FDA's tandem review of the macrolide antibiotics clarithromycin (Abbott's Biaxin) and azithromycin (Pfizer's Zithromax) continued right up to approval on Oct. 31 and Nov. 1, respectively. Abbott's Biaxin (clarithromycin) was approved for treatment of sinusitis, pharyngitis/tonsillitis, pneumonia, bronchitis, and skin and skin structure infections. Pfizer's Zithromax (azithromycin) received FDA clearance late in the day on Nov. 1. Both antibiotics went before FDA's Anti-Infective Drugs Advisory Committee July 18 and both reached approvable status Aug. 29. Pfizer has been pursuing Zithromax indications for upper and lower respiratory tract infections (pharyngitis, sinusitis, and pneumonia and bronchitis), skin and skin structure infections, chlamydia, and pediatric infections (otitis media). Focusing on three indications, the anti-infectives advisory committee unanimously agreed, at its July 18 meeting, that Zithromax is safe and effective for use against streptococcal pharyngitis (strep throat) and chlamydial cervicitis and urethritis ("The Pink Sheet" July 22, p. 10). The Biaxin NDA was approved after 22 months at FDA while Zithromax was okayed after a 19-month review. Both Biaxin, a broad-spectrum macrolide antibiotic, and Zithromax, an azalide antibiotic, were given FDA's "1B" rating, denoting a new chemical entity representing a modest therapeutic gain over existing therapies. In head-to-head trials, clarithromycin has shown efficacy similar to erythromycin, penicillins and cephalosporins; but the Abbott drug has a dosing advantage over erythromycin -- clarithromycin is given in twice-daily doses of 250 mg or 500 mg tablets, while erythromycin is usually given four times a day. Abbott has said that clarithromycin has a longer half-life (seven hours v. two) and greater bioavailability than erythromycin. Biaxin's labeling says that "in studies of pneumonia comparing clarithromycin to erythromycin base or erythromycin stearate, there were fewer adverse events involving the digestive system in clarithromycin-treated patients compared to erythromycin patients (13% v. 3%; p<0.01)." Pfizer's Zithromax has the added advantage of having a once- daily regimen. Pfizer also has reported that azithromycin has fewer gastrointestinal side effects than erythromycin. Clarithomycin labeling contains a warning in bold type that restricts the use of the antibiotic in pregnant women. "Clarithromycin should not be used in pregnant women except in clinical circumstances where no alternative therapy is appropriate," labeling states. The warning concurs with the advisory committee's recommendation that the drug's use be allowed in pregnant women for conditions "where no alternative therapy is appropriate." The advisory committee also discussed animal studies of clarithromycin that suggested that the drug had teratogenic potential. The committee unanimously agreed that clarithromycin is safe for use in women of childbearing potential despite the results of the animal studies. The committee was split on whether the antibiotic should be contraindicated in pregnant women. The clarithromycin warning notes that "if pregnancy occurs while taking this drug, the patient should be apprised of the potential hazard to the fetus. Clarithromycin has demonstrated adverse effects on pregnancy outcome and/or embryo-fetal development in monkeys, rats, mice, and rabbits at doses that produced plasma levels two to 17 times the serum levels achieved in humans treated at the maximum recommended human doses." Biaxin's approval letter notes that Abbott has committed "to study the potential for drug interaction between clarithromycin and terfenadine [Marion Merrell Dow's antihistamine Seldane]." Biaxin will be launched as "soon as possible," the company said. Abbott said that it has not set pricing for Biaxin, but that the the drug will be priced competitively with other antibiotics.
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Advanz Pharma would have had to show that the European Commission’s decision to revoke Ocaliva’s conditional marketing approval risked causing serious and irreparable harm, according to lawyers from Van Bael & Bellis.
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