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Reovirus destroys cancer cells

Victory for a Virus

July 2008

by Jill Byrd

In June 2007 Kenny Scott, 52, visited Ron Williams, M.D., Ph.D., a Health Science Center orthopaedic oncologist, at the Sarcoma Clinic at the Cancer Therapy & Research Center (CTRC). But what was supposed to be a regular checkup turned out to be far from normal. Scott learned that day what all cancer patients fear: his cancer had returned. The same type of cancer (synovial sarcoma) that had been removed from his arm 4 1/2 years earlier had metastasized to his lungs. He also learned there was no cure.

"Chemotherapy would prolong my days, but the type of chemo I needed would have such terrible side effects that I decided it was not a good option for me," Scott said. "I was told it might give me a few more weeks or months, but my quality of life would deteriorate immediately with no real chance of improvement. At that point my wife and I were praying for a miracle, for guidance to know the direction that God wanted us to go and for more faith."

Two weeks later, Scott received a call from Dr. Williams, who told him about another option to fight his terminal cancer. Researchers at the CTRC Institute for Drug Development were studying a novel anti-cancer therapy called REOLYSIN®. Dr. Williams was confident this experimental treatment might benefit Scott.

The reovirus eliminates cancer by entering the cancer cell, replicating within it, and destroying it.
The reovirus eliminates cancer by entering the cancer cell, replicating within it, and destroying it.

In the cancer cell, the enzyme PKR is suppressed, allowing the reovirus to replicate and eventually kill it.

To view a video on reovirus click here.


REOLYSIN®, which is a living virus, not a chemotherapy drug, is toxic to cancer cells but not harmful to normal cells. In earlier studies, the therapy had shown some possible hope in slowing tumor growth and even knocking cancers into remission.

According to Monica Mita, M.D., principal investigator of the REOLYSIN® study at the CTRC, the drug’s name was derived from the human reovirus, a mild virus that occurs naturally in the environment.

"This novel therapy has shown success because the reovirus replicates in and destroys the cancer cells within the patient’s body," Dr. Mita said. "Cancer cells have several molecular and genetic abnormalities. In normal, healthy cells, the reovirus is unable to reproduce because of an enzyme named PKR. The enzyme is suppressed in cancer cells, and therefore the reovirus can replicate in the cancer cell and kill it."

Oncolytics Biotech Inc., the biotechnology company sponsoring the study, announced in February that the therapy has been successful and has been approved to proceed to full enrollment for patients with various types of sarcomas that have spread to the lungs.

"REOLYSIN® typifies the true targeted therapy approach that seeks to use fundamental differences between cancer and normal cells as the basis for effective anti-cancer approaches, and we are thus very excited about this study," said Francis Giles, M.D., deputy director of the CTRC at the UT Health Science Center at San Antonio.

According to the study protocol, to proceed to full enrollment of 52 patients, at least one patient in the first 38 patients treated must experience a complete or partial response or stable disease for longer than six months.

Scott has responded well to the novel therapy. A computed tomography scan showed that his cancer stabilized for more than six months. These results were confirmed by a more advanced imaging technique called positron emission tomography or PET.

Francis Giles, M.D. and Monica Mita, M.D.
(L) Francis Giles, M.D., is professor and the A.B. Alexander Chair in Medical Oncology, deputy director and the AT&T Chair at the CTRC at the UT Health Science Center, director of the Institute for Drug Development, and program leader for the Experimental Therapeutics Program.

(R) Monica Mita, M.D., is assistant professor of Medicine/Hematology and Medical Oncology at the Health Science Center and a medical oncologist at the CTRC.
"Being diagnosed with cancer is a life-changing experience, but being in this study has been another life-changing experience because the therapy is actually doing what they want it to do," said Scott, who travels to the CTRC from Big Spring, Texas, to receive treatment. "My wife and I are better people than we were five years ago when I was diagnosed with cancer."

A total of 15 patients, all of whom have been treated at the CTRC, have received the new treatment to date. Eligible patients are those who have a bone or soft tissue sarcoma that has spread to the lungs, and who are deemed by their physician to be unresponsive to or untreatable by standard therapies. These include patients with osteosarcoma, Ewing sarcoma family tumors, malignant fibrous histiocytoma, synovial sarcoma, fibrosarcoma and leiomyosarcoma.

"We are very pleased to proceed to the second stage of this study," Dr. Mita said. "This unique targeted compound has met our expectations so far in terms of both tolerability and efficacy endpoints. An added benefit is that the side effects of the treatment are minimal, similar to those of a mild flu or cold, compared to the often more serious side effects caused by chemotherapy treatment. We feel it is very important to continue to offer this agent to our patients."

Scott said he is grateful to have benefited from the research at the CTRC and hopes others will, too.

"Sarcoma seems to be a mysterious type of cancer and one that is difficult to treat," said Scott, who was diagnosed in 2003. "Since this new drug is an experimental therapy, not all patient stories are positive ones. It is my hope that many people with sarcoma will benefit from this study. Being a part of a study that offers hope to other patients is exciting."





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