ChemMedChem

Cholesterol: A Key in the Pathogenesis of Alzheimer's Disease ()
Abstract Herein we highlight recent advances in our understanding of the role of cholesterol in Alzheimer′s disease (AD). It has been proposed that cholesterol could enhance the risk of AD, and the interaction between cholesterol and amyloid‐β peptide 42 (Aβ42) has been studied extensively, yet until recently, the specific interaction mechanisms between them and how this affects Aβ42 aggregation had not yet been fully explored and had remained ambiguous. Vendruscolo and co‐workers addressed these issues in their recent article entitled “Cholesterol catalyses Aβ42 aggregation through a heterogeneous nucleation pathway in the presence of lipid membranes” (Habchi et al., Nat. Chem. 2018, 10, 673). In this article, the authors revealed the mechanism behind cholesterol‐catalyzed Aβ42 aggregation, providing the potential to address the molecular origins of AD, thereby opening a new avenue for effective AD therapy.
>> Read More

Nucleobase Modified Adefovir (PMEA) Analogues as Potent and Selective Inhibitors of Adenylate Cyclases from Bordetella pertussis and Bacillus anthracis ()
Abstract A series of 13 acyclic nucleoside phosphonates (ANPs) as bisamidate prodrugs was prepared. Five compounds were found to be non‐cytotoxic and selective inhibitors of Bordetella pertussis adenylate cyclase toxin (ACT) in J774A.1 macrophage cell‐based assays. The 8‐aza‐7‐deazapurine derivative of adefovir (PMEA) was found to be the most potent ACT inhibitor in the series (IC50=16 nm) with substantial selectivity over mammalian adenylate cyclases (mACs). AC inhibitory properties of the most potent analogues were confirmed by direct evaluation of the corresponding phosphonodiphosphates in cell‐free assays and were found to be potent inhibitors of both ACT and edema factor (EF) from Bacillus anthracis (IC50 values ranging from 0.5 to 21 nm). Moreover, 7‐halo‐7‐deazapurine analogues of PMEA were discovered to be potent and selective mammalian AC1 inhibitors (no inhibition of AC2 and AC5) with IC50 values ranging from 4.1 to 5.6 μm in HEK293 cell‐based assays.
>> Read More

ω‐Phthalimidoalkyl Aryl Ureas as Potent and Selective Inhibitors of Cholesterol Esterase ()
Abstract Cholesterol esterase (CEase), a serine hydrolase thought to be involved in atherogenesis and thus coronary heart disease, is considered as a target for inhibitor development. We investigated recombinant human and murine CEases with a new fluorometric assay in a structure–activity relationship study of a small library of ω‐phthalimidoalkyl aryl ureas. The urea motif with an attached 3,5‐bis(trifluoromethyl)phenyl group and the aromatic character of the ω‐phthalimide residue were most important for inhibitory activity. In addition, an alkyl chain composed of three or four methylene groups, connecting the urea and phthalimide moieties, was found to be an optimal spacer for inhibitors. The so‐optimized compounds 2 [1‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐(3‐(1,3‐dioxoisoindolin‐2‐yl)propyl)urea] and 21 [1‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐(4‐(1,3‐dioxoisoindolin‐2‐yl)butyl)urea] exhibited dissociation constants (Ki) of 1–19 μm on the two CEases and showed either a competitive (2 on the human enzyme and 21 on the murine enzyme) or a noncompetitive mode of inhibition. Two related serine hydrolases—monoacylglycerol lipase and fatty acid amide hydrolase—were inhibited by ω‐phthalimidoalkyl aryl ureas to a lesser extent.
>> Read More

Toward Angiogenesis Inhibitors Based on the Conjugation of Organometallic Platinum(II) Complexes to RGD Peptides ()
Abstract A novel conjugate between a cyclometalated platinum(II) complex with dual antiangiogenic and antitumor activity and a cyclic peptide containing the RGD sequence (‐Arg‐Gly‐Asp‐) has been synthesized by combining solid‐ and solution‐phase methodologies. Although peptide conjugation rendered a non‐cytotoxic compound in all tested tumor cell lines (± αVβ3 and αVβ5 integrin receptors), the antiangiogenic activity of the Pt‐c(RGDfK) conjugate in human umbilical vein endothelial cells at sub‐cytotoxic concentrations opens the way to the design of a novel class of angiogenesis inhibitors through conjugation of metallodrugs with high antiangiogenic activity to cyclic RGD‐containing peptides or peptidomimetic analogues.
>> Read More

Experimental Characterization of the Binding Affinities between Proapoptotic BH3 Peptides and Antiapoptotic Bcl‐2 Proteins ()
Abstract The Bcl‐2 family proteins are key regulators of the intrinsic apoptotic pathway and are among the validated targets for developing anticancer drugs. Protein–protein interactions between the pro‐ and antiapoptotic members of this family determine mitochondrial outer‐membrane permeabilization. Elucidating such protein–protein interactions in a quantitative way is helpful for network pharmacology studies on the Bcl‐2 family, which, in turn, will provide valuable guidance for developing new anticancer therapies. In this study, the binding affinities of the BH3 peptides derived from eight proapoptotic BH3‐only proteins (i.e., Bid, Bim, Puma, Noxa, Bad, Bmf, Bik, Hrk) against five well‐studied antiapoptotic proteins (i.e., Bcl‐xL, Bcl‐2, Mcl‐1, Bcl‐w, Bfl‐1) in the Bcl‐2 family have been measured. Three different types of binding assay (i.e., surface plasmon resonance, fluorescence polarization, and homogeneous time‐resolved fluorescence) were employed for cross‐validation. The results confirmed that each proapoptotic BH3 peptide exhibited a distinct binding profile against the five antiapoptotic proteins. The binding data obtained herein serve as a fresh update or correction to existing knowledge. It is expected that such binding data will be helpful for building more accurate mathematical network models for depicting the complex protein–protein interactions within the Bcl‐2 family.
>> Read More

Synthesis of a Series of Structurally Diverse MB327 Derivatives and Their Affinity Characterization at the Nicotinic Acetylcholine Receptor ()
Abstract A novel series of 30 symmetric bispyridinium and related N‐heteroaromatic bisquaternary salts with a propane‐1,3‐diyl linker was synthesized and characterized for their binding affinity at the MB327 binding site of nicotinic acetylcholine receptor (nAChR) from Torpedo californica. Compounds targeting this binding site are of particular interest for research into new antidotes against organophosphate poisoning, as therapeutically active 4‐tert‐butyl‐substituted bispyridinium salt MB327 was previously identified as a nAChR re‐sensitizer. Efficient access to the target compounds was provided by newly developed methods enabling N‐alkylation of sterically hindered or electronically deactivated heterocycles exhibiting a wide variety of functional groups. Determination of binding affinities toward the MB327 binding site at the nAChR, using a recently developed mass spectrometry (MS)‐based Binding Assay, revealed that several compounds reached affinities similar to that of MB327 (pKi=4.73±0.03). Notably, the newly prepared lipophilic 4‐tert‐butyl‐3‐phenyl‐substituted bispyridinium salt PTM0022 (3 h) was found to have significantly higher binding affinity, with a pKi value of 5.16±0.07, thus representing considerable progress toward the development of more potent nAChR re‐sensitizers.
>> Read More

The Impact of Adrenomedullin Thr22 on Selectivity within the Calcitonin Receptor‐like Receptor/Receptor Activity‐Modifying Protein System ()
Abstract Adrenomedullin (ADM) is a peptide hormone of the calcitonin gene‐related peptide (CGRP) family. It is involved in the regulation of cardiovascular processes such as angiogenesis, vasodilation, and the reduction of oxidative stress. ADM mediates its effects by activation of the ADM‐1 and ‐2 receptors (AM1R/AM2R), but also activates the CGRP receptor (CGRPR) with reduced potency. It binds to the extracellular domains of the receptors with its C‐terminal binding motif (residues 41–52). The activation motif, consisting of a disulfide‐bonded ring structure (residues 16–21) and an adjacent helix (residues 22–30), binds to the transmembrane region and stabilizes the receptor conformation in the active state. While it was shown that the binding motif of ADM guides AM1R selectivity, there is little information on the activation motif itself. Here, we demonstrate that Thr22 of ADM contributes to the selectivity. By using solid‐phase peptide synthesis and cAMP‐based signal transduction, we studied the effects of analogues in the activation motif of ADM on AM1R and CGRPR activity. Our results indicate that Thr22 terminates the α‐helix and orients the ring segment by hydrogen bonding. Using olefin stapling, we showed that the α‐helical arrangement of the ring segment leads to decreased AM1R activity, but does not affect CGRPR activation. These results demonstrate that the conformation of the ring segment of ADM has a strong impact on the selectivity within the receptor system.
>> Read More

