Polymeric Multivalent Fc Binding Peptides‐Fabricated Clinical Compounding Bispecific Antibody Potentiates Dual Immunotherapy Targeting PD1 and CTLA‐4

Abstract Dual Opdivo plus Yervoy immunotherapy, targeting the immune checkpoints PD1 and CTLA‐4, is successful in clinical use. However, it is associated with a high incidence of adverse events, and its therapeutic efficacy needs improving. In this study, polymeric multivalent Fc‐binding peptides (PLG‐Fc‐III‐4C) are employed to fabricate a bispecific antibody (PD1/CTLA‐4 BsAb) to potentiate dual immunotherapy targeting PD1 and CTLA‐4. The PD1/CTLA‐4 BsAb is prepared by mixing PLG‐Fc‐III‐4C with aPD1 and aCTLA‐4 in an aqueous solution for 3 h using the clinically optimal 3:1 proportion of aPD1 to aCTLA‐4. PD1/CTLA‐4 BsAb significantly inhibits tumors in MC38 colon cancer‐bearing mice more effectively than the combination of aPD1 and aCTLA‐4, with tumor suppression rates of 96.8% and 77.3%, respectively. It also induces a higher percentage of CD8⁺ T cells and increases the secretion of effector cytokines while reducing Treg levels in tumors compared to phosphate‐buffered saline, indicating significant tumor immunity regulation. Mechanistically, a 6.3‐fold increase in PD1/CTLA‐4 BsAb accumulation in tumors due to the tumor targeting ability of aPD1, and the PD1/CTLA‐4 BsAb significantly reduces the adverse colitis event in healthy mice, compared to aPD1 and aCTLA‐4. Thus, these findings provide a novel approach to enhance antitumor therapy using aPD1 and aCTLA‐4.