CPI-169 EZH2 Inhibitor

In KARPAS-422 cells, CPI-169 shows a dose-dependent inhibitory effect on cell viability, and produces synergy anti-proliferative activity when used in combination with ABT-199. In 16 out of 25 NHL cell lines, this compound also suppresses cell growth with GI50 of <5 μM. [1]

Biochemical Assays

Compound potency is also assessed through incorporation of ³H-SAM into a biotinylated H3 peptide. Specifically, PRC2 containing either EZH1 (160 pM), wt EZH2 (40 pM), or Y641N mutant EZH2 (80 pM, both EZH2 prepared in-house) is pre-incubated with 3H-SAM (0.9 µM), 2 µM H3K27me3 activating peptide (H2N-RKQLATKAAR(Kme3)SAPATGGVKKP-amide) and this compound (as 10 point duplicate dose response titrations) for 120 min in a buffer consisting of 50 mM Tris (pH 8.5), 1 mM DTT, 0.07 mM Brij-35, 0.1% BSA, and 0.8% DMSO in a total volume of 12.5 µl in a black 384 well plate. Reaction is initiated with biotinylated H3 substrate peptides (H3K27me1 for wt EZH2, H3K27me2 for Y641N mutant EZH2; H2N-RKQLATKAAR(Kmen)SAPATGGVKKP-NTPEGBiot) as a 2 µM stock in 12.5 µL and allowed to react at room temperature for 5 h. Quenching is accomplished by addition of 20 µl of STOP solution (50 mM Tris (pH 8.5), 200 mM EDTA, 2 mM SAH). 35 µL of the quenched solution is transferred to Streptavidin Flashplates, incubated overnight, washed, and read in a TopCount Reader. For titrations all compound dilutions are in DMSO, final DMSO concentrations are 0.8% (v/v), and turnover is kept to less than < 5%. IC50s are calculated using non-linear least square four parameter fits (GraphPad 6.0).

In mice bearing KARPAS-422 xenografts, CPI-169 (200 mg/kg, s.c.) effectively suppresses H3K27me3 levels and results in lymphoma tumour regression without affecting body weight or causing any overt adverse effects. [1]