A Double-Blind, Placebo-Controlled, Parallel Group Design Trial of the Selective D3 Antagonist, GSK598809, Added to CBT and NRT for Smoking Cessation and Prevention of Very Early Relapse to Smoking

We propose to conduct a first test of the effect of the dopamine D3 receptor antagonist, GSK598809, on smoking behavior when treatment is started immediately following the quit date. To do this, we propose to conduct a 10-week, double-blind, placebo-controlled, proof of mechanism study in 90 adult smokers. Participants will complete baseline evaluations. They will receive manualized cognitive behavioral therapy, beginning prior to the quit date, and will set a quit date for the day before their week 2 study visit. They will be given short acting NRT (gum or lozenge) to use on their quit date. They will be asked to arrive for the week 2 visit with 18-24 hours abstinence and an expired air CO ≤ 10ppm. Those who do so will be randomly assigned to receive double blind GSK598809 or identical placebo for six weeks. Participants will begin double blind GSK598809 or placebo, both in conjunction with prn NRT up to 8 mg per day for two weeks. Participants will then continue double blind GSK598809 or placebo in the absence of NRT for 4 more weeks. At the end of this period (week 8 of the study), participants will then be followed 2 weeks after discontinuation of double blind treatment to complete the 10 weeks of the study.