Larry Feldberg

Bis(morpholino-1,3,5-triazine) derivatives: potent adenosine 5'-triphosphate competitive phosphatidylinositol-3-kinase/mammalian target of rapamycin inhibitors: discovery of compound 26 (PKI-587), a highly efficacious dual inhibitor.

The PI3K/Akt signaling pathway is a key pathway in cell proliferation, growth, survival, protein synthesis, and glucose metabolism. It has been recognized recently that inhibiting this pathway might provide a viable therapy for cancer. A series of bis(morpholino-1,3,5-triazine) derivatives were prepared and optimized to provide the highly efficacious PI3K/mTOR inhibitor 1-(4-{[4-(dimethylamino)piperidin-1-yl]carbonyl}phenyl)-3-[4-(4,6-dimorpholin-4-yl-1,3,5-triazin-2-yl)phenyl]urea 26 (PKI-587). Compound 26 has shown excellent activity in vitro and in vivo, with antitumor efficacy in both subcutaneous and orthotopic xenograft tumor models when administered intravenously. The structure-activity relationships and the in vitro and in vivo activity of analogues in this series are described.

Antitumor Efficacy of PKI-587, a Highly Potent Dual PI3K/mTOR Kinase Inhibitor

Purpose: The aim of this study was to show preclinical efficacy and clinical development potential of PKI-587, a dual phosphoinositide 3-kinase (PI3K)/mTOR inhibitor. Experimental Design: In vitro class 1 PI3K enzyme and human tumor cell growth inhibition assays and in vivo five tumor xenograft models were used to show efficacy. Results: In vitro, PKI-587 potently inhibited class I PI3Ks (IC50 vs. PI3K-α = 0.4 nmol/L), PI3K-α mutants, and mTOR. PKI-587 inhibited growth of 50 diverse human tumor cell lines at IC50 values of less than 100 nmol/L. PKI-587 suppressed phosphorylation of PI3K/mTOR effectors (e.g., Akt), and induced apoptosis in human tumor cell lines with elevated PI3K/mTOR signaling. MDA-MB-361 [breast; HER2+, PIK3CA mutant (E545K)] was particularly sensitive to this effect, with cleaved PARP, an apoptosis marker, induced by 30 nmol/L PKI-587 at 4 hours. In vivo, PKI-587 inhibited tumor growth in breast (MDA-MB-361, BT474), colon (HCT116), lung (H1975), and glioma (U87MG) xenograft models. In MDA-MB-361 tumors, PKI-587 (25 mg/kg, single dose i.v.) suppressed Akt phosphorylation [at threonine(T)308 and serine(S)473] for up to 36 hours, with cleaved PARP (cPARP) evident up to 18 hours. PKI-587 at 25 mg/kg (once weekly) shrank large (∼1,000 mm3) MDA-MB-361 tumors and suppressed tumor regrowth. Tumor regression correlated with suppression of phosphorylated Akt in the MDA-MB-361 model. PKI-587 also caused regression in other tumor models, and efficacy was enhanced when given in combination with PD0325901 (MEK 1/2 inhibitor), irinotecan (topoisomerase I inhibitor), or HKI-272 (neratinib, HER2 inhibitor). Conclusion: Significant antitumor efficacy and a favorable pharmacokinetic/safety profile justified phase 1 clinical evaluation of PKI-587. Clin Cancer Res; 17(10); 3193–203. ©2011 AACR.

Antitumor Efficacy Profile of PKI-402, a Dual Phosphatidylinositol 3-Kinase/Mammalian Target of Rapamycin Inhibitor

PKI-402 is a selective, reversible, ATP-competitive, equipotent inhibitor of class I phosphatidylinositol 3-kinases (PI3K), including PI3K-α mutants, and mammalian target of rapamycin (mTOR; IC50 versus PI3K-α = 2 nmol/L). PKI-402 inhibited growth of human tumor cell lines derived from breast, brain (glioma), pancreas, and non–small cell lung cancer tissue and suppressed phosphorylation of PI3K and mTOR effector proteins (e.g., Akt at T308) at concentrations that matched those that inhibited cell growth. In MDA-MB-361 [breast: Her2+ and PIK3CA mutant (E545K)], 30 nmol/L PKI-402 induced cleaved poly(ADP-ribose) polymerase (PARP), a marker for apoptosis. In vivo, PKI-402 inhibited tumor growth in MDA-MB-361, glioma (U87MG), and lung (A549) xenograft models. In MDA-MB-361, PKI-402 at 100 mg/kg (daily for 5 days, one round) reduced initial tumor volume of 260 mm3 to 129 mm3 and prevented tumor regrowth for 70 days. In MDA-MB-361 tumors, PKI-402 (100 mg/kg, single dose) suppressed Akt phosphorylation (at T308) and induced cleaved PARP. Suppression of phosphorylated Akt (p-Akt) was complete at 8 hours and still evident at 24 hours. Cleaved PARP was evident at 8 and 24 hours. In normal tissue (heart and lung), PKI-402 (100 mg/kg) had minimal effect on p-Akt, with no detectable cleaved PARP. Preferential accumulation of PKI-402 in tumor tissue was observed. Complete, sustained suppression of Akt phosphorylation may cause tumor regression in MDA-MB-361 and other xenograft models. We are testing whether dual PI3K/mTOR inhibitors can durably suppress p-Akt, induce cleaved PARP, and cause tumor regression in a diverse set of human tumor xenograft models. Mol Cancer Ther; 9(4); 976–84. ©2010 AACR.

