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Cytisinicline safely and effectively helped people quit smoking when used at a higher concentration than is traditional in Europe, the placebo-controlled found.

Administered as a 3-mg tablet taken orally three times daily for 6 weeks, cytisinicline resulted in higher continuous abstinence rates for smoking during weeks 3 to 6 (25.3% vs 4.4% for placebo, OR 8.0, 95% CI 3.9-16.3, P<0.001), and weeks 3 to 24 (8.9% vs 2.6%, OR 3.7, 95% CI 1.5-10.2, P=0.002) reported Nancy Rigotti, MD, of Massachusetts General Hospital, Boston, and co-authors.

Similar results were seen among patients taking cytisinicline for 12 weeks, with continuous abstinence rates of 32.6% vs 7.0% in the placebo group for weeks 9 to 12 (OR 6.3, 95% CI 3.7-11.6, P<0.001) and 21.1% vs 4.8% in weeks 9 to 24 (OR 5.3, 95% CI 2.8-11.1, P<0.001), according to the double-blind clinical trial published in .

All three groups in ORCA-2 reported high percentages of behavioral support compliance, with 92.8% of sessions finished in the 12-week group, 89.5% in the 6-week group, and 86.8% in the placebo cohort.

Nausea, abnormal dreams, and insomnia occurred in less than 10% of each group. Ultimately withdrawing from the trial due to adverse events were 2.9% of cytisinicline recipients and 1.5% of patients in the placebo group. Serious adverse events were seen in 3.3% vs 1.1%, respectively, but were deemed to not be related to the treatment.

"Cytisinicline reduced nicotine craving and was well tolerated by participants, who adhered to the treatment schedule at a high rate, even though the trial was conducted during the early phases of the U.S. COVID-19 pandemic," Rigotti and colleagues reported.

Their results would help build the case for FDA approval for cytisinicline, which already has a long history of use as an over-the-counter smoking cessation product in Central and Eastern Europe.

Already announced, topline results of the second large cytisinicline study, , reportedly support better smoking cessation during the last 4 weeks of cytisinicline treatment. A similar e-cigarette cessation benefit was also recently reported out of .

Rigotti's group noted that in the U.S., existing therapies for smoking cessation -- namely nicotine replacement, bupropion, and varenicline -- have modest long-term abstinence success and are associated with adverse events. "No smoking cessation pharmacotherapy has received FDA approval since 2006. New options are needed," study authors stressed.

The that smokers in the U.S. have three times the mortality rate compared with never-smokers. Excess mortality is attributed to cancer and respiratory and vascular disease.

"It is unfortunate that there has never been an 'Operation Warp Speed' to prevent the more than 480,000 deaths each year caused by smoking. It is, however, a very positive development that another new and effective drug may be added to the limited list that clinicians and individuals who smoke can choose from to help end their deadly addiction to cigarettes," wrote Jonathan Foulds, PhD, of Penn State College of Medicine, Hershey, and co-authors in .

The editorialists highlighted that the adverse events seen with cytisinicline treatment were not dissimilar from those for varenicline, but were seemingly both less severe and less frequent.

"The fact that cytisinicline has been used for smoking cessation in some Eastern European countries for more than 50 years (including over the counter) without a serious problem with adverse events emerging is also reassuring regarding the safety profile of the drug," Foulds' group commented.

A total of 810 patients (54.6% women, average age 52.5 years) were included in the ORCA-2 trial. Across all three treatment groups, 80% or more of the patients were white. Patients smoked an average of 19.4 cigarettes per day.

Following randomization, 270 patients were given 3 mg of cytisinicline to take three times each day for 12 weeks, 269 patients were given the same dosage for 6 weeks, and 271 were given placebo for 12 weeks. Behavioral support, consisting of visits with a trained smoking cessation counselor for up to 15 visits following randomization for the first 12 weeks, followed by shorter visits at 16, 20, and 24 weeks, was provided to all patients.

Of the total cohort, 76.3% of patients ended up completing the trial.

Limitations to ORCA-2 include the predominantly white patient population. Researchers also noted that adverse events were not assessed beyond 24 weeks, and both the trial's size and duration hindered opportunities to detect uncommon adverse events. Moreover, the results may have limited generalizability as patients diagnosed with mental illness conditions, as well as those with a recent history of unstable cardiovascular disease, were excluded from the study.

Correction: This article previously stated that a limitation of the study was that adverse events were not assessed until 24 weeks. It has been changed to reflect the correct timeframe.

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