XTX601 demonstrated protease-dependent, tumor-selective activation and potent anti-tumor activity in multiple preclinical models   Consistent with Xilio&#39;s clinically-validated masking technology, XTX601 was well

Xilio Therapeutics Announces New Preclinical Data at AACR Annual Meeting for XTX601, a Masked T Cell Engager Targeting CLDN18.2

Xilio's XTX601 Shows Strong Potential in Preclinical Cancer Trials

<section class="insight" data-version="1">
 <section data-block="information">
 <h3>Information</h3>
 XTX601 demonstrated protease-dependent, tumor-selective activation and potent anti-tumor activity in multiple preclinical models  Consistent with Xilio&amp;#39;s clinically-validated masking technology, XTX601 was well
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 <section data-block="ai-summary-paragraph">
 <h3>AI Summary</h3>
 Xilio Therapeutics presented positive preclinical data for XTX601 at AACR, featuring robust anti-tumor activity and excellent tolerability. This promising profile positions XTX601 favorably for upcoming IND-enabling studies slated for 2027, which could drive interest and investment in XLO.
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 <section data-block="ai-summary-bullets">
 <h3>Key Points</h3>
 <ul><li>XTX601 shows promising preclinical results against cancer targets CLDN18.2.</li><li>Well tolerated in non-human primates with no severe systemic toxicities.</li><li>Xilio plans to start IND-enabling studies for XTX601 in 2027.</li><li>The drug utilizes advanced masking technology to minimize side effects.</li><li>Presentation scheduled at AACR Annual Meeting from April 17 to 22, 2026.</li></ul>
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 <section data-block="companies-mentioned">
 <h3>Companies Mentioned</h3>
 <ul><li>Xilio Therapeutics, Inc. (XLO): Recent data on XTX601 strengthens its market position and future potential.</li></ul>
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 <section data-block="category">
 <h3>Research Analysis</h3>
 This analysis falls under &#039;Research Analysis&#039; as it focuses on new therapeutic data developments that could influence stock performance and investor perception of XLO.
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 <section data-block="market-moving">
 <h3>Market-Moving</h3>
 <ul><li>Positive preclinical data could increase investor interest and stock price.</li><li>Submission of IND application in 2027 could lead to major milestone-driven price action.</li><li>Strong safety profile may boost potential partnerships or licensing agreements.</li><li>The upcoming AACR presentation may attract attention from the investment community.</li></ul>
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 <section data-block="key-facts">
 <h3>Key Facts</h3>
 <ul><li>XTX601 targets CLDN18.2 in gastric, pancreatic and esophageal cancers.</li><li>Preclinical trials indicate a wide therapeutic index.</li><li>No severe side effects observed in non-human primates.</li><li>Xilio plans IND application submission for XTX601 in 2027.</li><li>AACR Annual Meeting occurs from April 17 to 22, 2026.</li></ul>
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 <section data-block="trading-thesis">
 <h3>Trading Thesis</h3>
 Investors may consider accumulating XLO shares ahead of anticipated IND study results.
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<link type="text/css" rel="stylesheet" href="https://www.globenewswire.com/styles/gnw_nitf.css"></link>XTX601 demonstrated protease-dependent, tumor-selective activation and potent anti-tumor activity in multiple preclinical models  Consistent with Xilio's clinically-validated masking technology, XTX601 was well tolerated in non-human primates with a favorable therapeutic index WALTHAM, Mass., April 17, 2026 (GLOBE NEWSWIRE) -- Xilio Therapeutics, Inc. (NASDAQ:<a class="ticker" href="https://www.benzinga.com/quote/XLO">XLO</a>), a clinical-stage biotechnology company discovering and developing masked immuno-oncology therapies for people living with