In Vitro

Kinase Assay: A PI3K Alphascreen assay is used to measure the activity of a panel of four phosphoinositide 3-kinases: PI3Kα, PI3Kβ, PI3Kγ, and PI3Kδ. Enzyme reaction buffer is prepared using sterile water and 50 mM Tris-HCl, pH 7, 14 mM MgCl2, 2 mM sodium cholate, and 100 mM NaCl. 2 mM DTT is added fresh on the day of the experiment. The Alphascreen buffer is made using sterile water and 10 mM Tris-HCl, pH 7.5, 150 mM NaCl, 0.10% Tween 20, and 30 mM EDTA. Then 1 mM DTT is added fresh on the day of the experiment. Compound source plates used for this assay are 384-well Greiner clear polypropylene plates containing test compounds at 5 mM and diluted 1:2 over 22 concentrations. Columns 23 and 24 contained only DMSO, as these wells comprised the positive and negative controls, respectively. Source plates are replicated by transferring 0.5 μL per well into 384-well Optiplates. Each PI3K isoform is diluted in enzyme reaction buffer to 2× working stocks. PI3Kα is diluted to 1.6 nM, PI3Kβ is diluted to 0.8 nM, PI3Kγ is diluted to 15 nM, and PI3Kδ is diluted to 1.6 nM. PI(4,5)P2 is diluted to 10 μM, and ATP was diluted to 20 μM. This 2× stock is used in the assays for PI3Kα and PI3Kβ. For assay of PI3Kγ and PI3Kδ, PI(4,5)P2 is diluted to 10 μM and ATP was diluted to 8 μM to prepare a similar 2× working stock. Alphascreen reaction solutions are made using beads from the anti-GST Alphascreen kit. Two 4× working stocks of the Alphascreen reagents are made in Alphascreen reaction buffer. In one stock, biotinylated-IP4 is diluted to 40 nM and streptavadin-donor beads are diluted to 80 μg/mL. In the second stock, PIP3-binding protein is diluted to 40 nM and anti-GST-acceptor beads were diluted to 80 μg/mL. As a negative control, a reference inhibitor at a concentration >>Ki (40 μM) is included in column 24 as a negative (100% inhibition) control. Using a 384-well Multidrop, 10 μL/well of 2× enzyme stock is added to columns 1–24 of the assay plates for each isoform. An amount of 10 μL/well of the appropriate substrate 2× stock (containing 20 μM ATP for the PI3Kα and -β assays and containing 8 μM ATP for the PI3Kγ and -δ assays) is then added to columns 1–24 of all plates. Plates are then incubated at room temperature for 20 min. In the dark, 10 μL/well of the donor bead solution is added to columns 1–24 of the plates to quench the enzyme reaction. The plates are incubated at room temperature for 30 min. Still in the dark, 10 μL/well of the acceptor bead solution is added to columns 1–24 of the plates. The plates are then incubated in the dark for 1.5 h. The plates are read on an Envision multimode plate reader using a 680 nm excitation filter and a 520–620 nm emission filter.

Cell Assay: B cells are purified from human peripheral blood mononuclear cells (PBMCs) by negative selection. Approximately 3 × 104 purified B cells per well are seeded into a 96-well plate. Compounds are dissolved in DMSO at a concentration of 10 mM, and a 10-point, 3-fold serial dilution of the compound is carried out in DMSO. Then 0.5 μL of compound is added to each well in duplicates so that the final DMSO concentration is 0.25% and the highest compound concentration is 10 μM. After preincubating for 30 min, B cells are treated with 2 μg/mL of anti-human IgM antibody plus 300 ng/mL human CD40L or 5 ng/mL human IL-4 plus 200 ng/mL of CD40L as a counterscreen to evaluate the off-target effects. The plates are incubated at 37 °C and 5%CO2 for 72 h, then pulsed with 0.5 μCi per well 3H thymidine for 18 h, and B cells are collected to count the incorporation of 3H thymidine.

AMG319 inhibits anti-IgM/CD40L-induced B cell proliferation with IC50 of 8.6 nM and reduces pAkt level with IC50 of 1.5 nM. AMG319 also inhibits anti-IgD-induce CD-69 expression in HWB.

In Vivo

In female Lewis rats, AMG319 (3 mg/kg, p.o.) inhibits the KLH-induced inflammatory response by 88%. In the transgenic (IgMm) mice, AMG319 (, p.o.) inhibits in vivo pAKT with IC50 of 1.9 nM.

Animal model

Female Lewis rats

Formulation & Dosage

Dissolved in 2% HPMC, 1% Pluronic F68, 10% Captisol, pH 2.0; 3 mg/kg; oral administration

References

[1] Cushing TD, et al. J Med Chem. 2015, 58(1), 480-511..