Reoviruses (Respiratory Enteric Orphan virus) are found in sewage and water supplies and, although infection in humans is quite common, most cases do not cause any clinical symptoms and go unnoticed. Over a decade ago, it was discovered that, whilst reoviruses are harmless to normal cells, they selectively kill cancer cells that have a constitutively activated Ras pathway. It is thought that the cycle of infection, replication and cell death is repeated until no cells with an activated Ras pathway remain. Cells with an activated Ras pathway are unable to mount a normal antiviral response mediated by the double-stranded RNA activated protein kinase, PKR. Activating mutations of Ras and mutations along the Ras pathway occur in approximately two-thirds of all tumours.
Now the Canadian company, Oncolytics, have announced that they intend to start a phase II/III study examining the effects of REOLYSIN®, the company’s proprietary formulation of the human reovirus, in combination with paclitaxel/carboplatin in refractory patients with head and neck cancers. In earlier studies, eight out of nine head and neck patients reported on to date had either a partial response or stabilization of disease, a response that exceeds the current standard of care treatment for this patient group. In a separate study, REOLYSIN® was found to be well tolerated and show promise for the treatment of bone/soft tissue sarcoma metastatic to the lung.