PI-103 Hydrochloride

PI-103 is a dual inhibitor of PI3K/Akt and mTOR with IC50 value of 0.002 μM , 0.003μM, 0.003μM, 0.015μM, 0.030μM for P110α, P110β, P110γ, P110 and mTOR, respectively [1].

PI3K/AKT/mTOR pathway is an intracellular signaling pathway and plays an important role in regulating cell cycle. It has been shown that PI3K/AKT/MTOR pathway is directly related to cellular quiescence, proliferation, cancer, and longevity. And many studies have shown that activation of the PI3K/Akt signaling pathway is correlated with poor prognosis in a variety of cancers which demonstrated that inhibition of the pathway may be regarded as a promising therapy [2, 3].

PI-103 is a selective PI3K/Akt and mTORC1 inhibitor. When tested with leukemic cell lines (MOLM14, OCI-AML3 and MV4-11) with activation of PI3K/Akt, mTORC1 and ERK/MAPK signaling pathways, PI-103 blocked cells proliferation via inhibiting PI3K/Akt and mTORC1 activity in a concentration of 1μM [4]. In HCC cell line--Huh7 cells, treated PI-103 alone or combined with sorafenib inhibited cells proliferation in a dose-dependent manner through inhibition of PI3K/Akt and mTORC1 pathways [5]. When tested with U87MG glioblastoma cells, PI-103 treatment in 30 nM/L showed significant inhibition of PI3K/Akt and mTORC1 phosphorylation [1]. In neuroblastoma cell lines SK-N-BE (2), IMR-32 with amplified MYCN, PI-103 inhibited cell growth in a time- and concentration-dependent manner via inhibiting PI3K/Akt and mTORC1 activity [3].

In SK-N-BE (2) with MYCN-mutant xenografted nude mice model, treated PI-103 intraperitoneally (10 mg/kg) markedly reduced the tumor volume index and tumor weight via inhibiting PI3K/ mTOR pathways [1].

References:
[1].  Raynaud, F.I., et al., Biological properties of potent inhibitors of class I phosphatidylinositide 3-kinases: from PI-103 through PI-540, PI-620 to the oral agent GDC-0941. Mol Cancer Ther, 2009. 8(7): p. 1725-38.
[2].  Hambright, H.G., et al., Inhibition of PI3K/AKT/mTOR axis disrupts oxidative stress-mediated survival of melanoma cells. Oncotarget, 2015.
[3].  Segerstrom, L., et al., Effects of small molecule inhibitors of PI3K/Akt/mTOR signaling on neuroblastoma growth in vitro and in vivo. Int J Cancer, 2011. 129(12): p. 2958-65.
[4].  Park, S., et al., PI-103, a dual inhibitor of Class IA phosphatidylinositide 3-kinase and mTOR, has antileukemic activity in AML. Leukemia, 2008. 22(9): p. 1698-706.
[5].  Gedaly, R., et al., PI-103 and sorafenib inhibit hepatocellular carcinoma cell proliferation by blocking Ras/Raf/MAPK and PI3K/AKT/mTOR pathways. Anticancer Res, 2010. 30(12): p. 4951-8.

A dual phosphoinositide-3-kinase alpha/mTOR inhibitor cooperates with blockade of epidermal growth factor receptor in PTEN-mutant glioma.[Pubmed:17804702]

Cancer Res. 2007 Sep 1;67(17):7960-5.

We have shown previously that blockade of epidermal growth factor receptor (EGFR) cooperates with a pan-selective inhibitor of phosphoinositide-3-kinase (PI3K) in EGFR-driven glioma. In this communication, we tested EGFR-driven glioma differing in PTEN status, treating with the EGFR inhibitor erlotinib and a novel dual inhibitor of PI3Kalpha and mTOR (PI-103). Erlotinib blocked proliferation only in PTEN(wt) cells expressing EGFR. Although erlotinib monotherapy showed little effect in PTEN(mt) glioma, PI-103 greatly augmented the antiproliferative efficacy of erlotinib in this setting. To address the importance of PI3K blockade, we showed in PTEN(mt) glioma that combining PI-103 and erlotinib was superior to either monotherapy or to therapy combining erlotinib with either rapamycin (an inhibitor of mTOR) or PIK-90 (an inhibitor of PI3Kalpha). These experiments show that a dual inhibitor of PI3Kalpha and mTOR augments the activity of EGFR blockade, offering a mechanistic rationale for targeting EGFR, PI3Kalpha, and mTOR in the treatment of EGFR-driven, PTEN-mutant glioma.