Lead Optimization of N-3-Substituted 7-Morpholinotriazolopyrimidines as Dual Phosphoinositide 3-Kinase/Mammalian Target of Rapamycin Inhibitors: Discovery of PKI-402

Herein we describe the identification and lead optimization of triazolopyrimidines as a novel class of potent dual PI3K/mTOR inhibitors, resulting in the discovery of 3 (PKI-402). Compound 3 exhibits good physical properties and PK parameters, low nanomolar potency against PI3Kalpha and mTOR, and excellent inhibition of cell proliferation in several human cancer cell lines. Furthermore, in vitro and in vivo biomarker studies demonstrated the ability of 3 to shut down the PI3K/Akt pathway and induce apoptosis in cancer cells. In addition, 3 showed excellent in vivo efficacy in various human cancer xenografts, validating suppression of PI3K/mTOR signaling as a potential anticancer therapy.

Synthesis and SAR of Novel 4-Morpholinopyrrolopyrimidine Derivatives as Potent Phosphatidylinositol 3-Kinase Inhibitors

Significant evidence suggests that deregulation of the PI3K/Akt pathway is important in tumor progression. Mechanisms include loss of function of the tumor suppressor PTEN and high frequency of mutation of the PI3K p110alpha isoform in human malignancies. This connection between PI3K and tumor genesis makes PI3K a promising target for cancer treatment. A series of 4-morpholinopyrrolopyrimidine derivatives were synthesized and evaluated as inhibitors of PI3Kalpha and mTOR, leading to the discovery of PI3Kalpha selective inhibitors (e.g., 9) and dual PI3Kalpha/mTOR kinase inhibitors (e.g., 46 and 48). PI3Kalpha/mTOR dual inhibitors demonstrated inhibition of tumor cell growth in vitro and in vivo and caused suppression of the pathway specific biomarkers [e.g., the phosphorylation of Akt at Thr308 (T308) and Ser473 (S473)] in the human breast cancer cell line MDA361. In addition, compound 46 demonstrated good in vivo efficacy in the MDA361 human breast tumor xenograft model.

Synthesis of Phosphatidylinositol 3-Kinase (PI3K) Inhibitory Analogues of the Sponge Meroterpenoid Liphagal

Analogues of the sponge meroterpenoid liphagal have been synthesized and evaluated for inhibition of PI3Kα and PI3Kγ as part of a program aimed at developing new isoform-selective PI3K inhibitors. One of the analogues, compound 24, with IC₅₀ values of 66 nM against PI3Kα and 1840 nM against PI3Kγ, representing a 27-fold preference for PI3Kα, exhibited enhanced chemical stability and modestly enhanced potency and selectivity compared with the natural product liphagal.

PKI-179: An orally efficacious dual phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitor

A series of mono-morpholino 1,3,5-triazine derivatives (8a-8q) bearing a 3-oxa-8-azabicyclo[3.2.1]octane were prepared and evaluated for PI3-kinase/mTOR activity. Replacement of one of the bis-morpholines in lead compound 1 (PKI-587) with 3-oxa-8-azabicyclo[3.2.1]octane and reduction of the molecular weight yielded 8m (PKI-179), an orally efficacious dual PI3-kinase/mTOR inhibitor. The in vitro activity, in vivo efficacy, and PK properties of 8m are discussed.

Novel purine and pyrazolo[3,4-d]pyrimidine inhibitors of PI3 kinase-α: Hit to lead studies

Series of purine and pyrazolo[3,4-d]pyrimidine inhibitors of phosphatidylinositol-3-kinases (PI3K) have been prepared. The optimized purine inhibitors show good potency in a PI3K p110alpha (PI3K-alpha) fluorescence polarization assay with good selectivity versus PI3K p110gamma (PI3K-gamma) and the mammalian target of rapamycin (mTOR). The related pyrazolo[3,4-d]pyrimidines show potent PI3K-alpha and mTOR inhibition with good selectivity versus PI3K-gamma. Representative compounds showed activity in a cellular proliferation assay against Caco-2 colorectal, LoVo colorectal and PC3MM2 prostate adenocarcinoma cancer cells. Signaling through the PI3K pathway was confirmed via inhibition of phospho-AKT in MDA-361 cells.

MEK (MAPKK) inhibitors. Part 2: structure-activity relationships of 4-anilino-3-cyano-6,7-dialkoxyquinolines.

A series of 4-anilino-3-cyano-6,7-dialkoxyquinolines with different substituents attached to the 4-anilino group has been prepared that are potent MEK (MAP kinase kinase) inhibitors. The best activity is obtained when a phenyl or a thienyl group is attached to the para-position of the aniline through a hydrophobic linker, such as an oxygen, a sulfur, or a methylene group. The most active compounds show low nanomolar IC(50)s against MEK (MAP kinase kinase), and have potent growth inhibitory activity in LoVo cells (human colon tumor line).

Identification of 2-oxatriazines as highly potent pan-PI3K/mTOR dual inhibitors.

We recently described several highly potent, triazine (1) and triazolopyrimidine (2) scaffold-based, dual PI3K/mTOR-inhibitors (e.g., 1, PKI-587) that were efficacious in both in vitro and in vivo models. In order to further optimize these compounds we devised a novel series, the 2-oxatriazines, which also exhibited excellent potency and good metabolic stability. Some 2-oxatriazines showed promising in vivo biomarker suppression and induced apoptosis in the MDA-MB-361 breast cancer xenograft model.