This will reduce the number of outstanding shares of Xilio’s common stock from approximately 73.5 million shares to approximately 5.2 million shares. The reverse stock split will not change the number of authorized shares of the company’s common stock or the par value of the common stock. All outstanding warrants and other securities entitling their holders to purchase or otherwise receive shares of common stock will be adjusted as a result of the reverse split, as required by the terms of each security. In addition, proportionate adjustments will be made to the number of shares of common stock available for issuance under the company's equity incentive plans and the number of shares underlying and, in the case of stock options, the exercise prices of, outstanding equity awards under such plans, in accordance with their respective terms and as described in the company's proxy statement for its Special Meeting of Stockholders as filed with the Securities and Exchange Commission (SEC) on January 26, 2026 (the Proxy Statement).

No fractional shares will be issued if, as a result of the reverse stock split, a stockholder would otherwise become entitled to a fractional share because the number of shares of common stock they hold before the reverse stock split is not evenly divisible by the split ratio. Instead, each such stockholder will be entitled to receive a cash payment in lieu of a fractional share.

Computershare Trust Company, N.A. is acting as the exchange agent and transfer agent for the reverse stock split. Stockholders holding their shares electronically are not required to take any action to receive post-split shares. Stockholders owning shares through a bank, broker or other nominee will have their positions adjusted to reflect the reverse stock split and will receive payment for any fractional shares in accordance with the processes at their respective bank, broker or nominee. Additional information regarding the reverse stock split can be found in the Proxy Statement.

About Xilio Therapeutics

Xilio Therapeutics is a clinical-stage biotechnology company discovering and developing masked immuno-oncology (I-O) therapies with the goal of significantly improving outcomes for people living with cancer without the systemic side effects of current I-O treatments. The company is leveraging its proprietary masking technology to advance a pipeline of novel, masked I-O molecules that are designed to optimize the therapeutic index by localizing anti-tumor activity within the tumor microenvironment. Learn more by visiting www.xiliotx.com and follow us on LinkedIn (Xilio Therapeutics, Inc.).

Cautionary Note Regarding Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, statements regarding the reverse stock split and the timing thereof, the impact of the reverse stock split on stockholders and other securityholders; and the potential for Xilio to increase its share price and regain compliance with the Nasdaq continued listing rules. The words “aim,” “may,” “will,” “could,” “would,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “project,” “potential,” “continue,” “seek,” “target” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Any forward-looking statements in this press release are based on management’s current expectations and beliefs and are subject to a number of important risks, uncertainties and other factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this press release, including, without limitation, risks related to general market conditions and geopolitical uncertainties; risks and uncertainties related to ongoing and planned research and development activities, including initiating, conducting or completing preclinical studies and clinical trials and the timing and results of such preclinical studies or clinical trials; the delay of any current or planned preclinical studies or clinical trials or the development of Xilio’s current or future product candidates; Xilio’s need to obtain additional cash resources to advance its pipeline of tumor-activated I-O molecules; the impact of international trade policies on Xilio’s business, including U.S. and China trade policies; and Xilio’s ability to maintain its collaboration or partnership agreements with AbbVie, Gilead and Roche. These and other risks and uncertainties are described in greater detail in the sections entitled “Risk Factor Summary” and “Risk Factors” in Xilio’s filings with the SEC, including Xilio’s most recent Quarterly Report on Form 10-Q and any other filings that Xilio has made or may make with the SEC in the future. Any forward-looking statements contained in this press release represent Xilio’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, Xilio explicitly disclaims any obligation to update any forward-looking statements.

This press release contains hyperlinks to information that is not deemed to be incorporated by reference in this press release.

Investor Contact 
Alex Lobo, Precision AQ
alex.lobo@precisionaq.com 

Media Contact 
Josie Butler, 1AB
josie@1abmedia.com