U.S. FDA panel backs BioMarin’s Morquio A Syndrome drug

• Drug News • • Genetics • Nov 19, 13

An experimental drug to treat Morquio A Syndrome, a rare genetic disorder that causes skeletal malformation and a variety of related lung, eye, ear and heart problems, should be approved, an advisory panel to the U.S. Food and Drug Administration concluded on Tuesday.

The 21-member panel voted overwhelmingly in favor of approval, saying the benefits of the drug, Vimizim, which is made by BioMarin Pharmaceutical Inc, outweigh its risks. The FDA is not obliged to follow the recommendations of its advisory panels but typically does so.

Morquio A Syndrome is characterized by a deficiency of an enzyme known as N-acetylgalactosamine-6-sulfatase, which causes excessive storage in the body of long chains of sugars known as glycosaminoglycans.

This build-up can lead to short stature and joint abnormalities that limit mobility and endurance. The disease can also cause hearing loss, eye problems and heart disease. Symptoms often appear before the age of five.

Children who took the drug during clinical testing saw an improvement in energy and endurance, allowing them to better socialize, learn and function independently, families who testified before the panel said.

The main goal of the trial was to improve symptoms as measured by a six-minute walk test. A secondary goal was change measured by a three-minute stair climb test.

Synonyms of Morquio Syndrome

Morquio Disease
MPS IV
Mucopolysaccharidosis IV

Disorder Subdivisions

Morquio Syndrome A
Morquio Syndrome B

Morquio syndrome (mucopolysaccharidosis type IV; MPS IV) is a mucopolysaccharide storage disease that exists in two forms (Morquio syndromes A and B) and occurs because of a deficiency of the enzymes N-acetyl-galactosamine-6-sulfatase and beta-galactosidase, respectively. A deficiency of either enzyme leads to the accumulation of mucopolysaccharides in the body, abnormal skeletal development, and additional symptoms. In most cases, individuals with Morquio syndrome have normal intelligence. The clinical features of MPS IV-B are usually fewer and milder than those associated with MPS IV-A. Symptoms may include growth retardation, a prominent lower face, an abnormally short neck, knees that are abnormally close together (knock knees or genu valgum), flat feet, abnormal sideways and front-to-back or side-to-side curvature of the spine (kyphoscoliosis), abnormal development of the growing ends of the long bones (epiphyses), and/or a prominent breast bone (pectus carinatum). Hearing loss, weakness of the legs, and/or additional abnormalities may also occur.

The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders. Lysosomes function as the primary digestive units within cells. Enzymes within lysosomes break down or digest particular nutrients, such as certain carbohydrates and fats. In individuals with MPS disorders, deficiency or malfunction of specific lysosomal enzymes leads to an abnormal accumulation of certain complex carbohydrates (mucopolysaccharides or glycosaminoglycans) in the arteries, skeleton, eyes, joints, ears, skin, and/or teeth. These accumulations may also be found in the respiratory system, liver, spleen, central nervous system, blood, and bone marrow. This accumulation eventually causes progressive damage to cells, tissues, and various organ systems of the body. There are several different types and subtypes of mucopolysaccharidosis. These disorders, with one exception, are inherited as autosomal recessive traits.

After 24 weeks of treatment with the drug, Vimizim increased patients’ six-minute walk distance by 22.5 meters compared with a placebo, a benefit the FDA reviewers called “modest.” There was no statistically meaningful improvement in the stair climb test.

Nonetheless, the panel decided that the walk test probably captured only a portion of the benefits conferred by the drugs, though the exact nature of the additional benefits and their magnitude remain unclear.

Vimizim, also known as elosulfase alfa, is expected to generate sales of $532 million by 2018 if approved, according to the average estimate of eight analysts polled by Thomson Reuters.

Presentation

Patients with Morquio’s syndrome appear healthy at birth. They often present with spinal deformity, there is growth retardation or genu valgus in the second or third year of life.

Short stature (flat vertebrae cause a short trunk), short neck, moderate kyphosis or scoliosis, mild pectus carinatum (pigeon chest)
Cervical spine: odontoid hypoplasia, atlanto-axial instability; may be associated with myelopathy with gradual loss of walking ability
Joint laxity, mild dysostosis multiplex, dysplastic hips, large unstable knees, large elbows and wrists, and flat feet
The combined abnormalities usually result in a duck-waddling gait
Mid-face hypoplasia and mandibular protrusion
Thin teeth enamel
Corneal clouding
Mild hepatosplenomegaly

Morquio A Syndrome is one of a group of lysosomal storage disorders known as mucopolysaccharidoses (MPS). Lysosomal storage disorders are typically chronic and progressive, and involve multiple organs of the body.

Vimizim has been given “orphan drug” status by the FDA, which means it will receive seven years of market exclusivity if approved. An orphan drug treats diseases that affect fewer than 200,000 patients.

The main safety concerns of the drug relate to anaphylaxis and allergic reactions. The panel said such side effects are consistent with other enzyme replacement therapies and that the benefits outweigh the risks.

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(Reuters)