July 15, 2011 -- As our first line of defense against cancer, chemotherapy targets fast-growing cells like those typically found in rapidly growing tumors. But while chemotherapy can shrink tumors, they often grow back and become resistant to the treatment.
To combat this resistance, chemotherapy is now often combined with other treatments that have different mechanisms for attacking and killing cancer cells. One approach that has proven quite promising is called oncolytic virotherapeutics. Here, viruses are harnessed to infect, multiply within and shred cancer cells; the virus targets tumors without affecting normal tissue.
Several types of oncolytic viruses have been developed. These include the adenovirus, the Newcastle-disease virus, and poxviruses, the most advanced of which is probably Jennerex’s JX-594, which has performed well in Phase II liver cancer testing. The herpes simplex virus is also under consideration as an oncolytic virus; many engineered versions are in clinical trials. Picornaviruses and vesicular stomatitis virus are two other varieties in earlier-stage trials.
One of the most intriguing oncolytic viruses is the reovirus. This virus preferentially replicates in cancer cells that feature a common mutation known as an “activated Ras pathway,” while sparing normal cells. This makes it intrinsically tumor-selective without the need for genetic manipulation.
Tumors bearing an activated Ras pathway cannot activate the antiviral response mediated by the host cellular protein, PKR. Studies have shown that reovirus actively replicates in transformed cell lines with an active Ras signaling pathway, eventually killing the host cell and freeing the viral progeny that go on to infect and kill more Ras-activated tumor cells. When normal cells are infected with reovirus, the immune system can neutralize the virus. Approximately one-third of human cancers have activating mutations in the Ras gene itself, and it is possible that more than two-thirds of cancer cells have an activated Ras signaling pathway because of activating mutations in genes upstream or downstream of Ras. “Reovirus is a virus with no known associated disease,” says Brad Thompson, PhD, President and CEO of Calgary-based Oncolytics Biotech Inc., which has developed a biologic agent, REOLYSIN, from naturally occurring reovirus. “It has demonstrated impressive results in clinical trials on its own, but particularly in combination with certain chemotherapeutics. In preclinical studies in a wide variety of cancer cell lines, investigators have found that when used together, reovirus and chemotherapy resulted in more efficient and synergistic anti-cancer activity than when each agent was used on its own.” These combinations are showing extremely good results in human trials, particularly in refractory head and neck cancer patients. Many head and neck cancer patients treated with a combination of REOLYSIN and chemotherapy to date have experienced dramatic and prolonged tumor shrinkage, without increasing adverse side effects.
I would be happy to arrange an interview with Dr. Thompson to discuss the latest results in harnessing REOLYSIN as a potential treatment for certain types of cancers. In the meantime, I encourage you to visit www.oncolyticsbiotech.com to learn more.
Janet Vasquez
The Investor Relations Group
212-825-3210
jvasquez@investorrelationsgroup.com