Varenicline versus bupropion SR or placebo for smoking cessation: A pooled analysis
ABSTRACT To evaluate varenicline's efficacy for smoking cessation versus bupropion SR and placebo and to explore whether factors typically predictive of abstinence influence varenicline's efficacy versus placebo, as measured by the week 9-12 continuous abstinence rate (CAR9-12).
Smokers in 2 randomized, placebo-controlled trials received varenicline 1 mg BID (n=696), bupropion SR 150 mg BID (n=671), or placebo (n=685) for 12 weeks. Nontreatment followup lasted 40 weeks.
CAR(9-12) was greater for varenicline (44.0%) versus bupropion SR (29.7%; P<0.0001) and placebo (17.7%; P<0.0001). CAR(9-12) for varenicline versus placebo was not affected by age, gender, or nicotine dependence level.
Varenicline was more efficacious than bupropion SR or placebo. Varenicline's efficacy versus placebo was not influenced by factors predictive of abstinence.
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- "While many adult smokers wish to quit, approximately 95% who attempt to do so without assistance will relapse within a year . Even with the use of pharmacological treatments, such as nicotine replacement (e.g., gums, patches), or prescription drugs with agonist/ antagonist activity at the receptor level (e.g., varenicline, bupropion), only 10–25% of treated subjects will remain abstinent at the end of one year   . Anti-nicotine vaccines potentially offer a novel mechanism of action for smoking cessation. "
ABSTRACT: Anti-nicotine vaccines aim to prevent nicotine entering the brain, and thus reduce or eliminate the reward that drives nicotine addiction. Those tested in humans to date have failed to improve quit rates over placebo, possibly because antibody (Ab) responses were insufficient to sequester enough nicotine in the blood in the majority of subjects. We have previously shown in mice that the carrier, hapten and linker used in the nicotine conjugate antigen each influence the function (nicotine-binding capacity) of the Ab induced. Herein we have evaluated immunogenicity in mice of 27 lots of NIC7-CRM, a conjugate of 5-aminoethoxy-nicotine (Hapten 7) and a mutant nontoxic form of diphtheria toxin (CRM197), that differed in three antigen attributes, namely hapten load (number of haptens conjugated to each molecule of CRM197), degree of conjugate aggregation and presence of adducts (small molecules attached to CRM197 via a covalent bond during the conjugation process). A range of functional responses (reduced nicotine in the brain of immunized animals relative to non-immunized controls) were obtained with the different conjugates, which were adjuvanted with aluminum hydroxide and CpG TLR9 agonist. Trends for better functional responses in mice were obtained with conjugates having a hapten load of 11 to 18, a low level of high molecular mass species (HMMS) (i.e., not aggregated) and a low level of adducts and a more limited testing in cynomolgus monkeys confirmed these results. Thus hapten load, conjugate aggregation and presence of adducts are key antigen attributes that can influence Ab function induced by NIC7-CRM. Copyright © 2015. Published by Elsevier B.V.International Immunopharmacology 02/2015; 25(2). DOI:10.1016/j.intimp.2015.02.030 · 2.47 Impact Factor
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- "The addictive properties of nicotine (the active alkaloid involved in smoking addiction) as well as the activity of varenicline (Chantix®, Champix®) for smoking cessation therapy  are primarily mediated by their interactions with nicotinic acetylcholine receptors (nAChRs). "
ABSTRACT: To determine the structural components underlying differences in affinity, potency, and selectivity of varenicline for several human (h) nicotinic acetylcholine receptors (nAChRs), functional and structural experiments were performed. The Ca(2+) influx results established that: (a) varenicline activates (μM range) nAChR subtypes with the following rank sequence: hα7>hα4β4>hα4β2>hα3β4≫>hα1β1γδ; (b) varenicline binds to nAChR subtypes with the following affinity order (nM range): hα4β2~hα4β4>hα3β4>hα7≫>Torpedo α1β1γδ. The molecular docking results indicating that more hydrogen bond interactions are apparent for α4-containing nAChRs in comparison to other nAChRs may explain the observed higher affinity; and that (c) varenicline is a full agonist at hα7 (101%) and hα4β4 (93%), and a partial agonist at hα4β2 (20%) and hα3β4 (45%), relative to (±)-epibatidine. The allosteric sites found at the extracellular domain (EXD) of hα3β4 and hα4β2 nAChRs could explain the partial agonistic activity of varenicline on these nAChR subtypes. Molecular dynamics simulations show that the interaction of varenicline to each allosteric site decreases the capping of Loop C at the hα4β2 nAChR, suggesting that these allosteric interactions limit the initial step in the gating process. In conclusion, we propose that in addition to hα4β2 nAChRs, hα4β4 nAChRs can be considered as potential targets for the clinical activity of varenicline, and that the allosteric interactions at the hα3β4- and hα4β2-EXDs are alternative mechanisms underlying partial agonism at these nAChRs. Copyright © 2014 Elsevier B.V. All rights reserved.Biochimica et Biophysica Acta (BBA) - Biomembranes 12/2014; 1848(2). DOI:10.1016/j.bbamem.2014.11.003 · 3.84 Impact Factor
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- "Current pharmacotherapies typically either replace the source of nicotine (nicotine replacement therapy such as gums, patches, etc.) or act on sites in the central nervous systems to reduce nicotine reward and/or withdrawal symptoms. Treatment periods are relatively brief (typically up to 12 weeks) and relapse is prevalent, especially after treatment ends, such that long-term outcomes remain poor, with only 12–22% of treated subjects remaining abstinent at the end of one year  . "
ABSTRACT: Tobacco smoking is one of the most preventable causes of morbidity and mortality, but current smoking cessation treatments have relatively poor long term efficacy. Anti-nicotine vaccines offer a novel mechanism of action whereby anti-nicotine antibodies (Ab) in circulation prevent nicotine from entering the brain, thus avoiding the reward mechanisms that underpin nicotine addiction. Since antibody responses are typically long lasting, such vaccines could potentially lead to better long-term smoking cessation outcomes. Clinical trials of anti-nicotine vaccines to date have not succeeded, although there was evidence that very high anti-nicotine Ab titers could lead to improved smoking cessation outcomes, suggesting that achieving higher titers in more subjects might result in better efficacy overall. In this study, we evaluated CpG (TLR9 agonist) and aluminum hydroxide (Al(OH)3) adjuvants with a model anti-nicotine antigen comprising trans-3'aminomethylnicotine (3'AmNic) conjugated to diphtheria toxoid (DT). Anti-nicotine Ab titers were significantly higher in both mice and non-human primates (NHP) when 3'AmNic-DT was administered with CpG/Al(OH)3 than with Al(OH)3 alone, and affinity was enhanced in mice. CpG also improved functional responses, as measured by nicotine brain levels in mice after intravenous administration of radiolabeled nicotine (30% versus 3% without CpG), or by nicotine binding capacity of NHP antisera (15-fold higher with CpG). Further improvement should focus on maximizing Ab function, which takes into account both titer and avidity, and this may require improved conjugate design in addition to adjuvants.International immunopharmacology 04/2013; 16(1). DOI:10.1016/j.intimp.2013.03.021 · 2.47 Impact Factor