Cytisinicline for Smoking Cessation: A Randomized Clinical Trial

Importance

Cytisinicline (cytisine) is a plant-based alkaloid that, like varenicline, binds selectively to α4β2 nicotinic acetylcholine receptors, which mediate nicotine dependence. Although not licensed in the US, cytisinicline is used in some European countries to aid smoking cessation, but its traditional dosing regimen and treatment duration may not be optimal.

Objective

To evaluate the efficacy and tolerability of cytisinicline for smoking cessation when administered in a novel pharmacokinetically based dosing regimen for 6 or 12 weeks vs placebo.

Design, Setting, and Participants

A 3-group, double-blind, placebo-controlled, randomized trial (ORCA-2) compared 2 durations of cytisinicline treatment (6 or 12 weeks) vs placebo, with follow-up to 24 weeks, among 810 adults who smoked cigarettes daily and wanted to quit. It was conducted at 17 US sites from October 2020 to December 2021.

Interventions

Participants were randomized (1:1:1) to cytisinicline, 3 mg, 3 times daily for 12 weeks (n = 270); cytisinicline, 3 mg, 3 times daily for 6 weeks then placebo 3 times daily for 6 weeks (n = 269); or placebo 3 times daily for 12 weeks (n = 271). All participants received behavioral support.

Main Outcomes and Measures

Biochemically verified continuous smoking abstinence for the last 4 weeks of cytisinicline treatment vs placebo (primary) and from end of treatment to 24 weeks (secondary).

Results

Of 810 randomized participants (mean age, 52.5 years; 54.6% female; mean of 19.4 cigarettes smoked daily), 618 (76.3%) completed the trial. For the 6-week course of cytisinicline vs placebo, continuous abstinence rates were 25.3% vs 4.4% during weeks 3 to 6 (odds ratio [OR], 8.0 [95% CI, 3.9-16.3]; P < .001) and 8.9% vs 2.6% during weeks 3 to 24 (OR, 3.7 [95% CI, 1.5-10.2]; P = .002). For the 12-week course of cytisinicline vs placebo, continuous abstinence rates were 32.6% vs 7.0% for weeks 9 to 12 (OR, 6.3 [95% CI, 3.7-11.6]; P < .001) and 21.1% vs 4.8% during weeks 9 to 24 (OR, 5.3 [95% CI, 2.8-11.1]; P < .001). Nausea, abnormal dreams, and insomnia occurred in less than 10% of each group. Sixteen participants (2.9%) discontinued cytisinicline due to an adverse event. No drug-related serious adverse events occurred.

Conclusions and Relevance

Both 6- and 12-week cytisinicline schedules, with behavioral support, demonstrated smoking cessation efficacy and excellent tolerability, offering new nicotine dependence treatment options.

Trial Registration

ClinicalTrials.gov Identifier: NCT04576949.

Cytisine Therapy Improved Smoking Cessation in the Randomized Screening and Multiple Intervention on Lung Epidemics Lung Cancer Screening Trial

INTRODUCTION

Cytisine, a partial agonist-binding nicotine acetylcholine receptor, is a promising cessation intervention. We conducted a single-center, randomized, controlled trial (RCT) in Italy to assess the efficacy and tolerability of cytisine as a smoking cessation therapy among lung cancer screening participants.

METHODS

From July 2019 to March 2020, the Screening and Multiple Intervention on Lung Epidemics RCT enrolled 869 current heavy tobacco users in a low-dose computed tomography screening program, with a randomized comparison of pharmacologic intervention with cytisine plus counseling (N = 470) versus counseling alone (N = 399). The primary outcome was continuous smoking abstinence at 12 months, biochemically verified through carbon monoxide measurement.

RESULTS

At the 12-month follow-up, the quit rate was 32.1% (151 participants) in the intervention arm and 7.3% (29 participants) in the control arm. The adjusted OR of continuous abstinence was 7.2 (95% confidence interval: 4.6-11.2). Self-reported adverse events occurred more frequently in the intervention arm (399 events among 196 participants) than in the control arm (230 events among 133 participants, p < 0.01). The most common adverse events were gastrointestinal symptoms, comprising abdominal swelling, gastritis, and constipation.

CONCLUSIONS

The efficacy and safety observed in the Screening and Multiple Intervention on Lung Epidemics RCT indicate that cytisine, a very low-cost medication, is a useful treatment option for smoking cessation and a feasible strategy to improve low-dose computed tomography screening outcomes with a potential benefit for all-cause mortality.