Bafetinib (INNO-406)

Bafetinib is a potent and selective dual inhibitor of Bcr-Abl/Lyn tyrosine kinase with IC50 values of 5.8nM and 19nM, respectively [1].

Bafetinib is a specific dual Abl-Lyn inhibitor. For 79 other tyrosine kinases, 0.1μM bafetinib can inhibit 4 of these enzymes including Abl, Abl-related gene, Fyn and Lyn. Bafetinib can block the autophosphorylation of Bcr-Abl. In K562 and 293T cells transfected with wt Bcr-Abl, bafetinib shows inhibition with IC50 values of 11nM and 22nM, respectively. In the in vitro kinase assays, bafetinib shows inhibition of a variety of Abl kinase mutants such as M244V, G250E, Y253F and F317L. It has no effect on T315I in vitro. Bafetinib also suppresses the growth of Bcr-Abl–positive leukemic cell lines including K562, KU812 and BaF3/wt. The BaF3/E255K cells are also sensitive towards bafetinib. Moreover, bafetinib is highly potent to inhibit tumor growth in murine tumor models [1].

References:
[1] Kimura S, Naito H, Segawa H, et al. NS-187, a potent and selective dual Bcr-Abl/Lyn tyrosine kinase inhibitor, is a novel agent for imatinib-resistant leukemia. Blood, 2005, 106(12): 3948-3954.

KIT polymorphisms and mutations determine responses of neoplastic mast cells to bafetinib (INNO-406).[Pubmed:20685234]

Exp Hematol. 2010 Sep;38(9):782-91.

OBJECTIVE: Advanced systemic mastocytosis (SM) is characterized by uncontrolled growth of neoplastic mast cells (MC) and drug resistance. The tyrosine kinase receptor KIT is often mutated and activated and thus contributes to malignant growth of MC. Therefore, KIT-targeting drugs are currently tested for their ability to block growth of malignant MC. MATERIALS AND METHODS: We determined the effects of the multikinase inhibitor INNO-406 (bafetinib) on primary neoplastic MC, the canine mastocytoma cell line C2, the human MC leukemia cell line HMC-1.1 bearing the KIT mutant V560G, and HMC-1.2 cells harboring KIT V560G and KIT D816V. RESULTS: INNO-406 was found to inhibit proliferation in HMC-1.1 cells (IC(50): 30-40 nM), but not in HMC-1.2 cells or primary neoplastic cells in patients with KIT D816V-positive SM. In canines, growth-inhibitory effects of INNO-406 were seen in C2 cells (IC(50): 50-100 nM) exhibiting a KIT exon 11 internal tandem-duplication and in primary neoplastic MC harboring wild-type exon 11, whereas no effects were seen in MC exhibiting a polymorphism at amino acid 581 in exon 11. INNO-406 was found to block KIT phosphorylation and expression in HMC-1.1 cells and C2 cells, but not in HMC-1.2 cells, whereas Lyn-phosphorylation was blocked by INNO-406 in all types of MC. CONCLUSIONS: In neoplastic MC, the major target of INNO-406 appears to be KIT. Drug responses may depend on the presence and type of KIT mutation. In human MC, the KIT D816V mutant introduces resistance, and in canine mastocytomas, an exon 11 polymorphism may be indicative of resistance against INNO-406.

Bafetinib (INNO-406) reverses multidrug resistance by inhibiting the efflux function of ABCB1 and ABCG2 transporters.[Pubmed:27157787]

Sci Rep. 2016 May 9;6:25694.

ATP-Binding Cassette transporters are involved in the efflux of xenobiotic compounds and are responsible for decreasing drug accumulation in multidrug resistant (MDR) cells. Discovered by structure-based virtual screening algorithms, bafetinib, a Bcr-Abl/Lyn tyrosine kinase inhibitor, was found to have inhibitory effects on both ABCB1- and ABCG2-mediated MDR in this in-vitro investigation. Bafetinib significantly sensitized ABCB1 and ABCG2 overexpressing MDR cells to their anticancer substrates and increased the intracellular accumulation of anticancer drugs, particularly doxorubicin and [(3)H]-paclitaxel in ABCB1 overexpressing cells; mitoxantrone and [(3)H]-mitoxantrone in ABCG2 overexpressing cells, respectively. Bafetinib stimulated ABCB1 ATPase activities while inhibited ABCG2 ATPase activities. There were no significant changes in the expression level or the subcellular distribution of ABCB1 and ABCG2 in the cells exposed to 3 muM of bafetinib. Overall, our study indicated that bafetinib reversed ABCB1- and ABCG2-mediated MDR by blocking the drug efflux function of these transporters. These findings might be useful in developing combination therapy for MDR cancer treatment.