Xifaxan rifaximin regulatory update
FDA issued draft guidance for developing generic versions of Salix's 550 mg Xifaxan rifaximin to reduce the risk of hepatic encephalopathy recurrence. The agency recommended companies seeking an ANDA for the 550 mg dose conduct a pair of single-dose, 2-way crossover bioequivalence studies with pharmacokinetic endpoints in healthy volunteers. For the 200 mg dose, which is approved to treat traveler's diarrhea caused by noninvasive strains of Escherichia coli, the agency recommends a single randomized, double-blind, placebo-controlled efficacy study in patients with traveler's diarrhea. The design of the trial of the 200 mg dose is similar to one required under draft guidance released in November. The guidance required a clinical trial to demonstrate comparative efficacy between a generic and Xifaxan, based on a primary endpoint of clinical cure at the test of cure (TOC) visit on study day 5. Comments are due by April 13. Salix reported $264.4 million in Xifaxan revenues for the first 9 months of 2011. Patents covering Xifaxan expire in 2024 and 2025. ...