cancer, today announced new preclinical data for XTX601, a masked T cell engager targeting claudin 18.2 (CLDN18.2), at the American Association for Cancer Research (AACR) Annual Meeting, taking place from April 17–22, 2026 at the San Diego Convention Center in San Diego, California. "The data to be presented at AACR underscore the significant potential of our clinically-validated masking technology to address the central challenge that has limited the advancement of T cell engagers in solid tumors – namely, the inability to achieve meaningful anti-tumor activity without inducing severe systemic toxicities," said Uli Bialucha, Ph.D., chief scientific officer of Xilio Therapeutics. "XTX601 has demonstrated a promising preclinical profile, including potent tumor cell killing across multiple CLDN18.2-expressing tumor models and a favorable tolerability profile in non-human primates, supporting its potential to achieve a wide therapeutic index. Importantly, our modular architecture for masked T cell engagers provides flexibility to rapidly evaluate multiple designs in parallel, including masking of the CLDN18.2 binding domain and/or the addition of a co-stimulatory domain, which enables us to seek to optimize the molecule for the best possible clinical profile." Masked T Cell Engager Design XTX601 is a potentially first-in-class masked T cell engager designed to selectively target CLDN18.2, a tumor-associated antigen expressed in gastric, pancreatic and esophageal cancers. XTX601 incorporates Xilio's clinically-validated masking technology and advanced tumor-activated cell engager (ATACR) format, which consists of a T cell engager with a masked CD3 targeting domain, with the goal of minimizing systemic T cell engagement in healthy tissue and overcoming the significant systemic toxicities that have limited non-masked T cell engagers targeting CLDN18.2. In addition, XTX601 is designed with a conditional half-life modulation element for antibody-like pharmacokinetics in its masked state and a short half-life upon activation in the tumor microenvironment to further limit peripheral exposure. Preclinical Data Highlights Presented at AACR In preclinical studies, XTX601 demonstrated the potential to achieve a wide therapeutic index. <ul type="disc"><li style="text-align:justify;">XTX601 demonstrated protease-dependent activation and tumor cell killing in high- and low-expression settings for CLDN18.2, with effective masking of the anti-CD3 domain.</li><li style="text-align:justify;">XTX601 exhibited robust, dose-dependent anti-tumor activity in multiple murine cell line-derived xenograft models, including GSU gastric carcinoma and OE19 esophageal adenocarcinoma models engrafted with human T cells.</li><li style="text-align:justify;">Consistent with its masked design, XTX601 was well tolerated in non-human primates (NHP) with no evidence of cytokine release syndrome and no changes in liver enzymes.</li><li style="text-align:justify;">Integration of drug exposure data from murine tumor models and NHP studies indicated a favorable, positive therapeutic index for XTX601 and supports the potential for XTX601 to achieve meaningful anti-tumor activity at doses that are well-tolerated systemically. </li></ul> Xilio plans to advance its masked T cell engager program targeting CLDN18.2 into investigational new drug (IND)-enabling studies and submit an IND application for this program in 2027. Presentation Details Xilio's poster presentation at AACR is listed below, and a copy of the presentation will be available under the "Our Approach—Presentations &amp; Publications" section of the company's website at <a href="https://www.globenewswire.com/Tracker?data=Zmu5T2hFC4EpVjbJD_YuNMWaBDd1PB-N3iTQ0SkBL6qVk4DbqNAqthE_QQFg4uOIKTBRJ5IC_Ln7nMlB8wQ-YpPV9ay6StSRqYDsCr0PduE=" rel="nofollow" target="_blank">www.xiliotx.com</a>. Title: Discovery and Optimization of XTX601, a Masked Claudin 18.2-Targeting T Cell Engager Session Category: Immunology Session Title: T Cell Engagers 1 Session Date and Time: Monday, Apr. 20, 2026, from 9:00 a.m. to 