Purple Biotech Ltd. ("Purple Biotech" or the "Company") (NASDAQ/TASE: PPBT), a clinical-stage oncology company developing a next-generation immunotherapy platform designed to maximize anti-cancer potency while minimizing toxicity, today announced the presentation of new preclinical data from its lead CAPTN-3 program, IM1240, at the European Association for Cancer Research (EACR) 2026 Annual Congress, being held June 8-11, 2026, in Budapest, Hungary.

A non-GLP toxicology study in NHPs validates the CAPTN-3 masking strategy and supports the planned advancement of IM1240 toward a first-in-human clinical study in 2027. Additionally, efficacy data in patient-derived samples from PD-1-resistant head and neck squamous cell carcinoma (HNSCC) metastatic lymph nodes, NSCLC and bladder cancer, generated in collaboration with the laboratory of Dr. Amir Horowitz at the Tisch Cancer Institute at the Icahn School of Medicine at Mount Sinai, highlight the essential role of the NKG2A arm in IM1240-mediated anti-tumor immunity and further strengthen CAPTN-3's differentiation and clinical potential.

Poster Title: Toxicology study results in NHP validated improved PK and safety profile of CAPTN-3 masking design, revealing an extended therapeutic window

Abstract: EACR26-0695

Session: Immunotherapy

Date: Wednesday, June 10, 2026

Summary of data presented at EACR 2026:

• IM1240 induced apoptosis of PD-1-resistant patient-derived biopsies from six HNSCC metastatic lymph node samples and one enfortumab vedotin/pembrolizumab-resistant muscle-invasive bladder cancer sample, with both the CD3 and NKG2A functional arms required for full activity.
• In a PD-1/chemotherapy-resistant NSCLC patient-derived explant, IM1240 induced mature tertiary lymphoid structures (TLS) – immune cell organizations associated with effective anti-tumor immunity and favorable clinical prognosis – while increasing CD8 T cell and NK cell abundance and reducing regulatory T cells (Tregs) and tumor cells. These effects were not observed with IM1340, the NKG2A loss-of-function variant, underscoring the essential and differentiated contribution of the NKG2A arm.
• In a non-GLP dose-range finding toxicology study in NHPs, IM1240 demonstrated markedly superior pharmacokinetics (PK) compared to the non-capped variant IM1222, including an approximately 8-fold longer half-life and 16-fold greater systemic exposure. IM1240 showed dose-proportional PK with a broad therapeutic window, as systemic exposure associated with tumor regression in mouse models remained well below the tolerated levels in NHPs.
• The CAPTN-3 masking strategy effectively mitigated peripheral T-cell activation and prevented systemic cytokine release in NHPs, which is associated with one of the main safety challenges of T-cell engagers, cytokine release syndrome (CRS):
  • IM1240 induced minimal IL-6 and TNF-α at 10 mg/kg dose, whereas the non-capped IM1222 induced robust cytokine release at just 0.03 mg/kg – a more than 300-fold difference in the dose required to trigger cytokine release.
  • The IM1240 capping design also improved the PK profile by reducing the CD3-mediated antigen sink effect and incorporating human serum albumin to further extend half-life, as compared to the non-capped variant IM1222.
  • IM1240 demonstrated ~14-fold slower clearance than active non-capped IM1222, supporting extended exposure and potential efficacy; rapid clearance of peripherally released non-capped IM1222 reduces systemic accumulation and lowers CRS risk and off-tumor toxicity.