Molecule

Description

Cancer

Description

PP242 is a selective mTOR inhibitor with IC50 of 8 nM.

Targets

IC₅₀

In Vitro

PP242 exhibits potent selectivity for mTOR over other PI3K family kinases such as p110α, p110β, p110γ, p110δ, and DNA-PK with IC50 of 1.96 μM, 2.2 μM, 1.27 μM, 0.102 μM, and 0.408 μM, respectively. PP242 displays some inhibitory activity against Ret, PKCα, PKCβ, and JAK2, while exhibits remarkable selectivity against 215 other protein kinases. Unlike rapamycin, PP242 inhibits both mTORC1 and mTORC2. In BT549 cells, PP242 treatment (0.04-10 μM) inhibits the phosphorylation of Akt, the mTOR substrate p70S6K, and its downstream target S6 in a dose-dependent manner. ^[1] PP242 potently inhibits PKCα with IC50 of 49 nM. Low concentrations of PP242 inhibit the phosphorylation of Akt S473 and higher concentrations partially inhibit Akt T308-P in addition to S473-P. As PP242 is a more effective mTORC1 inhibitor than rapamycin, PP242 inhibits the proliferation of primary MEFs, and the phosphorylation of 4EBP1 at T36/45 and S65, more potently than rapamycin. PP242 but not rapamycin potently inhibits cap-dependent translation, by causing a higher level of binding between 4EBP1 and eIF4E than rapamycin. ^[2] PP242 potently inhibits the proliferation of p190-transformed murine BM, SUP-B15, and K562 cells with GI50 of 12 nM, 90 nM, and 85 nM, respectively. PP242 also inhibits the growth of solid tumor cell lines such as SKOV3, PC3, 786-O, and U87 with GI50 of 0.49 μM, 0.19 μM, 2.13 μM, and 1.57 μM, respectively. ^[3] PP242 is also more effective than rapamycin in achieving cytoreduction and apoptosis in multiple myeloma (MM) cells. ^[4]

In Vivo

Administration of PP242 is able to completely inhibit the phosphorylation of Akt at S473 and T308 in fat and liver of mice. PP242 only partially inhibits the phosphorylation of Akt in skeletal muscle and is more effective at inhibiting the phosphorylation of T308 than S473, despite able to fully inhibit the phosphorylation of 4EBP1 and S6. ^[2] Oral administration PP242 potently delays the leukemia onset in the mice model, and induces leukemia regression by inhibiting mTORC2 and mTORC1 activation that correlates with loss in cell size. ^[3] PP242 treatment potently inhibits the growth of 8226 cells in mice. ^[4]

Clinical Trials

Features

PP242 is a first selective inhibitor that targets ATP domain of mTOR.

Description

PP242 augments the effects of the current front-line tyrosine kinase inhibitors such as imatinib and dasatinib in leukemia xenograft model, more effectively than does rapamycin. ^[3] PP242 in combination with bortezomib leads to synergistic anti-MM effects. ^[4]

In vitro mTOR (FRAP1) kinase assay

Recombinant mTOR is incubated with PP242 at 2-fold dilutions over a concentration range of 50-0.001 μM in an assay containing 50 mM HEPES, pH 7.5, 1 mM EGTA, 10 mM MgCl₂, 0.01% Tween, 10 μM ATP (2.5 μCi of γ-³²P-ATP), and 3 μg/mL BSA. Rat recombinant PHAS-1/4EBP1 (2 mg/mL) is used as a substrate. Reactions are terminated by spotting onto nitrocellulose, which is washed with 1 M NaCl/1% phosphoric acid (approximately 6 times, 5-10 minutes each). Sheets are dried and the transferred radioactivity quantitated by phosphorimaging. IC50 value is calculated by fitting the data to a sigmoidal dose-response curve using the Prism software package.

Cell Lines

MEFs

Concentrations

Dissolved in DMSO, final concentrations ~10 μM

Incubation Time

72 hours

Methods

Cells are treated with increasing concentrations of PP242 for 72 hours in 96-well plates. After 72 hours of treatment, 10 μL of 440 μM resazurin sodium salt is added to each well, and after 18 hours, the florescence intensity in each well is measured using a top-reading florescent plate reader with excitation at 530 nm and emission at 590 nm.

Animal Models

Syngeneic (Balbc/J) mice with mouse p190-transformed BM cells to initiate leukemia, and female NSG mice injected (i.v.) with SUP-B15ffLuc cells or human Ph+ leukemia

Formulation

Dissolved in PEG400 (Carbowax polyethylene glycol)

Doses

~60 mg/kg/day

Administration

Oral gavage