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Cinacalcet Proves Ineffective for Primary Hyperparathyroidism, Accelerates Bone Loss Over Time: Presented at ENDO 08

By Bryan DeBusk, PhD

SAN FRANCISCO -- June 20, 2008 -- Cinacalcet, as an alternative to parathyroid surgery, failed to show relief of primary hyperparathyroidism (PHPT) symptoms and was associated with a significant decrease in bone density, according to research presented here at the Endocrine Society's 90th Annual Meeting (ENDO 08).

James Norman, MD, Norman Parathyroid Clinic, Tampa, Florida, presented the results in an oral session on June 15.

"Although cinacalcet has been used for several years in dialysis patients with secondary hyperparathyroidism due to chronic renal failure, not much is known about this drug in patients with primary hyperparathyroidism," Dr. Norman explained.

The study was designed to evaluate cinacalcet as a possible alternative to surgery for patients with PHPT.

Dr. Norman identified 90 patients (73% female) aged 19 to 90 years (mean, 62 years) with PHPT who agreed to take cinacalcet as an alternative to surgery. Patients received a starting dose of cinacalcet 30 mg QD, increased to 60 mg QD or 90 mg QD when necessary. Therapy was continued as long as the drug was tolerated and if no complications arose.

Prior to initiating therapy, participants completed a PHPT symptom questionnaire and had a bone density scan. Bone density scans were repeated annually, and serum calcium and parathyroid hormone (PTH) levels were obtained every 3 to 4 months.

At baseline, average serum calcium levels were 11.7 mg (range, 11.0-15.1), average PTH levels were 126 pg/mL (range, 88-815), and participants had an average of 5.3 symptoms (range, 0-9) prior to starting treatment.

A total of 19 (21%) patients discontinued cinacalcet within 3 months of starting treatment due to nausea and vomiting. The remaining 71 participants continued therapy for 8 to 34 months.

Although 98% of participants experienced a decrease in serum calcium and/or PTH levels during treatment, none achieved sustained reductions. Despite decreases in calcium, only 5 (7%) patients reported improvement in symptoms (P = .08) and 11 (15.5%) patients reported worsening of symptoms (P < .05).

Of 23 patients who tolerated treatment for more than 1.5 years, 83% had significant reductions in bone density of 1.5 to 2.9 standard deviations below their starting point (P < .01). The magnitude of bone density loss was correlated with length of treatment (R = 0.83).

All patients eventually underwent minimally invasive parathyroidectomy, and 96% achieved partial or complete relief of symptoms within 2 months (P < .001).

"When [cinacalcet is] given to patients with primary hyperparathyroidism, their calcium drops very predictably, but their PTH does not," Dr. Norman summarised.

"Most troubling is that long-term use appears to be associated with a very significant decrease in bone density; some patients go from normal bones to significant osteoporosis in just 2 years. It appears that this drug isn't protective and provides no benefits that can be measured," he added.

Dr. Norman concluded that clinical use of cinacalcet for PHPT is not warranted given the results of trials to date. "Until a large, randomised trial is done to prove efficacy of this drug, in how patients feel and some protective effect on their bones, cinacalcet should not be used off label in patients with primary hyperparathyroidism," he said.


[Presentation title: Cinacalcet (Sensipar) Provides No Measurable Clinical Benefits for Patients With Primary Hyperparathyroidism and Significantly Accelerates Bone Loss With Prolonged Use. Abstract OR14-4]

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