| Target | IC50: p110δ:12.7 nM; p110γ:1389 nM; p110β:3377 nM; p110α:5441 nM; hVps34:12682 nM; DNA-PK:18749 nM |
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| In Vitro | Acalisib (GS-9820) is more selective for PI3Kδ (IC50=12.7 nM) relative to other PI3K class I enzymes (IC50: PI3Kα, 5,441 nM; PI3Kβ, 3,377 nM; PI3Kγ, 1,389 nM). Acalisib is also 103-fold more selective against PI3Kδ than against related kinases, such as PI3KCIIβ (IC50>10 nM), hVPS34 (IC50=12.7 μM), DNA-PK (IC50=18.7 μM), and mTOR (IC50>10 nM). In fibroblasts, the PDGF receptor signals through PI3Kα and the GPCR for lysophosphatidic acid (LPA) signals through PI3Kβ. Acalisib reduces PDGF-induced pAkt by only 50% at 11,585 nM, and LPA-induced pAkt by 50% at 2,069 nM. |
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| In Vivo | To dissect the relative contribution of PI3Kα and PI3Kδ inhibition in the reduction of obesity, obese hyperphagic ob/ob mice are treated with a selective PI3Kα inhibitor, BYL-719, or with a selective PI3Kδ inhibitor, Acalisib (GS-9820). Remarkably, BYL-719 reduces body weight after 15 days of treatment to a similar extent as CNIO-PI3Ki, whereas Acalisib has no significant effect at the same doses as BYL-719. It should be noted that 10 mg/kg of Acalisib is sufficient to reduce the growth of multiple myeloma xenografts in mice[2]. |
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| Kinase Assay | Biochemical in vitro lipid kinase assays are performed. A stock solution of Acalisib (GS-9820) is prepared in DMSO at a concentration of 10 mM. Ten-point kinase inhibitory activities are measured over a concentration range (5 to 104 nM) with ATP at a concentration consistent with the Km of each of the enzymes[1]. |
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| Cell Assay | The effect of inhibitors on RAW264.7 cell survival is evaluated using the MTT assay. RAW264.7 cells are seeded in Falcon flat bottom 96-well plates at a density of 2.5-3×104 cells/cm2 in 100 μL of DMEM with 10% FBS and 1% antibiotic solution. After seeding, the cells are allowed to attach for 24 h then exposed to control or Acalisib (GS-9820) (100 pM to 10 μM) for 24 h. After incubation at 37°C in 5% CO2, MTT substrate is added at a final concentration of 0.5 mg/mL for 4 h. Following a 4-h incubation, 100 μL of solubilization solution is added to each well to dissolve the formazan crystals and samples are analyzed after 24 h. Absorbance of the samples is assessed using a plate reader using a wavelength of 550 nm and a reference wavelength of 700 nm[1]. |
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| Animal Exp | Mice[2] Ob/ob C57BL6J mice and Wild-type C57BL6J/Ola.Hsd mice are housed under specific pathogen free (SPF) conditions, at 22°C, and with 12 hours dark/light cycles (light cycle from 8 am to 8 pm). All mice used are males of 20 weeks of age. Mice are fed with standard chow diet (18% of fat-based caloric content). PI3K inhibitors are administered daily by oral gavage during 15 or 16 days as follows, BYL-719 (5 and 10 mg/kg) and Acalisib (5 and 10 mg/kg), CNIO-PI3Ki (1 and 5 mg/kg), dissolved in PEG-300 and 10% N-methyl-2-pyrrolidone. |
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| References | [1]. Effects of isoform-selective phosphatidylinositol 3-kinase inhibitors on osteoclasts: actions on cytoskeletal organization, survival, and resorption. J Biol Chem. 2013 Dec 6;288(49):35346-57. [2]. PI3Kα inhibition reduces obesity in mice. Aging (Albany NY). 2016 Nov 4;8(11):2747-2753 |
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