Xilio Therapeutics Announces New Preclinical Data at AACR Annual Meeting for XTX601, a Masked T Cell Engager Targeting CLDN18.2
Rhea-AI Summary
Xilio Therapeutics (Nasdaq: XLO) presented new preclinical data for XTX601, a masked T cell engager targeting CLDN18.2, at AACR (Apr 17–22, 2026). XTX601 showed protease‑dependent, tumor‑selective activation, dose‑dependent anti‑tumor activity in multiple murine xenograft models, and favorable tolerability in non‑human primates with no cytokine release syndrome or liver enzyme changes. Xilio plans IND‑enabling studies and an IND submission for the program in 2027. The poster presentation is scheduled Apr 20, 2026, Poster Section 10, Board 11.
Positive
- Protease‑dependent, tumor‑selective activation demonstrated in preclinical studies
- Dose‑dependent anti‑tumor activity in multiple murine CLDN18.2 xenograft models
- Well tolerated in non‑human primates with no cytokine release syndrome and no liver enzyme changes
- Company plans IND‑enabling studies and an IND submission in 2027
Negative
- Efficacy shown only in preclinical murine xenograft models, not yet in humans
- Program remains pre‑IND; clinical safety and efficacy in patients are unproven
News Market Reaction – XLO
In the Apr 20 session, XLO declined 1.40%, reflecting a mild negative market reaction.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Historical Context
| Date | Event | Sentiment | 24h Move | Catalyst |
|---|---|---|---|---|
| Apr 16 | Board change | Neutral | -0.6% | New director appointed and another resigned with outlined committee roles. |
| Apr 03 | Inducement grants | Neutral | -0.6% | Inducement stock options granted to new employees under incentive plan. |
| Mar 23 | Earnings and pipeline | Positive | +0.0% | Stronger 2025 results, cash of $137.5M, and runway through end of 2027. |
| Mar 17 | AACR preview | Positive | +2.3% | Announcement of upcoming AACR poster on masked CLDN18.2 T cell engager. |
| Mar 12 | Reverse split | Negative | -5.3% | 1-for-14 reverse stock split to address Nasdaq minimum bid requirement. |
24h Move is the share-price change in the day after each event; other market factors may also have contributed.
Recent news often saw price moves roughly aligned with the qualitative tone, except for flat trading on a positive 2025 update.
Over recent months, Xilio has combined pipeline updates with balance sheet and listing actions. A 1-for-14 reverse split in March 2026 aimed to restore Nasdaq compliance, while an 8-K reported stronger 2025 results and collaboration revenue with cash of $137.5M and runway to end of 2027. Governance changes added a new director and option grants, and prior AACR-related CLDN18.2 poster news on March 17, 2026 coincided with a positive price move, offering relevant context for today’s detailed preclinical data.
Key Terms
t cell engager medical
claudin 18.2 medical
tumor microenvironment medical
xenograft medical
cytokine release syndrome medical
pharmacokinetics medical
therapeutic index medical
ind application regulatory
AI-generated analysis. How Rhea-AI works. Not financial advice.
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: XLO), 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.
- 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.
- 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.
- 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.
- 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.
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 & Publications” section of the company’s website at www.xiliotx.com.
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 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 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
alex.lobo@precisionaq.com
Media Contact
Josie Butler, 1AB
josie@1abmedia.com
