Researchers have released positive results in gene-therapy trials treating several types of cancer, and will soon begin the final phase of trials.
Introgen Therapeutics and Aventis Pharmaceuticals are collaborating on gene-therapy treatments that could reduce the side effects associated with cancer treatment and possibly provide an alternative to radiation and chemotherapy.
Using a tumor suppressor gene called p53, the best results were in lung-cancer studies.
"The most remarkable thing is of the 15 patients that completed the treatment, 80 percent showed no cancer cells at biopsy. Historically, the results are less than 20 percent with radiotherapy alone," said David Nance, president and CEO of Houston-based Introgen.
The results were presented on Sunday at the 36th American Society of Clinical Oncology annual meeting in New Orleans. Introgen also reported positive results in gene-therapy studies involving prostate and head and neck cancers.
Three weeks after treatment, nine of the 15 patients in the study had no active cancer cells at the tumor site treated with gene therapy. Five patients showed no evidence of cancer cells in tumors distant from the primary tumor treated with gene therapy. This gives researchers hope that the therapy can have a widespread effect.
"Many researchers are choosing to test in combination so the patient doesn't have to choose between the new agent and no treatment at all -- they get treated one way or another," said Frank McCormick, director of the cancer center at the University of California at San Francisco,
and founder of Onyx, a cancer therapy company which is developing a therapy similar to Introgen's.
Although the results are encouraging, more studies are needed to determine the efficiency and safety of the treatment, he said.
"This is an early stage study so it's difficult to assess if there's any effect or not. The numbers are small so I wouldn't say it's too encouraging or discouraging," McCormick said. "It's obviously worth pursuing, but the numbers are not clear enough."
Since last September, when 18-year-old Jesse Gelsinger died during a gene-therapy experiment at the University of Pennsylvania, the procedure has come under close scrutiny by the Food and Drug Administration, the National Institutes of Health, and the public.
Soon after Gelsinger's death, gene-therapy researchers across the country admitted to over 1,000 unreported adverse events. The FDA and the NIH are reviewing new regulations for the oversight of gene therapy.
The vector -- or vehicle for carrying the gene therapy into the body -- used in the Gelsinger experiment was an altered virus, called an adenovirus, and is the main suspect in his death. The Introgen researchers used the same vector, but researchers did not see any serious toxicity in their experiment, which began in 1998.
"There are some side effects, but they are generally very minor (including) fever and cold or flu-like symptoms," Nance said. "When you contrast that with chemo and radio-therapy, which have really devastating side effects, that's what greatly encourages us about gene therapy."
"Patients and investigators both tell us this is one of the safest and well-tolerated drugs they've ever used -- even the patients say that. That's what's interesting to me because even if it only works as well or marginally better (than chemotherapy or radiation therapy), the object is to treat patients without a lot of severe side effects," Nance said.
Despite the negative publicity gene therapy has received, Nance said he's confident gene therapy will prove its merit within the next few years.
"I think that the image of gene therapy will be rehabilitated in the future. With many scientific advancements there's a lot of hope and optimism and even hype with a new type of technological development. But history shows that it takes about ten years for technologies to be transferred to actual clinical products. We're nearing the last few years for product development and in the next few years products will likely be approved."
The companies expect their gene therapy experiment to enter Phase 3 trials later this year.
