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Gene Therapy Improves Exercise Time in Angina Patients: Presented at AHA

By Ed Susman

CHICAGO, IL -- November 21, 2002 -- A technique which involves injecting a gene vector that helps promote blood vessel growth is well tolerated by patients with angina and continues to improve their exercise capacity and quality of life over at least six months.

Dr. Duncan Stewart, head of cardiology at St. Michael's Hospital at the University of Toronto, Ontario, Canada, said the results of the REVASC (revisualization) study "represents achievement of proof of concept" that gene therapy can offer a sustained benefit to patients. He reported his results here November 20 at the 2002 Scientific Sessions of the American Heart Association (AHA).

After performing a thoracotomy, doctors injected the adenovirus vector, AdVEGF121, into 13 regions of the ventricle wall, he said. Patients then performed treadmill stress tests to determine if exercise tolerance had improved from baseline. The 32 patients who received the gene therapy were compared to the 35 patients who were randomised to receive best medical management of their Class 2 to Class 4 angina.

"At six months there was a marked improvement among these gene therapy patients," Dr. Stewart reported. Patients receiving the adenovirus gene vector were able to exercise more than a minute longer than their baseline measurements when compared to the medically-managed patients before ST-segment depression was recorded. That difference was found to be significant to the p=0.024 level.

"A one-and-one-half minute improvement among these patients in this subjective test is quite impressive," said Augustus Grant, MD, professor of medicine at Duke University, Durham, North Carolina, United States, and program chairman for the AHA meeting. He said the findings were "especially important for this group of patients who have no other treatment options available to them."

Dr. Stewart said the researchers found no improvement in the patients getting the gene therapy injections over the medically-managed patients in the first three months. But there was a distinct difference seen at six months. He also measured time to moderate angina -- when a patient feels chest pain -- and found that about half the patients getting the gene therapy were able to increase time to angina by one minute; one third of the patients extended that time by three minutes. Those results were statistically significant to the p<0.002 level.

"There have been a lot of very promising clinical trials in this area, suggesting that it is possible for genes or other factors to induce the growth of new blood vessels in the regions of the heart which are starved for blood supply," Dr. Stewart said.

He said other trials might not have succeeded because the gene therapy was not efficient in maintaining production of the factors needed to grow blood vessels. In his trial, the genes are implanted with a genetically-modified virus that limits the amount of infection possible and allows for continued production of the proteins that drive blood vessel growth.

"It may be due to the fact that the protein factors that have been used in some of these trials have been very unstable and may not last long enough for biological benefit," he suggested.

Although well tolerated, three patients in the gene therapy arm of the trial died. Two patients did not survive surgery, Dr. Stewart said. For that reason, he said further experiments with the gene agent would likely be injected by using catheters. Another person in the gene therapy group died of a heart attack that was not believed to have been related to the procedure, he said.

"Overall," he said, "the effect of this treatment appears to be durable. The gene vector is well-tolerated, and patients continue to improve their exercise capacity and their quality of life over at least six months."

GenVec, based in Gaithersburg, Maryland, United States, maker of AdVEGF121, sponsored Dr. Stewart's trial.

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