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Abstract: TH-PO145

Efficacy and Safety of Tenapanor in Japanese Peritoneal Dialysis Patients with Hyperphosphatemia: Results of a Phase 3 Study

Session Information

Category: Bone and Mineral Metabolism

  • 502 Bone and Mineral Metabolism: Clinical

Authors

  • Kubota, Minoru, Hakuhoukai Ouji Hospital, Tokyo, Japan
  • Ikejiri, Kazuaki, Kyowa Kirin Co., Ltd., Tokyo, Japan
  • Kusakabe, Miho, Kyowa Kirin Co., Ltd., Tokyo, Japan
  • Nakanishi, Kaoru, Kyowa Kirin Co., Ltd., Tokyo, Japan
  • Fukagawa, Masafumi, Tokai University School of Medicine, Kanagawa, Japan
  • Akizawa, Tadao, Showa University School of Medicine, Tokyo, Japan
Background

Hyperphosphatemia develops in most peritoneal dialysis (PD) patients and is treated with diet and phosphorus binders (PBs), however some patients do not respond adequately to these treatments. Tenapanor is a novel drug for hyperphosphatemia that blocks intercellular influx of phosphorus from intestinal tract by binding the sodium/hydrogen exchanger 3 transporter (NHE3) expressed on the apical membrane of intestinal epithelial cells. This is the first study to evaluate the efficacy and safety of tenapanor in Japanese PD patients with hyperphosphatemia.

Methods

This was a multicenter, open-label, single-arm, phase 3 study in Japanese PD patients with hyperphosphatemia. The study consisted of a screening period, PB-washout period, and treatment period. Patients were enrolled if serum phosphorus level was 3.5−7.0 mg/dL at screening and elevated to 6.1−9.9 mg/dL after PB-washout. Tenapanor dose was started at 5 mg and titrated to a maximum of 30 mg for 16 weeks to manage serum phosphorus levels within the target range of 3.5−6.0 mg/dL. After week 8, use of only one PB was allowed when serum phosphorus levels were not in the target range. The primary endpoint was the mean change in serum phosphorus at week 8 from baseline. The data for the change in serum phosphorus levels from baseline were carried forward for missing changes using the last observation carried forward method.

Results

A total of 54 subjects received tenapanor. Serum phosphorus levels decreased from a baseline of 7.65 mg/dL to 6.14 mg/dL in week 8 and 5.44 mg/dL in week 16. The change in serum phosphorus at week 8 (primary endpoint) and at week 16 from baseline was −1.18 mg/dL (95% confidence interval −1.54 mg/dL, −0.81 mg/dL) and −1.65 mg/dL, respectively. The proportion of patients who achieved the target levels at week 8 and at week 16 was 46.3% (19/41) and 76.5% (26/34), respectively. The most common adverse event was diarrhea (74.1%, 40/54). All were mild or moderate in severity and only three subjects (5.6%) discontinued due to diarrhea. These results were comparable to those of the phase 3 study in Japanese hemodialysis (HD) patients.

Conclusion

Tenapanor could be a new treatment option for PD patients with hyperphosphatemia as well as HD patients.

Funding

  • Commercial Support – Kyowa Kirin Co., Ltd.