FDA OKs First Therapy for Alpha-Mannosidosis

The FDA approved the enzyme replacement therapy velmanase alfa (Lamzede) for alpha-mannosidosis, developer Chiesi Global Rare Diseases announced on Thursday.

Approved as a 10 mg weekly injection, velmanase alfa is specifically indicated for treating non-central nervous system (CNS) manifestations in adult and pediatric patients with the progressive, ultra-rare disease that globally affects about one in every 500,000 to 1 million babies.

The inherited lysosomal storage disorder is caused by genetic changes in the MAN2B1 gene that results in a deficiency in alpha-mannosidase, an enzyme that typically breaks down mannose-rich oligosaccharides and prevents their accumulation in various tissues of the body. The buildup of these complex sugars can lead to various symptoms, which vary from individual to individual and may progress over time.

Symptoms of alpha-mannosidosis include recurrent chest and ear infections, hearing loss, and muscle weakness, along with visual, cognitive, and skeletal or joint abnormalities. The disease can also cause distinctive facial features, such as a protruding jaw or prominent forehead, the FDA noted in its approval announcement.

Support for velmanase alfa's approval came in part from a phase III multicenter placebo-controlled trial involving 25 European participants with alpha-mannosidosis, including 13 adults (mean 25 years) and 12 pediatric patients (mean 11 years).

At 52 weeks, patients assigned to velmanase alfa injections (1 mg/kg weekly IV dose) had significantly greater reductions in serum oligosaccharides compared with the placebo group (-77.6% vs -24.1%), a co-primary endpoint.

Change from baseline in the 3-minute stair climbing test, the study's other co-primary endpoint, showed a numerical improvement for patients assigned to velmanase alfa (0.5% vs -3.6% in the placebo group). Other secondary outcomes also favored the enzyme replacement therapy group.

According to velmanase alfa's drug label, commonly reported adverse events in the study were nasopharyngitis in 66% of patients, pyrexia in 40%, headache in 33%, arthralgia in 20%, and hypersensitivity reactions in 13%.

The drug has a boxed warning over the risk of severe hypersensitivity reactions, including anaphylaxis. The drug should be immediately discontinued should a severe hypersensitivity reaction occur, though "a desensitization procedure" may be considered, Chiesi noted. Other warnings included the risk for embryo-fetal toxicity.

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