Zhao, Suling

Background: In patients with irritable bowel syndrome with constipation (IBS-C), rapid, sustained relief from constipation and abdominal symptoms, such as pain, discomfort, and bloating, can improve quality of life. Objective: This post hoc analysis evaluates the time to constipation and abdominal symptom relief achieved with tenapanor. Design: Post hoc analysis of data pooled from three randomized placebo-controlled studies (phase IIb, T3MPO-1, and T3MPO-2) of tenapanor 50 mg twice daily in patients with IBS-C. Methods: The time to first response for complete spontaneous bowel movement (CSBM) frequency, abdominal pain, discomfort, bloating, and 3-item abdominal score (AS3) were assessed. The AS3 was derived as the average of the weekly scores for abdominal pain, discomfort, and bloating. Cumulative incidences of response over time were estimated using the Kaplan–Meier method. A Cox proportional hazards model was used to assess the effect of baseline and demographic characteristics on the time to first response. Results: Among 1372 patients with IBS-C (684 tenapanor; 688 placebo), median time to first CSBM response was 2 weeks, and median time to abdominal pain, discomfort, bloating, or AS3 response was 4–5 weeks in those treated with tenapanor, with 67.8%–76.7% achieving first response in CSBM frequency and abdominal symptoms by week 12. These time frames were shorter than those observed with the placebo (4 weeks for CSBM and 6–8 weeks for pain, discomfort, bloating, and AS3), of whom 59.1%–69.4% achieved the first response in CSBM and abdominal symptoms by week 12. Higher weekly response rates were observed with tenapanor than with placebo for all endpoints in each week of the 12-week treatment period. Conclusion: This novel post hoc analysis demonstrates that, compared with placebo, tenapanor reduces the time to first response in CSBM frequency and abdominal symptoms and consistently increases the weekly response rate during 12 weeks of treatment. Trial registration: NCT01923428; NCT02621892; NCT02686138.

INTRODUCTION: This post hoc analysis evaluated the efficacy of tenapanor on abdominal symptoms in patients with irritable bowel syndrome with constipation. Abdominal symptoms assessed included pain, discomfort, bloating, cramping, and fullness. METHODS: The abdominal symptom data were pooled from 3 randomized controlled trials (NCT01923428, T3MPO-1 [NCT02621892], and T3MPO-2 [NCT02686138]). Weekly scores were calculated for each abdominal symptom, and the Abdominal Score (AS) was derived as the average of weekly scores for abdominal pain, discomfort, and bloating. The overall change from baseline during the 12 weeks was assessed for each symptom weekly score and the AS. The AS 6/12-week and 9/12-week response rates (AS improvement of ≥2 points for ≥6/12- or ≥9/12-week) were also evaluated. The association of weekly AS response status (reduction of ≥30%) with weekly complete spontaneous bowel movement (CSBM) status (=0 and >0) was assessed. RESULTS: Among 1,372 patients (684 tenapanor [50 mg twice a day] and 688 placebo), the least squares mean change from baseline in AS was −2.66 for tenapanor vs −2.09 for placebo ( P < 0.0001). The 6/12-week AS response rate was 44.4% for tenapanor vs 32.4% for placebo ( P < 0.0001), and for 9/12-week AS, 30.6% for tenapanor vs 20.5% for placebo ( P < 0.0001). A significant association between weekly CSBM status and weekly AS response status was observed each week ( P < 0.0001), with a greater proportion achieving an AS reduction in patients with >0 CSBMs in a week. DISCUSSION: Tenapanor significantly reduced abdominal symptoms in patients with irritable bowel syndrome with constipation, particularly pain, discomfort, and bloating measured by AS, compared with placebo.