Zhao-Peng Liu

Preparation of S14161 and its analogues and the discovery of 6-bromo-8-ethoxy-3-nitro-2H-chromene as a more potent antitumor agent in vitro

The small chemical compound 8-ethoxy-2-(4-fluorophenyl)-3-nitro-2H-chromene (S14161) was recently identified as an inhibitor of the phosphoinositide 3-kinase (PI3K). In the present study, we designed a novel synthesis of S14161 and prepared a series of its analogues via the oxa-Michael-Henry reaction in the presence of catalytic amounts of l-proline and triethylamine. Further structural simplification led to the identification of 6-bromo-8-ethoxy-3-nitro-2H-chromene (BENC-511) that exhibited potent antiproliferative activities against a panel of 12 tumor cell lines. Compared with S14161, BENC-511 was more potent in blocking the AKT phosphorylation and inducing cancer cell apoptosis. BENC-511 also displayed more potent effects on human umbilical vein epithelial cells (HUVEC) migration, suggesting its anti-angiogenesis activity.

The development of MetAP-2 inhibitors in cancer treatment.

Methionine aminopeptidases (MetAPs), which remove methionine residue from newly synthesized polypeptide chains, are a class of metalloproteases ubiquitously distributed in both eukaryotes and prokaryotes. MetAP-2 inhibition can induce G1 cell cycle arrest, cytostasis in tumor cells in vitro and inhibition of tumor growth in vivo. The discovery of fumagillin with potent antiangiogenic and antiproliferative activities promoted the development of fumagillin analogues as a novel class of anticancer agents. Early drug discovery efforts have focused on analogs of fumagillin, which irreversibly inhibit MetAP-2 through covalent modification of an epoxide. Several fumagillin analogs, like CKD-732, TNP-470 and PPI-2458, were found to be potent selective inhibitors of MetAP-2 (proteolytic activity) and endothelial cell proliferation. Further, they have entered in clinical trials for the treatment of different types of tumors. Recently, attention has been paid to reversible human MetAP-2 inhibitors, such as bengamides, 2-hydroxy-3-aminoamides, anthranilic acid sulfonamides and triazole analogs, which have demonstrated their potential to inhibit angiogenesis and tumor growth in vivo as well. This review article mainly discussed the development of MetAP-2 inhibitors in cancer therapy and also summarized their structure-activity relationships.

Tubulin colchicine binding site inhibitors as vascular disrupting agents in clinical developments.

Tumor vasculature is an important target in cancer treatment. Two distinct vasculartargeting therapeutic strategies are applied to attack cancer cells indirectly. The antiangiogenic approach intervenes in the neovascularization processes and blocks the formation of new blood vessels, while th e antivascular approach targets the established tumor blood vessels, making vascular shutdown and resulting in rapid haemorrhagic necrosis and tumor cell death. A number of compounds with diverse structural scaffolds have been designed to target tumor vasculature and they are called vascular disrupting agents (VDAs). The biological or ligand-directed VDAs utilize antibodies, peptides or growth factors to deliver toxins or pro-coagulants or proapoptotic affectors to tumor-related blood vessels, while the small-molecule VDAs selectively target tumor blood vessels and have little effects on the normal endothelium. Among the small-molecule VDAs, the tubulin colchicine binding site inhibitors have been extensively studied and many of them have entered the clinical trials, including CA-4P, CA-1P, AVE8062, OXi4503, CKD-516, BNC105P, ABT-751, CYT- 997, ZD6126, NPI-2358, MN-029 and EPC2407. This review makes a summary of the small-molecule VDAs in clinical developments and highlights some potential VDA leads or candidates for the treatment of tumors.

Design, Synthesis, and Biological Evaluation of 1-Methyl-1,4-dihydroindeno[1,2-c]pyrazole Analogues as Potential Anticancer Agents Targeting Tubulin Colchicine Binding Site

By targeting a new binding region at the interface between αβ-tubulin heterodimers at the colchicine binding site, we designed a series of 7-substituted 1-methyl-1,4-dihydroindeno[1,2-c]pyrazoles as potential tubulin polymerization inhibitors. Among the compounds synthesized, 2-(6-ethoxy-3-(3-ethoxyphenylamino)-1-methyl-1,4-dihydroindeno[1,2-c]pyrazol-7-yloxy)acetamide 6a and 2-(6-ethoxy-3-(3-ethoxyphenylamino)-1-methyl-1,4-dihydroindeno[1,2-c]pyrazol-7-yloxy)-N-hydroxyacetamide 6n showed noteworthy low nanomolar potency against HepG2, Hela, PC3, and MCF-7 cancer cell lines. In mechanism studies, 6a inhibited tubulin polymerization and disorganized microtubule in A549 cells by binding to tubulin colchicine binding site. 6a arrested A549 cells in G2/M phase that was related to the alterations in the expression of cyclin B1 and p-cdc2. 6a induced A549 cells apoptosis through the activation of caspase-3 and PARP. In addition, 6a inhibited capillary tube formation in a concentration-dependent manner. In nonsmall cell lung cancer xenografts mouse model, 6a suppressed tumor growth by 59.1% at a dose of 50 mg/kg (ip) without obvious toxicity, indicating its in vivo potential as anticancer agent.

