Scientists on path to a cure for sickle cell -- St. Jude researcher tells audience it could happen in our lifetime

April 13, 2006 --

Amid a national meeting packed with reports on strategies for easing symptoms and extending lives of sickle cell patients, a Memphis investigator stepped to the podium Wednesday to talk about a possible cure.

Dr. Arthur Nienhuis of St. Jude Children's Research Hospital said although progress has been more gradual than some predicted, gene therapy still holds the promise of cure.

"Hopefully in our lifetime or that of those we train, it will reach its full potential," said Nienhuis, who has returned to research after retiring as St. Jude's director.

Scientists have already used gene therapy to cure the disease in mice. That milestone was reported in 2001. The first human trial began last year in Paris. Plans call for enrolling five patients with sickle cell and five more with beta thalassemia, another inherited blood disorder.

"They may not fully succeed, but we hope they will start us on a path to a cure," he said.

The study comes as treatment advances during the past 25 years have pushed average life expectancy for Americans with sickle cell from their 20s to their 40s or 50s. But Nienhuis said the national sickle cell meeting that ended Wednesday at The Peabody was a reminder of how devastating the disease is for some patients.

About 75,000 Americans, primarily African-Americans, have sickle cell disease.

They've inherited mistakes in assembling hemoglobin, which carries oxygen in the blood. One consequence of that mistake is that their red blood cells can turn from their normal pliable donut shape to brittle, sticky sickle-shaped cells that clog tiny blood vessels.

Yvonne Carroll, a St. Jude registered nurse and manager of hematology patient services, said even as new strategies are developed to dramatically reduce episodes of pain or prevent stroke, patients want a cure.

St. Jude follows about 800 children and teenagers with sickle cell. Nearly 500 are cared for at the Diggs Kraus Sickle Cell Center at the Regional Medical Center at Memphis.

Currently, bone marrow transplants offer the only cure. But the procedure is expensive, risky and an option for only the small percentage of patients lucky enough to have a genetically matched donor. Research is under way at St. Jude and other centers to expand the pool of possible donors.

The foundation for gene therapy was laid in the early 1980s. It sounds simple. Replace a missing or defective gene with one that carries the correct instructions for assembling a particular protein. To do that, the new gene is packed into a virus engineered to deliver the gene to the target cells, but not churn out more virus.

It's already been used internationally to cure nearly 30 patients with three genetic diseases. But safety concerns and technological challenges have slowed development.

Nienhuis said that while there have been safety advances, sickle cell still poses greater challenges than the diseases successfully treated so far.

Curing sickle cell will likely require that at least half the targeted cells carry the replacement gene. Current strategies have achieved rates of 5 to 20 percent in monkeys. The percentage fell to 3 to 10 percent after three years.

- Mary Powers: 529-2383

This article is ﾩ 2006- Commercial Appeal, The (Memphis, TN)