Efficacy of bupropion and varenicline genetic markers in choosing pharmacological treatment for smoking cessation, and implications for combining drugs: A randomized controlled trial - GENTSMOKING.

INTRODUCTION: Smoking cessation is the best strategy for reducing tobacco-related morbimortality. The goal of this randomized controlled trial was to test whether using the genetically favorable markers to choose a smoking cessation drug treatment (precision medicine) was superior to using the most effective drug (varenicline) in terms of abstinence rates. Additionally, combination therapy was tested when monotherapy failed. METHODS: This partially blind, single-center study randomized (1:1) 361 participants into two major groups. In the genetic group (n=184), CYP2B6 rs2279343 (genotype AA) participants started treatment with bupropion, and CHRNA4 rs1044396 (genotype CT or TT) participants started treatment with varenicline; when genetic favorable to both, participants started treatment with bupropion, and when favorable to neither, on both drugs. In the control group (n=177), participants started treatment with varenicline, regardless of genetic markers. Drug treatment lasted 12 weeks. Efficacy endpoints were abstinence rates at Weeks 4, and Weeks 8-12, biochemically validated by carbon monoxide in exhaled air. Participants who did not achieve complete abstinence at Week 4, regardless of group, were given the choice to receive combination therapy. RESULTS: Abstinence rates were 42.9% (95% CI: 36-64) in the control group versus 30.4% (95% CI: 23-37) in the genetic group at Week 4 (p=0.01); and 74% (95% CI: 67-80) versus 52% (95% CI: 49-64) at Week 12 (p<0.001), respectively. The strategy of combining drugs after Week 4 increased abstinence rates in both groups and the significant difference between genetic and control groups was maintained. CONCLUSIONS: Results show that using these selected genetic markers was inferior to starting treatment with varenicline (control group), which is currently the most effective smoking cessation drug; moreover, the addition of bupropion in cases of varenicline monotherapy failure improves the efficacy rate until the end of treatment. CLINICAL TRIAL IDENTIFIER: NCT03362099.

Cue restricted smoking increases quit rates with varenicline.

INTRODUCTION: Varenicline effectively helps smokers quit by reducing withdrawal symptoms and blocking the reward of smoking. However, most quitters return to smoking within one year. 'Cue Restricted Smoking' is a behavioral technique designed to increase quit rates by asking smokers attempting to quit to restrict smoking to the standing position, while alone, in an isolated area facing a wall, with the cigarette as the only stimulus. METHODS: Using retrospective clinic records we compared quit rates in 281 smokers (50% males) instructed in the cue restricted smoking cessation method during 2016-2018 to quit rates in 324 smokers (46% males) advised to completely stop smoking on the target quit date which we previously used during 2011-2014. All were prescribed varenicline for 12 weeks alone, with the addition of bupropion if needed after 4 weeks. Follow-up consisted of behavioral support at 4-6 visits during active drug treatment and telephone counselling at 24 and 52 weeks. The smoking cessation rate was confirmed with exhaled carbon monoxide at the clinic visit at 12 weeks and only by telephone at 52 weeks. RESULTS: The mean age of smokers was 49 years in both groups and the number of cigarettes smoked daily was similar (18/day in the cue restricted vs 19/day in the target quit day group). The smoking cessation rate at 12 weeks was 75% in the cue restricted versus 45% in the target quit day group (relative risk, RR=1.8; 95% CI: 1.4-2.2, p<0.001). At 52 weeks the quit rate was 65% vs 34%, respectively (RR=1.9; 95% CI: 1.5-2.4, p<0.001). CONCLUSIONS: Cue restricted smoking was associated with a substantially increased chance of quitting compared with standard advice during treatment with varenicline. These results should be further studied in a randomized controlled trial.

CHRNA4 rs1044396 is associated with smoking cessation in varenicline therapy.

BACKGROUND: The large individual variability in response to drugs for smoking cessation suggests that specific treatments can be more effective in particular subgroups of smokers. In the context of personalized medicine, the main aim of the present study was to evaluate whether the CHRNA4 and CHRNB2 polymorphisms are associated with response to smoking cessation therapies in patients from a smoker assistance program. METHODS: This cohort study enrolled 483 smoking patients who received behavioral counseling and drug treatment (varenicline, bupropion, and/or nicotine replacement therapy). Smoking cessation success was considered for patients who completed 6 months of continuous abstinence. Fagerström test for nicotine dependence (FTND) and Issa situational smoking scores were analyzed for nicotine dependence. The CHRNA4 (rs1044396 and rs2236196) and CHRNB2 (rs2072660 and rs2072661) polymorphisms were genotyped by high resolution melting analysis. RESULTS: Patients with rs1044396 CC genotype had lower success rate in treatment with varenicline (29.5%) compared with carriers of CT or TT genotypes (50.9%; p = 0.007, n = 167). The CT or TT genotypes were associated with higher odds ratio for success (OR = 1.67, 95% CI = 1.10-2.53, p = 0.02), in a multivariate model. We did not observe significant differences in the FTND and Issa scores according to the studied polymorphisms. CONCLUSION: The CHRNA4 rs1044396 is associated with smoking cessation in individuals on varenicline therapy. We suggest that this polymorphism influences the varenicline response, but replications of this finding are needed.