Synthesis and Antiviral Evaluation of TriPPPro‐AbacavirTP, TriPPPro‐CarbovirTP, and Their 1′,2′‐cis‐Disubstituted Analogues ()
Abstract Herein we describe the synthesis of lipophilic triphosphate prodrugs of abacavir, carbovir, and their 1′,2′‐cis‐substituted carbocyclic analogues. The 1′,2′‐cis‐carbocyclic nucleosides were prepared by starting from enantiomerically pure (1R,2S)‐2‐((benzyloxy)methyl)cyclopent‐3‐en‐1‐ol by a microwave‐assisted Mitsunobu‐type reaction with 2‐amino‐6‐chloropurine. All four nucleoside analogues were prepared from their 2‐amino‐6‐chloropurine precursors. The nucleosides were converted into their corresponding nucleoside triphosphate prodrugs (TriPPPro approach) by application of the H‐phosphonate route. The TriPPPro compounds were hydrolyzed in different media, in which the formation of nucleoside triphosphates was proven. While the TriPPPro compounds of abacavir and carbovir showed increased antiviral activity over their parent nucleoside, the TriPPPro compounds of the 1′,2′‐cis‐substituted analogues as well as their parent nucleosides proved to be inactive against HIV.
>> Read More

Discovery of Aporphine Analogues as Potential Antiplatelet and Antioxidant Agents: Design, Synthesis, Structure–Activity Relationships, Biological Evaluations, and in silico Molecular Docking Studies ()
Abstract To explore the potential of aporphine alkaloids, a novel series of functionalized aporphine analogues with alkoxy (OCH3, OC2H5, OC3H7) functional groups at C1/C2 of ring A and an acyl (COCH3 and COPh) or phenylsulfonyl (SO2Ph and SO2C6H4‐3‐CH3) functionality at the N6 position of ring B of the aporphine scaffold were synthesized and evaluated for their arachidonic acid (AA)‐induced antiplatelet aggregation inhibitory activity and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free‐radical‐scavenging antioxidant activity, with acetylsalicylic acid and ascorbic acid as standard references, respectively. The preliminary structure–activity relationship related to AA‐induced platelet aggregation inhibitory activity results showed that the aporphine analogues 1‐[1,2,9,10‐tetramethoxy‐6a,7‐dihydro‐4H‐dibenzo[de,g]quinolin‐6(5H)‐yl]ethanone and 1‐[2‐(benzyloxy)‐1,9,10‐trimethoxy‐6a,7‐dihydro‐4H‐dibenzo[de,g]quinolin‐6(5H)‐yl]ethanone to be the best compounds of the series. Moreover, the DPPH free‐radical‐scavenging antioxidant activity results demonstrated that the aporphine analogues 1,2,9,10‐tetramethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 2‐ethoxy‐1,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 1‐ethoxy‐2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, 2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐1‐propoxy‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline, and 1‐(benzyloxy)‐2,9,10‐trimethoxy‐6‐(methylsulfonyl)‐5,6,6a,7‐tetrahydro‐4H‐dibenzo[de,g]quinoline were the best compounds of the series. Moreover, in silico molecular docking simulation studies of the active analogues were also performed.
>> Read More

Antibiotic Drug Discovery: New Targets and Molecular Entities. Edited by Steven M. Firestine and Troy Lister ()
ChemMedChem, Volume 13, Issue 17, Page 1848-1849, September 6, 2018.
>> Read More

Theranostics and Image Guided Drug Delivery. Edited by Maya Thanou ()
ChemMedChem, Volume 13, Issue 17, Page 1851-1852, September 6, 2018.
>> Read More

Drug Discovery for Leishmaniasis. Edited by Luis Rivas and Carmen Gil ()
ChemMedChem, Volume 13, Issue 17, Page 1850-1850, September 6, 2018.
>> Read More

Front Cover: Toward Angiogenesis Inhibitors Based on the Conjugation of Organometallic Platinum(II) Complexes to RGD Peptides (ChemMedChem 17/2018) ()
ChemMedChem, Volume 13, Issue 17, Page 1741-1741, September 6, 2018.
>> Read More

Brain‐Penetrant Triazolopyrimidine and Phenylpyrimidine Microtubule Stabilizers as Potential Leads to Treat Human African Trypanosomiasis ()
Abstract In vitro whole‐organism screens of Trypanosoma brucei with representative examples of brain‐penetrant microtubule (MT)‐stabilizing agents identified lethal triazolopyrimidines and phenylpyrimidines with sub‐micromolar potency. In mammalian cells, these antiproliferative compounds disrupt MT integrity and decrease total tubulin levels. Their parasiticidal potency, combined with their generally favorable pharmacokinetic properties, which include oral bioavailability and brain penetration, suggest that these compounds are potential leads against human African trypanosomiasis.
>> Read More

Quinone‐Fused Pyrazoles through 1,3‐Dipolar Cycloadditions: Synthesis of Tricyclic Scaffolds and in vitro Cytotoxic Activity Evaluation on Glioblastoma Cancer Cells ()
Abstract A novel and straightforward synthesis of highly substituted isoquinoline‐5,8‐dione fused tricyclic pyrazoles is reported. The key step of the synthetic sequence is a regioselective, Ag2CO3 promoted, 1,3‐dipolar cycloaddition of C‐heteroaryl‐N‐aryl nitrilimines and substituted isoquinoline‐5,8‐diones. The broad functional group tolerability and mild reaction conditions were found to be suitable for the preparation of a small library of compounds. These scaffolds were designed to interact with multiple biological residues, and two of them, after brief synthetic elaborations, were analyzed by molecular docking studies as potential anticancer drugs. In vitro studies confirmed the potent anticancer effects, showing promising IC50 values as low as 2.5 μm against three different glioblastoma cell lines. Their cytotoxic activity was finally positively correlated to their ability to inhibit PI3K/mTOR kinases, which are responsible for the regulation of diverse cellular processes in human cancer cells.
>> Read More

Exploration of Sulfur‐Containing Analogues for Imaging Vesicular Acetylcholine Transporter in the Brain ()
Abstract Sixteen new sulfur‐containing compounds targeting the vesicular acetylcholine transporter (VAChT) were synthesized and assessed for in vitro binding affinities. Enantiomers (−)‐(1‐(3‐hydroxy‐1,2,3,4‐tetrahydronaphthalen‐2‐yl)piperidin‐4‐yl)(4‐(methylthio)phenyl)methanone [(−)‐8] and (−)‐(4‐((2‐fluoroethyl)thio)phenyl)(1‐(3‐hydroxy‐1,2,3,4‐tetrahydronaph‐thalen‐2‐yl)piperidin‐4‐yl)methanone [(−)‐14 a] displayed high binding affinities, with respective Ki values of 1.4 and 2.2 nm for human VAChT, moderate and high selectivity for human VAChT over σ1 (≈13‐fold) and σ2 receptors (>420‐fold). Radiosyntheses of (−)‐[11C]8 and (−)‐[18F]14 a were achieved using conventional methods. Ex vivo autoradiography and biodistribution studies in Sprague–Dawley rats indicated that both radiotracers have the capacity to penetrate the blood–brain barrier, with high initial brain uptake at 5 min and rapid washout. The striatal region had the highest accumulation for both radiotracers. Pretreating the rats with the VAChT ligand (−)‐vesamicol decreased brain uptake for both radiotracers. Pretreating the rats with the σ1 ligand YUN‐122 (N‐(4‐benzylcyclohexyl)‐2‐(2‐fluorophenyl)acetamide) also decreased brain uptake, suggesting these two radiotracers also bind to the σ1 receptor in vivo. The microPET study of (−)‐[11C]8 in the brain of a non‐human primate showed high striatal accumulation that peaked quickly and washed out rapidly. Although preliminary results indicated these two sulfur‐containing radiotracers have high binding affinities for VAChT with rapid washout kinetics from the striatum, their σ1 receptor binding properties limit their potential as radiotracers for quantifying VAChT in vivo.
>> Read More

Prodrugs of Nucleoside Triphosphates as a Sound and Challenging Approach: A Pioneering Work That Opens a New Era in the Direct Intracellular Delivery of Nucleoside Triphosphates ()
Abstract Synthetic nucleosides, designed to mimic naturally occurring nucleosides, are important antiviral and anticancer chemotherapeutic agents. However, nucleosides are not active as such and need to be metabolized, step by step, to their corresponding active nucleoside triphosphates (NTPs). This is mediated by phosphorylating enzymes, mainly host cellular kinases with strong specificity for their substrates; in many cases, this specificity prevents efficient conversion into the NTPs. To circumvent this metabolic handicap, successful nucleo(s/t)ide prodrugs have been developed as a valuable concept in the design of effective drugs. The unique concept of the TriPPPro approach, developed by Chris Meier and colleagues, is a powerful tool for the intracellular delivery of active NTPs, bypassing all the phosphorylation steps required by nucleosides to yield the active NTP metabolites. This concept is illustrated herein with general examples.
>> Read More

