Pictilisib (GDC-0941)

Br J Cancer,2012 Apr 10;106(8):1386-94.

The synergistic interaction of MEK and PI3K inhibitors is modulated by mTOR inhibition.[Pubmed: 22415236]

Combined targeting of MAPK and PI3K signalling pathways may be necessary for optimal therapeutic activity in cancer. This study evaluated the MEK inhibitors AZD6244 and PD0325901, alone and in combination with the dual mTOR/PI3K inhibitor NVP-BEZ235 or the PI3K inhibitor GDC-0941, in three colorectal cancer cell lines.
METHODS AND RESULTS:
Growth inhibition, survival and signal transduction were measured using the Sulforhodamine B assay, clonogenicity and western blotting, respectively, in HCT116, HT29 and DLD1 cell lines. All MEK/PI3K inhibitor combinations exhibited marked synergistic growth inhibition; however, GDC-0941 displayed greater synergy in combination with either MEK inhibitor. NVP-BEZ235 exhibited stronger inhibition of 4EBP1 phosphorylation, and similar inhibition of S6 and AKT phosphorylation, compared with GDC-0941. Both PD0325901 and AZD6244 inhibited ERK phosphorylation, and with MEK/PI3K inhibitor combinations inhibition of S6 phosphorylation was increased. The reduced synergy exhibited by NVP-BEZ235 in combination with MEK inhibitors, compared with GDC-0941, may be due to inhibition of mTOR, and the addition of the mTORC1/2 inhibitor KU0063794 compromised the synergy of GDC-0941:PD0325901 combinations.
CONCLUSIONS:
These studies confirm that dual targeting of PI3K and MEK can induce synergistic growth inhibition; however, the combination of specific PI3K inhibitors, rather than dual mTOR/PI3K inhibitors, with MEK inhibitors results in greater synergy.

Br J Cancer,2011 Mar 29;104(7):1116-25.

Effect of PI3K- and mTOR-specific inhibitors on spontaneous B-cell follicular lymphomas in PTEN/LKB1-deficient mice.[Pubmed: 21407213]

The PI3K-mTOR (phosphoinositide 3-kinase-mammalian target of rapamycin kinase) pathway is activated in the majority of tumours, and there is interest in assessing whether inhibitors of PI3K or mTOR kinase have efficacy in treating cancer. Here, we define the effectiveness of specific mTOR (AZD8055) and PI3K (GDC-0941) inhibitors, currently in clinical trials, in treating spontaneous B-cell follicular lymphoma that develops in PTEN(+/-)LKB1(+/hypo) mice.
METHODS AND RESULTS:
The PTEN(+/-)LKB1(+/hypo) mice were administered AZD8055 or GDC-0941, and the volumes of B-cell follicular lymphoma were measured by MRI. Tumour samples were analysed by immunohistochemistry, immunoblot and flow cytometry. The AZD8055 or GDC-0941 induced ∼40% reduction in tumour volume within 2 weeks, accompanied by ablation of phosphorylation of AKT, S6K and SGK (serum and glucocorticoid protein kinase) protein kinases. The drugs reduced tumour cell proliferation, promoted apoptosis and suppressed centroblast population. The AZD8055 or GDC-0941 treatment beyond 3 weeks caused a moderate additional decrease in tumour volume, reaching ∼50% of the initial volume after 6 weeks of treatment. Tumours grew back at an increased rate and displayed similar high grade and diffuse morphology as the control untreated tumours upon cessation of drug treatment.
CONCLUSIONS:
These results define the effects that newly designed and specific mTOR and PI3K inhibitors have on a spontaneous tumour model, which may be more representative than xenograft models frequently employed to assess effectiveness of kinase inhibitors. Our data suggest that mTOR and PI3K inhibitors would benefit treatment of cancers in which the PI3K pathway is inappropriately activated; however, when administered alone, may not cause complete regression of such tumours.

J Med Chem,2008 Sep 25;51(18):5522-32.

The identification of 2-(1H-indazol-4-yl)-6-(4-methanesulfonyl-piperazin-1-ylmethyl)-4-morpholin-4-yl-thieno[3,2-d]pyrimidine (GDC-0941) as a potent, selective, orally bioavailable inhibitor of class I PI3 kinase for the treatment of cancer.[Pubmed: 18754654]

Recombinant human PI3Kα, PI3Kβ, and PI3Kδ are coexpressed in a Sf9 baculovirus system with the p85α regulatory subunit and purified as GST-fusion proteins using affinity chromatography on glutathione-sepharose. Recombinant human PI3Kγ is expressed as monomeric GST-fusions and purified similarly. GDC-0941 is dissolved in DMSO and added to 20 mM Tris-HCl (pH 7.5) containing 200 μg yttrium silicate (Ysi) polylysine SPA beads, 4 mM MgCl2, 1 mM dithiothreitol (DTT), 1 μM ATP, 0.125 μCi [γ-33P]-ATP, and 4% (v/v) DMSO in a total volume of 50 μL. The recombinant GST-fusion of PI3Kα (5 ng), PI3Kβ (5 ng), PI3Kδ (5 ng), or PI3Kγ (5 ng) is added to the assay mixture to initiate the kinase reaction. After incubation for 1 hour at room temperature, the kinase reaction is terminated with 150 μL PBS. The mixture is then centrifuged for 2 minutes at 2000 rpm and read using a Wallac Microbeta counter. The reported IC50 values are calculated using a sigmoidal, dose-response curve fit in MDL Assay Explorer.

Cancer Cell,2009 May 5;15(5):429-40.

Ligand-independent HER2/HER3/PI3K complex is disrupted by trastuzumab and is effectively inhibited by the PI3K inhibitor GDC-0941.[Pubmed: 19411071]

Cell lines:SKBR-3, BT474-M1, AU-565, HCC-1419, ZR75-30, KPL-4, JIMT-1, BT474-EEI, HCC-1954, MCF-7, CALU-3, SKOV-3, and MKN-7 cells.
Concentrations:  Dissolved in DMSO, final concentrations ~10 μM
Incubation Time: 48 and 72 hours
Method:
Cells are exposed to various concentrations of GDC-0941 for 48, and 72 hours. Proliferation/viability of cells is detected by using the CellTiter-Glo Luminescent Cell Viability Assay. The pAkt (Ser473), cleaved caspase-3, and cleaved PARP are analyzed by western blot. The Caspase-Glo 3/7 assay and the Cell Death Detection ELISAplus assay are used to detect caspase 3/7 activity, and apoptosis, respectively.