Pfizer ($PFE) has secured an exclusive option to acquire Western Oncolytics’ WO-12. The deal gives Pfizer a chance to pick up the oncolytic vaccinia virus once it has completed Phase I, something the Big Pharma will work to achieve with its new partner.
WO-12 is currently in preclinical testing, but Pfizer has already seen enough in the data to envisage a place for the asset in its immuno-oncology portfolio. The virus, which has shown potential against kidney cancer in mice, is designed to replicate in cancer cells while delivering genes that support the immune response against the tumor. Western Oncolytics thinks the virus could hit multiple types of solid tumors and, importantly for Pfizer, play a role in combination treatments.
To achieve this profile, Western Oncolytics has taken a vaccinia virus, armed it with TRIF and HPGD genes and stripped its surface of anything that could cause the immune system to recognize it as an intruder. Once delivered intravenously or intratumorally, the virus should pass unmolested around the body. Upon entering a healthy cell, a gene modification in the virus is supposed to take effect, limiting the extent to which it replicates.
This safety switch lies dormant when the virus is in a cancer cell. When exposed to the chemistry found in cancer cells, Western Oncolytics expects WO-12 will replicate, resulting in virus numbers increasing until they destroy their host. The newly released viruses then infect neighboring cancer cells, continuing the process.
In concert, the presence of TRIF is intended to stimulate cytotoxic T cells. The inclusion of HPGD is expected to support the actions of the T cells by taking out immunosuppressors.
If the virus works in practice as in theory, these multiple mechanisms will shrink the tumor. And the presence of lysed material will support an adaptive immune response, equipping the body to identify and eliminate cancer cells.
The final step in the process is the removal of the engineered viruses. While the WO-12 virus has a deglycosylated surface, the viruses made in the body lack this defense. As such, the immune system should remove them over time, limiting the risk of side effects.
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