Xilio Therapeutics appoints Yariv J. Houvras, M.D., Ph.D. as chief medical officer. Dr. Houvras brings over two decades of executive leadership across premier industry and academic research institutions in clinical development, translational medicine and immuno-oncology. WALTHAM, Mass., Sept. 28, 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 the appointment of Dr. Yariv Houvras as chief medical officer. "We are thrilled to welcome Yariv at this exciting time for Xilio as we advance XTX501, our bispecific PD-1 / masked IL-2, in the clinic and our next generation of multi-specific, masked T cell engagers," said René Russo, Pharm.D., president and chief executive officer of Xilio. "Yariv is an accomplished physician-scientist with a proven track record of leading complex global clinical development programs from first-in-human studies through registrational Phase 3 trials and regulatory approvals. His deep scientific rigor and expertise in immuno-oncology will be invaluable as we continue towards our goal of unlocking the full potential of our pipeline of masked I-O therapies." "I believe Xilio's best-in-class masking technology and protein engineering capabilities have tremendous potential to deliver transformative, tumor-selective I-O therapies," said Dr. Houvras. "In the near-term, I am particularly excited about the potential for XTX501 as a backbone therapy for oncology, and I look forward to building upon Xilio's strong clinical foundation and working closely with the company's talented team." Yariv J. Houvras, M.D., Ph.D. Dr. Houvras brings more than 20 years of leadership experience across premier industry and academic research institutions in clinical development, translational medicine and immuno-oncology, including hematologic malignancies and solid tumors. Prior to joining Xilio, he served as senior vice president of clinical and translational development of Tubulis, GmbH (Tubulis) through its acquisition by Gilead Sciences, Inc. At Tubulis, Dr. Houvras was the global head of clinical development and was responsible for scientific and medical oversight of Tubulis' antibody-drug conjugate (ADC) programs in solid tumors. In this role, he led multiple first-in-human and registration-enabling clinical studies. Prior to Tubulis, he served as senior medical director of hematology and translational sciences at Regeneron Pharmaceuticals, Inc. where he was the physician for linvoseltamab, a bispecific T cell engager targeting BCMA and CD3, from first-in-human studies through accelerated and conditional regulatory approval in the U.S. and European Union. Earlier in his career, Dr. Houvras served in academic roles of increasing responsibility at Weill Cornell Medical College and Harvard Medical School. He completed his internal medicine residency at Massachusetts General Hospital (MGH) and his medical oncology and hematology fellowships at Dana-Farber Cancer Institute and MGH. In addition, Dr. Houvras has served on various leadership boards, including Director of the International Thyroid Oncology Group, and he has authored over 30 peer-reviewed publications in journals such as Nature, Cell and the Journal of Clinical Oncology. He received his B.S. in biology and English literature from the University of Michigan - Ann Arbor and an M.D. and Ph.D. from the Mount Sinai School of Medicine. 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 applicable securities laws and regulations, including, without limitation, statements regarding plans, expectations, development timelines and anticipated milestones for Xilio's programs, including advancing XTX501 and the company's next generation of multi-specific T cell engagers; the potential for XTX501 as a backbone therapy for oncology; and Xilio's strategy, goals, business plans and focus, including the potential to deliver transformative, tumor-selective I-O therapies and to unlock the value of the company's pipeline of such therapies. 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 and license agreements with AbbVie and Gilead. 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 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.

Xilio Therapeutics, a clinical-stage biotechnology company developing masked immuno-oncology therapies, has appointed Ben Harshbarger as chief legal officer. Harshbarger brings over 20 years of executive leadership and legal expertise in the biopharmaceutical industry. Most recently, he served as chief legal officer at Astria Therapeutics until its acquisition by BioCryst Pharmaceuticals. At Astria, Harshbarger helped lead strategic initiatives including the company's transition from Catabasis Pharmaceuticals and its growth from pre-clinical to late-stage clinical operations. The appointment comes as Xilio advances its pipeline of multi-specific immuno-oncology therapies, including XTX501, a bispecific PD-1/masked IL-2 treatment. Harshbarger previously held senior legal positions at Novelion Therapeutics, Aegerion Pharmaceuticals, Cubist Pharmaceuticals and Biogen.

Xilio Therapeutics appoints Ben Harshbarger as chief legal officer. WALTHAM, Mass., June 29, 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 the appointment of Ben Harshbarger as chief legal officer. "Ben is a proven leader, with deep legal and strategic experience across all stages of biotechnology companies," said René Russo, Pharm.D., president and chief executive officer of Xilio. "He joins our leadership team at an important time at Xilio, as we advance our pipeline of next-generation, multi-specific I-O therapies toward the clinic, including XTX501, a potential best-in-class bispecific PD-1 / masked IL-2, and multiple masked T-cell engagers." "Xilio has built an impressive pipeline leveraging its clinically-validated masking technology, and I am excited to work alongside the team to help drive its strategic and operational goals and advance its promising pipeline of masked multi-specific I-O therapies," said Mr. Harshbarger. Ben Harshbarger Mr. Harshbarger brings over 20 years of executive leadership and legal expertise within the biopharmaceutical industry. Most recently, he served as chief legal officer at Astria Therapeutics, Inc. until its acquisition by BioCryst Pharmaceuticals, Inc. At Astria, Mr. Harshbarger served on the leadership team and helped lead strategic and operational initiatives, including the company's transition from Catabasis Pharmaceuticals, Inc. to Astria, its growth from a pre-clinical organization to a late-stage clinical company and its acquisition. Prior to Astria, he served as interim chief executive officer and general counsel at Novelion Therapeutics Inc. and as general counsel at Aegerion Pharmaceuticals, Inc., which was a subsidiary of Novelion. Earlier in his career, he served in legal roles of increasing responsibility at Cubist Pharmaceuticals, Inc., ViaCell, Inc., and Biogen, Inc. Mr. Harshbarger received his B.A. in political science from the University of Richmond and his J.D. from Boston College Law School. 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 applicable securities laws and regulations, including, without limitation, statements regarding plans, expectations, development timelines and anticipated milestones for Xilio's programs; and Xilio's strategy, goals, business plans and focus. 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 and license agreements with AbbVie and Gilead. 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 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.