Identification of α‐Mangostin as an Agonist of Human STING ()
Abstract The xanthone derivate 5′,6′‐dimethylxanthenone‐4‐acetic acid (DMXAA, also known as ASA404 or vadimezan) is a potent agonist of murine STING (stimulator of interferon genes), but cannot activate human STING. Herein we report that α‐mangostin, which bears the xanthone skeleton, is an agonist of human STING, but activates murine STING to a lesser extent. Biochemical and cell‐based assays indicate that α‐mangostin binds to and activates human STING, leading to activation of the downstream interferon regulatory factor (IRF) pathway and production of type I interferons. Furthermore, our studies show that α‐mangostin has the potential to repolarize human monocyte‐derived M2 macrophages to the M1 phenotype. The agonist effect of α‐mangostin in the STING pathway might account for its antitumor and antiviral activities.
>> Read More

Synthesis and Biological in vitro and in vivo Evaluation of 2‐(5‐Nitroindazol‐1‐yl)ethylamines and Related Compounds as Potential Therapeutic Alternatives for Chagas Disease ()
Abstract Chagas disease, a neglected tropical disease caused by infection with the protozoan parasite Trypanosoma cruzi, is a potentially life‐threatening illness that affects 5–8 million people in Latin America, and more than 10 million people worldwide. It is characterized by an acute phase, which is partly resolved by the immune system, but then develops as a chronic disease without an effective treatment. There is an urgent need for new antiprotozoal agents, as the current standard therapeutic options based on benznidazole and nifurtimox are characterized by limited efficacy, toxicity, and frequent failures in treatment. In vitro and in vivo assays were used to identify some new low‐cost 5‐nitroindazoles as a potential antichagasic therapeutic alternative. Compound 16 (3‐benzyloxy‐5‐nitro‐1‐vinyl‐1H‐indazole) showed improved efficiency and lower toxicity than benznidazole in both in vitro and in vivo experiments, and its trypanocidal activity seems to be related to its effect at the mitochondrial level. Therefore, compound 16 is a promising candidate for the development of a new anti‐Chagas agent, and further preclinical evaluation should be considered.
>> Read More

Synthesis, Structural Characterization, and Antiangiogenic Activity of Polyfluorinated Benzamides ()
Abstract The introduction of fluorine into bioactive molecules is a matter of importance in medicinal chemistry. In this study, representatives of various chemical entities of fluoroaromatic compounds were synthesized. Depending on the reaction conditions, either tetrafluorophthalimides or ammonium tetrafluorophthalamates are accessible from tetrafluorophthalic anhydride and primary amines. Tetrafluorophthalamic acids undergo thermal decarboxylation to yield tetrafluorobenzamides. These could be successfully converted upon treatment with primary amines, in the course of an aromatic nucleophilic substitution, to 2,3,5‐trifluorobenzamides with respective amino substituents at the 4‐position. The five structure types were characterized by means of spectroscopic and crystallographic methods. The synthesized compounds were evaluated as inhibitors of angiogenesis by measuring microvessel outgrowth in a rat aortic ring assay. The biological activity was maintained throughout these different polyfluorinated chemotypes.
>> Read More

Structural Mapping of Anion Inhibitors to β‐Carbonic Anhydrase psCA3 from Pseudomonas aeruginosa ()
Abstract Pseudomonas aeruginosa is a Gram‐negative facultative anaerobe belonging to the Pseudomonadaceae family. It is a multidrug‐resistant opportunistic human pathogen, a common cause of life‐threatening nosocomial infections, and a key bacterial agent in cystic fibrosis and endocarditis. The bacterium exhibits intrinsic resistance to most antibacterial agents, including aminoglycosides and quinolones. Hence, the identification of new drug targets for P. aeruginosa is ongoing. PsCA3 is a β‐class carbonic anhydrase (β‐CA) that catalyzes the reversible hydration of carbon dioxide to bicarbonate and represents a new class of antimicrobial target. Previously, inhibitor screening studies of psCA3 have shown that a series of small anions including sulfamide (SFN), imidazole (IMD), and 4‐methylimidazole (4MI), and thiocyanate (SCN) inhibit the enzyme with efficiencies in the micro‐ to millimolar range. Herein the X‐ray crystal structures of these inhibitors in complex with psCA3 are presented and compared with human CA II. This structural survey into the binding modes of small anions forms the foundation for the development of inhibitors against β‐CAs and more selective inhibitors against P. aeruginosa.
>> Read More

Synthesis, Computational Docking Study, and Biological Evaluation of a Library of Heterocyclic Curcuminoids with Remarkable Antitumor Activity ()
Abstract In a continuing search for curcuminoid (CUR) compounds with antitumor activity, a novel series of heterocyclic CUR–BF2 adducts and CUR compounds based on indole, benzothiophene, and benzofuran along with their aryl pyrazoles were synthesized. Computational docking studies were performed to compare binding efficiency to target proteins involved in specific cancers, namely HER2, proteasome, VEGFR, BRAF, and Bcl‐2, versus known inhibitor drugs. The majority presented very good binding affinities, similar to, and even more favorable than those of known inhibitors. The indole‐based CUR–BF2 and CUR compounds and their bis‐thiocyanato derivatives exhibited high anti‐proliferative and apoptotic activity by in vitro bioassays against a panel of 60 cancer cell lines, more specifically against multiple myeloma (MM) cell lines (KMS11, MM1.S, and RPMI‐8226) with significantly lower IC50 values versus healthy PBMC cells; they also exhibited higher anti‐proliferative activity in human colorectal cancer cells (HCT116, HT29, DLD‐1, RKO, SW837, and Caco2) than the parent curcumin, while showing notably lower cytotoxicity in normal colon cells (CCD112CoN and CCD841CoN).
>> Read More

Exploiting the Thiobarbituric Acid Scaffold for Antibacterial Activity ()
Abstract Thiobarbituric acid (TBA) has been considered a privileged structure for developing antimicrobial agents. Diversity was obtained at positions N and at C5 through acylation, Schiff base formation, Knoevenagel condensation, and thioamide and enamine formation. The present work describes the synthesis of small libraries based on the TBA moiety and above‐mentioned reactions. Preliminary antimicrobial activity screening of the prepared compounds against selected bacteria (both Gram‐positive and ‐negative) showed the best results for the Boc‐Phe‐TBA derivative. These results could be useful for designing and building libraries based on other amino acids with distinct protecting groups.
>> Read More

Decoding the Rich Biological Properties of Noble Gases: How Well Can We Predict Noble Gas Binding to Diverse Proteins? ()
Abstract The chemically inert noble gases display a surprisingly rich spectrum of useful biological properties. Relatively little is known about the molecular mechanisms behind these effects. It is clearly not feasible to conduct large numbers of pharmacological experiments on noble gases to identify activity. Computational studies of the binding of noble gases and proteins can address this paucity of information and provide insight into mechanisms of action. We used bespoke computational grid calculations to predict the positions of energy minima in the interactions of noble gases with diverse proteins. The method was validated by quantifying how well simulations could predict binding positions in 131 diverse protein X‐ray structures containing 399 Xe and Kr atoms. We found excellent agreement between calculated and experimental binding positions of noble gases. 94 % of all crystallographic xenon atoms were within 1 Xe van der Waals (vdW) diameter of a predicted binding site, and 97 % lay within 2 vdW diameters. 100 % of crystallographic krypton atoms were within 1 Kr vdW diameter of a predicted binding site. We showed the feasibility of large‐scale computational screening of all ≈60 000 unique structures in the Protein Data Bank. This will elucidate biochemical mechanisms by which these novel ‘atomic drugs’ elicit their valuable biochemical properties and identify new medical uses.
>> Read More

X‐ray Structures and Feasibility Assessment of CLK2 Inhibitors for Phelan–McDermid Syndrome ()
Abstract CLK2 inhibition has been proposed as a potential mechanism to improve autism and neuronal functions in Phelan–McDermid syndrome (PMDS). Herein, the discovery of a very potent indazole CLK inhibitor series and the CLK2 X‐ray structure of the most potent analogue are reported. This new indazole series was identified through a biochemical CLK2 Caliper assay screen with 30k compounds selected by an in silico approach. Novel high‐resolution X‐ray structures of all CLKs, including the first CLK4 X‐ray structure, bound to known CLK2 inhibitor tool compounds (e.g., TG003, CX‐4945), are also shown and yield insight into inhibitor selectivity in the CLK family. The efficacy of the new CLK2 inhibitors from the indazole series was demonstrated in the mouse brain slice assay, and potential safety concerns were investigated. Genotoxicity findings in the human lymphocyte micronucleus test (MNT) assay are shown by using two structurally different CLK inhibitors to reveal a major concern for pan‐CLK inhibition in PMDS.
>> Read More

