Endocrine Abstracts

Introduction: Pasireotide (SOM230) is a multi-receptor targeted somatostatin analogue with high binding affinity for sst_1,2,3 and sst₅. In a Phase II study of pasireotide in patients with active acromegaly, 27% achieved biochemical control after 1 month of octreotide s.c. followed by 3 months of pasireotide, and pituitary tumor volume decreased by >20% in 39% of patients. Results from the study’s extension phase are presented.

Methods: The extension phase enrolled patients who achieved biochemical control (GH ≦2.5 μg/l and normalized IGF1) or clinically relevant improvement during the core study. Patients received pasireotide at the dose at which clinical benefit was achieved (200, 400 or 600 μg s.c. bid), with dose adjustments up to 900 μg s.c. bid if required. Efficacy and safety were assessed every 3 months. Patients underwent pituitary MRI at the core and extension baselines and every 6 months.

Results: Thirty patients entered the extension phase. Biochemical control was achieved in 6/26 patients (23%) at 9 months and 3/9 (33%) at 27 months. 12/26 (46%) and 13/26 (50%) patients achieved GH control and IGF1 normalization at 9 months, respectively; 5/9 (56%) and 5/9 (56%) achieved these goals at 27 months, respectively. 16/29 patients (55%) who had a core baseline MRI achieved significant tumor volume reduction by the time they exited the extension phase. Mean percent (±S.E.M.) tumor volume reduction was 13±3.9% at extension baseline (n=25), 26±5.9% by 9 months (n=16), and 38±11% by 27 months (n=5). All patients experienced an adverse event (AE), with diarrhea and nausea the most common (n=15 each). Two serious AEs with a suspected-drug relationship were worsening of diabetes mellitus and gallbladder polyp. Four patients discontinued the study because of an AE.

Conclusions: Extended pasireotide treatment maintained biochemical control and tumor volume reduction in patients with acromegaly. AEs were mostly mild or moderate.