Transient PI3K inhibition induces apoptosis and overcomes HGF-mediated resistance to EGFR-TKIs in EGFR mutant lung cancer.[Pubmed:21220474]

Clin Cancer Res. 2011 Apr 15;17(8):2260-9.

PURPOSE: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI), such as gefitinib and erlotinib, show favorable response to EGFR mutant lung cancer. However, the responders acquire resistance almost without exception. We recently reported that hepatocyte growth factor (HGF) induces EGFR-TKI resistance by activating MET that restores downstream mitogen activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK)1/2 and phosphoinositide 3-kinase (PI3K)/Akt signaling. The purpose of this study was to determine whether inhibition of PI3K, a downstream molecule of both EGFR and MET, could overcome HGF-mediated EGFR-TKI resistance in EGFR mutant lung cancer cells PC-9 and HCC827. EXPERIMENTAL DESIGN: We explored therapeutic effect of a class I PI3K inhibitor PI-103 on HGF-induced EGFR-TKI resistance in vitro and in vivo. RESULTS: Unlike gefitinib or erlotinib, continuous exposure with PI-103 inhibited proliferation of PC-9 and HCC827 cells, even in the presence of HGF. On the other hand, in gefitinib-resistant xenograft model by using PC-9 cells mixed with HGF high producing fibroblasts, PI-103 monotherapy did not inhibit tumor growth. However, PI-103 combined with gefitinib successfully regressed gefitinib-resistant tumor. In vitro experiments by considering short half-life of PI-103 reveal that transient exposure of PI-103 combined with gefitinib caused sustained inhibition of Akt phosphorylation, but not ERK1/2 phosphorylation, resulting in induction of tumor cell apoptosis even in the presence of HGF. CONCLUSIONS: These results indicate that transient blockade of PI3K/Akt pathway by PI-103 and gefitinib could overcome HGF-mediated resistance to EGFR-TKIs by inducing apoptosis in EGFR mutant lung cancer.

Effects of epidermal growth factor receptor and phosphatase and tensin homologue gene expression on the inhibition of U87MG glioblastoma cell proliferation induced by protein kinase inhibitors.[Pubmed:23110505]

Clin Exp Pharmacol Physiol. 2013 Jan;40(1):13-21.

The aim of the present study was to analyse the antiproliferative effects and mechanisms of action of protein kinase inhibitors (PKIs) in human glioblastoma multiforme (GBM) cells with different epidermal growth factor receptor (EGFR) and phosphatase and tensin homologue (PTEN) status. The GBM cell models were established by transfection of plasmids carrying wild-type EGFR, mutated EGFRvIII or PTEN and clonal selection in U87MG cells. Phosphatidylinositol 3-kinase (PI3-K)/AKT pathway-focused gene profiles were examined by real-time polymerase chain reaction-based assays, protein expression was evaluated by western blotting and the antiproliferative effects of PKI treatment were determined by the 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay in GBM cells. The cell model with intact PTEN and low EGFR levels was the most sensitive to treatment with the EGFR inhibitor erlotinib, whereas the model with EGFRvIII was the most resistant to treatment with the mitogen-activated protein kinase kinase inhibitor U0126. The dual PI3-K and mammalian target of rapamycin (mTOR) inhibitor PI103 had the most potent antiproliferative effects against all GBM cells tested. Following simultaneous stimulation of AKT and extracellular signal-regulated kinase, rapamycin concentrations > 0.5 nmol/L failed to exhibit a further growth inhibitory effect. Concurrent inhibition of mTOR and ribosomal protein s6 activity may underlie the inhibition of GBM proliferation by PKI. In conclusion, overexpression of EGFR or EGFRvIII, accompanied by a loss of PTEN, contributed to the activation of multiple intracellular signalling pathways in GBM cells. Rigorous examination of biomarkers in tumour tissues before and after treatment may be necessary to determine the efficacy of PKI therapy in patients with GBM.

