Purple Biotech Presents New IM1240 Data at EACR 2026
Purple Biotech announced the presentation of new preclinical data from its CAPTN-3 program, IM1240, at the European Association for Cancer Research, or EACR, 2026 Annual Congress, being held June 8-11, 2026, in Budapest, Hungary. 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 - 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 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 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: IM1240 induced minimal IL-6 and TNF-a 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 an approximately 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.
