• 3/25/2005
  • San Francisco, CA
  • Reuters News (reported by cancersourcemd.com)

A genetically engineered mouthwash is effective in keeping mouth sores from becoming cancerous, researchers said here on Tuesday.

The mouthwash is a formulation of ONYX-015, a virus that has been engineered to replicate in and kill cancer cells that have a dysfunctional p53 tumor-suppressor gene– while sparing normal cells that have a functioning p53 gene. ONYX-015 is being jointly developed by Onyx and Pfizer Inc.

Researchers from the University of Chicago reported the results from a small trial of 10 patients here at a meeting of the American Society of Clinical Oncology.

Since oral cancer is frequently preceded by growths called dysplastic lesions, the idea was to find out if a novel gene therapy for killing cancer cells would work as a mouthwash –which comes into direct contact with the cells–to prevent the development of cancer.

Heavy smokers, tobacco chewers and drinkers are at highest risk for developing the lesions and cancer of the mouth.

The p53 gene is considered one of the body’s most important naturally occurring tumor-suppressor genes. These genes are believed to help control runaway growth of cells and thereby prevent cancer. But when slight changes, or mutations, to the p53 gene occur, it is believed to lose its tumor-preventing effectiveness.

The data presented on Tuesday were from 10 patients who were given ONYX-015 as a mouthwash once a week for 12 weeks after which tissues were biopsied and patients who showed improvement continued the therapy for another 12 weeks. So far, two of the patients in the trial have seen their mouth patches disappear.

Improvements in the severity of the patches was shown in four patients, three had progression of disease despite therapy, and one had initial improvement followed by progression, according to the study. No significant clinical toxicity has so far been observed in the trial, which was funded by Onyx.

“We have been able to develop viruses that target the mutations that cause most cancers,” Hollings Renton, Onyx’s chief executive, told Reuters.

The product is currently in a Phase III clinical trial for head and neck cancer and in Phase I and II clinical trials for a number of different additional cancer indications.

“It has been tested in over 300 patients altogether. It is well-tolerated. Elevated temperature and chills are the side effects and they are manageable,” Renton said.

In previously reported results from a Phase II trial of ONYX-015 in patients with advanced head and neck cancer, 10% saw their tumors disappear and 24% saw their tumors shrink by at least 50%, the CEO said. But even better results were found when the drug was combined with chemotherapy, he noted.