Data follows on from FDA’s recent approval of antibiotic for reducing risk of hepatic encephalopathy.

Positive data from Phase III trials with Salix Pharmaceuticals’ Xifaxan 550 mg (rifaximin) antibiotic  against nonconstipation irritable bowel syndrome (NC-IBS) have led the company to confirm plans for a relevant NDA filing with FDA by the end of June.

Presented at the recent annual “Digestive Disease Week” in New Orleans, data from the identically designed Target 1 and Target 2 trials showed that a 14-day course of the nonsystemic antibiotic was significantly better than placebo at providing relief from NC-IBS symptoms, for up to three months, Salix claims. Assessment of secondary endpoint data also showed the drug provided adequate relief from bloating for at least two of the first four weeks following the two-week treatment period. The statistically significant weekly findings in primary and key secondary endpoints were supported by the patients’ daily assessments of global IBS symptoms.

Specifically, the combined study data showed that rifaximin therapy resulted in 41% of patients reporting adequate relief from their IBS symptoms, compared with 32% of patients receiving placebo; 40% of patients given rifaximin reported adequate relief from bloating, compared with 30% of placebo patients.

“The effectiveness of rifaximin demonstrated during both the acute and sustained time periods measured in the trials, as well as the consistency of effectiveness achieved over a broad range of endpoints, generate a high level of confidence in rifaximin’s utility to treat the underlying causes of IBS symptoms,” according to Bill Forbes, Pharm.D., chief development officer and executive vp of R&D.

The NC-IBS trial data follows on from the FDA’s March approval of rifaximin for reducing the risk of overt hepatic encephalopathy recurrence in patients aged 18 years or older.

Salix negotiated North American licensing rights to rifaximin from Alfa Wassermann. The drug was first approved in the U.S. in 2004 for the treatment E. coli-related travelers’ diarrhea in patients over 12 years of age and is now available in 33 countries, Salix claims. Rifaximin has been marketed in Italy (as Normix® and Rifacol®) since 1988.

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