FDA reviewers say Pfizer's Chantix should keep its black box

FDA staffers aren't as impressed with new safety data on Chantix as Pfizer ($PFE) wants them to be. In briefing documents filed in advance of Thursday's advisory committee meeting, reviewers say the stop-smoking remedy should keep its black-box warning about potential psychiatric side effects.

The reviewers' stance sets the stage for a spirited argument Thursday, where the FDA's expert advisors will consider whether to keep that black box on Chantix's label, or scrap it as Pfizer requests.

The company has reason to hope: The FDA let Pfizer add some favorable safety data to Chantix's label last month. But that concession could end up being a consolation prize.

In a 398-page analysis of data submitted by Pfizer, plus agency stats and other submissions, agency reviewers said that removing a boxed warning has "limited precedent," and that it really should wait till next year's results from a controlled trial designed to evaluate Chantix's risks.

Here's where the reviewers come down on the evidence. They point out limitations in Pfizer's meta-analyses, and conclude that the drugmaker's observational studies "provided evidence of insufficient quality" to rule out an increased risk of suicide, suicide attempt or psychiatric hospitalization.

Meanwhile, recent adverse event reports to the agency "were consistent with the findings ... that led to the current boxed warning," the reviewers write. And they point out that some of those reports show that neuropsychiatric side effects disappeared when patients stopped using Chantix, and/or recurred when therapy resumed.

The review leaves a door open for Pfizer, however. The agency "has determined that some information about these data could be included in the [Chantix] labeling." As for removing the boxed warning? That's why the committee is meeting--to see whether Pfizer's meta-analyses and observational data, given the limitations outlined in the review are enough to prompt the change, the reviewers say.

Thursday's meeting is just the latest in a series of debates over Chantix safety, thanks to side effects reports that started rolling in soon after the drug's launch in 2006. The black-box warning was added in 2009. Before the side effects reports started rolling in, Chantix was churning out sales; in fact, until Vertex Pharmaceuticals' ($VRTX) hep C drug Incivek hit the market, Chantix was the industry's fastest launch. But by last year, sales had dropped by $648 million, down slightly from 2013--and from $846 million in 2008. The company cited the "lingering impact of negative media attention" for the slide.

Last year, Pfizer paid more than $275 million to settle thousands of lawsuits alleging that Chantix triggered suicides, suicidal thoughts and other psychiatric problems. The company says it stands by the drug and its risk-benefits profile. In late 2011, based on new study data, the FDA said that the drug doesn't appear to increase the risk of psychiatric hospitalization. But at the time, the agency affirmed that the black-box warning was still necessary.

- read the FDA review (PDF)

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