Neratinib

Neratinib weakly inhibits tyrosine kinases KDR and Src with IC50 of 0.8 μM and 1.4 μM, respectively, being 14- and 24-fold less active compared with HER2. Neratinib displays no activity against other serine-threonine kinases such as Akt, cyclin D1/cdk4, cyclin E/cdk2, cyclin B1/cdk1, IKK-2, MK-2, PDK1, c-Raf, and Tpl-2, as well as the tyrosine kinase c-Met. Neratinib selectively inhibits the proliferation of 3T3 cells transfected with the HER2 (3T3/neu), as well as two other HER-2-overexpressing SK-Br-3 and BT474 cells with IC50 values of 2-3 nM, displaying >230-fold potency compared with non-transfected 3T3 cells as well as MDA-MB-435 and SW620 which are EGFR- and HER2-negative. Neratinib also inhibits the proliferation of EGFR-dependent A431 cells with an IC50 of 81 nM. Neratinib reduces HER2 receptor autophosphorylation in BT474 cells with an IC50 of 5 nM, and EGF-dependent phosphorylation of EGFR in A431 cells with IC50 of 3 nM. Blocking of HER-2 by Neratinib results in inhibition of downstream MAPK and Akt pathways with IC50 of 2 nM, more potently than Trastuzumab. Neratinib inhibits the cyclin D1 expression and the phosphorylation of the Rb-susceptibility gene production in BT474 cells with IC50 of 9 nM, leading to G1-S arrest and ultimately decreased cell proliferation. ^[1]