Exploring The Main Mechanisms Of Anti-Tumor And Immunotherapy-Related Adverse Events For Safer And Effective Anti-Ctla-4 Immunotherapy

Abstract Targeting CTLA-4 has shown remarkable long-term benefit and thus remains a valuable tool for cancer immunotherapy if the immunotherapy-related adverse effects (irAEs) can be brought under control. Here, we systematically studied the immunotherapeutic effect of anti-human CTLA-4 mAbs and suggest that Fc/Fc receptor mediated intra-tumor Treg depletion rather than the widely held mechanism of checkpoint blockade contribute to the cancer immunotherapeutic effect, which raised the reappraisal of CTLA-4 checkpoint blockade in cancer immunotherapy. Meanwhile, an animal model, which recapitulates clinical irAE and cancer immunotherapeutic effect (CITE), would be valuable for developing safer CTLA-4-targeting reagents. We established such an irAEs model and found that the Ipilimumab (or TremeIgG1) induced severe irAEs especially when combined with an anti-PD-1 antibody; whereas HL12/HL32 induced comparable CITE with very mild irAE under the same conditions. Furthermore we tried to uncouple the undesired irAEs from the beneficial CITE by exploring the mechanism of irAEs of anti-CTLA-4 antibodies in our irAEs model, and found that while irAE-prone Ipilimumab and TremeIgG1 rapidly direct cell surface CTLA-4 for lysosomal degradation, the non-irAE-prone antibodies we generated, HL12 or HL32, dissociate from CTLA-4 after endocytosis and allow CTLA-4 recycling to cell surface, increasing the pH sensitivity of TremeIgG1 by introducing designed tyrosine-to-histidine mutations prevents antibody-triggered lysosomal CTLA-4 downregulation and dramatically attenuates irAE. Our data establish a new paradigm for cancer research that allows for abrogating irAE while increasing CITE of anti-CTLA-4 antibodies.