An Fc Binding Peptide-Based Facile and Versatile Build Platform for Multispecific Antibodies

Multispecific antibodies (MsAbs) maintain the specificity of versatile antibodies while simultaneously addressing different epitopes for a cumulative, collaborative effect. They could be an alternative treatment to chimeric antigen receptor-T cell therapy by helping to redirect T cells to tumors in vivo. However, one major limitation of their development is their relatively complex production process, which involves performance of a massive screen with low yield, inconsistent quality, and nonnegligible impurities. Here, a poly(l-glutamic acid)-conjugated multiple Fc binding peptide-based synthesis nanoplatform was proposed, in which MsAbs were constructed by mixing the desired monoclonal antibodies (mAbs) with polymeric Fc binding peptides in aqueous solution without purification. To determine its efficacy, a dual immune checkpoint-based PD1/OX40 bispecific antibody and PDL1/CD3e/4-1BB trispecific antibody-based T cell engager were generated to trigger antitumor CD8⁺ T responses in mice, showing superior tumor suppression over free mixed mAbs. In this study, a facile, versatile build platform for MsAbs was established.

Polymeric PD1/PDL1 bispecific antibody enhances immune checkpoint blockade therapy

Immune checkpoint blockade (ICB) therapy, particularly PD1/PDL1 inhibition, has demonstrated success in bolstering durable responses in patients. However, the response rate remains below 30 %. In this study, we developed a polymeric bispecific antibody (BsAb) targeting PD1/PDL1 to enhance ICB therapy. Specifically, poly(L-glutamic acid) (PGLU) was conjugated with a double cyclic Fc binding peptide, Fc-III-4C, through condensation reactions between the -COOH group of PGLU and the -NH2 group of Fc-III-4C. This conjugate was then mixed with αPD1 and αPDL1 monoclonal antibodies (mAbs) in an aqueous solution. Mechanistically, the PD1/PDL1 BsAb (BsAbαPD1+αPDL1) acts as a bridge between tumor cells and CD8+ T cells, continuously activating CD8+ T cells to a greater extent. This leads to significantly suppressed tumor growth and prolonged survival in a mouse model of colon cancer compared to treatment with either a single mAb or a mixture of free mAbs. The tumor suppression rate achieved by the BsAbαPD1+αPDL1 was 90.1 %, with a corresponding survival rate of 83.3 % after 48 days. Thus, this study underscores the effectiveness of the BsAbαPD1+αPDL1 as a synchronizing T cell engager and dual ICBs, offering theoretical guidance for clinical ICB therapy.