OncoVEX^mGM-CSFexpands tumor antigen-specific CD8+ T-cell response in preclinical models

Abstract

BackgroundCheckpoint inhibitors targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) have demonstrated clinical efficacy in advanced melanoma, but only a subset of patients with inflamed tumors are responsive. Talimogene laherparepvec (T-VEC), a modified herpes simplex virus type 1 (HSV-1) expressing granulocyte-macrophage colony-stimulating factor (GM-CSF), is a first-in-class oncolytic immunotherapy approved for the treatment of melanoma and has been shown to inflame the tumor microenvironment. To evaluate the potential and mechanisms of T-VEC to elicit systemic antitumor immunity and overcome resistance to checkpoint inhibitors in murine tumor models, OncoVEXmGM-CSFwas developed similarly to T-VEC, except the human GM-CSF transgene was replaced with murine GM-CSF. Previous work had demonstrated that OncoVEXmGM-CSFgenerated systemic antitumor immunity dependent on CD8+ T cells in an immune checkpoint-sensitive tumor cell model.MethodsA novel B16F10 syngeneic tumor model with both HSV-1−permissive subcutaneous tumors and HSV-1−refractory experimental lung metastasis was used to study the local and systemic effects of OncoVEXmGM-CSFtreatment alone or in combination with checkpoint inhibitors.ResultsIntratumoral injection of OncoVEXmGM-CSFin combination with an anti-CTLA-4 or anti-PD-1 blocking antibody led to increased tumor growth inhibition, a reduction in the number of lung metastases, and prolonged animal survival. OncoVEXmGM-CSFinduced both neoantigen-specific and tumor antigen-specific T-cell responses. Furthermore, cured mice from the combination treatment of OncoVEXmGM-CSFand anti-CTLA-4 antibody rejected tumor rechallenges.ConclusionsThese data support the concept that T-VEC and checkpoint inhibition may be an effective combination to treat patients with advanced melanoma.

Cytokine-armed oncolytic herpes simplex viruses: a game-changer in cancer immunotherapy?

“… 24 The antitumor efficacy of OncoVEX mGM-CSF was further enhanced by immune checkpoint inhibitors (ICIs), such as anti-cytotoxic T lymphocyte antigen 4 (anti-CTLA-4) or anti-programmed death 1 (anti-PD-1), with the combination therapy eliciting significant inhibition of B16F10-mNectin tumor growth and lung metastasis, and extension of median survival compared with monotherapies. 8 …”