Description

Cancer

Description

GDC-0980 (RG7422) is a potent, selective inhibitor of PI3Kα, PI3Kβ, PI3Kδ and PI3Kγ with IC50 of 5 nM, 27 nM, 7 nM, and 14 nM, and also a mTOR inhibitor with K_i of 17 nM.

Targets

IC₅₀

In Vitro

GDC-0980 shows the potent and selective inhibitory activities against class I PI3K and mTOR kinase versus a large panel of kinases with K_i of 17 nM for mTOR and IC50 of 5 nM, 27 nM, 7 nM, and 14 nM for PI3Kα, β, δ, and γ, respectively. ^[1] In vitro, GDC-0980 significantly inhibits cell proliferation in PC3 and MCF7 cells with IC50 of 307 nM and 255 nM, respectively. ^[1] A recent study shows that GDC-0980 reduces cancer cell viability by inhibiting cell-cycle procession and inducing apoptosis with most potency in prostate (IC50 < 200="" nm="" 50%),=""><500 nm="" 100%),="" breast="" (ic50=""><200 nm="" 37%,=""><500 nm="" 78%)="" and="" nsclc="" lines="" (ic50=""><200 nm="" 29%,=""><500 nm="" 88%)="" and="" less="" potency="" in="" pancreatic="" (ic50=""><200 nm="" 13%,=""><500 nm="" 67%)="" and="" melanoma="" cell="" lines="" (ic50=""><200 nm="" 0%,=""><500 nm="" 33%).="">^[2]

In Vivo

In both PC-3 and MCF-7 neo/HER2 xenograft models, GDC-0980 at a dose of 1 mg/kg, exhibits significant antitumor activity by causing tumor growth delay. Furthermore, GDC-0980 results in tumor stasis or regressions at the maximum tolerated dose of 7.5 mg/kg. ^[1] In mice, intravenous GDC-0980 administration at 1 mg/kg leads to low clearance (Cl_p: 9.2 mL/min/kg, V_ss: 1.7 L/kg). While, oral administration at 5 mg/kg in 80% PEG400 and at 50 mg/kg as a crystalline suspension in 0.5% methylcellulose/0.2% Tween-80 also results in favorable pharmacokinetic parameters. ^[1]

Clinical Trials

GDC-0980 is currently in Phase II clinical trials in patients with recurrent or persistent endometrial carcinoma.

Features

GDC-0980 (RG7422) is a potent, selective, and orally available inhibitor of PI3Kα, β, δ, γ and mTOR.

Description

In PC-3 and 786-0 cells, combination treatment of sunitinib and GDC-0980 results in a synergistic induction of DNA fragmentation. ^[3] GDC-0980 in combination with paclitaxel with or without bevacizumab is currently in Phase I clinical trials in patients with locally recurrent or metastatic breast cancer.

Enzymatic activity

Enzymatic activity of the Class I PI3K isoforms is measured using a fluorescence polarization assay that monitors formation of the product 3,4,5-inositoltriphosphate molecule as it competes with fluorescently labeled PIP3 for binding to the GRP-1 pleckstrin homology domain protein. An increase in phosphatidyl inositide-3-phosphate product results in a decrease in fluorescence polarization signal as the labeled fluorophore is displaced from the GRP-1 protein binding site. Class I PI3K isoforms are expressed and purified as heterodimeric recombinant proteins. PI3K isoforms are assayed under initial rate conditions in the presence of 10 mM Tris (pH 7.5), 25 μM ATP, 9.75 μM PIP2, 5% glycerol, 4 mM MgCl₂, 50 mM NaCl, 0.05% (v/v) Chaps, 1 mM dithiothreitol, 2% (v/v) DMSO at the following concentrations for each isoform: PI3Kα,β at 60 ng/mL; PI3Kγ at 8 ng/mL; PI3Kδ at 45 ng/mL. After assay for 30 minutes at 25°C, reactions are terminated with a final concentration of 9 mM EDTA, 4.5 nM TAMRA-PIP3, and 4.2 μg/mL GRP-1 detector protein before reading fluorescence polarization on an Envision plate reader. IC50s are calculated from the fit of the dose?response curves to a 4-parameter equation.Human recombinant mTOR(1360?2549) is expressed and purified from insect cells and assayed using a Lanthascreen fluorescence resonance energy transfer format in which phosphorylation of recombinant green fluorescent protein (GFP)-4-EBP1 is detected using a terbium-labeled antibody to phospho-threonine 37/46 of 4-EBP1. Reactions are initiated with ATP and conducted in the presence of 50 mM Hepes (pH 7.5), 0.25 nM mTOR, 400 nM GFP-4E-BP1, 8 μM ATP, 0.01% (v/v) Tween 20, 10 mM MnCl₂, 1 mM EGTA, 1 mM dithiothreitol, and 1% (v/v) DMSO. Assays are conducted under initial rate conditions at room temperature for 30 minutes before terminating the reaction and detecting product in the presence of 2 nM Tb-anti-p4E-BP1 antibody and 10 mM EDTA. Dose?response curves are fit to an equation for competitive tight-binding inhibition and apparent Ki' s are calculated using the determined K_m for ATP of 6.1 μM.

Cell Lines

PC3 and MCF7.1

Concentrations

0 to 10 μM

Incubation Time

72 hours or 96 hours

Methods

Antiproliferative cellular assays are conducted using PC3 and MCF7.1 human tumor cell lines. MCF7.1 is an in vivo selected line and originally derived from the parental human MCF7 breast cancer cell line. Cell lines are cultured in RPMI supplemented with 10% fetal bovine serum, 100 units/mL penicillin, and 100 μg/mL streptomycin, 10 mM HEPES, and 2 mM glutamine at 3°C under 5% CO₂. MCF7.1 cells or PC3 cells are seeded in 384-well plates in media at 1000 cells/well or 3000 cells/well, respectively, and incubated overnight prior to the addition of GDC-0980 to a final DMSO concentration of 0.5% v/v. MCF7.1 cells and PC3 cells are incubated for 3 days and 4 days, respectively, prior to the addition of CellTiter-Glo reagen and reading of luminescence using an Analyst plate reader. For antiproliferative assays, a cytostatic agent such as aphidicolin and a cytotoxic agent such as staurosporine are included as controls. Dose?response curves are fit to a 4-parameter equation and relative IC50s are calculated using Assay Explorer software.

Animal Models

PC3 and MCF7.1 cells are injected s.c. into the right hind flank of athymic nu/nu (nude) mice.

Formulation

GDC-0980 is dissolved in 0.5% methylcellulose with 0.2% Tween-80 (MCT).

Doses

≤7.5 mg/kg

Administration

Administered via p.o.