• RBT-101, Radiant’s lead oncology program and 4-1BB agonist, demonstrated robust, durable and complete tumor regression without liver toxicity in MC38 colorectal mouse tumor model
• Poster presentation scheduled on Friday, November 7, 2025

Radiant Biotherapeutics, a biotechnology company committed to advancing a breakthrough antibody approach, the Multabody™, for a broad range of therapeutic areas, including cancer and infectious diseases, announced new data at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting demonstrating its lead oncology candidate, RBT-101, exhibited robust, durable and complete tumor regression while avoiding liver toxicity, in a MC38 colorectal mouse tumor model.

Radiant’s proprietary Multabody™ technology uniquely harnesses natural mechanisms to effectively engage multiple disease targets with unmatched strength, precise tunability, and exceptional breadth. 4-1BB is a clinically validated immune checkpoint target that elicits potent anti-tumor immunity and enhanced T cell responses but has eluded safe and effective therapeutic targeting by traditional 4-1BB agonists due to systemic and Fc-mediated liver toxicity. Radiant has leveraged its Multabody™ platform to develop RBT-101, a multivalent 4-1BB agonist that does not rely on traditional antibody methods to enhance potency, binding strength or durability.

Key Highlights from SITC 2025 Poster Presentation:

• RBT-101 achieved sustained complete tumor regression in MC38 colorectal mouse tumor model
• RBT-101 demonstrated long-lived anti-tumor immunological memory; no detectable tumor growth was observed in mice that were re-challenged with MC38 tumor cells after previous successful treatment
• RBT-101 demonstrated no signs of liver toxicity, in contrast to benchmark 4-1BB agonist urelumab

“Our data to be presented at SITC demonstrates that RBT-101 achieves what first-generation 4-1BB agonists could not – delivering robust anti-tumor activity without liver toxicity,” said Jo Hulme, Ph.D., CSO of Radiant. “This validates our Multabody platform’s potential to address a broad range of therapeutic targets while avoiding the inherent limitations of conventional antibody-based approaches, as RBT-101 drove potent, tunable and safe agonism of 4-1BB that more closely mimicked natural ligand biology. We look forward to the continued development of Multabodies as promising therapeutics in oncology and other disease areas.”

The poster, titled “Multabodies: A next-generation approach for cancer immunotherapy and 4-1BB agonist therapy,” will be presented onsite on Friday, November 7, 2025, and will also be available on the SITC virtual meeting platform beginning November 7 at 9 a.m. ET.

About Radiant Biotherapeutics

Radiant Biotherapeutics is a biotechnology company advancing breakthrough Multabody™ therapeutics that deliver unmatched strength, tunability, and breadth in a single molecule. The company’s proprietary platform leverages apoferritin scaffolding and sophisticated protein engineering to create antibodies with unprecedented therapeutic potential across a broad range of disease areas, including cancer and infectious diseases. The platform is compatible with standard antibody manufacturing processes, bringing flexibility, modularity and scalability. For more information, please visit radiantbio.com.

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