Patients with acromegaly are treated with surgery, radiation therapy, and drugs to reduce hypersecretion of growth hormone, but the treatments may be ineffective and have adverse effects. Pegvisomant is a genetically engineered growth hormone–receptor antagonist that blocks the action of growth hormone.

We conducted a 12-week, randomized, double-blind study of three different daily doses of pegvisomant (10 mg, 15 mg, and 20 mg) and placebo, given subcutaneously, in 112 patients with acromegaly.

The mean (±SD) serum concentration of insulin-like growth factor I (IGF-I) decreased from base line by 4.0±16.8 percent in the placebo group, 26.7± 27.9 percent in the group that received 10 mg of pegvisomant per day, 50.1±26.7 percent in the group that received 15 mg of pegvisomant per day, and 62.5±21.3 percent in the group that received 20 mg of pegvisomant per day (P<0.001 for the comparison of each pegvisomant group with placebo), and the concentrations became normal in 10 percent, 54 percent, 81 percent, and 89 percent of patients, respectively (P<0.001 for each comparison with placebo). Among patients treated with 15 mg or 20 mg of pegvisomant per day, there were significant decreases in ring size, soft-tissue swelling, the degree of excessive perspiration, and fatigue. The score for total symptoms and signs of acromegaly decreased significantly in all groups receiving pegvisomant (P≤0.05). The incidence of adverse effects was similar in all groups.

On the basis of these preliminary results, treatment of patients who have acromegaly with a growth hormone–receptor antagonist results in a reduction in serum IGF-I concentrations and in clinical improvement.