A Canadian multi-centre, open-label long-term study of Pegvisomant treatment in refractory acromegaly.

PURPOSE Acromegaly is a rarely diagnosed condition with potentially serious complications including accelerated heart disease and reduced survival. After a mean interval of nearly 9 years from onset of disease, a significant proportion of patients are diagnosed with invasive adenomas precluding complete surgical resection. Furthermore, strict normalization of the growth hormone (GH) target insulin-like growth factor I (IGF-I) cannot always be achieved by adjunctive medical therapy with somatostatin analogues. Here we report the results of a Canadian multi-centre study open-label, dose-titrated long-term study examining safety and efficacy outcomes of a growth hormone receptor antagonist, pegvisomant in 19 patients with refractory acromegaly. METHODS Previously pegvisomant-treated and treatment-naïve refractory acromegalic patients at least 18 yr of age were eligible (n=19). Patients received open-label daily subcutaneous injections of pegvisomant adjusted according to IGF-I levels. Safety and IGF-I levels were assessed every 4 to 6 wk. Baseline and follow-up visits at 3-month intervals also included administration of the Signs and Symptoms of Acromegaly Questionnaire. This study is registered with ClinicalTrials.gov, NCT00151437. RESULTS We show that, in escalating doses, pegvisomant results in age-adjusted normalization of IGF-I in nearly all such patients. This IGF-I normalization occurred early on and was maintained throughout the study period of 27 months (IGF-I standard deviation score (SDS), mean +/- SE: 1.66 +/- 0.36, P=0.0003 vs baseline), with a nadir at 18 months (IGF-I SDS, mean +/- SE: 1.50 +/- 0.38, P=0.0010 vs baseline). IGF-I control was also accompanied by measurable improvements in disease-associated symptoms and without radiographic evidence of pituitary tumour progression. Overall, the safety profile of pegvisomant therapy in this patient population was found to be satisfactory and suitable for a long-term treatment. CONCLUSION Our findings provide support for the long-term safety and efficacy of the GH receptor antagonist pegvisomant in achieving IGF-I control in patients with refractory acromegaly.