Reovirus could be used to treat many forms of advanced cancer

An experimental drug called Reolysin may give hope to patients suffering from advanced cancers, according to research presented at this year's meeting of the American Society of Clinical Oncology (ASCO).

In a world first, 30 patients received various intravenous dosages of Reolysin in a Phase I trial in the United Kingdom. The results demonstrated that Reolysin may have stopped the growth of tumors in some patients, or even shrunk tumors without the side effects normally associated with more traditional forms of cancer therapy.

"This is a really novel concept in cancer therapy," said Dr. Matt Coffey, Chief Scientific Officer of Oncolytics Biotech Inc. "Billions of particles of Reolysin, derived from the naturally occurring reovirus, were administered daily to cancer patients who had failed all other cancer therapies, or for whom no viable cancer treatments exist," he said. "The results demonstrated anti-tumor activity in patients with colorectal, prostate, pancreatic, bladder and non-small cell lung (NSCL) cancers."

Two colorectal patients had tumor stabilization at three and six months, and CEA reduction (a cancer marker) of 27% and 60% respectively. One patient with metastatic prostate cancer had stable disease at four months, with a 50% reduction in PSA (prostate specific antigen), and extensive tumour cell death. One patient with metastatic bladder cancer had stable disease at four months, with a minor tumor response in a metastatic lymph node lesion. A patient with NSCL cancer and a pancreatic cancer patient also each had stable disease at four months.

The study has demonstrated that when the virus invades a Ras-activated cancer cell, it proceeds to replicate until it kills the host tumor cell. When the cancer cell dies, thousands of progeny virus particles are released, which proceed to infect and kill adjacent cancer cells. But normal cells are unharmed by reovirus infection.

More recently, a secondary immune response has been observed after reovirus treatment. Researchers believe that once the reovirus infects a cancer cell, it may educate the immune system to recognize and kill that type of cancer cell. "But there is still more to be learned about this remarkable virus," said Dr. Coffey.

A similar intravenous trial being conducted at the Montefiore Medical Center in New York is expected to wrap up later this year. Other trials are expected to follow in the U.K. and the U.S., including two trials sponsored by the U.S. National Cancer Institute (NCI) which will include a Phase II trial for melanoma patients, and a Phase I/II trial for ovarian cancer patients.