Semi‐synthesis and Structure–Activity Relationship of Neuritogenic Oleanene Derivatives ()
Abstract (3S,4R)‐23,28‐Dihydroxyolean‐12‐en‐3‐yl (2E)‐3‐(3,4‐dihydroxyphenyl)acrylate (1 a), which possesses significant neuritogenic activity, was isolated from the traditional Chinese medicine (TCM) plant, Desmodium sambuense. To confirm the structure and to assess biological activity, we semi‐synthesized 1 a from commercially available oleanolic acid. A series of novel 1 a derivatives was then designed and synthesized for a structure–activity relationship (SAR) study. All synthetic derivatives were characterized by analysis of spectral data, and their neuritogenic activities were evaluated in assays with PC12 cells. The SAR results indicate that the number and position of the hydroxy groups on the phenyl ring and the triterpene moiety, as well as the length of the (saturated or unsaturated) alkyl chain that links the phenyl ring with the triterpene critically influence neuritogenic activity. Among all the tested compounds, 1 e [(3S,4R)‐23,28‐dihydroxyolean‐12‐en‐3‐yl (2E)‐3‐(3,4,5‐trihydroxyphenyl)acrylate] was found to be the most potent, inducing significant neurite outgrowth at 1 μm.
>> Read More

d‐Polyarginine Lipopeptides as Intestinal Permeation Enhancers ()
Abstract An estimated 285 million people were living with diabetes in 2010, and this number is expected to reach 440 million by 2030. Current treatment of this disease involves the intradermal injection of insulin analogues. Many alternative administration routes have been proposed, the oral route being the most widely studied. One of the most interesting approaches for insulin delivery is the use of permeation enhancers to increase its transport across the gastrointestinal tract (GIT). Cell‐penetrating peptides (CPPs) are a remarkable example of this family of compounds. Another alternative is the use of medium‐chain fatty acids (MCFAs) to temporally disrupt the tight junctions of the GIT, thereby allowing greater drug transport. A combination of both strategies can provide a synergistic way to increase drug transport through the GIT. In this study we evaluated the complexation of insulin glulisine, an insulin analogue administered subcutaneously or intravenously in clinical practice, with a well‐known CPP modified with the MCFA lauric acid. We prepared several formulations, examined their stability, and tested the best candidates in an intestinal cell‐based model. In particular, two compounds (C12‐r4 and C12‐r6) were found to significantly increase the transport of insulin, and therefore show promise as a new delivery system worthy of further evaluation.
>> Read More

Self‐Assembled Supramolecular Nanoparticles for Targeted Delivery and Combination Chemotherapy ()
Abstract It is challenging but imperative to merge imaging agents and small molecule therapeutics into one nanoentity for diagnosis and treatment. Herein, we constructed polymeric nanoparticles for targeted delivery and combination chemotherapy, which formed through host–guest interactions among three elements: 1) β‐cyclodextrin polymer (poly‐β‐CD), as the backbone of nanoparticles; 2) two antitumor drugs—doxorubicin (DOX) and docetaxel (DTX); and 3) aptamers labeled with adamantane and fluorescein (Ad‐aptamer‐FAM), as recognition elements. First, polymeric nanoparticles, termed self‐assembled supramolecular nanoparticles (SSNPs), were formulated by combining hydrophobic DTX and DOX with poly‐β‐CD via host–guest interactions. Then, the surface of SSNPs modified the aptamer to acquire targeting ability; such nanoparticles were termed targeted self‐assembled supramolecular nanoparticles (T‐SSNPs). As evidenced by MTS assay data, T‐SSNPs exhibited significant selective cytotoxicity toward target cells. The results also indicated that combination drugs achieved a good synergistic effect with a combination index of 0.43. Thus, an effective and simple drug delivery system was constructed for targeted delivery and combination chemotherapy.
>> Read More

Synthesis and Biological Evaluation of Tripartin, a Putative KDM4 Natural Product Inhibitor, and 1‐Dichloromethylinden‐1‐ol Analogues ()
Abstract The natural product tripartin has been reported to inhibit the N‐methyl‐lysine histone demethylase KDM4A. A synthesis of tripartin starting from 3,5‐dimethoxyphenylacrylic acid was developed, and the enantiomers were separated by chiral HPLC. We observed that both tripartin enantiomers manifested an apparent increase in H3K9me3 levels when dosed in cells, as measured by western blot analysis. Thus, there is no enantiomeric discrimination toward this natural product in terms of its effects on cellular histone methylation status. Interestingly, tripartin did not inhibit isolated KDM4A–E under our assay conditions (IC50>100 μm). Tripartin analogues with a dichloromethylcarbinol group derived from the indanone scaffold were synthesized and found to be inactive against isolated recombinant KDM4 enzymes and in cell‐based assays. Although the precise cellular mode of action of tripartin is unclear, our evidence suggests that it may affect histone methylation status via a mechanism other than direct inhibition of the KDM4 histone demethylases.
>> Read More

Design and Synthesis of DNA‐Interactive β‐Carboline–Oxindole Hybrids as Cytotoxic and Apoptosis‐Inducing Agents ()
Abstract A new series of (E)‐3‐[(1‐aryl‐9H‐pyrido[3,4‐b]indol‐3‐yl)methylene]indolin‐2‐one hybrids were synthesized and evaluated for their in vitro cytotoxic activity against a panel of selected human cancer cell lines, namely, HCT‐15, HCT‐116, A549, NCI‐H460, and MCF‐7, including HFL. Among the tested compounds, (E)‐1‐benzyl‐5‐bromo‐3‐{[1‐(2,5‐dimethoxyphenyl)‐9H‐pyrido[3,4‐b]indol‐3‐yl]methylene}indolin‐2‐one (10 s) showed potent cytotoxicity against HCT‐15 cancer cells with an IC50 value of 1.43±0.26 μm and a GI50 value of 0.89±0.06 μm. Notably, induction of apoptosis by 10 s on the HCT‐15 cell line was characterized by using different staining techniques, such as acridine orange/ethidium bromide (AO/EB) and DAPI. Further, to understand the mechanism of anticancer effects, various assays such as annexin V‐FITC/PI, DCFDA, and JC‐1were performed. The flow cytometric analysis revealed that compound 10 s arrests the HCT‐15 cancer cells at the G0/G1 phase of the cell cycle. Additionally, western blot analysis indicated that treatment of 10 s on HCT‐15 cancer cells led to decreased expression of anti‐apoptotic Bcl‐2 and increased protein expression of both pro‐apoptotic Bax and caspase‐3, ‐8, and ‐9, and cleaved PARP with reference to actin. Next, a clonogenic assay revealed the inhibition of colony formation in HCT‐15 cancer cells by 10 s in a dose‐dependent manner. Moreover, upon testing on normal human lung cells (HFL), the compounds were observed to be safer with a low toxicity profile. In addition, viscosity and molecular‐docking studies showed that compound 10 s has typical intercalation with DNA.
>> Read More

RASPELD to Perform High‐End Screening in an Academic Environment toward the Development of Cancer Therapeutics ()
Abstract The identification of compounds for dissecting biological functions and the development of novel drug molecules are central tasks that often require screening campaigns. However, the required architecture is cost‐ and time‐intensive. Herein we describe the devices and technologies that comprise a Robotics‐Assisted Screening Platform for Efficient Ligand Discovery (RASPELD), which we set up in an academic laboratory. RASPELD provides semi‐automated high‐end screening, and it can be maintained by graduate students. We demonstrate its successful application in biochemical and cellular screens for the identification and validation of bioactive chemical entities as candidate cancer‐relevant inhibitors. Specifically, we examined the interaction between a transcription factor, Nrf2, and its key regulator, Keap1. We also examined drug‐resistant mutants of the epidermal growth factor receptor (EGFR). Screening campaigns with more than 30 000 compounds were performed in a reasonable period of time. We identified the molecule RSL6586 as a starting point for hit optimization, which is currently ongoing.
>> Read More

An Endogenous Reactive Oxygen Species (ROS)‐Activated Histone Deacetylase Inhibitor Prodrug for Cancer Chemotherapy ()
Abstract Suberoylanilide hydroxamic acid (SAHA, vorinostat) is a potent small‐molecule pan‐inhibitor of histone deacetylases (HDACs) approved for treatment of cutaneous T‐cell lymphoma (CTCL). However, SAHA exhibits poor selectivity for cancer cells over noncancer cells. With an aim to improving its selectivity for cancer cells, we generated a novel SAHA prodrug (SAHA‐OBP) that is activated in the presence of hydrogen peroxide, a reactive oxygen species (ROS) known to be overexpressed in cancer cells. The high endogenous ROS content in cancer cells triggers rapid removal of the 4‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)benzyl carbonyl (OBP) cap to release active SAHA. The SAHA‐OBP prodrug demonstrates selective activity against multiple cancer cell lines such as HeLa, MCF‐7, MDA‐MB‐231, and B16‐F10, while remaining benign toward noncancer cells. The downstream effects of SAHA released from SAHA‐OBP in cancer cells is the induction of apoptosis. SAHA‐OBP was also found to be effective on multicellular tumor spheroids (MCTS). The SAHA prodrug designed in this study undergoes rapid ROS‐dependent activation and imparts much‐needed selectivity to SAHA for cancer cells.
>> Read More

