Alpha-1 gene therapy safely tested in first three patients

September 13, 2004

GAINESVILLE, Fla. — A gene therapy to combat one of the most common hereditary disorders, alpha-1 antitrypsin deficiency, appears safe in the first three patients to participate in a landmark clinical trial, University of Florida researchers have found.

“It is very reassuring to have data from human patients that suggests that they are not producing antibodies to fight the therapeutic gene product,” said Dr. Terence Flotte, a pediatrician, geneticist and microbiologist with UF’s College of Medicine and a member of the Powell Gene Therapy Center and the UF Genetics Institute.

Flotte, who presented the findings Friday at the international Parvovirus Workshop in St. Petersburg, said the trial represents the first time gene therapy has ever been tested in people with alpha-1 antitrypsin deficiency, a disorder that can cause liver and lung disease in children and adults.

About 100,000 Americans have alpha-1 antitrypsin deficiency, according to the Miami-based nonprofit Alpha-1 Foundation. The trial is funded by a $1.4 million National Institutes of Health grant, but the Alpha-1 Foundation played a key role in helping to build the infrastructure to support the research, Flotte said.

The experimental strategy used in the UF study relies on a molecular vehicle known as the adeno-associated virus, or AAV, which already exists without symptoms in many people. The main purpose of the phase 1 study is to test the safety of the therapy, a crucial step that must take place before determining the therapy’s effectiveness and the best dose to treat patients.

UF scientists equip the virus with an important passenger, the healthy gene for alpha-1 antitrypsin, a protein that is made naturally in the liver and protects the lungs by counteracting certain products of inflammation that gradually can destroy lung tissue. A person with alpha-1 does not generate enough of the protein to adequately protect the lungs and permanent damage results. As they evaluate the therapy’s safety, scientists are closely looking for signs that the DNA from the virus has spread to other organs, which would produce unknown effects. In addition, it is conceivable that patients could develop immunities that would block the treatment.

“We don’t show that we are at a final treatment dose, but we are defining the limits of the dose we can work with and can begin to see the effects,” said Flotte, who works closely with Dr. Mark Brantly, a UF professor of medicine and of molecular genetics and microbiology. “There was some immune response to the AAV capsid, the outer protein shell of the virus, but that was expected and shouldn’t affect the gene transfer.”

It is encouraging that the patients’ immune systems responded to the virus but not to the therapeutic alpha-1 antitrypsin gene, because it indicates the dose may be large enough to influence the body’s production of the alpha-1 antitrypsin protein, UF researchers say. It doesn’t matter that the body might build resistance to the virus, because researchers believe only a single dose is needed.

“Viral vectors are packaging,” said Richard J. Samulski, a professor of pharmacology and director of the University of North Carolina’s Gene Therapy Center. “Their job is to deliver the payload to the target. After they perform their function, they degrade. When you take the contents out of the box, the box has served its purpose, so you get rid of it. The question now is to find out whether the patients’ genes will be able to express the alpha-1 protein, and beyond that, whether the protein is being expressed at levels that will help the patient.”

In this phase of the trial, physicians inject three consecutive doses of 1.1 milliliters of the virus containing the gene for alpha-1 antitrypsin into each patient’s upper arm. The procedure takes less than 30 minutes. Since the trial started in late March, three patients have been injected with the gene therapy agent. In all, 12 patients will receive the therapy.

“About one in 20 individuals walking down the street carries a single mutation on the alpha-1 gene,” Flotte said. “A person has to have two mutations to get the disease. If parents each have a mutation, their child has a one-in-four risk of having alpha-1. It’s a major problem.”

Alpha-1 is often misdiagnosed as asthma or chronic obstructive pulmonary disease. Less than 5 percent of affected individuals are diagnosed, and often it is not until they are in their mid- to late-30s, after extensive lung damage occurs. Current treatment for alpha-1 includes avoiding cigarette smoke and weekly intravenous injections of alpha-1 antitrypsin. The 12 patients who will participate in the trial will resume their regular alpha-1 antitrypsin protein replacement therapy 75 days after the injections.

“Without the Alpha-1 Foundation, this work could never have begun so quickly,” Flotte said. “There are millions of dollars of basic costs that had to be met before we could do a phase 1 trial. The gene therapy facility at UF had to be upgraded with the personnel, supplies, equipment, and environmental monitoring necessary to produce the reagent and meet FDA certification.”

Special skills and experience are required to combine the genetic material with the viral vector to make the reagent, and strict Food and Drug Administration requirements must be met. The laboratory must be kept within strict cleanliness specifications – even the air is “scrubbed” – and the reagent is tested for sterility and purity from the beginning of the manufacturing process until the end. Only until a quality assessment group makes a final review is a product released for use.