Pfizer has moved a giant leap closer to getting the strongest warning of serious neuropsychiatric events removed from the labelling of its anti-smoking drug Chantix in the US.

Advisors to the US Food and Drug Administration's Psychopharmacologic Drugs Advisory Committee and Drug Safety Risk Management Advisory Committee have voted by a majority to have the boxed warning pulled from the drug's label following a review of data from the EAGLES (Evaluating Adverse Events in a Global Smoking Cessation Study) trial.

The drug giant said it has proposed retaining the Warnings and Precautions section in the labelling regarding the possibility of serious neuropsychiatric events in patients attempting to quit smoking and updating it with EAGLES data, in the belief that such a warning would be sufficient.

Results from the Lancet-published EAGLES trial show that use of Chantix (Champix in the EU; varenicline) and buprion (originally GlaxoSmithKline's Zyban but now generically available) is not linked with an increased risk of neuropsychiatric side effects, as was previously feared.

The study's primary safety endpoint was the occurrence of at least one treatment-emergent severe adverse event of anxiety, depression, feeling abnormal, or hostility and/or the occurrence of at least one treatment-emergent moderate or severe adverse event of agitation, aggression, delusions, hallucinations, homicidal ideation, mania, panic, paranoia, psychosis, suicidal ideation, suicidal behaviour or completed suicide.

The incidence of the primary safety endpoint in patients without a history of psychiatric disorders was 1.3 percent for Chantix/Champix, 2.2 percent for buprion, 2.5 percent for the nicotine patch and 2.4 percent for placebo, while the incidence rates in patients with a history of psychiatric disorders were 6.5 percent, 6.7 percent, 5.2 percent and 4.9 percent, respectively.

The findings, which have already warned EU regulators to remove the black triangle warning from the drug's label, follow those of separate study, also published in the Lancet last year, showing that people taking varenicline were at no higher risk of depression or suffering a heart attack than those using other drugs or nicotine-replacement therapy.

"The totality of available scientific evidence, including the outcomes of EAGLES, supports the safety and efficacy of Chantix," said Freda Lewis-Hall, Pfizer's chief medical officer. "We are pleased with the Committees' recommendation to remove the boxed warning and believe this is an important step toward updating the Chantix labelling to more accurately reflect its neuropsychiatric safety profile and help patients and prescribers make informed decisions about treatment options."

In the US, smoking causes more than 480,000 deaths each year and is a leading cause of preventable death and disease.