Rare break for kids with rare diseases

The US Food and Drug Administration (FDA) recently approved the first drug to receive a Rare Pediatric Disease Priority Review Voucher, a new FDA program that aims to encourage development of new drugs and biologics for the prevention and treatment of rare pediatric diseases by helping speed such agents to market.

The new drug is elosulfase alfa (Vimizim), a new type of enzyme replacement therapy and the first agent approved to address the cause of Mucopolysaccharidosis type IVA (MPS IVA), Morquio A syndrome.

Morquio A is a rare autosomal recessive lysosomal storage disease caused by a deficiency in N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Absence of this enzyme causes problems with bone development, growth, and mobility. The new drug replaces the missing GALNS enzyme. About 800 people in the United States and about 3,000 in the developed world have the syndrome.

The FDA based its approval decision on a 24-week, randomized, double-blind, placebo-controlled clinical trial involving 176 participants with Morquio A syndrome, ranging in age from 5 to 57 years. Those treated with Vimizim (2 mg/kg once per week) showed greater improvement in the 6-minute walk test than participants treated with placebo. On average, the Vimizim-treated group walked 22.5 meters farther in 6 minutes than did those who received placebo.

The most common side effects were fever, vomiting, headache, nausea, abdominal pain, chills, and fatigue. Safety and effectiveness have not been established in children aged younger than 5 years.

The FDA approved the product with the caveat of a boxed warning to include the risk of anaphylaxis because during clinical trials, some life-threatening anaphylactic reactions occurred during Vimizim infusions.

Vimizim is made by BioMarin Pharmaceutical Inc based in Novato, California.

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