Mere days before a Food and Drug Administration (FDA) advisory committee reviews new clinical data to decide whether to recommend removing the black box warning on Pfizer’s smoking cessation drug Chantix regarding psychological side effects such as agitation, depression and suicidal thinking, the FDA is questioning whether Pfizer adequately captured the number of adverse events, biasing the research in favor of the drug.
The clinical trial data was requested by the FDA after a high rate of suicidal thoughts and suicides were linked to Chantix. The trials also included GlaxoSmithKline’s anti-smoking drug Zyban, and pitted both against a placebo.
In a report released earlier this week, the FDA questioned the lack of consistency in how Pfizer collected neuropsychiatric events. The study was difficult to design in the first place, attempting to capture 16 different categories of neuropsychiatric side effects that could be broken down into 261 separate preferred medical terms. For example, “agitation” was one of the 16 side effects, but it could also be defined as “restlessness,” “disturbance in attention,” or “hyperkinesia.”
The FDA added that the data collection process also didn’t capture enough information to gauge the severity of side effects, and that the harshness of some side effects were downgraded.
The agency also noted that study sites where researchers had been paid more than $25,000 by Pfizer recorded a lower percentage of neuropsychiatric events compared to sites where researchers received less than $25,000.
The FDA advisory committee of independent experts is expected to review the data as well as the FDA’s concerns and then offer its recommendation on whether to remove the black box warning from Chantix. The FDA is not required to follow the committee’s recommendation, though it usually does.
Chantix was approved by the FDA in 2006, and almost immediately caught flack over side effects including suicidal thinking, aggression, depression and agitation. The FDA added the boxed warning in 2009, and updated the information in it in 2009.
In 2015, Pfizer petitioned the FDA to remove the boxed warning regarding suicide and suicidal thoughts. The agency refused without more clinical data, and then ordered a new warning regarding interactions with alcohol.
Chantix brought in $671 million in sales for Pfizer last year.