Combined Ligand‐ and Receptor‐Based Virtual Screening Methodology to Identify Structurally Diverse Protein Tyrosine Phosphatase 1B Inhibitors ()
Abstract Protein tyrosine phosphatase 1B (PTP1B) is a potential drug target for diabetes and obesity. However, the design of PTP1B inhibitors that combine potency and bioavailability is a great challenge, and new leads are needed to circumvent this problem. Virtual screening (VS) workflows can be used to find new PTP1B inhibitors with little chemical similarity to existing inhibitors. Unfortunately, previous VS workflows for the identification of PTP1B inhibitors have several limitations, such as a small number of experimentally tested compounds and the low bioactivity of those compounds. We developed a VS workflow capable of identifying 15 structurally diverse PTP1B inhibitors from 20 compounds, the bioactivity of which was tested in vitro. Moreover, we identified two PTP1B inhibitors with the highest bioactivity reported by any VS campaign (i.e., IC50 values of 1.4 and 2.1 μm), which could be used as new lead compounds.
>> Read More

Development of Potent Inhibitors of Fatty Acid Amide Hydrolase Useful for the Treatment of Neuropathic Pain ()
Abstract The unique role of fatty acid amide hydrolase (FAAH) in terminating endocannabinoid (EC) signaling supports its relevance as a therapeutic target. Inhibition of EC metabolizing enzymes elicits indirect agonism of cannabinoid receptors (CBRs) and therapeutic efficacy devoid of psychotropic effects. Based on our previous ligands, and aiming at the discovery of new selective FAAH inhibitors, we developed a series of 12 new compounds characterized by functionalized tricyclic scaffolds. All the developed compounds display negligible activity on monoacylglycerol lipase (MAGL) and CBRs. The most potent FAAH inhibitors of the newly developed series, 6‐oxo‐5,6‐dihydro‐4H‐benzo[f]pyrrolo[1,2‐a][1,4]diazepin‐9‐yl‐6‐phenylhexylcarbamate (5 h) and 4‐oxo‐5,6‐dihydro‐4H‐benzo[f]pyrrolo[1,2‐a][1,4]diazepin‐9‐yl‐(6‐phenylhexyl)carbamate (5 i) (nanomolar FAAH inhibitors, the latter of which also shows micromolar affinity at the CB1R), were selected for further studies. Results of cell‐based studies on a neuroblastoma cell line (IMR32) demonstrated 5 h, 5 i, and our reference compound 3 ([3‐(3‐carbamoylpyrrol‐1‐yl)phenyl] N‐(5‐phenylpentyl)carbamate) to lack any cytotoxic effect, while all three showed the ability to decrease oxidative stress by reducing the expression of the redox‐sensitive transcription factor NF‐κB. Encouraged by these data, these compounds were studied in vivo and were dosed orally in a mouse model of neuropathic pain. At 10 mg kg−1 all the compounds were able to relieve the hypersensitivity induced by oxaliplatin.
>> Read More

A More Sustainable Process for Preparation of the Muscarinic Acetylcholine Antagonist Umeclidinium Bromide ()
Abstract A more sustainable process for the synthesis of the long‐acting muscarinic acetylcholine antagonist umeclidinium bromide is described. Specifically, we report the synthesis of ethyl 1‐(2‐chloroethyl)‐4‐piperidinecarboxylate, a key intermediate in the preparation of umeclidinium bromide, in good yields using triethylamine, as well as the identification and characterization of the by‐product formed in this reaction. This new method of synthesis leads to an improvement in yield over that of previously reported protocols using potassium carbonate as base (65.6 % versus 38.6 %). Moreover, in the final synthetic step of the process to obtain umeclidinium bromide, we were able to replace the use of toxic solvents (acetonitrile/chloroform) with water. The use of this green solvent allowed precipitation of the active pharmaceutical ingredient (API) from the reaction medium with high purity and in high yield. Overall, we have developed a more efficient and environmentally friendly process for the synthesis of the umeclidinium bromide API with a higher overall yield (37.8 % versus previously reported overall yield of 9.7 %).
>> Read More

Synthesis and Biological Evaluation of Reniochalistatins A–E and a Reniochalistatin E Analogue ()
Abstract The total synthesis of reniochalistatins A–E, along with a reniochalistatin E analogue (inverso‐E) was successfully achieved through Fmoc‐based solid‐phase peptide synthesis and subsequent macrolactamization with PyBOP and DIEA. The biological activities of these reniochalistatins and a key linear peptide intermediate were systematically evaluated. Among these seven synthesized compounds, linear reniochalistatin B was found to have potent activity against several cancer cell lines not shown by the cyclic reniochalistatin B counterpart. In addition, linear reniochalistatin B was found to have antitubercular activity (IC50=1.4 μm). Inverso‐E possesses increasing cytotoxicity against the HeLa and LNCaP cell lines after simple alternation of the sequence of amino acids in reniochalistatin E. The results of these studies provide a feasible method to further investigate the structure–activity relationships (SARs) of reniochalistatins A–E.
>> Read More

Structural Basis of Substrate Recognition and Covalent Inhibition of Cdu1 from Chlamydia trachomatis ()
Abstract Based on the similarity between the active sites of the deubiquitylating and deneddylating enzyme ChlaDub1 (Cdu1) and the evolutionarily related protease adenain, a target‐hopping screening approach on a focused set of adenain inhibitors was investigated. The cyanopyrimidine‐based inhibitors identified represent the first active‐site‐directed small‐molecule inhibitors of Cdu1. High‐resolution crystal structures of Cdu1 in complex with two covalently bound cyanopyrimidines, as well as with its substrate ubiquitin, were obtained. These structural data were complemented by enzymatic assays and covalent docking studies to provide insight into the substrate recognition of Cdu1, active‐site pocket flexibility and potential hotspots for ligand interaction. Combined, these data provide a strong basis for future structure‐guided medicinal chemistry optimization of this cyanopyrimidine scaffold into more potent and selective Cdu1 inhibitors.
>> Read More

Molecular Recognition of a Thomsen–Friedenreich Antigen Mimetic Targeting Human Galectin‐3 ()
Abstract Overexpression of the Thomsen–Friedenreich (TF) antigen in cell membrane proteins occurs in 90 % of adenocarcinomas. Additionally, the binding of the TF antigen to human galectin‐3 (Gal‐3), also frequently overexpressed in malignancy, promotes cancer progression and metastasis. In this context, structures that interfere with this specific interaction have the potential to prevent cancer metastasis. A multidisciplinary approach combining the optimized synthesis of a TF antigen mimetic with NMR, X‐ray crystallography methods, and isothermal titration calorimetry assays was used to unravel the molecular structural details that govern the Gal‐3/TF mimetic interaction. The TF mimetic has a binding affinity for Gal‐3 similar to that of the TF natural antigen and retains the binding epitope and bioactive conformation observed for the native antigen. Furthermore, from a thermodynamic perspective, a decrease in the enthalpic contribution was observed for the Gal‐3/TF mimetic complex; however, this behavior is compensated by a favorable gain in entropy. From a structural perspective, these results establish our TF mimetic as a scaffold to design multivalent solutions to potentially interfere with Gal‐3 aberrant interactions and for likely use in hampering Gal‐3‐mediated cancer cell adhesion and metastasis.
>> Read More

Discovery of a Potent, Long‐Acting, and CNS‐Active Inhibitor (BIA 10‐2474) of Fatty Acid Amide Hydrolase ()
Abstract Fatty acid amide hydrolase (FAAH) can be targeted for the treatment of pain associated with various medical conditions. Herein we report the design and synthesis of a novel series of heterocyclic‐N‐carboxamide FAAH inhibitors that have a good alignment of potency, metabolic stability and selectivity for FAAH over monoacylglycerol lipase (MAGL) and carboxylesterases (CEs). Lead optimization efforts carried out with benzotriazolyl‐ and imidazolyl‐N‐carboxamide series led to the discovery of clinical candidate 8 l (3‐(1‐(cyclohexyl(methyl)carbamoyl)‐1H‐imidazol‐4‐yl)pyridine 1‐oxide; BIA 10‐2474) as a potent and long‐acting inhibitor of FAAH. However, during a Phase I clinical trial with compound 8 l, unexpected and unpredictable serious neurological adverse events occurred, affecting five healthy volunteers, including the death of one subject.
>> Read More

Organoruthenium Prodrugs as a New Class of Cholinesterase and Glutathione‐S‐Transferase Inhibitors ()
Abstract A small library of 17 organoruthenium compounds with the general formula [RuII(fcl)(chel)(L)]n+ (in which fcl=face capping ligand, chel=chelating bidentate ligand, and L=monodentate ligand) were screened for inhibitory activity against cholinesterases and glutathione‐S‐transferases of human and animal origins. Compounds were selected to include different chelating ligands (i.e., N,N‐, N,O‐, O,O‐, S,O‐) and monodentate ligands that can modulate the aquation rate of the metal species. Compounds with a labile ruthenium chloride bond that provided rapid aquation were found to inhibit both sets of enzymes in reversible competitive modes and at pharmaceutically relevant concentrations. When applied at concentrations that completely abolish the activity of human acetylcholinesterase, the lead compound [(η6‐p‐cymene)Ru(pyrithionato)Cl] (C1 a) showed no undesirable physiological responses on the neuromuscular system. Finally, C1 a was not cytotoxic against non‐transformed cells at pharmaceutically relevant concentrations.
>> Read More

