The efficacy of therapeutics is dependent on a drug binding to its cognate target. Optimization of target engagement by drugs in cells is often challenging, because drug binding cannot be monitored inside cells. We have developed a method for evaluating drug binding to target proteins in cells and tissue samples. This cellular thermal shift assay (CETSA) is based on the biophysical principle of ligand-induced thermal stabilization of target proteins. Using this assay, we validated drug binding for a set of important clinical targets and monitored processes of drug transport and activation, off-target effects and drug resistance in cancer cell lines, as well as drug distribution in tissues. CETSA is likely to become a valuable tool for the validation and optimization of drug target engagement.

http://science.sciencemag.org/content/sci/341/6141/84.full.pdf

Monitoring Drug Target Engagement in Cells and Tissues Using the Cellular Thermal Shift Assay

HIV-1 protease inhibitors continue to play an important role in the treatment of HIV/AIDS, transforming this deadly ailment into a more manageable chronic infection. Over the years, intensive research has led to a variety of approved protease inhibitors for the treatment of HIV/AIDS. In this review, we outline current drug design and medicinal chemistry efforts toward the development of next-generation protease inhibitors beyond the currently approved drugs.

/pdf/recent-progress-in-the-development-of-hiv-1-protease-mdtz8rj5j7.pdf

Recent Progress in the Development of HIV-1 Protease Inhibitors for the Treatment of HIV/AIDS.

The nitro group is considered to be a versatile and unique functional group in medicinal chemistry. Despite a long history of use in therapeutics, the nitro group has toxicity issues and is often categorized as a structural alert or a toxicophore, and evidence related to drugs containing nitro groups is rather contradictory. In general, drugs containing nitro groups have been extensively associated with mutagenicity and genotoxicity. In this context, efforts toward the structure–mutagenicity or structure–genotoxicity relationships have been undertaken. The current Perspective covers various aspects of agents that contain nitro groups, their bioreductive activation mechanisms, their toxicities, and approaches to combat their toxicity issues. In addition, recent advances in the field of anticancer, antitubercular and antiparasitic agents containing nitro groups, along with a patent survey on hypoxia-activated prodrugs containing nitro groups, are also covered.

Nitro-Group-Containing Drugs

A drug must engage its intended target to achieve its therapeutic effect. However, conclusively measuring target engagement (TE) in situ is challenging. This complicates preclinical development and is considered a key factor in the high rate of attrition in clinical trials. Here, we discuss a recently developed, label-free, biophysical assay, the cellular thermal shift assay (CETSA), which facilitates the direct assessment of TE in cells and tissues at various stages of drug development. CETSA also reveals biochemical events downstream of drug binding and therefore provides a promising means of establishing mechanistic biomarkers. The implementation of proteome-wide CETSA using quantitative mass spectrometry represents a novel strategy for defining off-target toxicity and polypharmacology and for identifying downstream mechanistic biomarkers. The first year of CETSA applications in the literature has focused on TE studies in cell culture systems and has confirmed the broad applicability of CETSA to many d...

The Cellular Thermal Shift Assay: A Novel Biophysical Assay for In Situ Drug Target Engagement and Mechanistic Biomarker Studies

During tumor formation and expansion, increasing glucose metabolism is necessary for unrestricted growth of tumor cells. Expression of key glycolytic enzyme alpha-enolase (ENO1) is controversial and its modulatory mechanisms are still unclear in non-small cell lung cancer (NSCLC). The expression of ENO1 was examined in NSCLC and non-cancerous lung tissues, NSCLC cell lines, and immortalized human bronchial epithelial cell (HBE) by quantitative real-time reverse transcription PCR (qRT-PCR), immunohistochemistry, and Western blot, respectively. The effects and modulatory mechanisms of ENO1 on cell glycolysis, growth, migration, invasion, and in vivo tumorigenesis and metastasis in nude mice were also analyzed. ENO1 expression was increased in NSCLC tissues in comparison to non-cancerous lung tissues. Similarly, NSCLC cell lines A549 and SPCA-1 also express higher ENO1 than HBE cell line in both mRNA and protein levels. Overexpressed ENO1 significantly elevated NSCLC cell glycolysis, proliferation, clone formation, migration, and invasion in vitro, as well as tumorigenesis and metastasis in vivo by regulating the expression of glycolysis, cell cycle, and epithelial-mesenchymal transition (EMT)-associated genes. Conversely, ENO1 knockdown reversed these effects. More importantly, our further study revealed that stably upregulated ENO1 activated FAK/PI3K/AKT and its downstream signals to regulate the glycolysis, cell cycle, and EMT-associated genes. This study showed that ENO1 is responsible for NSCLC proliferation and metastasis; thus, ENO1 might serve as a potential molecular therapeutic target for NSCLC treatment.

