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Abstract: TH-PO143

Optimal Initiation of Tenapanor Treatment Analyzed by Baseline Phosphate Binder Dose: A Subanalysis of the OPTIMIZE Study

Session Information

Category: Bone and Mineral Metabolism

  • 502 Bone and Mineral Metabolism: Clinical

Authors

  • Sprague, Stuart M., NorthShore University HealthSystem, Evanston, Illinois, United States
  • Meyer, Jill M., Balboa Nephrology Group, San Diego, California, United States
  • Rosenbaum, David P., Ardelyx, Inc., Waltham, Massachusetts, United States
  • Yang, Yang, Ardelyx, Inc., Waltham, Massachusetts, United States
  • Zhao, Suling, Ardelyx, Inc., Waltham, Massachusetts, United States
  • Spiegel, David M., Ardelyx, Inc., Waltham, Massachusetts, United States
Background

Tenapanor (TEN) is a novel phosphate absorption inhibitor that blocks paracellular phosphate absorption by local inhibition of the intestinal sodium hydrogen exchanger isoform 3 (NHE3). TEN is being evaluated for control of serum phosphate (sP) in adult patients (pts) with chronic kidney disease (CKD) on maintenance dialysis. Real world data shows that nearly 80% of pts are unable to consistently maintain adequate control of sP over a 6-month period with the use of phosphate binders (PBs) alone. OPTIMIZE (NCT04549597) was an open-label study of TEN initiation in pts on dialysis that evaluated sP control, pill burden, and quality of life (QOL).

Methods

OPTIMIZE study design was previously described. In Cohort 1 (C1; n=151) pts stopped PBs and initiated TEN 30 mg bid. In Cohort 2 (C2; n=152) pts reduced PB dose by ≥50% and added TEN 30 mg bid. The PB/TEN dose could be adjusted to achieve sP ≤5.5 mg/dL. Dose up-titration for PBs was not allowed until week (wk) 2. Pts in C1 and C2 were categorized into two groups: low PB (LPB) dose (≤6 pills/day at baseline) and high PB (HPB) dose (>6 pills/day at baseline). We evaluated sP response (sP reduction ≥1.2 mg/dL at ≥2 of 3 measurements) at wks 1–4 and wks 6–10 of treatment. A QOL survey was administered at the end of wk 10.

Results

Overall, 87 and 93 HPB pts and 60 and 55 LPB pts were randomized to C1 and C2, respectively. For HPB pts, sP response was achieved at wk 4 by 24.1% (C1) and 47.3% (C2) of pts. Median sP-lowering pill burden (including TEN) reduction at wk 4 was 7 (C1) and 4 (C2) pills/day. For LPB pts, sP response was achieved at wk 4 by 38.3% (C1) and 47.3% (C2) of pts. Median sP-lowering pill burden reduction was 2.5 (C1) and 1 (C2) pills/day. Overall, 60–80% of those who achieved a sP response at wk 4 continued to have a sP response later. Both cohorts achieved consistent sP control throughout the entire study by adding TEN, independent of how TEN was initiated.

Conclusion

Both cohorts experienced improved sP control, self-assessed QOL, and reduction in PB pill burden. HPB pts may have better early sP control by initiating TEN with a 50% reduction in PB dose, while LPB appeared to have a similar early response regardless of TEN initiation method.

Funding

  • Commercial Support – Ardelyx, Inc.