On the Implication of Water on Fragment‐to‐Ligand Growth in Kinase Binding Thermodynamics ()
Abstract A ligand‐binding study is presented focusing on thermodynamics of fragment expansion. The binding of four compounds with increasing molecular weight to protein kinase A (PKA) was analyzed. The ligands display affinities between low‐micromolar to nanomolar potency despite their low molecular weight. Binding free energies were measured by isothermal titration calorimetry, revealing a trend toward more entropic and less enthalpic binding with increase in molecular weight. All protein–ligand complexes were analyzed by crystallography and solution NMR spectroscopy. Crystal structures and solution NMR data are highly consistent, and no major differences in complex dynamics across the series are observed that would explain the differences in the thermodynamic profiles. Instead, the thermodynamic trends result either from differences in the solvation patterns of the conformationally more flexible ligand in aqueous solution prior to protein binding as molecular dynamics simulations suggest, or from local shifts of the water structure in the ligand‐bound state. Our data thus provide evidence that changes in the solvation pattern constitute an important parameter for the understanding of thermodynamic data in protein–ligand complex formation.
>> Read More

Exploiting Peptidomimetics to Synthesize Compounds That Activate Ryanodine Receptor Calcium Release Channels ()
Abstract Ryanodine receptor (RyR) Ca2+‐release channels are essential for contraction in skeletal and cardiac muscle and are prime targets for modification of contraction in disorders that affect either the skeletal or heart musculature. We designed and synthesized a number of compounds with structures based on a naturally occurring peptide (A peptides) that modifies the activity of RyRs. In total, 34 compounds belonging to eight different classes were prepared. The compounds were screened for their ability to enhance Ca2+ release from isolated cardiac sarcoplasmic reticulum (SR) vesicles, with 25 displaying enhanced Ca2+ release. Competition studies with the parent peptides indicated that the synthetic compounds act at a competing site. The activity of the most effective of the compounds, BIT 180, was further explored using Ca2+ release from skeletal SR vesicles and contraction in intact skeletal muscle fibers. The compounds did not alter tension in intact fibers, indicating that (as expected) they are not membrane permeable, but importantly, that they are not toxic to the intact cells. Proof in principal that the compounds would be effective in intact muscle fibers if rendered membrane permeable was obtained with a structurally related membrane‐permeable scorpion toxin (imperatoxin A), which was found to enhance contraction.
>> Read More

Synthesis and in vitro Evaluation of ADAM10 and ADAM17 Highly Selective Bioimaging Probes ()
Abstract A disintegrin and metalloproteinase (ADAMs) are membrane‐bound metalloproteases responsible for the ectodomain shedding of various transmembrane proteins and play important roles in multiple relevant biological processes. Their altered expression is involved in several pathological conditions, and in particular ADAM10 or ADAM17 overexpression is found in various forms of cancer. To better understand how they are regulated in the cellular context, it is useful to visualize the specific ADAMs pathway by means of molecular imaging techniques. For this purpose, we synthesized bioactive fluorescent probes suitable for cell imaging and that are able to specifically target ADAM10 or ADAM17. Two previously developed ADAM17‐ and ADAM10‐selective inhibitors were chosen for conjugation, respectively, to a Cy5.5 dye and to Cy5.5 and FITC dyes. Herein we also report the synthesis of a gold‐labeled compound as an additional bioimaging probe for ADAM10. The newly synthesized ligands were found to be active in vitro on human recombinant ADAM10 and/or ADAM17, showing IC50 values in the nanomolar range and a good selectivity over matrix metalloproteinases (MMPs). Finally, these newly developed probes were successfully used for ADAMs staining on different lymphoma cell lines and lymph node mesenchymal stromal cells.
>> Read More

Triaryl Pyrazole Toll‐Like Receptor Signaling Inhibitors: Structure–Activity Relationships Governing Pan‐ and Selective Signaling Inhibitors ()
Abstract The immune system uses members of the toll‐like receptor (TLR) family to recognize a variety of pathogen‐ and host‐derived molecules in order to initiate immune responses. Although TLR‐mediated, pro‐inflammatory immune responses are essential for host defense, prolonged and exaggerated activation can result in inflammation pathology that manifests in a variety of diseases. Therefore, small‐molecule inhibitors of the TLR signaling pathway might have promise as anti‐inflammatory drugs. We previously identified a class of triaryl pyrazole compounds that inhibit TLR signaling by modulation of the protein–protein interactions essential to the pathway. We have now systematically examined the structural features essential for inhibition of this pathway, revealing characteristics of compounds that inhibited all TLRs tested (pan‐TLR signaling inhibitors) as well as compounds that selectively inhibited certain TLRs. These findings reveal interesting classes of compounds that could be optimized for particular inflammatory diseases governed by different TLRs.
>> Read More

Antitrypanosomatid Pharmacomodulation at Position 3 of the 8‐Nitroquinolin‐2(1H)‐one Scaffold Using Palladium‐Catalysed Cross‐Coupling Reactions ()
Abstract An antikinetoplastid pharmacomodulation study at position 3 of the recently described hit molecule 3‐bromo‐8‐nitroquinolin‐2(1H)‐one was conducted. Twenty‐four derivatives were synthesised using the Suzuki–Miyaura cross‐coupling reaction and evaluated in vitro on both Leishmania infantum axenic amastigotes and Trypanosoma brucei brucei trypomastigotes. Introduction of a para‐carboxyphenyl group at position 3 of the scaffold led to the selective antitrypanosomal hit molecule 3‐(4‐carboxyphenyl)‐8‐nitroquinolin‐2(1H)‐one (21) with a lower reduction potential (−0.56 V) than the initial hit (−0.45 V). Compound 21 displays micromolar antitrypanosomal activity (IC50=1.5 μm) and low cytotoxicity on the human HepG2 cell line (CC50=120 μm), having a higher selectivity index (SI=80) than the reference drug eflornithine. Contrary to results previously obtained in this series, hit compound 21 is inactive toward L. infantum and is not efficiently bioactivated by T. brucei brucei type I nitroreductase, which suggests the existence of an alternative mechanism of action.
>> Read More

Drug Selectivity: An Evolving Concept in Medicinal Chemistry. Edited by Norbert Handler and Helmut Buschmann ()
ChemMedChem, EarlyView.
>> Read More

Successful Drug Discovery Volume 3. Edited by János Fischer, Christian Klein and Wayne E. Childers ()
ChemMedChem, EarlyView.
>> Read More

Corrigendum: Structure‐Based Design of a Monosaccharide Ligand Targeting Galectin‐8 ()
ChemMedChem, EarlyView.
>> Read More

Progress in the Development of Platelet‐Activating Factor Receptor (PAFr) Antagonists and Applications in the Treatment of Inflammatory Diseases ()
Abstract Platelet‐activating factor (PAF) and its receptor (PAFr) have been implicated in a wide range of diseases and disorders that originate from the activation of inflammatory pathways. Although the exact structure of the binding site on the PAFr remains unknown, the PAFr is a well‐established therapeutic target, and an array of structurally diverse PAFr antagonists have been identified. These include compounds that are structurally similar to the natural PAF ligand, synthetic heterocycles, complex polycyclic natural products, and various metal complexes. This review provides an update on more than 20 years of progress in this area. The development and synthesis of new PAFr antagonists, structure–activity relationship studies, the biological activity of these molecules, and their therapeutic potential are discussed.
>> Read More

Recent Advances in Functional‐Polymer‐Decorated Transition‐Metal Nanomaterials for Bioimaging and Cancer Therapy ()
Abstract In this review, we focus on recent advances in the synthesis of polymer‐functionalized transition‐metal‐based nanomaterials and follow this up by discussing their applications in bioimaging diagnosis and cancer therapy. Transition‐metal‐based nanomaterials show great potential in cancer therapy owing to their intensive near‐IR absorption, excellent photothermal conversion efficiency, strong X‐ray attenuation, and magnetic properties. Functional polymers are usually introduced by a one‐step or multistep method to further endow these nanomaterials with great biocompatibility and physiological stability. Polymer‐decorated transition‐metal nanomaterials show great potential in multimodal imaging diagnosis (photoacoustic imaging, computed tomography, photoluminescence imaging, positron emission tomography, etc.) and cancer therapy (chemotherapy, photothermal therapy, microwave therapy, radiotherapy, photodynamic therapy). At the end of this review, the prospects of these polymer‐decorated transition‐metal‐based nanomaterials are also discussed.
>> Read More

