ML-18 is a non-peptide bombesin receptor subtype 3 (BB3) antagonist that inhibits [125I]BA1 binding to NCI-H1299 lung cancer cells transfected with human BB3 receptors (IC50 = 4.8 μM). It is selective for BB3 over the gastrin releasing peptide receptor (GRPR) and the neuromedin B receptor (NMBR) with IC50 values of 16 and >100 μM, respectively, in a radioligand binding assay. ML-18 (16 μM) reversibly inhibits BA1-induced increases in cytosolic calcium in NCI-H1299 cells. It also inhibits BA1-induced phosphorylation of ERK and EGFR and reduces proliferation of NCI-H1299 cells.
