New drug to treat rare Pompe disease gets FDA approval

May 1 2006

The Food and Drug Administration in the U.S. has given approval for the first drug to treat a rare, debilitating muscle disease that can kill infants within a year.

Genzyme Corp. developed the drug, Myozyme, to treat Pompe disease, which affects fewer than 10,000 people worldwide.

Pompe disease causes severe muscle weakness and breathing difficulties that can be fatal.

The disease varies in how it progresses, if it emerges in infancy, it usually causes an enlarged heart and kills within a baby's first year of life.

Where symptoms appear during childhood, adolescence or adulthood, it causes progressive respiratory failure.

Pompe disease is inherited and is caused by the deficiency of the enzyme acid alpha-glucosidase which leads to a build-up of carbohydrates in muscles and drastically reduces a person's muscle and respiratory function.

Myozyme replaces that enzyme.

The FDA approved Myozyme after reviewing studies of 39 patients who received their first dose at ages ranging from one month to 3.5 years.

The drug was administered intravenously every two weeks for up to two years.

In one group of 18 children, all survived a year and only three needed ventilators to help them breathe, while one died after 14 months of treatment and another after 25 months.

Without treatment, life expectancy for infants with Pompe disease is 18 months at the most.

FDA officials says although the children's progress was substantially better than would be expected without treatment, the drug did not return them to normal health and their long-term prognosis is unclear.

Drug company Genzyme is now studying the drug's effects in people with late-onset Pompe disease.

About 40,000 individuals suffer from Pompe disease.

Myozyme gained Orphan Drug designation and was approved under a priority review.

Orphan Drug Designation involves drugs developed to treat rare conditions or diseases which affect fewer than 200,000 people in the USA.

The drug's approval has a seven year exclusive marketing period in order to encourage drug companies to develop products that do not sell to big markets.

Myozyme's most serious reported adverse events were heart and lung failure and allergic shock.

A warning has been included on the Myozyme label to warn about the possibility of life-threatening allergic reactions.

The rare neuromuscular disease is one of 40 genetic diseases known as Lysosomal Storage Disorders and does not appear to affect mental development.

Pompe disease affects both men and women equally and also appears more or less equally among all ethnic groups, with a slightly higher incidence among African-Americans, as well as in Southern China and Taiwan.