Rifaximin and IBS-D

Rifaximin and IBS-D

Dr. Anthony Lembo of Beth Israel Deaconess Medical Center announced that he will present the results of TARGET 3 at the American College of Gastroenterology meeting.  TARGET 3 is a Phase 3 study of the efficacy and safety of repeat treatment with rifaximin in subjects with IBS-D that previously responded to an initial treatment course of rifaximin and subsequently experienced a recurrence of their IBS-D symptoms.  Rifaximin, is widely used to treat small intestinal bacterial overgrowth, but is not currently approved for use in IBS-D and is currently under review by the FDA. The TARGET 3 study was designed with both an open-label and a double-blind phase.

The study included 2,579 patients of which 1, 074 were diagnosed with  IBS-D.   Subjects were assessed for their initial response and subsequent relapse following 2 weeks of open-label rifaximin therapy. In this phase, 42% of subjects responded based on the FDA-required composite endpoint of symptomatic relief in both abdominal pain and stool consistency. In regards to relapse following the initial treatment response, over one third of the subjects that responded to rifaximin never experienced relapse of their symptoms over the follow-up period. In addition to the 42% of the patients meeting the FDA-required composite endpoint, an additional 30% of open-label subjects obtained some relief as measured by meeting the responder criteria for either abdominal pain or stool consistency; however, these subjects did not qualify for further participation in the study and were not included in the double-blind phase evaluating the assessment of repeat treatment efficacy and safety.

Forty two percent (42%) (n=1074 of 2579) of IBS-D patients were deemed responders from a two week treatment course of rifaximin 550 mg at the end of the 4-week treatment free follow-up period following the open-label phase. Of the 1074 patients who responded to rifaximin 550 mg, 36% (n=382) did not experience recurrent IBS-D symptoms when followed for up to 18 weeks following the initial two week treatment.

Of 692 patients who experienced recurrent IBS-D symptoms, 636 (mean age 46.8 years, 69% female) were randomized to receive rifaximin 550 mg TID (n=328) or placebo (n=308). Of note, the 636 patients entered into the double-blind phase presented with a lesser degree of symptom severity than at study entry for both abdominal pain and stool consistency.

The primary endpoint, based on abdominal pain or stool consistency, compared the proportion of responders between the rifaximin 550 mg repeat treatment and placebo group and significantly favored rifaximin 550 mg repeat treatment (33% vs. 25%, p=0.02). During the second double-blind repeat treatment phase, the percentage of responders was again statistically significant for rifaximin 550 mg vs. placebo-treated patients (37% vs. 29%, p=0.04). Adverse effects (AEs) were reported in 43% and 46% of patients taking rifaximin 550 mg and placebo, respectively.

Ref: Salix Pharmaceutical Company Press Release October 2014