Tenapanor for peritoneal dialysis patients with hyperphosphatemia: a phase 3 trial
Masaaki Nakayama, Shuhei Kobayashi, Miho Kusakabe, Meiko Ohara, Kaoru Nakanishi, Tadao Akizawa, Masafumi Fukagawa
Abstract
BACKGROUND: Tenapanor is a novel selective inhibitor of intestinal sodium/hydrogen exchanger 3 transporter. This is the first trial to assess the efficacy and safety of tenapanor in Japanese patients with hyperphosphatemia who are undergoing peritoneal dialysis. METHODS: This phase 3, open-label, multicenter, single-arm clinical trial targeted patients whose serum phosphorus was within 3.5-7.0 mg/dL with phosphate binders at screening. After phosphate binder washout, tenapanor was orally administered twice-daily, stepwise from 5 to 30 mg/dose for 16 weeks. The primary endpoint, mean change in serum phosphorus level, was evaluated at week 8. The 16-week treatment period was completed with tenapanor alone, and only one phosphate binder type was allowed for combined use after the primary endpoint. RESULTS: Of the 54 patients enrolled, 34 completed the study. At week 8, the primary endpoint, mean change in serum phosphorus level (last observation carried forward), was - 1.18 mg/dL (95% confidence interval: - 1.54, - 0.81 mg/dL) with tenapanor. From a baseline value of 7.65 mg/dL, serum phosphorus decreased to 6.14 and 5.44 mg/dL at weeks 8 and 16, respectively, and 46.3% and 76.5% of patients achieved serum phosphorus within 3.5-6.0 mg/dL at week 8 and week 16, respectively. The most common adverse event, diarrhea, occurred in 74.1% of patients; the severity of diarrhea was mild or moderate. Thus, the discontinuation percentage due to diarrhea was low at 5.6%. CONCLUSIONS: Administration of tenapanor resulted in a sufficient reduction in serum phosphorus level at week 8 and was considered safe and tolerable. TRIAL REGISTRATION: NCT04766385.