Research ArticleCancer

MEK inhibition enhances oncolytic virus immunotherapy through increased tumor cell killing and T cell activation

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Science Translational Medicine  12 Dec 2018:
Vol. 10, Issue 471, eaau0417
DOI: 10.1126/scitranslmed.aau0417

Enabling immunotherapy with an oncolytic virus

Immunotherapy treatments have been pioneered in the setting of melanoma, and although subsets of patients are able to survive long term, some tumors are resistant. Bommareddy and colleagues inquired whether combining certain treatments may lead to even better therapeutic responses. They examined two approved therapies, an oncolytic herpesvirus and a MEK inhibitor. This combination led to increased survival in mouse melanoma models, which was further extended with the addition of PD-1 blockade. The immune response behind this enhanced antitumor activity was dissected. The results of these studies suggest that combining these treatments may be beneficial for patients with melanoma.


Melanoma is an aggressive cutaneous malignancy, but advances over the past decade have resulted in multiple new therapeutic options, including molecularly targeted therapy, immunotherapy, and oncolytic virus therapy. Talimogene laherparepvec (T-VEC) is a herpes simplex type 1 oncolytic virus, and trametinib is a MEK inhibitor approved for treatment of melanoma. Therapeutic responses with T-VEC are often limited, and BRAF/MEK inhibition is complicated by drug resistance. We observed that the combination of T-VEC and trametinib resulted in enhanced melanoma cell death in vitro. Further, combination treatment resulted in delayed tumor growth and improved survival in mouse models. Tumor regression was dependent on activated CD8+ T cells and Batf3+ dendritic cells. We also observed antigen spreading and induction of an inflammatory gene signature, including increased expression of PD-L1. Triple therapy with the combination of T-VEC, MEK inhibition, and anti–PD-1 antibody further augmented responses. These data support clinical development of combination oncolytic viruses, MEK inhibitors, and checkpoint blockade in patients with melanoma.

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