ERK2-dependent reactivation of Akt mediates the limited response of tumor cells with constitutive K-RAS activity to PI3K inhibition.[Pubmed:24351425]

Cancer Biol Ther. 2014 Mar 1;15(3):317-28.

K-RAS mutated (K-RASmut) non-small cell lung cancer (NSCLC) cells are resistant to EGFR targeting strategies. We investigated the impact of K-RAS activity irrespective of mutational status in the EGFR-independent increase in clonogenic cell survival. An analysis of the K-RAS activity status revealed a constitutively high K-RAS activity in K-RASmut NSCLC cells and also in head and neck squamous cell carcinoma (HNSCC) cells overexpressing wild-type K-RAS (K-RASwt). Similar to K-RAS-mutated cells, increased K-RAS activity in HNSCC cells overexpressing K-RASwt was associated with the stimulated production of the EGFR ligand amphiregulin and resistance to EGFR tyrosine kinase (EGFR-TK) inhibitors such as erlotinib. Expression of mutated K-RAS stimulated Akt phosphorylation and increased plating efficiency. Conversely, knockdown of K-RAS in K-RASmut NSCLC cells and in HNSCC cells presenting overexpression of K-RASwt resulted in sensitization to the anti-clonogenic activity of erlotinib. K-RAS activity results in EGFR-dependent and EGFR-independent Akt activity. The short-term treatment (2 h) of cells with EGFR-TK or PI3K inhibitors (erlotinib and PI-103) resulted in the repression of Akt activation, whereas long-term treatment (24 h) with inhibitors led to the reactivation of Akt and improved clonogenicity. The Akt re-activation was MAPK-ERK2-dependent and associated with a lack of complete response to anti-clonogenic activity of PI-103. A complete response was observed when PI-103 was combined with MEK inhibitor PD98059. Together, clonogenicity inhibition in tumor cells presenting constitutive K-RAS activity independent of K-RAS mutational status can be achieved by targeting of EGFR downstream pathways, i.e., PI3K alone or the combination of PI3K and MAPK inhibitors.

Akt and autophagy cooperate to promote survival of drug-resistant glioma.[Pubmed:21062993]

Sci Signal. 2010 Nov 9;3(147):ra81.

Although the phosphatidylinositol 3-kinase to Akt to mammalian target of rapamycin (PI3K-Akt-mTOR) pathway promotes survival signaling, inhibitors of PI3K and mTOR induce minimal cell death in PTEN (phosphatase and tensin homolog deleted from chromosome 10) mutant glioma. Here, we show that the dual PI3K-mTOR inhibitor PI-103 induces autophagy in a form of glioma that is resistant to therapy. Inhibitors of autophagosome maturation cooperated with PI-103 to induce apoptosis through the mitochondrial pathway, indicating that the cellular self-digestion process of autophagy acted as a survival signal in this setting. Not all inhibitors of mTOR synergized with inhibitors of autophagy. Rapamycin delivered alone induced autophagy, yet cells survived inhibition of autophagosome maturation because of rapamycin-mediated activation of Akt. In contrast, adenosine 5'-triphosphate-competitive inhibitors of mTOR stimulated autophagy more potently than did rapamycin, with inhibition of mTOR complexes 1 and 2 contributing independently to induction of autophagy. We show that combined inhibition of PI3K and mTOR, which activates autophagy without activating Akt, cooperated with inhibition of autophagy to cause glioma cells to undergo apoptosis. Moreover, the PI3K-mTOR inhibitor NVP-BEZ235, which is in clinical use, synergized with the lysosomotropic inhibitor of autophagy, chloroquine, another agent in clinical use, to induce apoptosis in glioma xenografts in vivo, providing a therapeutic approach potentially translatable to humans.

Pharmacologic characterization of a potent inhibitor of class I phosphatidylinositide 3-kinases.[Pubmed:17575152]

Cancer Res. 2007 Jun 15;67(12):5840-50.