12:00 p.m. PST Location: Poster Section 10, Poster Board 11 Abstract Number: 1619 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. Leveraging our clinically-validated masking technology and capabilities, Xilio is developing I-O therapies designed to selectively activate within the tumor microenvironment to achieve durable efficacy without the severe side effects associated with systemically active I-O agents. Learn more by visiting <a href="https://www.globenewswire.com/Tracker?data=Zmu5T2hFC4EpVjbJD_YuNN4sCzdXSzg3o5Vkbq_JzUnQEPLfxn09cTN-Tg9FsvYIwtLMp62KtdgJ3H8dZtkcAg8e8aqmY5tsNQ4EGfMUxIM=" rel="nofollow" target="_blank">www.xiliotx.com</a> and follow us on LinkedIn (<a href="https://www.globenewswire.com/Tracker?data=qvGwGMJ7qpU3bgdoro1H1GwLiAnCfHohfvAlb8WXd8mCrK2nwmQK22-ntuXmVVFwz97qOoYZXKkq_Nny41Nipv46ZZBnHl-dIh57D_Tbs7wjpY5kGvGo6fMK4zUCKF5c" rel="nofollow" target="_blank">Xilio Therapeutics, Inc.</a>). 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 plans, expectations, development timelines and anticipated milestones for XTX601; the potential for XTX601 to achieve meaningful anti-tumor activity, a wide therapeutic index or address systemic toxicity; and Xilio's ability to optimize molecules using its modular architecture. 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 ability to obtain and maintain sufficient preclinical and clinical supply of current or future product candidates; initial, preliminary, interim or retrospective preclinical or clinical data or results may not be replicated in or predictive of future preclinical or clinical data or results; Xilio's ability to successfully demonstrate the safety and efficacy of its product candidates and gain approval of its product candidates on a timely basis, if at all; results from preclinical studies or clinical trials for Xilio's product candidates may not support further development of such product candidates; actions of regulatory agencies may affect the initiation, timing and progress of current or future clinical trials; Xilio's ability to obtain, maintain and enforce patent and other intellectual property protection for current or future product candidates; Xilio's need to obtain additional cash resources to advance its pipeline of masked 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 U.S. Securities and Exchange Commission (SEC), including Xilio's most recent Annual Report on Form 10-K 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 <a href="https://www.globenewswire.com/Tracker?data=OfV7a1LPRORFGHHw4_F1EZ3ciqzD8lsUnvmNyN0kHbx8l0vxHeeKq9QB6TCvcmvnm2PLDqKFQ-FMfeqWqipT76yeqAdSSpNiZMcWsPZCdUKJoxGtFVMMBmDrRH8JBOgy" rel="nofollow" target="_blank">alex.lobo@precisionaq.com</a> Media Contact  Josie Butler, 1AB <a href="https://www.globenewswire.com/Tracker?data=Os9TTQM2DOfRvlkYfvN8f_tZMn74SpzBHx5hO80AFudv7jAEN0QTvWaXZoBCASP1AoRmVbis1O2sgkA-VokZeyq-oRahy0n1zdWReVf2z8Y=" rel="nofollow" target="_blank">josie@1abmedia.com</a> <img alt="" class="__GNW8366DE3E__IMG" src="https://www.globenewswire.com/newsroom/ti?nf=OTY5MjAzMyM3NTQxNTUwIzIyMDk4MDQ="></img> <img alt="" src="https://ml.globenewswire.com/media/YTlkNjEyMGQtYjVjMy00NWI1LTk3YWEtYjBlNDdmYmU2NTE3LTEyMjEzNTctMjAyNi0wNC0xNy1lbg==/tiny/Xilio-Therapeutics-Inc-.png" referrerpolicy="no-referrer-when-downgrade"></img><a href="https://www.globenewswire.com/NewsRoom/AttachmentNg/7e55cc25-f46f-423c-bf2a-e77ebaf69665"><img src="https://ml.globenewswire.com/media/7e55cc25-f46f-423c-bf2a-e77ebaf69665/small/xilio-full-clr-logo-cmyk-png.png" border="0" width="150" height="94" alt="Primary Logo"></img></a>

Xilio Therapeutics presented positive preclinical data for XTX601 at AACR, featuring robust anti-tumor activity and excellent tolerability. This promising profile positions XTX601 favorably for upcoming IND-enabling studies slated for 2027, which could drive interest and investment in XLO.

Xilio Therapeutics Announces New Preclinical Data at AACR Annual Meeting for XTX601, a Masked T Cell Engager Targeting CLDN18.2

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