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NATPARA™: The bioengineered response to hypoparathyroidism



NATPARA is a bioengineered replica of human parathyroid hormone.  NPS reported positive findings from a Phase 3 registration study of NATPARA, known as REPLACE, which met the primary efficacy endpoint with a statistically higher responder rate versus placebo.  In an intent-to-treat analysis, 53 percent (48/90) of NATPARA-treated patients achieved the primary endpoint versus 2 percent (1/44) of placebo-treated patients (p<0.0001). The primary efficacy endpoint was defined as a 50 percent or greater reduction in oral calcium supplementation and active vitamin D therapy and a total serum calcium concentration that was normalized or maintained compared to baseline after 24 weeks of treatment. At week 24, 43 percent (36/84) of patients treated with NATPARA were able to achieve independence from active vitamin D therapy and a calcium supplementation dose of 500 mg/day or less, as compared to five percent (2/37) for patients treated with placebo (p<0.0001).

The REPLACE study showed that NATPARA was well-tolerated. Thirteen of the 134 randomized subjects discontinued the study early, of which seven were placebo-treated and six were NATPARA-treated. Overall, the incidence of adverse events and serious adverse event were similar among both groups.

The REPLACE study consisted of an average 10-week screening and stabilization period followed by a 24-week treatment period marked by randomization (2:1) to 50 µg once daily NATPARA or placebo. Following randomization, subjects underwent staged reductions in calcium and vitamin D supplementation, while maintaining stabilized serum calcium. If needed, step-wise up-titration of study drug (NATPARA or placebo) to a dose of 75 µg and then if necessary to 100 µg over a six to eight week period was performed.  Subjects continued on their final dose through week 24. A follow-up period without study drug lasted from week 24 to week 28.

Because NATPARA is identical instructure to the 84-amino acid single-chain polypeptide human parathyroid hormone and mimics the action of the natural parathyroid hormone, NPS believes it has the ideal mechanism of action to fulfill the unmet need of this chronic condition and offers a more physiological treatment outcome than is possible with existing palliative approaches.


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