A study published in Cancer Research last week has shown that a cancer-killing (oncolytic) virus currently in clinical trials may also function as a cancer vaccine. In addition to killing some cancer cells directly, the virus alerts the immune system to the presence of a tumour, triggering a powerful, widespread immune response that kills cancer cells far outside the virus-infected region.

The researchers suggest combining the oncolytic virus with immunotherapy drugs such as checkpoint inhibitors, which release the brakes on the immune system to enable it to fight the cancer.

Viruses appear capable of attacking tumours in a number of different ways – by directly infecting them, by releasing tumour proteins that trigger a broad immune response against the cancer, and by damaging the blood supply tumours need to survive.

An oncolytic viral therapy called Pexa-Vec, is currently in phase III and phase Ib/II clinical trials for use against primary liver and colorectal cancers, respectively. Pexa-Vec is an engineered virus based on the harmless vaccinia cowpox virus, which formed basis for the original smallpox vaccine.

The company developing Pexa-Vec, SillaJen Biotherapeutics, recently announced a new clinical trial in collaboration with Regeneron to test Pexa-Vec and REGN2810, a PD-1 checkpoint inhibitor, in combination against renal cell carcinoma (RCC).

“The preclinical work …… has been extremely informative in helping us understand that Pexa-Vec is working like a vaccine to sensitise the immune system to attack cancer,” said James Burke, CMO of SillaJen Biotherapeutics. “Our ongoing collaboration will help us understand how best to combine Pexa-Vec with immune-modulation such as anti-PD1 antibody therapy to maximise anti-tumour immune response. If the virus is igniting a fire within the tumor, we want to see if we can use these immune modulators to pour gas on the flames.”

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