M7824, a novel bifunctional anti-PD-L1/TGFβ Trap fusion protein, promotes anti-tumor efficacy as monotherapy and in combination with vaccine

Tumors evade host immune surveillance through multiple mechanisms, including the generation of a tumor microenvironment that suppresses immune effector function. Secretion of TGF beta and upregulation of immune checkpoint programmed cell death ligand-1 (PD-L1) are two main contributors to immune evasion and tumor progression. Here, we examined the efficacy of a first-in-class bifunctional checkpoint inhibitor, the fusion protein M7824, comprising the extracellular domain of human TGF beta RII (TGF beta Trap) linked to the C-terminus of human anti-PD-L1 heavy chain (alpha PD-L1). We demonstrate that M7824 reduces plasma TGF beta 1, binds to PD-L1 in the tumor, and decreases TGF beta-induced signaling in the tumor microenvironment in mice. In murine breast and colon carcinoma models, M7824 decreased tumor burden and increased overall survival as compared to targeting TGF beta alone. M7824 treatment promoted CD8+ T cell and NK cell activation, and both of these immune populations were required for optimal M7824-mediated tumor control. M7824 was superior to TGF beta- or alpha PD-L1-targeted therapies when in combination with a therapeutic cancer vaccine. These findings demonstrate the value of using M7824 to simultaneously target TGF beta and PD-L1/PD-1 immunosuppressive pathways to promote anti-tumor responses and efficacy. The studies also support the potential clinical use of M7824 as a monotherapy or in combination with other immunotherapies, such as therapeutic cancer vaccines, including for patients who have progressed on alpha PD-L1/alpha PD-1 checkpoint blockade therapies.