Chronic myeloid leukemia (CML), a hematological cancer of bone marrow white blood cells, constitutes about 15% of adult leukemia and usually 1-2 patient is diagnosed with CML per 100,000 people/per year in US. It is characterized by a reciprocal chromosomal translocation between chromosome 9 and 22 of the break point cluster region (BCR) gene with the Abelson (ABL) gene for ABL kinase, which leads to a shortened chromosome 22. The fusion tyrosine kinase BCR-ABL is constitutively active and causes uncontrolled myeloid cell proliferation through downstream mediators such as Stat5 and extracellular signal-regulated kinase (ERK).
Despite of the great clinical success, the Food and Drug Administration (FDA) approved that targeting BCR-ABL kinase for the CML drugs all potently inhibit other targets such as DDR1/2, c-KIT and so on besides ABL kinase. Although the role of off-targets inhibition in the clinical aspect remains unclear, the highly selective BCR-ABL inhibitor is still highly demanded as far as both the preclinical pathological and clinical side effects mechanistic study concerned.
Based on the X-ray structure of ABL kinase, a study team led by LIU Qingsong and LIU Jing from High Magnetic Field Laboratory,Hefei Institutes of Physical Science, Chinese Academy of Sciences (CHMFL) designed a highly potent (ABL1: IC50 of 70 nM) and selective (S score (1) = 0.02) BCR-ABL kinase inhibitor, CHMFL-ABL-053. The CHMFL-ABL-053 did not exhibit apparent inhibitory activity against c-KIT kinase, which is the common target of currently clinically used BCR-ABL inhibitors. CHMFL-ABL-053 almost completely suppressed BCR-ABL kinase autophosphorylation at the Y245 site in K562, KU812 and MEG-01 at the concentration of 300 nM. BCR-ABL kinase downstream mediator Stat5, crk-like protein (CrkL), and ERK phosphorylation was also significantly inhibited in a concentration-dependent manner.
In addition, even in the early 12 hours, CHMFL-ABL-053 could dose-dependently arrest the cell cycle progression in the G0/G1 phase in these cells. Upon 24 or 48 hours of drug treatment, 100 nM concentration of CHMFL-ABL-053 could significantly induce apoptotic cell death. CHMFL-ABL-053 displayed potent antiproliferation efficacy against K562 cells (GI50: 0.014 μM) and P210-BaF3 cells (GI50: 0.007 μM) and exhibited good selectivity over parental BaF3 cells (GI50: > 10 μM). CHMFL-ABL-053 inhibited the proliferation of CML cell lines K562 (GI50 = 14 nM), KU812 (GI50 = 25 nM) and MEG-01 (GI50 = 16 nM), but not other AML cell lines, implying strong and selective on-target effects. Furthermore, CHMFL-ABL-053 did not display any apparent activity against the Chinese hamster lung (CHL) cell line, indicating a good nonspecific toxicity profile.
In the study of PK profiling in rats, compound CHMFL-ABL-053 exhibited good systemic exposure (AUC = 1715.51 ng/mL·h, Cmax = 367.61 ng/mL), favorable oral bioavailability (F = 24.19%), and acceptable half-life (t1/2 = 4.33 h) following oral administration of a single dose of 10 mg/kg. The in vivo antitumor study of CHMFL-ABL-053 was performed in the K562 cell inoculated xenograft mouse model. After 16 days of continuous treatment, compound CHMFL-ABL-053 dose-dependently inhibited the growth of the K562 tumor, and a 50 mg/kg/ day dosage could almost completely suppress tumor progression. As a potential useful drug candidate for CML, CHMFL-ABL-053 is under extensive preclinical safety evaluation now.
The results were published in ACS Journal of Medicinal Chemistry, entitled "Discovery of 2-((3-amino-4-methylphenyl)amino)-N-(2-methyl-5-(3-(trifluoromethyl)benzamido)phenyl)-4-(methylamino)pyrimidine-5-carboxamide (CHMFL-ABL-053) as a potent, selective and orally available BCR-ABL/SRC/p38 kinase inhibitor for Chronic Myeloid Leukemia”.
This research was supported by the Scientific Research Grant of Hefei Science Center of CAS, the grant of “Cross-disciplinary Collaborative Teams Program for Science, Technology and Innovation ” from Chinese Academy of Sciences, Anhui Province Natural Science Foundation Annual Key Program, China “Thousand Talent Program” , “Hundred Talent Program” of the Chinese Academy of Sciences and the National Natural Science Foundation of China.
CHMFL-ABL-053 anti-tumor efficacy in K562 xenograft model.(image by LIANG Xiaofei and ZOU Fengming)
LIU Qingsong, PhD
High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences
350 Shushanhu Road, Hefei, Anhui, P. R. China, 230031