In vitro activity: CX-6258 shows antiproliferative activity against a panel of human cancer cell lines with IC50 of 0.02-3.7 μM, mostly sensitive to acute leukemia cell lines. Combinations of CX-6258 with doxorubicin (10:1 molar ratio) and CX-6258 with paclitaxel (100:1 molar ratio) produces synergistic cell killing with combination index (CI50) values equal to 0.4 and 0.56, respectively. CX-6258 causes dose dependent inhibition of the phosphorylation of two pro-survival proteins, Bad and 4E-BP1, at the Pim kinase specific sites S112 and S65 and T37/46, respectively.

Kinase Assay: Pim-1 and Pim-2 inhibitions are measured in radiometric assays using human recombinant Pim-1 at [ATP] = 30 μM (substrate RSRHSSYPAGT) and human recombinant Pim-2 at [ATP] = 5 μM (substrate RSRHSSYPAGT). The radiometric assay for Pim-3 uses RSRHSSYPAGT as a substrate in the presence of [ATP] = 155 μM.

Cell Assay: CX-6258 showed robust antiproliferative potencies against all cell lines tested derived from human solid tumors and hematological malignancies. In mechanistic cellular assays with MV-4-11 human AML cells, (13) caused dose-dependent inhibition of the phosphorylation of 2 pro-survival proteins, Bad and 4E-BP1, at the Pim kinase specific sites S112 and S65 and T37/46, respectively[1]. Pim-1 inhibition using the small molecule inhibitor CX-6258 (12 mM, 3 h) diminishes endogenous NKX3.1 steady state levels in 22RV1 and LNCaP cells. CX-6258 treatment (12 mM, 3 h) treatment diminished steady-state levels of ectopic NKX3.1 in PC3 cells. CX-6258 treatment resulted in a significant reduction in NKX3.1 half-life. While ectopically expressed NKX3.1 in control cells had a half-life of _90 min, Pim-1 inhibition reduced the half-life to _52 min

ACS Med. Chem. Lett., 2012, 3 (2), pp 135–139.