FDA advisory panels back removal of warning from anti-smoking therapy Chantix

Pfizer announced that two FDA advisory panels recommended by a majority vote to remove the boxed warning regarding serious neuropsychiatric adverse events from the label of the smoking-cessation therapy Chantix (varenicline).

In 2009, the FDA determined that Chantix and GlaxoSmithKline's smoking cessation product Zyban (bupropion) should carry a boxed warning about the risk of serious neuropsychiatric events, while the regulator also requested that the companies conduct a post-marketing study. Pfizer has been trying to get the boxed warning removed from the Chantix label, although an FDA advisory panel in 2014 recommended that it be kept, with agency staff noting at the time that no decision should be made until the post-marketing requirement is completed.

Earlier this year, Pfizer submitted a supplemental application to the FDA requesting removal of the boxed warning, with the filing including data from the EAGLES trial, which had concluded that neither Chantix nor Zyban were associated with a significant increase in neuropsychiatric adverse events relative to nicotine patch or placebo. Ahead of the latest advisory committee meeting, agency reviewers raised concerns over the study, including that inconsistencies in data collection and characterisation of the severity of adverse events may have biased results in favour of Chantix.

However, after reviewing the study data, 10 committee members backed removal of the boxed warning on Chantix, noting that the benefits of quitting smoking far outweighed the potential severe side effects of the drug, and that the evidence of causality between Chantix and the side effects was not clear enough to warrant such a warning. Meanwhile, four panel members called for an update to the label's language, with five recommending that the boxed warning be retained.

In May, regulators in Europe, where Pfizer markets the therapy under the name Champix, removed a similar warning on the product's label. Sales of the drug reached $671 million last year.

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