Endocrine Abstracts (2008) 16 P709

Cinacalcet reduces serum calcium in intractable primary hyperparathyroidism (PHPT)

Claudio Marcocci1, Laureano Fernández-Cruz2, Cheng Sunfa3, Lulu Ren3 & Munro Peacock4

1Department of Endocrinology, University of Pisa, Pisa, Italy; 2Department of Surgery, University of Barcelona, Barcelona, Spain; 3Amgen Inc., Thousand Oaks, California, USA; 4Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.

Patients with persistent PHPT after parathyroidectomy (PTX) or contraindications for PTX often require chronic treatment for hypercalcemia, representing an unmet medical need. In an open-label, single-arm study in the US and EU, 17 patients underwent a variable length titration phase (maximum 16 weeks) with a maintenance phase (MP) of up to 3 years. Patients were eligible if they had (1) persistent PHPT following PTX or were considered contraindicated for PTX, and (2) serum calcium (sCa) >3.1 mmol/l (12.4 mg/dl). Possible dose increases occurred every 2 weeks during a titration phase until sCa ≤2.5 mmol/l (10.0 mg/dl), or the patient reached the highest dose (90 mg qid) allowed, or adverse events (AEs) precluded further dose increases. The primary endpoint of sCa reduction by ≥0.25 mmol/l (1 mg/dl) at the end of titration (EOT) was reached by 15 patients, while 9 reached the secondary endpoint of sCa reduction to ≤2.6 mmol/l (10.3 mg/dl) at the EOT. Mean values (SE) for sCa and iPTH showed a decrease in sCa and a rise in iPTH. However, median iPTH (Q1, Q3) decreased from 29.3 pmol/l (14.9, 33.0) at baseline to 19.0 pmol/l (14.4, 32.4) at EOT. Three patients were treated for up to 72 weeks in the maintenance phase, at which point mean (SE) sCa was 2.5 (0.23) mmol/l and mean (SE) iPTH was 11.9 (4.5) pmol/l. The most frequent treatment-related AEs were nausea, vomiting, and paresthesia. Only 1 patient had a treatment-related adverse event that led to withdrawal from the study.

BaselineEnd of titration
Mean sCa (S.E.M.)3.2 (0.05) mmol/l, N=172.6 (0.08) mmol/l, N=17
Mean iPTH (S.E.M.)26.7 (2.9) pmol/l, N=1643.5 (17.4) pmol/l, N=15

In conclusion, cinacalcet addresses an unmet need in patients with PHPT and hypercalcemia for which no approved therapy exists.

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