AT7519

Kinase assays for CDK1, CDK2 and GSK3-β are all carried out in a radiometric filter binding format. Assays for CDK5 are in DELFIA format and for CDKs 4 and 6 in ELISA format. For CDKs 1 and 2, the relevant CDK and 0.12 μg/mL Histone H1 are incubated in 20 mM MOPS, pH 7.2, 25 mM β-glycerophosphate, 5 mM EDTA, 15 mM MgCl₂, 1 mM sodium orthovanadate, 1 mM DTT, 0.1 mg/mL BSA, 45 μM ATP (0.78 Ci/mmol) and different concentrations of AT7519 for 2 or 4 hours respectively. For GSK3-β, the relevant enzyme and 5 μM glycogen synthase peptide 2 along with 10 mM MOPS pH 7.0, 0.1 mg/mL BSA, 0.001% Brij-35, 0.5% glycerol, 0.2 mM EDTA, 10 mM MgCl₂, 0.01% β-mercaptoethanol, 15 μM ATP (2.31 Ci/mmol) and different concentrations of AT7519 are incubated for 3 hours. Assay reactions are stopped by adding an excess of orthophosphoric acid and filtered using Millipore MAPH filter plates. The plates are then washed, scintillant added and radioactivity measured by scintillation counting on a Packard TopCount. For CDK5, CDK5/p35 and 1μM of a biotinylated Histone H1 peptide (Biotin-PKTPKKAKKL) are incubated in 25 mM Tris-HCl, pH 7.5, 2.5 mM MgCl₂, 0.025% Brij-35, 0.1 mg/mL BSA, 1 mM DTT, 15 μM ATP and different concentrations of AT7519 for 30 minutes. Assay reactions are stopped using EDTA, transferred to Neutravidin-coated plates and phosphorylated peptide quantified by means of a rabbit phospho-cdk1 substrate polyclonal antibody and DELFIA europium-labelled anti-rabbit IgG secondary antibody using time-resolved fluorescence at λ_ex=335nm, λ_em=620nm. For CDK 4 and 6 assays, plates are coated with GST- pRb769-921 and blocked with Superblock. CDK4 or 6 is incubated with 15 mM MgCl₂, 50 mM HEPES, pH 7.4, 1 mM DTT, 1 mM EGTA, pH 8.0, 0.02% Triton X-100, 2.5% DMSO and different concentrations of AT7519; the reaction is initiated by addition of ATP. After 30 minutes, reactions are stopped by the addition of 0.5 M EDTA pH 8.0. Plates are then washed and incubated for one hour with the primary antibody (anti- p-Rb Serine 780) diluted in Superblock followed by secondary antibody (alkaline phosphatase linked anti-rabbit) for a further hour. Plates are developed using the Attophos system and fluorescence read on a Spectramax Gemini plate reader at excitation 450 nm and emission 580 nm. In all cases, IC50 values are calculated from replicate curves, using GraphPad Prism software.

MM.1S, MM.1R, RPMI8226, U266, RPMI8266, RPMI-Dox40, OPM1 cells, primary MM cells and PBMNCs

Dissolved in DMSO at a concentration of 10 mM, final concentrations 0.25-4 μM

24 or 48 hours

Cells are incubated with different concentrations of AT7519 for 24 or 48 hours at 37 °C. Cell viability is assessed by measuring 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrasodium bromide (MTT) dye absorbance. DNA synthesis is measured by tritiated thymidine uptake (³H-TdR). Apoptosis is assessed by using Annexin V/PI staining. The percentage of cells undergoing apoptosis is defined as the sum of early apoptosis (Annexin V-positive cells) and late apoptosis (Annexin V-positive and PI-positive cells

Male SCID mice inoculated subcutaneously with MM.1S cells

15 mg/kg/day

Dosed i.p.