Varenicline-¹⁵N,¹³C,d₂ is ¹⁵N and deuterated labeled Varenicline (HY-10019). Varenicline (CP 526555) is an orally active partial agonist of α4β2 nicotinic acetylcholine receptor (α4β2 nAChR, IC₅₀=250 nM), which is the principal mediator of nicotine dependence. Varenicline is also a partial agonist of α6β2 nAChR and a full agonist of α6β2 nAChR. Varenicline blocks the direct agonist effects of nicotine on nAChR while stimulates nAChR in a more moderate way, being widely used as an aid of smoking cessation^{[1][2][3][4][5]}.