/pdf/alpha-enolase-promotes-cell-glycolysis-growth-migration-and-nsh5bb6yao.pdf

Alpha-enolase promotes cell glycolysis, growth, migration, and invasion in non-small cell lung cancer through FAK-mediated PI3K/AKT pathway

Recent advances in the discovery of potent and selective HDAC6 inhibitors.

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.

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

The invention discloses an indenopyrazole small-molecule tubulin inhibitor, which is characterized by having a structure represented by general formula I: 
wherein R represents NH 2 or NHOH; the invention also discloses a preparation method of the indenopyrazole compound, or pharmaceutical salts thereof. The compound of the present invention is an indenopyrazole small-molecule tubulin inhibitor having a novel structure, and has very strong proliferation inhibition activity to human hepatocellular carcinoma (HepG2) cells, human prostate carcinoma (PC3) cells, human cervical carcinoma (HeLa) cells, human breast adenocarcinoma (MCF-7) cells, and human leukemia (K562) cells; the compound is similar to colchicine in mechanism of action, and thus capable of inhibiting tubulin polymerization; the compound is significant for enhancing the specificity and effectiveness of drugs, reducing toxic and side effects, preventing drug tolerance, and so on.

Design, synthesis, and biological evaluation of 1-methyl-1, 4-dihyrdoindeno[1,2-C]pyrazole analogues as potential anticaner agents targeting tubulin colchicine binding site

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.

The development of MetAP-2 inhibitors in cancer treatment.

We previously reported a PI3K inhibitor S14161 which displays a promising preclinical activity against multiple myeloma (MM) and leukemia, but the chiral structure and poor solubility prevent its further application. Six S14161 analogs were designed based on the structure–activity relationship; activity of the compounds in terms of cell death and inhibition of PI3K were analyzed by flow cytometry and Western blotting, respectively; anti-myeloma activity in vivo was performed on two independent xenograft models. Among the six analogs, BENC-511 was one of the most potent compounds which significantly inhibited PI3K activity and induced MM cell apoptosis. BENC-511 was able to inactivate PI3K and its downstream signals AKT, mTOR, p70S6K, and 4E-BP1 at 1 μM but had no effects on their total protein expression. Consistent with its effects on PI3K activity, BENC-511 induced MM cell apoptosis which was evidenced by the cleavage of Caspase-3 and PARP. Notably, addition of insulin-like growth factor 1 and interleukin-6, two important triggers for PI3K activation in MM cells, partly blocked BENC-511-induced MM cell death, which further demonstrated that PI3K signaling pathway was critical for the anti-myeloma activity of BENC-511. Moreover, BENC-511 also showed potent oral activity against myeloma in vivo. Oral administration of BENC-511 decreased tumor growth up to 80% within 3 weeks in two independent MM xenograft models at a dose of 50 mg/kg body weight, but presented minimal toxicity. Suppression of BENC-511 on MM tumor growth was associated with decreased PI3K/AKT activity and increased cell apoptosis. Because of its potent anti-MM activity, low toxicity (LD50 oral >1.5 g/kg), and easy synthesis, BENC-511 could be developed as a promising agent for the treatment of MM via suppressing the PI3K/AKT signaling pathway.

/pdf/identification-of-a-promising-pi3k-inhibitor-for-the-35bqddyg6i.pdf

Zhao-Peng Liu

Papers

Recent advances in the discovery of potent and selective HDAC6 inhibitors.

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

Design, synthesis, and biological evaluation of 1-methyl-1, 4-dihyrdoindeno[1,2-C]pyrazole analogues as potential anticaner agents targeting tubulin colchicine binding site

The development of MetAP-2 inhibitors in cancer treatment.

Identification of a promising PI3K inhibitor for the treatment of multiple myeloma through the structural optimization