Cotreatment with Pegvisomant and a Somatostatin Analog (SA) in SA-Responsive Acromegalic Patients

Context: Cotreatment of acromegaly with pegvisomant and a somatostatin analog (SA) has proven feasible. Previous studies in the field have focused on patients with an insufficient response to SA monotherapy in whom pegvisomant was added without changing the SA dose. Objective: The objective of the study was to study whether patients sufficiently controlled on SA monotherapy can be transferred to combination therapy with low-dose pegvisomant and a reduced SA dose. Design: Eighteen acromegalic patients well controlled on SA monotherapy, mean +/- SE aged 54 +/- 3 yr, were randomized in a parallel study over 24 wk to unchanged SA monotherapy or cotreatment with pegvisomant (15-30 mg twice a week) and SA (half the usual dosage). Setting: This was an investigator-initiated study in a single tertiary referral center. Main Outcome Measures: Glucose tolerance, substrate metabolism, insulin sensitivity, body composition, and quality of life were measured. Results: Median pegvisomant dose was 52.5 mg/wk (range 30-60). IGF-I (micrograms per liter) was comparable both at baseline (P = 0.88) and after 24 wk of treatment (P = 0.48). The change in IGF-I between baseline and wk 24 also did not differ between groups (P = 0.15). Apart from increased peak insulin levels during the oral glucose tolerance test in the cotreatment group, no substantial differences between the two groups were detected. Moderately elevated liver enzymes were found in 17% of the patients on pegvisomant therapy. Conclusion: Acromegalic patients well controlled on SA monotherapy can maintain safe IGF-I levels during 24 wk of cotreatment with low-dose pegvisomant and a 50% reduced SA dose. This treatment modality, however, does not seem to provide significant benefits for the patients. (J Clin Endocrinol Metab 96: 2405-2413, 2011)