Salix Pharmaceuticals receives three U.S. patents relating to rifaximin

Salix Pharmaceuticals, Ltd. (NASDAQ:SLXP) today announced that the U.S. Patent and Trademark Office has issued three patents relating to rifaximin.

U.S. Patent No. 7,928,115 (the '115 patent), which issued April 19, 2011, provides protection to methods of treating Travelers' Diarrhea (TD) with rifaximin. This patent should provide protection until July 24, 2029. This invention was a product of Salix's internal innovation and Salix is the assignee of all the rights and title to this patent. The '115 patent provides protection for the TD indication for the rifaximin 200mg product that the Company markets in the United States under the trade name XIFAXAN^®.

U.S. Patent No. 7,906,542 (the '542 patent), which issued March 15, 2011, provides protection relating to pharmaceutical compositions comprising rifaximin in polymorphic forms. This patent should provide protection until June 1, 2025. Additionally, U.S. Patent No. 7,902,206 (the '206 patent), which issued March 8, 2011 provides protection relating to rifaximin in polymorphic form alpha free from other polymorphic forms of rifaximin not derived from Form alpha by water absorption or release. This patent should provide protection until June 19, 2024.

Salix has an exclusive license to the '542 and '206 patents from Alfa Wassermann S.p.A. to use, sell, have sold and import licensed rifaximin products, which the Company markets in the United States under the trade names XIFAXAN^® (200mg) and XIFAXAN550^™ (550mg). The '542 and '206 patents provide protection for all indications currently marketed and being assessed.

XIFAXAN^® (rifaximin)

Rifaximin is a gut-selective antibiotic with negligible systemic absorption and broad-spectrum activity in vitro against both gram-positive and gram-negative pathogens. Rifaximin has a similar tolerability profile to that of placebo.

Rifaximin tablets 200 mg is approved in over 30 countries worldwide. Alfa Wassermann S.p.A. in Bologna, Italy has marketed rifaximin in Italy under the trade name Normix^® for over 30 years. Salix acquired rights to market rifaximin in North America from Alfa Wassermann.

Important Safety Information

Rifaximin tablets 200 mg, which Salix markets in the U.S. under the trade name XIFAXAN^® (rifaximin) tablets 200 mg, currently is approved for the treatment of patients, 12 years of age or older, with travelers' diarrhea (TD) caused by non-invasive strains of Escherichia coli. XIFAXAN should not be used in patients with diarrhea complicated by fever or blood in the stool or diarrhea due to pathogens other than Escherichia coli. XIFAXAN should be discontinued if diarrhea symptoms get worse or persist more than 24-48 hours, and alternative antibiotic therapy should be considered. In clinical trials, XIFAXAN was generally well-tolerated. The most common side effects (versus placebo) were flatulence 11.3 percent (versus 19.7 percent), headache 9.7 percent (versus 9.2 percent), abdominal pain 7.2 percent (versus 10.1 percent) and rectal tenesmus 7.2 percent (versus 8.8 percent).

XIFAXAN 550 mg tablets are indicated for reduction in risk of overt hepatic encephalopathy (HE) recurrence in patients ≥ 18 years of age. In the trials of XIFAXAN 550 mg tablets for HE, 91 percent of the patients were using lactulose concomitantly. XIFAXAN 550 mg tablets have not been studied in patients with MELD scores > 25, and only 8.6 percent of patients in the controlled trial had MELD scores over 19. There is increased systemic exposure in patients with more severe hepatic dysfunction. Therefore, caution should be exercised when administering XIFAXAN 550 mg tablets to patients with severe hepatic impairment (Child-Pugh C).

XIFAXAN 550 mg tablets are contraindicated in patients with a hypersensitivity to rifaximin, any of the rifamycin antimicrobial agents, or any of the components in XIFAXAN 550 mg tablets. Hypersensitivity reactions have included exfoliative dermatitis, angioneurotic edema, and anaphylaxis.

Clostridium difficile-associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including XIFAXAN 550 mg tablets, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon which may lead to overgrowth of C. difficile. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued.

The most common adverse reactions occurring in >8 percent of patients in the clinical study were edema peripheral (15 percent), nausea (14 percent), dizziness (13 percent), fatigue (12 percent), ascites (11 percent), muscle spasms (9 percent), pruritus (9 percent), and abdominal pain (9 percent).