Gene Therapy May Reverse Hemophilia

Dec. 10, 2011 -- Sebastian Misztal recently cut himself shaving. The bleeding stopped.

Such a mundane occurrence wouldn’t usually make medical headlines. But for Misztal, a 31-year-old London businessman, and others with the inherited blood disorder hemophilia, it was a big deal. 

“It’s huge,” says Katherine Ponder, MD, a professor of medicine at Washington University in St. Louis.

In the past, Misztal has given himself regular injections to replace a protein that his body can’t make. The protein is called Factor IX (FIX). It helps blood clot.

Those injections have kept him alive. People with the severe hemophilia can bleed even if they are not injured. Spontaneous bleeding in the brain can be fatal.

But injections of clotting factors are also inconvenient and expensive. Hemophiliacs generally need the shots two to three times a week. Treatment costs run from $150,000 to $200,000 a year.

So Misztal recently became one of six men to try an experimental repair for the genetic defect that causes their condition.

Sneaking Genes Into Cells

Researchers altered the DNA of a common virus so that it would include the instructions for making FIX. 

They then injected the men with the altered virus. They hoped that it would do what all viruses do: infect cells and hijack their operating instructions.

Ordinarily when viruses infect cells, they turn the cells into factories that crank out more copies of the virus. That keeps the infection going.

In this case, the infected cells churned out the missing protein.

After a single treatment, four of the six men in the study have been able to stop their weekly protein injections altogether. Two others have been able to stretch the time between their shots from days to up to two weeks.

“You’ve got people who are maybe not quite cured,” says Ponder, an expert on blood disorders who was not involved in the research.  

The study and an editorial by Ponder are published in The New England Journal of Medicine.

The results are also scheduled to be presented at the annual meeting of the American Society of Hematology in San Diego.

Hope on the Horizon for Hemophilia and Other Diseases

So far, researchers have only been able to coax the body to make the protein that helps people with the less common form of the disease, hemophilia B.

But researchers say this approach could work for people who have the more common form, hemophilia A, too. They just need to find the right virus to deliver the genes that would help that disease.

“I think this approach will lead to a cure. I think it’s not there yet,” says study researcher Andrew M. Davidoff, MD, a pediatric surgeon at St. Jude Children’s Research Hospital in Memphis, Tenn.