XL388

Kinase experiment:

The measurement of mTOR enzyme activity is performed in an ELISA format following the phosphorylation of 4E-BP1 protein. All experiments are performed in the 384-well format. Generally, 0.5 μL of DMSO containing varying concentrations of the test compound is mixed with 15 μL of the enzyme solution. Kinase reactions are initiated with the addition of 15 μL of a solution containing the substrate. The assay conditions are as follows: 0.2 nM mTOR, 10 μM ATP, and 50 nM NHis-tagged 4E-BP1 in 20 mM Hepes, pH 7.2, 1 mM DTT, 50 mM NaCl, 10 mM MnCl2, 0.02 mg/mL BSA, 0.01% CHAPS, 50 mM β-glycerophophate. Following an incubation of 120 min at ambient temperature, 20 μL of the reaction mixture is transferred to a Ni-chelate-coated 384-well plate. The binding step of the 4E-BP1 protein proceeded for 60 min, followed by washing four times each with 50 μL of Tris-buffered saline solution (TBS). Anti-phospho-4E-BP1 rabbit immunoglobulin G (IgG; 20 μL, 1:5000) in 5% BSA-TBST (0.2% Tween-20 in TBS) is added, and the reaction mixuture is further incubated for 60 min. Incubation with a secondary horseradish peroxidase (HRP)-tagged anti-IgG is similarly performed after the primary antibody is washed off (four washes of 50 μL). Following the final wash step with TBST, 20 μL of SuperSignal ELISA Femto is added and the luminescence measured using an EnVision plate reader. Data are reported as the mean (n≥2) [1].

Cell experiment:

U2OS, SaOs-2 and MG-63 OS cell lines as well as the murine calvaria-derived osteoblastic MC3T3-E1 cells are maintained and culture. The OB-6 human osteoblastic cells are cultured. For primary culture of murine osteoblasts, the trimmed calvariae of neonatal mice are digested with 0.1% collagenase I and 0.25% dispase. The resolving cell suspensions are neutralized with complete culture medium and are filtered. The calvarial osteoblasts are then resuspended in 10 mL α-MEM containing 15% FBS, and are cultured. Cells (5×104/well) are suspended in 1 mL of DMEM with 1% agar, 10 % FBS and with indicated XL388 (5, 25, 100 and 200nM) treatment. The cell suspension is then added on top of a pre-solidified 1% agar in a 100 mm culture dish. The drug containing medium is refreshed every 2 days. After 10-day incubation, the number of remaining colonies are stained and manually counted[2].

Animal experiment:

Mice, Rats, Dogs and Monkeys[1]Pharmacokinetic studies of XL388 are determined in female athymic nude mice, female CD rats, male beagle dogs, and male cynomolgus monkeys. XL388 is administered intravenously and by oral gavage at 10 mg/kg as a solution formulated in EPW (5% ethanol/45% PEG400/water+1:2 HCl (m/m)) to mice, 3 mg/kg as a solution formulated in EPW (5% ethanol/45% PEG400/water+1:2 HCl (m/m)) to CD rats and male beagle dogs, and 3 mg/kg as a solution formulated in EPW (5% ethanol/45% PEG400/water+1:1.5 HCl (m/m)) to male cynomolgus monkeys. The plasma levels of XL388 are monitored over a 24 h period.

References:

[1]. Takeuchi CS, et al. Discovery of a novel class of highly potent, selective, ATP-competitive, and orally bioavailable inhibitors of the mammalian target of rapamycin (mTOR). J Med Chem. 2013 Mar 28;56(6):2218-34.
[2]. Zhu YR, et al. The anti-cancer activity of the mTORC1/2 dual inhibitor XL388 in preclinical osteosarcoma models. Oncotarget. 2016 Aug 2;7(31):49527-49538.