What Has Come out from Phytomedicines and Herbal Edibles for the Treatment of Cancer? ()
Abstract Several modern treatment strategies have been adopted to combat cancer with the aim of minimizing toxicity. Medicinal plant‐based compounds with the potential to treat cancer have been widely studied in preclinical research and have elicited many innovations in cutting‐edge clinical research. In parallel, researchers have eagerly tried to decrease the toxicity of current chemotherapeutic agents either by combining them with herbals or in using herbals alone. The aim of this article is to present an update of medicinal plants and their bioactive compounds, or mere changes in the bioactive compounds, along with herbal edibles, which display efficacy against diverse cancer cells and in anticancer therapy. It describes the basic mechanism(s) of action of phytochemicals used either alone or in combination therapy with other phytochemicals or herbal edibles. This review also highlights the remarkable synergistic effects that arise between certain herbals and chemotherapeutic agents used in oncology. The anticancer phytochemicals used in clinical research are also described; furthermore, we discuss our own experience related to semisynthetic derivatives, which are developed based on phytochemicals. Overall, this compilation is intended to facilitate research and development projects on phytopharmaceuticals for successful anticancer drug discovery.
>> Read More

Direct Comparison of SIRT2 Inhibitors: Potency, Specificity, Activity‐Dependent Inhibition, and On‐Target Anticancer Activities ()
Abstract Sirtuin inhibitors have attracted much interest due to the involvement of sirtuins in various biological processes. Several SIRT2‐selective inhibitors have been developed, and some exhibit anticancer activities. To facilitate the choice of inhibitors in future studies and the development of better inhibitors, we directly compared several reported SIRT2‐selective inhibitors: AGK2, SirReal2, Tenovin‐6, and TM. In vitro, TM is the most potent and selective inhibitor, and only TM could inhibit the demyristoylation activity of SIRT2. SirReal2, Tenovin‐6, and TM all showed cytotoxicity in cancer cell lines, with Tenovin‐6 being the most potent, but only TM showed cancer‐cell‐specific toxicity. All four compounds inhibited the anchorage‐independent growth of HCT116 cells, but the effect of TM was most significantly affected by SIRT2 overexpression, suggesting that the anticancer effect of TM depends more on SIRT2 inhibition. These results not only provide useful guidance about choosing the right SIRT2 inhibitor in future studies, but also suggest general practices that should be followed for small‐molecule inhibitor development activities.
>> Read More

Employing Photoredox Catalysis for DNA‐Encoded Chemistry: Decarboxylative Alkylation of α‐Amino Acids ()
Abstract A new procedure for the photoredox‐mediated conjugate addition of radicals that can be conveniently generated from α‐amino acids to DNA‐tagged Michael acceptors and styrenes is presented. This C(sp3)−C(sp3) coupling tolerates a broad array of structurally diverse radical precursors, including all of the 20 proteinogenic amino acids. Importantly, this reaction proceeds under mild conditions and in DNA‐compatible aqueous media. Furthermore, the presented reaction conditions are compatible with DNA, making this reaction platform well suited for the construction of DNA‐encoded libraries. The scope and limitations of the chemistry are discussed herein along with proposals for how this methodology might be used to construct DNA‐encoded libraries.
>> Read More

Folates in Trypanosoma brucei: achievements and opportunities ()
Trypanosoma brucei (T. brucei) is the agent of Human African Trypanosomiasis (HAT), a neglected disease that threats the life of 65 million people in sub Saharan Africa every year. Unfortunately, available therapy is unsatisfactory, mainly due to safety issues and developing resistances. Significant efforts over the last decades have been made in the discovery of new potential agents from the World Health Organization and public‐private partnership organizations such as the Drugs for Neglected Diseases Initiative (DNDi). Whereas antifolates have been a precious source of drugs against bacterial infections and malaria, no effective molecules towards T. brucei have been identified so far. Considering the simple T. brucei folate metabolism, and the results obtained up to now in this research field, we believe that further investigation might lead to effective chemotherapeutic agents. We present herein a selected collection of the more promising results obtained so far in this field, underlining the opportunities that could lead to successful therapeutic approaches in the future.
>> Read More

The Curtius Rearrangement: Applications in Modern Drug Discovery and Medicinal Chemistry ()
The Curtius rearrangement is the thermal decomposition of an acyl azide derived from carboxylic acid to produce an isocyanate as the initial product. The isocyanate can undergo further reactions to provide amines and their derivatives. Due to its tolerance for a large variety of functional groups and complete retention of stereochemistry during rearrangement, the Curtius rearrangement has been utilized in the synthesis of a wide variety of medicinal agents with amines and amine‐derived functional groups such as ureas and urethanes The current review outlines various applications of the Curtius rearrangement in drug discovery and medicinal chemistry. In particular, the review highlights some widely utilized rearrangement methods, syntheses of some key agents for popular drug targets and FDA approved drugs. In addition, the review highlights application of the Curtius rearrangement in continuous flow protocols for the scaling up of active pharmaceutical ingredients.
>> Read More

Cationic Branched Polyethylenimine (BPEI) Disables Antibiotic Resistance in Methicillin‐Resistant Staphylococcus epidermidis (MRSE) ()
Staphylococcus epidermidis is one of the most prevalent prokaryotic species on human skin and mucosal membranes that constitute the commensal flora. S. epidermidis has become one of the most common causes of primary bacteremia. Infections are difficult to diagnose because the pathogen has natural niches on human skin and the ability to adhere to inanimate surfaces via biofilms. Alarmingly, S. epidermidis has acquired resistance to many antibiotics, which presents a danger to human health. Most clinical isolates of S. epidermidis in North America exhibit β‐lactam resistance primarily due to the presence of mecA, a gene that bestows β‐lactam antibiotic resistance in a manner similar to methicillin‐resistant Staphylococcus aureus (MRSA). MecA encodes for expression of penicillin‐binding protein 2a (PBP2a), which is absent in β‐lactam susceptible strains of S. epidermidis. We can disable this resistance factor in MRSE with 600‐Da branched polyethylenimine (BPEI). Cationic BPEI targets anionic wall teichoic acid (WTA), an essential cofactor for proper functioning of PBP2a. We found that BPEI synergizes the activity of β‐lactam antibiotics against MRSE. Growth curves suggest that the combination of BPEI and oxacillin is bactericidal. Electron micrographs indicate abnormalities in the cellular septa and cell walls of treated samples. Therefore, first‐line clinical treatments can be effective against MRSE when used in combination with BPEI.
>> Read More

Symmetrical diamidates as a class of phosphate prodrugs to deliver the 5'‐monophosphate form of anticancer nucleoside analogues ()
We herein report on the application of phosphorodiamidate technology to both pyrimidine and purine nucleosides with anticancer activity. Sixteen symmetrical phosphorodiamidates esterified with natural amino acids such as L‐alanine and glycine were synthesized. All the compounds were evaluated for their cytotoxic activity in a wide panel of solid and leukemic tumour cell lines. In addition, a carboxypeptidase Y assay was performed on a representative phosphorodiamidate in order to reveal the putative bioactivation pathway for the reported phosphorodiamidate‐type prodrugs.
>> Read More

In Vivo Anticancer Activity of a Non‐Toxic Inert Phenolato Ti Complex: High Efficacy on Solid Tumors Alone and Combined with Pt Drugs ()
Due to the toxicity of platinum compounds used in the clinic as anticancer chemotherapies, the safe titanium serves as an attractive alternative. Lately, we introduced a new family of Ti complexes based on readily available phenolato ligands, demonstrating an incredibly high hydrolytic stability, with the lead compound phenolaTi demonstrating a wide cytotoxic activity towards the NCI‐60 panel of NIH human cancer cell lines, with an average GI50 of 4.7±2 µM. Herein, we evaluated in vivo: (a) the safety, and (b) the growth inhibitory (efficacy) of this compound. PhenolaTi was effective in vivo against colon (CT‐26) and lung (LLC‐1) murine cell lines in syngeneic hosts and towards a human colon cancer (HT‐29) cell line in immune deficient (Nude) mice, with an efficacy similar to that of known chemotherapy. Notably, no clinical signs of toxicity were observed in the treated mice; namely, no effect on body weight, spleen weight or kidney function, unlike observed with the positive control Pt drugs. Studies of combinations of PhenolaTi and Pt drugs evinced that similar efficacy with reduced toxicity may be achieved, which is highly valuable for medicinal applications.
>> Read More

An Update on Patents Covering Agents That Interfere with the Cancer Glycolytic Cascade ()
Many tumors exhibit altered metabolic characteristics relative to normal and healthy tissues. Their metabolic profile highlights a strong prevalence of glycolysis over oxidative phosphorylation, regardless their exposure to different oxygen levels (“Warburg effect”). This condition originates from a set of gene regulations, consisting in the overexpression of some enzymes or transporters involved in the glycolytic pathway. Therefore, these effectors may constitute appealing targets for the implementation of selective therapeutic interventions against cancer. Recently, significant progress has been made in the discovery of molecules acting at various levels of the glycolytic pathway of tumor cells. So far, some of the most widely explored targets of the glycolytic cascade are represented by glucose transporters, hexokinase, 6‐phosphofructokinase, enolase, pyruvate kinase, lactate dehydrogenase, and monocarboxylate transporters. The purpose of this mini‐review is to provide an update about some of the most recently patented bioactive molecules, that are able to interfere with cancer glycolysis, as well as about their use in specific combination therapies.
>> Read More

