Pfizer ($PFE) has been trying to get the FDA to take the black box warning off its smoking cessation drug, Chantix, after regulators warned that the med could be linked to serious psychiatric side effects. Now, the company is celebrating some positive study results for the drug that could work in its favor.

A large international study of Chantix and GlaxoSmithKline’s ($GSK) Zyban found that the meds do not increase patients’ risks of neuropsychiatric side effects. The meds also beat a nicotine patch and placebo at helping people quit smoking, according to results recently published in The Lancet.

The randomized controlled trial, called EAGLES, included 8,144 smokers in 16 countries. For 12 weeks, patients used either a placebo, a nicotine patch, Chantix or Zyban, and then had 12 weeks of follow-up. The active ingredient in Zyban is also sold as an antidepressant under the brand name Wellbutrin.

Patients were also divided into two groups: those without psychiatric disorders and those with preexisting psychiatric disorders. Researchers found that 1.3% of people without psychiatric problems who were taking Chantix had moderate to severe side effects. That compares to 2.2% of Zyban patients, 2.5% of nicotine patch users and 2.4% in the placebo arm.

Patients with psychiatric disorders had slightly higher rates of neuropsychiatric side effects. About 6.5% of people taking Chantix had moderate to severe side effects, compared with 6.7% for Zyban, 2.5% for the nicotine patch and 2.4% for placebo.

Chantix came out the winner when it came to helping patients abstain from smoking, the study found. More patients taking the med abstained than those who used Zyban, the patch or a placebo. Zyban plus a patch also helped more patients abstain than a placebo did.

“This is the largest randomized, controlled trial to date comparing these smoking-cessation medications directly and comparing them with placebo,” Robert Anthenelli, professor of psychiatry at the UC San Diego School of Medicine and lead author of the study, told MedPage Today. “We are hoping that the recognition that these medications are safe for smokers with and without psychiatric disorders will encourage people to try and quit, and feel comfortable that they can use any of the available medications.”

Pfizer is hoping that the results get the FDA to change its tune about Chantix’s safety. Back in 2009, the agency slapped the drug with a black box warning amid reports “changes in behavior, hostility, agitation, depressed mood, and suicidal thoughts or actions” in people taking the med. Regulators also called for the current post-marketing study to further examine Chantix’s risks.

In 2014, Pfizer asked the FDA to remove the black box while the trial was still going on. But the agency nixed that request and said that it would keep the black box until the study was finished.

New study results for Chantix could go a long way for Pfizer. “We believe the available scientific information doesn’t support a boxed warning,” Pfizer CMO Freda Lewis-Hall, M.D. told The Associated Press. The study data adds to “the large body of clinical evidence characterizing the neuropsychiatric safety and efficacy of (Chantix)” and highlights the drug “as an important treatment option for people who want to quit smoking,” Lewis-Hall said in a statement.

Pfizer “is in the process of submitting these data to regulatory authorities worldwide, as appropriate, and looks forward to discussing these data with them,” the company told FiercePharma in an email.

Whether the FDA will buy that argument remains to be seen. The agency “will review the findings of this study along with additional scientific evidence as we continue to evaluate this issue, as well as take follow-up action and update the public as appropriate,” the FDA told the AP.

 

Emily Wasserman, for FiercePharma