Endocrine Abstracts

Introduction: In a recent 16-week Phase II study in patients with de novo, persistent or recurrent acromegaly, pasireotide effectively controlled GH and/or IGF-I levels in 56% of patients, and reduced tumor volume by >20% in 39% of patients. We present preliminary 6-month results from the ongoing extension phase of this study.

Methods: This extension study enrolled patients who achieved biochemical control (GH ≤2.5 μg/l and normalized IGF-I), or clinically relevant improvement, during 12 weeks’ pasireotide treatment in the core study. Patients received pasireotide at the dose (200, 400 or 600 μg sc bid) at which biochemical control was achieved in the core study, with dose adjustments up to 900 μg sc bid if required. Patients continued treatment for as long as benefit was derived. Pituitary MRI scans, acquired at months 0, 3 and 6, included T1-weighted sagittal and coronal, enhanced and unenhanced sequences, digitally assessed at a central laboratory. Tumor volume was calculated from coronal enhanced scans, as the sum of the tumor area on each image, multiplied by the effective section thickness.

Results: Thirty patients entered the extension study. Of 26 patients who received pasireotide for at least 6 months, 65% achieved GH ≤2.5 μg/l and/or normalized IGF-I, 62% had normalized IGF-I and 42% achieved GH ≤2.5 μg/l. Nineteen patients had both baseline and per-protocol follow-up MRI scans at 6 months. Mean tumor volume reduction at 6 months was 18.1±4.6% S.E.M. for all 19 patients. In 10 of the 19 patients (53%), tumor volumes decreased by a mean of 33.4±4.2% (20% measurement error threshold).

Conclusions: These preliminary results show that pasireotide significantly reduced pituitary tumor volume in 53% of patients after 6 months of treatment, and reduced GH and/or IGF-I levels in 65% of patients, including those resistant to prior surgical or medical therapy.