Toxicology, pharmacokinetics, and immunogenicity studies of CCR4-IL2 bispecific immunotoxin in rats and minipigs

We have developed a diphtheria toxin-based recombinant human CCR4-IL2 bispecific immunotoxin (CCR4-IL2-IT) for targeted therapy of cutaneous T-cell lymphoma (CTCL). CCR4-IL2-IT demonstrated superior efficacy in an immunodeficient mouse CTCL model. Recently, we have compared the in vivo efficacy of CCR4-IL2-IT versus Brentuximab (FDA approved leading drug in CTCL market) in the same immunodeficient mouse CTCL model. The comparison demonstrated that CCR4-IL2-IT was significantly more effective than Brentuximab. In this study, we have performed non-GLP (Good Laboratory Practice) toxicology, pharmacokinetics, immunogenicity studies of CCR4-IL2-IT in both rats and minipigs. CCR4-IL2-IT demonstrated excellent safety profiles in both rats and minipigs. The maximum tolerated dose of CCR4-IL2-IT was determined as 0.4 mg/kg in both rats and minipigs. Complete blood count and chemistry analysis did not show significant difference for all measured parameters between the blood samples of pre-injection versus post-injection from the five-day toxicology studies of CCT4-IL2-IT in both rats and minipigs. Histology analysis did not show difference between the PBS treatment group versus CCR4-IL2-IT treatment group at 50 μg/kg in both rats and minipigs. The half-life of CCR4-IL2-IT was determined as about 45 min in rats and 30 min in minipigs. The antibodies against CCR4-IL2-IT were detected in about two weeks after CCR4-IL2-IT treatment. CCR4-IL2-IT did not induce cytokine release syndrome in a peripheral blood mononuclear cell derived humanized mouse model. The depletion of CCR4⁺ cell and CD25⁺ cell (two target cell populations of CCR4-IL2-IT) was observed in minipigs. The excellent safety profile promoted us to further develop CCR4-IL2-IT towards clinical trials.