Tenapanor Improves Abdominal Symptoms Irrespective of Changes in Complete Spontaneous Bowel Movement Frequency in Adults with Irritable Bowel Syndrome with Constipation

Abstract

Introduction: Tenapanor is a first-in-class, minimally absorbed intestinal sodium/hydrogen exchanger isoform 3 inhibitor approved by the US Food and Drug Administration for adults with irritable bowel syndrome with constipation (IBS-C). Pooled data from the phase 2b (NCT01923428) and phase 3 T3MPO-1 (NCT02621892) and T3MPO-2 (NCT02686138) studies examined the effects of tenapanor on abdominal symptoms independent of tenapanor's effect on complete spontaneous bowel movement (CSBM) frequency in adults with IBS-C. Methods: This post hoc analysis was performed for patients with no CSBMs in ≥6 of the first 12 weeks of treatment (no-CSBM subgroup). The three-itemabdominal score (AS3; the average of weekly abdominal pain, bloating, and discomfort scores) measured abdominal symptomresponse in tenapanor versus placebo. The overall change from baseline and response rate (improvement of ≥2 points or a reduction of ≥30%) in AS3 and individual abdominal scores during the 12 weeks were assessed. Results: In the pooled safety analysis set (N = 1,382), 641 patients were classified as no-CSBM patients and 640 were included in the efficacy analysis. Among the no-CSBM subgroup, tenapanor-treated patients experienced a greater improvement in AS3 in week 12 versus placebo-treated patients (least squares mean change, -1.74 vs. -1.29; p = 0.007), and the AS3 responder rate was higher for tenapanor (40.2% vs. 29.6%; p = 0.008). Similar improvements were displayed across individual abdominal symptom scores. Diarrhea was the most common adverse event in tenapanor-treated patients. Conclusion: Tenapanor was observed to improve abdominal symptoms independent of its effect on bowel symptoms in adults with IBS-C.