Recent Developments of Small Molecule EGFR Inhibitors Based on the Quinazoline Core Scaffolds

Progress in identifying and understanding the molecular and cellular causes of cancer has led to the discovery of anomalies that characterize cancer cells and that represent targets for the development of cancer therapeutics. One such target is the epidermal growth factor receptor (EGFR), a transmembrane protein that is frequently dysregulated in cancer cells and associated with the development, progression and aggressiveness of a number of malignancies. Inhibition of EGFR signaling has thus been identified as an attractive strategy in control of tumor proliferation, and over a decade of intense activity in the field has culminated in the discoveries and subsequent approvals of gefitinib and erlotinib for the treatment of non-small cell lung cancer. However, the drugs resistance to gefitinib and erlotinib has been clinically observed. Therefore, intensive efforts have been made in the discovery of novel potent and selective EGFR inhibitors. This review will focus on the developments of small molecule EGFR inhibitors based on the quinazoline core scaffolds in recent 5 years. Diverse EGFR inhibitors are classified as 4-anilinoquinazolines and 4-nonanilininoquinazolines, their biological data are described, and the structure-activity relationships (SARs) are discussed.

Recent developments of p38α MAP kinase inhibitors as antiinflammatory agents based on the imidazole scaffolds.

Rheumatoid arthritis (RA) and other chronic inflammatory diseases are always the major therapeutic challenges. Recent research efforts provided new insights into the molecular basis of these diseases and new opportunities for developing improved anti-inflammatory drugs. The p38 mitogen-activated protein (MAP) kinase plays a central role in the regulation of the biosynthesis and release of several proinflammatory cytokines including tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β). Hence, inhibition of the p38 MAP kinase is regarded as a promising therapeutic strategy for controlling inflammatory diseases. A diverse range of p38α MAP kinase inhibitors have been developed as potential anti-inflammatory agents, and some of them have entered the phase II clinical trials. The imidazole derivatives are known as competitive inhibitors at the ATP binding site of the p38α MAP kinase. Modifications on the imidazole scaffold have led to a large amount of potent p38α MAP kinase inhibitors. This review will summarize the developments of small molecule p38α MAP kinase inhibitors based on the imidazole core scaffolds in recent 10 years. Variations at the N1, C2, C4 and C5 positions of imidazole were introduced, and the structure-activity relationships of these imidazole inhibitors were also discussed.

Recent advances in the discovery of potent and selective HDAC6 inhibitors

Histone deacetylase HDAC6, a member of the class IIb HDAC family, is unique among HDAC enzymes in having two active catalytic domains, and has unique physiological function. In addition to the modification of histone, HDAC6 targets specific substrates including α-tubulin and HSP90, and are involved in protein trafficking and degradation, cell shape and migration. Selective HDAC6 inhibitors are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Therefore, extensive investigations have been made in the discovery of selective HDAC6 inhibitors. Based on their different zinc binding groups (ZBGs), in this review, HDAC6 inhibitors are grouped as hydroxamic acids, a sulfur containing ZBG based derivatives and other ZBG-derived compounds, and their enzymatic inhibitory activity, selectivity and other biological activities are introduced and summarized.

A novel PI3K inhibitor displays potent preclinical activity against an androgen-independent and PTEN-deficient prostate cancer model established from the cell line PC3

Recent studies demonstrated that targeting the phosphatidylinositide 3-kinase (PI3K)/AKT signaling pathway is a major strategy for the treatment of androgen-independent prostate cancer. In the present study, we developed an analog BENC-511 from a recently reported PI3K inhibitor S14161 by structural optimization. Using PC3 and DU145 as the model cell lines, we found PTEN-deficient PC3 cells were more sensitive than PTEN-expressing DU145 ones in terms of cell proliferation, apoptosis, and caspase-3 activation. These findings were consistent with the inhibition on PI3K/AKT signals. BENC-511 preferably suppressed AKT activation in PC3 over DU145 cells. Notably, PTEN restoration attenuated BENC-511 induced apoptosis. Moreover, BENC-511 displayed great therapeutic efficacy in a PC3-derived prostate cancer model in nude mice. With an oral dosage of 50mg/kg, BENC-511 decreased tumor growth more than 50% in 27 days, which was accompanied with PARP cleavage, but did not show overt toxicity. This study lays a solid rationale for the development of BENC-511 as a drug for the treatment of PTEN-deficient and androgen-independent prostate cancers.

Synthesis and evaluation of trehalose-based compounds as novel inhibitors of cancer cell migration and invasion.

As a continuous research for the discovery of trehalose‐based anti‐invasive agents, we developed a convenient synthetic approach for the preparation of 6,6′‐dideoxy‐6,6′‐bis(acylamino)‐α,α‐D‐trehaloses. A series of trehalose‐based amides were prepared through the trityl protection of the two primary hydroxyls of α,α‐D‐trehalose, benzoylation, the removal of the trityl protective group, mesylation, azidation, catalytic hydrogenation in the presence of hydrochloride, coupling reaction with a variety of acids, and subsequent debenzoylation and deacetylation in some cases. Compound 8b, 6,6′‐dideoxy‐6,6′‐bis(2‐hydroxybenzamide)‐α,α‐D‐trehalose, was just as potent as the natural brartemicin against the invasion of murine colon 26‐L5 cells. It exhibited no cytotoxicity on human breast adenocarcinoma MDA‐MB‐231 and murine colon 26‐L5 cells. It can significantly inhibit the migration and invasion of the MDA‐MB‐231 cells. The anti‐invasive effect of 8b was possibly related to its inhibitory activity on MMP‐9, its suppression on the expression of MMP‐9 and VEGF, and its deactivation of Akt.

Design and synthesis of highly potent HIV-1 protease inhibitors with novel isosorbide-derived P2 ligands.

The design, synthesis, and biological evaluation of a series of six HIV-1 protease inhibitors incorporating isosorbide moiety as novel P2 ligands are described. All the compounds are very potent HIV-1 protease inhibitors with IC50 values in the nanomolar or picomolar ranges (0.05-0.43 nM). Molecular docking studies revealed the formation of an extensive hydrogen-bonding network between the inhibitor and the active site. Particularly, the isosorbide-derived P2 ligand is involved in strong hydrogen bonding interactions with the backbone atoms.