PFIZER’s ZITHROMAX (AZITHROMYCIN) LAUNCH DELAYED
Executive Summary
PFIZER's ZITHROMAX (AZITHROMYCIN) LAUNCH DELAYED pending FDA review of 19 "serious adverse events" omitted by the company in clinical trial data it provided to the agency, Pfizer announced Dec. 30. Pfizer says that it decided to delay the Zithromax launch voluntarily until the FDA review of the adverse events is complete. The data "supporting the use of Zithromax to treat mild to moderate pneumonia," was left out of information given to FDA between May and the approval of the broad-spectrum azalide antibiotic on Nov. 1 ("The Pink Sheet" Nov. 4, p. 8). In the omitted data, seven of the 19 patients were pneumonia cases, of whom four "died from complications of their disease." The remaining 12 events occurred in "non-pneumonia patients" and the company said that these cases should not change "the safety and efficacy profile of Zithromax." Pfizer would not comment on the nature of any of the adverse events or the specific infections for which the 19 patients were treated. Pfizer pointed out that "the severity and nature of the pneumonia infection present in the patients who died indicated a high risk of mortality" and that "none of the patients who died would have been a candidate for Zithromax therapy under the FDA- approved labeling." The company said it "immediately notified FDA" of the omission and that FDA will look at the seven pneumonia cases "in the context of the entire pneumonia data base." The company said that FDA "is expediting the review" of the adverse events data and that "Pfizer does not anticipate any major change in the previously approved labeling as a result of the review." Approved labeling currently indicates Zithromax for upper and lower respiratory infections, including pneumonia due to Streptococcus pneumoniae or Haemophilus influenzae. The product is also indicated for skin and skin structure infections and non- gonococcal urethritis and cervicitis due to Chlamydia trachomatis. Pfizer says it cannot predict when the FDA review of the adverse events data will be completed. Pfizer had said it would begin shipping Zithromax "as soon as possible" upon approval, with a launch in early 1992. Zithromax was the first azalide antibiotic to be approved and gained a "1B" rating from FDA, denoting a new chemical entity representing a modest gain over existing therapies. Pfizer has emphasized its once-a-day dosing regimen and low gastrointestinal side effect profile as advantages over erythromycin.
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