Bafetinib

Bafetinib blocks WT Bcr-Abl autophosphorylation and its downstream kinase activity with IC50 of 11 nM and 22 nM in K562 and 293T cells, respectively. Bafetinib suppresses the growth of the Bcr-Abl-positive cell lines including K562, KU812, and BaF3/wt cells potently without effects on the proliferation of the Bcr-Abl-negative U937 cell line. Moreover, Bafetinib exhibits a dose-dependent antiproliferative effect against Bcr-Abl point mutant cell lines, such as BaF3/E255K cells. ^[1] In Bcr-Abl+ leukemia cell lines, Bafetinib induces both caspase-mediated and caspase-independent cell death by blocking the phosphorylation of Bcr-Abl. ^[2]

In Bcr-Abl–positive KU812 mouse model, Bafetinib (0.2 mg/kg/day) significantly inhibits tumor growth, and completely inhibits tumor growth without adverse effects at 20 mg/kg/day. For Balb/c mice, Bafetinib shows maximal tolerated dose of 200 mg/kg/d and bioavailability value (BA) of 32%. ^[1] In a Central nervous system (CNS) leukemia model bearing Ba/F3/wt bcr-ablGFP, Ba/F3/Q252H, or Ba/F3/M351T cells, combination treatment of Bafetinib (60 mg/kg) and cyclosporine A (CsA) (50 mg/kg) leads to more significant inhibition of leukemia growth in the brain than either Bafetinib or CsA alone. ^[3]

• Kinase assay

  Bcr-Abl kinase assays are performed in 25 μL of reaction mixture containing 250 μM peptide substrate, 740 Bq/μL [γ-³³P]ATP, and 20 μM cold adenosine triphosphate (ATP) by using the SignaTECT protein tyrosine kinase assay system. Each Bcr-Abl kinase is used at a concentration of 10 nM. Kinase assays for Abl, Src, and Lyn are carried out with an enzyme-linked immunosorbent assay (ELISA) kit. The inhibitory effects of NS-187 against 79 tyrosine kinases are tested with KinaseProfiler.

• Cell lines

  K562, BaF3/wt, BaF3/E255K, and BaF3/T315I cells

• Concentrations

  0-10 μM

• Incubation Time

  72 hours

• Method

  K562, BaF3/wt, BaF3/E255K, and BaF3/T315I cells are plated at 1 × 10³ in 96-well plates, whereas KU812 and U937 cells are plated at 5 × 10³ in 96-well plates. Cells are incubated with serial dilutions of Bafetinib for 3 days. Cell proliferation is measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Nacalai Tesque) assay, and the 50% inhibitory concentration (IC50) values are calculated by fitting the data to a logistic curve.

• Animal Models

  KU812 xenograft is established by subcutaneous injection of KU812 cells into the right flank of Balb/c-nu/nu female mice.

• Dosages

  ≤20 mg/kg/day

• Administration

  Administered via p.o.