Candidate genes of interest included the genes identified on Chr15q25 (including the CHRNA5, CHRNA3, and CHRNB4 gene cluster), the remaining nAChR subunit genes, genes encoding the varenicline transporter (SLC22A2) and serotonergic targets hypothesized to be involved in varenicline-induced nausea (HTR3A, HTR3B), as well as cytochrome P450 (CYP) genes involved in nicotine and bupropion metabolism (Box 2). Varenicline is highly selective for the α4β2 nicotinic receptor (Ki=0.17 nM) (Pfizer, 2010), but also shows moderate affinity (Ki=350 nM) for the 5-HT3 receptor and other common nicotinic receptors.
