Endocrine Abstracts

Introduction: Pasireotide (SOM230) is a novel multi-ligand somatostatin analogue with high binding affinity for four of the five somatostatin receptor subtypes (sst_1,2,3 and sst₅). A randomized study of 59 patients showed that pasireotide effectively controls GH and IGF-I levels in patients with acromegaly and reduces pituitary tumor size. The impact of pasireotide on GH levels during glucose suppression and glucose metabolism in 12 patients enrolled in the study is reported.

Methods: Patients in this study had GH levels >5 μg/L, elevated IGF-I and lack of suppression of GH to <1 μg/L post-OGTT. After treatment with octreotide 100 μg sc tid for 28 days, patients received pasireotide 200, 400 and 600 μg sc bid in random order for 28 days each. Glucose and GH levels were measured during OGTT in 12 patients prior to treatment, after octreotide treatment and after each pasireotide treatment phase.

Results: During glucose suppression, 4 of the 12 patients had a similar GH nadir (<10% difference) after pasireotide (−71.0%) or octreotide (−72.3%) treatment, and 8 patients had a stronger GH suppression with pasireotide (−75.1%) than with octreotide (−22.8%). Under fasting conditions prior to therapy, 7 patients had normal glucose tolerance (NGT), 2 patients had impaired glucose tolerance (IGT), and 3 patients had diabetes mellitus (DM). At the last assessment during treatment with pasireotide, 9 patients remained in the same category, 1 patient improved, and 2 patients had increased glucose levels. Similar results were seen for glucose metabolism 120 minutes post-OGTT.

Conclusions: Pasireotide suppressed GH levels during OGTT to a similar extent (4/12 patients) or greater extent (8/12 patients) than octreotide, indicating that it may be effective in patients with octreotide-resistant acromegaly. Furthermore, using stringent criteria, the majority of patients did not demonstrate relevant changes in glucose metabolism by the end of the pasireotide treatment period.