Extensive evidence implicates activation of the lipid phosphatidylinositide 3-kinase (PI3K) pathway in the genesis and progression of various human cancers. PI3K inhibitors thus have considerable potential as molecular cancer therapeutics. Here, we detail the pharmacologic properties of a prototype of a new series of inhibitors of class I PI3K. PI103 is a potent inhibitor with low IC50 values against recombinant PI3K isoforms p110alpha (2 nmol/L), p110beta (3 nmol/L), p110delta (3 nmol/L), and p110gamma (15 nmol/L). PI103 also inhibited TORC1 by 83.9% at 0.5 micromol/L and exhibited an IC50 of 14 nmol/L against DNA-PK. A high degree of selectivity for the PI3K family was shown by the lack of activity of PI103 in a panel of 70 protein kinases. PI103 potently inhibited proliferation and invasion of a wide variety of human cancer cells in vitro and showed biomarker modulation consistent with inhibition of PI3K signaling. PI103 was extensively metabolized, but distributed rapidly to tissues and tumors. This resulted in tumor growth delay in eight different human cancer xenograft models with various PI3K pathway abnormalities. Decreased phosphorylation of AKT was observed in U87MG gliomas, consistent with drug levels achieved. We also showed inhibition of invasion in orthotopic breast and ovarian cancer xenograft models and obtained evidence that PI103 has antiangiogenic potential. Despite its rapid in vivo metabolism, PI103 is a valuable tool compound for exploring the biological function of class I PI3K and importantly represents a lead for further optimization of this novel class of targeted molecular cancer therapeutic.

A dual PI3 kinase/mTOR inhibitor reveals emergent efficacy in glioma.[Pubmed:16697955]

Cancer Cell. 2006 May;9(5):341-9.

The PI3 kinase family of lipid kinases promotes cell growth and survival by generating the second messenger phosphatidylinositol-3,4,5-trisphosphate. To define targets critical for cancers driven by activation of PI3 kinase, we screened a panel of potent and structurally diverse drug-like molecules that target this enzyme family. Surprisingly, a single agent (PI-103) effected proliferative arrest in glioma cells, despite the ability of many compounds to block PI3 kinase signaling through its downstream effector, Akt. The unique cellular activity of PI-103 was traced directly to its ability to inhibit both PI3 kinase alpha and mTOR. PI-103 showed significant activity in xenografted tumors with no observable toxicity. These data demonstrate an emergent efficacy due to combinatorial inhibition of mTOR and PI3 kinase alpha in malignant glioma.

A pharmacological map of the PI3-K family defines a role for p110alpha in insulin signaling.[Pubmed:16647110]

Cell. 2006 May 19;125(4):733-47.

Phosphoinositide 3-kinases (PI3-Ks) are an important emerging class of drug targets, but the unique roles of PI3-K isoforms remain poorly defined. We describe here an approach to pharmacologically interrogate the PI3-K family. A chemically diverse panel of PI3-K inhibitors was synthesized, and their target selectivity was biochemically enumerated, revealing cryptic homologies across targets and chemotypes. Crystal structures of three inhibitors bound to p110gamma identify a conformationally mobile region that is uniquely exploited by selective compounds. This chemical array was then used to define the PI3-K isoforms required for insulin signaling. We find that p110alpha is the primary insulin-responsive PI3-K in cultured cells, whereas p110beta is dispensable but sets a phenotypic threshold for p110alpha activity. Compounds targeting p110alpha block the acute effects of insulin treatment in vivo, whereas a p110beta inhibitor has no effect. These results illustrate systematic target validation using a matrix of inhibitors that span a protein family.

PI-103 Hydrochloride is a dual PI3K and mTOR inhibitor with IC50s of 8 nM, 88 nM, 48 nM, 150 nM, 20 nM, and 83 nM for p110α, p110β, p110δ, p110γ, mTORC1, and mTORC2. PI-103 Hydrochloride also inhibits DNA-PK with an IC50 of 2 nM. PI-103 Hydrochloride induces autophagy.

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