Acromegaly Treatment Approved by FDA
Although the protein portion of pegvisomant resembles growth hormone and binds at its receptors on cell surfaces, the structural differences enable the medication to block a patient's own growth hormone from interacting with cells. This antagonism at the growth hormone receptors, the company said, is useful for patients with acromegaly, a chronic disease caused by the secretion of too much growth hormone and associated with a tumor in the pituitary gland. A constant high level of growth hormone causes various complications, including insulin resistance, glucose intolerance, and a characteristic enlargement of the hands, feet, and jaw. The polyethylene glycol polymers, or "peg," in pegvisomant delay the body's destruction of the protein.
According to the product's labeling, pegvisomant is to be used in patients with acromegaly who have not responded adequately to surgery, radiation therapy, or other medical therapies or who are not candidates for these treatments.
The recommended dosage is an initial 40 mg of pegvisomant protein injected subcutaneously into the upper arm, upper thigh, stomach area, or buttocks followed by 10 mg daily, with this dose adjusted on the basis of the patient's serum concentration of insulin-like growth factor-I (IGF-I). IGF-I mediates the growth and replication of cells. During pegvisomant therapy, the serum IGF-I concentration should be measured every four to six weeks. The product's labeling states that the daily maintenence dose of pegvisomant protein should not exceed 30 mg.
Somavert is contraindicated in patients with a hypersensitivity to any component in the product. The stopper on the drug vials contains latex.
During the clinical studies of pegvisomant, the company said, the most commonly reported adverse events related to the medication were infection, pain, flu syndrome, abnormal liver-function-test results, diarrhea, nausea, and reactions at the injection site.
Pharmacia said Somavert will be available in mid-April in single-dose vials containing 10, 15, or 20 mg of pegvisomant protein. The vials should be stored at 28 degrees C until reconstituted. Once reconstituted, the medication should be injected within six hours.
Each package will also have a single-dose vial containing 10 mL of sterile water for injection, although only 1 mL is needed to reconstitute the medication.
According to the product's labeling, Abbott Laboratories manufactures Somavert for Pharmacia.