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FDA Approves Asfotase Alfa for Hypophosphatasia

Cheryl Thompson

Cheryl A. ThompsonDirector
News Center

Asfotase alfa, a tissue nonspecific alkaline phosphatase produced by recombinant DNA technology, was approved by FDA on October 23 and, according to manufacturer Alexion Pharmaceuticals Inc., is now commercially available.

FDA called asfotase alfa the first approved treatment for hypophosphatasia that manifests when patients are infants or juveniles.

The rare genetic disease, the agency said, is characterized by defects in bone mineralization and can result in rickets and skeletal abnormalities.

According to the labeling for asfotase alfa injection, or Strensiq, the recommended dosage is 2 mg/kg by subcutaneous injection three times a week or 1 mg/kg by subcutaneous injection six times a week. In patients with perinatal- or infantile-onset hypophosphatasia, the dosage may be increased to 3 mg/kg by subcutaneous injection three times a week.

The most common adverse reactions to asfotase alfa during the clinical studies were injection-site reactions, lipodystrophy, ectopic calcifications, and hypersensitivity reactions, the labeling states. Injection-site reactions occurred in more than half of the patients, particularly those with juvenile-onset hypophosphatasia.

Strensiq is available in four types of vials, all for single use. Three of the vial types—18 mg/0.45 mL, 28 mg/0.7 mL, and 40 mg/mL—contain 40 mg of asfotase alfa per milliliter of drug solution. The fourth vial type, 80 mg/0.8 mL, contains 100 mg of asfotase alfa per milliliter of drug solution. Strensiq's labeling cautions against using the 80-mg/0.8-mL vials to prepare doses for patients weighing less than 40 kg because of lower systemic drug exposure from the higher-concentration formulation.

All Strensiq vials should be stored in their original carton under refrigeration at 2–8 °C. Vials removed from refrigeration should be used for administration within one hour.