Phosphatidylinositol-3-kinase (PI3K) is an important target in cancer due to the deregulation of the PI3K/ Akt signaling pathway in a wide variety of tumors. A series of thieno[3,2-d]pyrimidine derivatives were prepared and evaluated as inhibitors of PI3 kinase p110alpha. The synthesis, biological activity, and further profiling of these compounds are described. This work resulted in the discovery of 17, GDC-0941, which is a potent, selective, orally bioavailable inhibitor of PI3K and is currently being evaluated in human clinical trials for the treatment of cancer.

Alterations of the phosphoinositide-3 kinase (PI3K)/Akt signaling pathway occur broadly in cancer via multiple mechanisms including mutation of the PIK3CA gene, loss or mutation of phosphatase and tensin homolog (PTEN), and deregulation of mammalian target of rapamycin (mTOR) complexes. The dysregulation of this pathway has been implicated in tumor initiation, cell growth and survival, invasion and angiogenesis, thus, PI3K and mTOR are promising therapeutic targets for cancer. We discovered GDC-0980, a selective, potent, orally bioavailable inhibitor of Class I PI3 kinase and mTOR kinase (TORC1/2) with excellent pharmacokinetic and pharmaceutical properties. GDC-0980 potently inhibits signal transduction downstream of both PI3K and mTOR, as measured by pharmacodynamic (PD) biomarkers, thereby acting upon two key pathway nodes to produce the strongest attainable inhibition of signaling in the pathway. Correspondingly, GDC-0980 was potent across a broad panel of cancer cell lines, with the greatest potency in breast, prostate, and lung cancers and less activity in melanoma and pancreatic cancers, consistent with KRAS and BRAF acting as resistance markers. Treatment of cancer cell lines with GDC-0980 resulted in G1 cell-cycle arrest, and in contrast to mTOR inhibitors, GDC-0980 induced apoptosis in certain cancer cell lines, including those with direct pathway activation via PI3K and PTEN. Low doses of GDC-0980 potently inhibited tumor growth in xenograft models including those with activated PI3K, loss of LKB1 or PTEN, and elicited an exposure-related decrease in PD biomarkers. These preclinical data show that GDC-0980 is a potent and effective dual PI3K/mTOR inhibitor with promise for the clinic. Mol Cancer Ther; 10(12); 2426-36. Ó2011 AACR.

The discovery of 2 (GDC-0980), a class I PI3K and mTOR kinase inhibitor for oncology indications, is described. mTOR inhibition was added to the class I PI3K inhibitor 1 (GDC-0941) scaffold primarily through the substitution of the indazole in 1 for a 2-aminopyrimidine. This substitution also increased the microsomal stability and the free fraction of compounds as evidenced through a pairwise comparison of molecules that were otherwise identical. Highlighted in detail are analogues of an advanced compound 4 that were designed to improve solubility, resulting in 2. This compound, is potent across PI3K class I isoforms with IC(50)s of 5, 27, 7, and 14 nM for PI3Kα, β, δ, and γ, respectively, inhibits mTOR with a K(i) of 17 nM yet is highly selective versus a large panel of kinases including others in the PIKK family. On the basis of the cell potency, low clearance in mouse, and high free fraction, 2 demonstrated significant efficacy in mouse xenografts when dosed as low as 1 mg/kg orally and is currently in phase I clinical trials for cancer.

The PI3K/AKT/mTOR pathway has been shown to play an important role in cancer. Starting with compounds 1 and 2 (GDC-0941) as templates, (thienopyrimidin-2-yl)aminopyrimidines were discovered as potent inhibitors of PI3K or both PI3K and mTOR. Structural information derived from PI3K gamma-ligand cocrystal structures of 1 and 2 were used to design inhibitors that maintained potency for PI3K yet improved metabolic stability and oral bioavailability relative to 1. The addition of a single methyl group to the optimized 5 resulted in 21, which had significantly reduced potency for mTOR. The lead compounds 5 (GNE-493) and 21 (GNE-490) have good pharmacokinetic (PK) parameters, are highly selective, demonstrate knock down of pathway markers in vivo, and are efficacious in xenograft models where the PI3K pathway is deregulated. Both compounds were compared in a PI3K alpha mutated MCF7.1 xenograft model and were found to have equivalent efficacy when normalized for exposure.

Dysfunctional signaling through the phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway leads to uncontrolled tumor proliferation. In the course of the discovery of novel benzoxepin PI3K inhibitors, we observed a strong dependency of in vivo antitumor activity on the free-drug exposure. By lowering the intrinsic clearance, we derived a set of imidazobenzoxazepin compounds that showed improved unbound drug exposure and effectively suppressed growth of tumors in a mouse xenograft model at low drug dose levels. One of these compounds, GDC-0032 (11l), was progressed to clinical trials and is currently under phase I evaluation as a potential treatment for human malignancies.

Inhibition of phosphoinositide 3-kinase (PI3K) signaling is an appealing approach to treat brain tumors, especially glioblastoma multiforme (GBM). We previously disclosed our successful approach to prospectively design potent and blood-brain barrier (BBB) penetrating PI3K inhibitors. The previously disclosed molecules were ultimately deemed not suitable for clinical development due to projected poor metabolic stability in humans. We, therefore, extended our studies to identify a BBB penetrating inhibitor of PI3K that was also projected to be metabolically stable in human. These efforts required identification of a distinct scaffold for PI3K inhibitors relative to our previous efforts and ultimately resulted in the identification of GDC-0084 (16). The discovery and preclinical characterization of this molecule are described within.

Purpose: Glioblastoma (GBM), the most common primary brain tumor in adults, presents a high frequency of alteration in the PI3K pathway. Our objectives were to identify a dual PI3K/mTOR inhibitor optimized to cross the blood-brain barrier (BBB) and characterize its brain penetration, pathway modulation in the brain and efficacy in orthotopic xenograft models of GBM.Experimental Design: Physicochemical properties of PI3K inhibitors were optimized using in silico tools, leading to the identification of GNE-317. This compound was tested in cells overexpressing P-glycoprotein (P-gp) or breast cancer resistance protein (BCRP). Following administration to mice, GNE-317 plasma and brain concentrations were determined, and phosphorylated biomarkers (pAkt, p4EBP1, and pS6) were measured to assess PI3K pathway suppression in the brain. GNE-317 efficacy was evaluated in the U87, GS2, and GBM10 orthotopic models of GBM.Results: GNE-317 was identified as having physicochemical properties predictive of low efflux by P-gp and BCRP. Studies in transfected MDCK cells showed that GNE-317 was not a substrate of either transporter. GNE-317 markedly inhibited the PI3K pathway in mouse brain, causing 40% to 90% suppression of the pAkt and pS6 signals up to 6-hour postdose. GNE-317 was efficacious in the U87, GS2, and GBM10 orthotopic models, achieving tumor growth inhibition of 90% and 50%, and survival benefit, respectively.Conclusions: These results indicated that specific optimization of PI3K inhibitors to cross the BBB led to potent suppression of the PI3K pathway in healthy brain. The efficacy of GNE-317 in 3 intracranial models of GBM suggested that this compound could be effective in the treatment of GBM.

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