Tenapanor is associated with earlier and sustained symptom relief in IBS-C: a post hoc analysis

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.