Specifically blocking αvβ8-mediated TGF-β signaling to reverse immunosuppression by modulating macrophage polarization

BackgroundTargeting the TGF-beta pathway in tumor therapy has proven challenging due to the highly context-dependent functions of TGF-beta. Integrin alpha v beta 8, a pivotal activator of TGF-beta, has been implicated in TGF-beta signaling within tumors, as demonstrated by the significant anti-tumor effects of anti-alpha v beta 8 antibodies. Nevertheless, the expression profile of alpha v beta 8 remains a subject of debate, and the precise mechanisms underlying the anti-tumor effects of anti-alpha v beta 8 antibodies are not yet fully elucidated.MethodsWe utilized single-cell RNA sequencing to assess alpha v beta 8 expression across various human tumors. An anti-alpha v beta 8 antibody was developed and characterized for its binding and blocking properties in vitro. Cryo-EM single-particle analysis was employed to study the detailed interaction between alpha v beta 8 and the antibody Fab fragment. The anti-tumor efficacy of the antibody was evaluated in syngeneic mouse models with varying levels of alpha v beta 8 expression, both as a monotherapy and in combination with PD-1 antibodies. Human PBMCs were isolated to investigate alpha v beta 8 expression in myeloid cells, and macrophages were exposed to the antibody to study its impact on macrophage polarization. Pharmacokinetic studies of the alpha v beta 8 antibody were conducted in cynomolgus monkeys.ResultsIntegrin alpha v beta 8 is notably expressed in certain tumor types and tumor-infiltrating macrophages. The specific alpha v beta 8 antibody 130H2 demonstrated high affinity, specificity, and blocking potency in vitro. Cryo-EM analysis further revealed that 130H2 interacts exclusively with the beta 8 subunit, without binding to the alpha v subunit. In vivo studies showed that this antibody significantly inhibited tumor growth and alleviated immunosuppression by promoting immune cell infiltration. Furthermore, combining the antibody with PD-1 inhibition produced a synergistic anti-tumor effect. In human PBMCs, monocytes exhibited high alpha v beta 8 expression, and the antibody directly modulated macrophage polarization. Tumors with elevated alpha v beta 8 expression were particularly responsive to 130H2 treatment. Additionally, favorable pharmacokinetic properties were observed in cynomolgus monkeys.ConclusionsIn summary, integrin alpha v beta 8 is highly expressed in certain tumors and tumor-infiltrating macrophages. Targeting alpha v beta 8 with a blocking antibody significantly inhibits tumor growth by modulating macrophage polarization and enhancing immune cell infiltration. Combining alpha v beta 8 targeting with PD-1 treatment markedly increases the sensitivity of immune-excluded tumors. These results support further clinical evaluation of alpha v beta 8 antibodies.