On December 11, 2025 Purple Biotech Ltd. ("Purple Biotech" or the "Company") (NASDAQ/TASE: PPBT), a clinical-stage company developing first-in-class therapies that seek to overcome tumor immune evasion and drug resistance, reported positive new preclinical data from its CAPTN-3 tri-specific antibody platform presented at the ESMO (Free ESMO Whitepaper) Immuno-Oncology (ESMO IO) Congress 2025. The data presented was generated in collaboration with the laboratory of Dr. Amir Horowitz of the Tisch Cancer Institute at the Icahn School of Medicine at Mount Sinai.

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These new preclinical data successfully demonstrates that two CAPTN-3 tri-specific antibodies, IM1240 (capped-CD3×5T4×NKG2A) and IM1305 (capped-CD3×TROP2×NKG2A), each achieve strong anti-tumor activity across different tumor antigens. IM1240 has also shown anti-tumor activity in models resistant to prior PD1 therapy. These results indicate that the CAPTN-3 architecture can generate potent multi-arm activity beyond a single target, supporting the platform’s potential applicability across a range of solid tumors. The CAPTN-3 platform is designed to unite three functional mechanisms—T-cell engagement and activation, enhanced by NKG2A-mediated innate and adaptive immune activation, and tumor-antigen targeting—into a single tri-specific molecule intended to coordinate a synergistic immune response.

"Immune failure is one of the biggest obstacles in treating solid tumors, and CAPTN-3 was built to address that challenge," said Gil Efron, Chief Executive Officer of Purple Biotech. "The data we presented at ESMO (Free ESMO Whitepaper) IO shows that IM1240 can activate an immune response even in tumors that no longer respond to PD-1 therapy, and that each component of the molecule contributes to its overall effect. At the same time, the introduction of IM1305 demonstrates how CAPTN-3 can be adapted to different tumor targets, underscoring the versatility and scalability of the platform. These findings support our development roadmap as we prepare for anticipated key milestones in 2026 and advance CAPTN-3 toward IND-enabling studies."

"The NKG2A/HLA-E axis is emerging as a key post-treatment resistance mechanism, as previously shown by Dr. Horowitz of the Tisch Cancer Institute at the Icahn School of Medicine at Mount Sinai," said Dr. Hadas Reuveni, VP Research and Development at Purple Biotech. "The added value of the aNKG2A arm in IM1240 design, shown both in vivo and in vitro through reactivation of suppressed immune cell subsets, is now further supported by enhanced anti-tumor activity in PD-1–resistant patient-derived explants from non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC). These findings underscore the potential importance of the NKG2A arm in advanced and treatment-resistant disease."

Key New Findings:

Lead Program IM1240: Anti-Tumor Activity in PD-1–Resistant Models

· The Company’s lead CAPTN-3 program, IM1240, demonstrated significant anti-tumor activity in three PD1–resistant ex-vivo models, including new results in HNSCC patient-derived biopsies. In these studies, IM1240 induced tumor cell apoptosis, with anti-tumor activity dependent on both CD3 and NKG2A arms.

· Similarly, IM1240’s immune-mediated anti-tumor activity in PD1-resistant NSCLC patient-derived explants was evidenced by a significant increase in IFNγ secretion.

· To discern IM1240’s selectivity, a transcriptomic analysis of ~11,000 TCGA (The Cancer Genome Atlas) human samples showed that NKG2A expression co-occurs with 5T4 in solid tissues, which provides rationale for inclusion of the αNKG2A arm unique to the CAPTN-3 platform.

Platform Versatility: New TROP2-Targeting Candidate IM1305

· The Company’s new TROP2-targeting candidate, IM1305, further validates the adaptability of the CAPTN-3 platform and demonstrated high-affinity binding to both TROP2 and NKG2A (EC₅₀ ~2 nM).

· Potent PBMC-mediated tumor cell killing was observed at low concentrations (EC₅₀ 1–5 pM) across multiple tumor types, including triple-negative breast, gastric, pancreatic, and head and neck cancers.

· Like IM1240, IM1305’s anti-cancer activity and CD3 binding were fully restored after cap cleavage, a critical component of CAPTN-3’s conditional activation design.

In humanized triple-negative breast cancer mouse models, IM1305 induced sustained tumor regression at low doses (p < 0.0001), reinforcing the platform’s broad application potential. The poster will be accessible under the Publications section of the Purple Biotech website following the congress, or using the following link: View Source

(Press release, Purple Biotech, DEC 11, 2025, View Source [SID1234661374])