Blockade of CCR5 T Cell Accumulation in the Tumor Microenvironment Optimizes Anti-TGF-β/PD-L1 Bispecific Antibody.

In the previous studies, anti-TGF-β/PD-L1 bispecific antibody YM101 is demonstrated, with superior efficacy to anti-PD-L1 monotherapy in multiple tumor models. However, YM101 therapy can not achieve complete regression in most tumor-bearing mice, suggesting the presence of other immunosuppressive elements in the tumor microenvironment (TME) beyond TGF-β and PD-L1. Thoroughly exploring the TME is imperative to pave the way for the successful translation of anti-TGF-β/PD-L1 BsAb into clinical practice. In this work, scRNA-seq is employed to comprehensively profile the TME changes induced by YM101. The scRNA-seq analysis reveals an increase in immune cell populations associated with antitumor immunity and enhances cell-killing pathways. However, the analysis also uncovers the presence of immunosuppressive CCR5 T cells in the TME after YM101 treatment. To overcome this hurdle, YM101 is combined with Maraviroc, a widely used CCR5 antagonist for treating HIV infection, suppressing CCR5 T cell accumulation, and optimizing the immune response. Mechanistically, YM101-induced neutrophil activation recruits immunosuppressive CCR5 T cells via CCR5 ligand secretion, creating a feedback loop that diminishes the antitumor response. Maraviroc then cleared these infiltrating cells and offset YM101-mediated immunosuppressive effects, further unleashing the antitumor immunity. These findings suggest selectively targeting CCR5 signaling with Maraviroc represents a promising and strategic approach to enhance YM101 efficacy.