MG624 is an antagonist of neuronal nicotinic acetylcholine receptors (nAChRs; K = 0.055 µM in neuronal chick optic lobe membranes). It is selective for neuronal nAChRs over muscle-type AChRs (K = 70 µM in TE671 cells that express muscle-type AChRs). MG624 inhibits currents evoked by acetylcholine in Xenopus oocytes expressing chick α7 subunit-containing nAChRs (IC = 94 nM). It is selective for α7 subunit-containing nAChRs over α6, β2, and β4 subunit-containing nAChRs (Ks = 4.52, 12, and 9.2 µM, respectively). It selectively decreases vagus nerve stimulation-induced contractions of isolated guinea pig vagus nerve-stomach preparations (EC = 49.4 µM) over isolated rat phrenic nerve-hemidiaphragm preparations (EC = 486 µM). MG624 decreases protein levels of early growth response gene 1 (Egr-1) induced by nicotine in human microvascular endothelial cells of the lung (HMEC-Ls). It also decreases proliferation of HMEC-Ls and inhibits angiogenesis in vitro and ex vivo as well as in an H69 small cell lung cancer (SCLC) mouse xenograft model concomitant with a reduction in tumor growth when administered in the diet at a dose of approximately 10 mg/kg per day.