In silico prediction of chemical blood‐brain barrier permeability with machine learning and re‐sampling methods ()
Blood‐Brain Barrier (BBB) as a part of absorption protects the central nervous system by separating the brain tissue from the bloodstream. In recent years, BBB permeability has become a critical issue in chemical ADMET (absorption, distribution, metabolism, excretion, and toxicity) prediction, but almost all models were built with imbalanced datasets, which caused high false positive rate. Therefore, in this study, we tried to solve the bias problem and built a reliable classification model with 2358 compounds. Machine learning and re‐sampling methods were used for the refinement of models simultaneously, with both 2D molecular descriptors and molecular fingerprints to represent the chemicals. Through a series of evaluation, we realized that the re‐sampling methods (SMOTE and SMOTE + ENN) could effectively solve the imbalanced problem of our data sets, and MACCS fingerprint combining with SVM performed the best. With the final construction of a consensus model, the overall accuracy was improved to 0.966 for the final external set. Also, its accuracy for the test set was 0.919 with an excellent balanced capacity for predicting BBB positives of 0.925 (SE) and BBB negatives of 0.899 (SP). Compared with other BBB classification models, our models reduced the rate of false positives, and was more robust in prediction of BBB+ as well as BBB‐ compounds, which would be quite helpful in early drug discovery.
>> Read More

New ruthenium(II) polypyridyl complexes as photosensitizers for antibacterial photodynamic therapy: a structure‐activity study on clinical bacterial strains ()
As a growing public health concern, the worldwide spread of antimicrobial resistance urges the development of new therapies. Antibacterial photodynamic therapy (a‐PDT) may be an alternative to conventional antibiotherapy. Here, we report the synthesis and characterization of seven original reactive oxygen species (ROS) producing ruthenium(II) polypyridyl complexes. These are part of a collection of seventeen derivatives varying in terms of the nature of the substituent(s), molecular symmetry, electrical charge, and counter‐ions. They were characterized by considering (i) their physical properties (absorption coefficient at irradiation wavelength; 1O2 generation quantum‐yield; luminescence) and (ii) their antibacterial activity in a series of photodynamic assays using Gram‐positive as well as Gram‐negative bacteria of clinical relevance. The results unveiled some structure‐activity relationships; one derivative combining multiple beneficial features for a‐PDT was effective against all the bacteria considered, regardless of their Gram, species, and antibiotic resistance profile. This systematic study could guide the design of next generation ruthenium‐based complexes for enhanced antibacterial photodynamic strategies.
>> Read More

Design and Synthesis of Bioisosteres of Acylhydrazones as Stable Inhibitors of the Aspartic Protease Endothiapepsin ()
Acylhydrazone‐based dynamic combinatorial chemistry (DCC) is a powerful strategy for the rapid identification of novel hits. Even though acylhydrazones are important structural motifs in medicinal chemistry, their further progression in development may be hampered by major instability and toxicity issues under physiological conditions. It is therefore of paramount importance to identify stable replacements for acylhydrazone linkers. Here, we present the first report on the design and synthesis of stable bioisosteres of acylhydrazone‐based inhibitors of the aspartic protease endothiapepsin as a follow‐up to a DCC study. The most successful bioisostere is equipotent, bears an amide linker and we confirmed its binding mode by X‐ray crystallography. Having some validated bioisosteres of acylhydrazones readily available might accelerate hit‐to‐lead optimization for future acylhydrazone‐based DCC projects.
>> Read More

STRUCTURE‐BASED VIRTUAL SCREENING OF LSRK KINASE INHIBITORS TO TARGET QUORUM SENSING ()
In the era of increased antibiotic resistance, targeting enzymes involved in bacterial communication (quorum sensing) represents a new strategy to fight bacterial infections. LsrK is a kinase responsible for the phosphorylation of autoinducer‐2, a signal molecule involved in quorum sensing. Inhibiting LsrK would lead to quorum sensing inactivation and interfere with the pathogenesis. In this study, we built the first LsrK 3D model and performed virtual screening of a locally available database. Selected compounds were tested against LsrK and the analogue search conducted based on the positive hits led to the identification of low micromolar LsrK inhibitors. These results prove the usability of the model and provide the first class LsrK inhibitors to be further optimized as antivirulence agents.
>> Read More

Synthesis of Trifluoromethyl‐α,β‐unsaturated Lactones and Pyrazolinones and Discovery of Influenza Virus Polymerase Inhibitors ()
To explore potential biological activities of trifluoromethyl heterocycles, we recently developed a synthetic approach to assess a series of α‐trifluoromethyl‐α,β‐unsaturated lactones and trifluoromethyl pyrazolinones. The compounds were tested for their antimicrobial activity, and we found that some compounds had anti‐influenza viral activity. The β‐aryl‐α‐trifluoromethyl α,β‐unsaturated lactone derivatives 5g, 7b and the trifluoromethyl pyrazolinone 12c possessed promising inhibitory activity against influenza virus type A, strain A/WSN/33 (H1N1). These hit compounds 5g, 7b, and 12c were successfully optimized, and we identified that the most potent compound 5h showed inhibitory activity against various types of influenza A and B viruses in the low‐micromolar range without showing cytotoxicity. Moreover, 5h was more effective against the clinical isolate A/California/7/2009 (H1N1pdm) strain than the influenza viral polymerase inhibitor, favipiravir (T‐705). We also delineated the structure–activity relationship and obtained mechanistic insights into inhibition of the viral polymerase.
>> Read More

MetScore: Site of Metabolism Prediction Beyond CYP P450 Enzymes ()
The metabolism of xenobiotics by humans and other organisms is a complex process involving numerous enzymes that catalyze phase I (functionalization) and phase II (conjugation) reactions. We here introduce MetScore, a machine learning model that can predict both phase I and phase II reaction sites of drugs. We developed cheminformatics workflows to filter and process reactions to obtain suitable phase I and phase II data sets for model training. Employing a recently developed molecular representation based on quantum chemical partial charges, we constructed random forest machine learning models for phase I and phase II reactions. After combining these models with our previous cytochrome P450 model and calibrating the combination against Bayer in‐house data, we obtained the MetScore model that shows good performance with Matthews correlation coefficients of 0.61 and 0.76 for diverse phase I and phase II reaction types, respectively. We validated its potential applicability to lead optimization campaigns for a new and independent data set compiled from recent publications. The results of this study demonstrate the usefulness of quantum chemistry‐derived molecular representations for reactivity prediction.
>> Read More

Ectonucleotidase inhibitory and redox activity of imidazole‐based organic salts and ionic liquids ()
Cytotoxicity against cancerous and normal cells, inhibition of ectonucleotidase, and redox properties of a new group of imidazole‐based organic salts and ionic liquids have been explored. The tetrachloroferrate salt of a 1‐methylimidazole derivative of salicylic aldehyde has been shown to have most prominent inhibitory activity against ectonucleotidase, as well as a higher cytotoxicity against HeLa cells than that of the reference compound carboplatin, while having lower cytotoxicity towards BHK‐21 cells. The studied compounds have shown a moderate level of antioxidant activity with better results for the salicylic aldehyde derivatives than for the spiropyrans. Moreover, the compounds did not generate singlet oxygen formation.
>> Read More

Axitinib ‐ A Photoswitchable Approved Tyrosine Kinase Inhibitor ()
Axitinib is an approved drug targeting tyrosine kinases including the vascular endothelial growth factor receptor 2 (VEGFR2) and is licensed for second‐line therapy of renal cell carcinoma. Interestingly, axitinib contains a stilbene‐like double bond allowing for E/Z isomerization. In this study, we investigated the photoinduced E/Z isomerization of axitinib to explore if its inhibitory effect can be turned "on" and "off", triggered by light. Compared to the E‐isomer, the absorption of the Z‐isomer is red‐shifted indicating reversible photoswitching properties. When both isolated isomers were measured in a commercial available profiling under ambient light, no differences of biological activities could be determined. However, under controlled light conditions we could demonstrate that (Z) axitinib is 43 times less active compared to the (E) isomer in an VEGFR2 assays. Furthermore, we proved that kinase activity in HUVEC assays is reduced by (E)‐axitinib, but only weakly affected by (Z) axitinib. By irradiating (Z) axitinib in vitro with UV light (385 nm) it is possible to switch it almost quantitatively to the (E)‐isomer and to completely restore the biological activity of (E) axitinib. However, vice versa switching the biological activity "off" from (Z)‐ to (E)‐axitinib was not possible in aqueous solution due to a competing irreversible [2+2]‐photocycloaddition yielding a biologically inactive axitinib‐dimer.
>> Read More

Gold(I)‐coumarin‐caffeine‐based complexes as new potential anti‐inflammatory and anticancer trackable agents ()
Three new gold(I)‐coumarin‐based trackable therapeutic complexes and two non‐trackable analogues have been synthesized and fully characterized. They all display antiproliferative properties on several types of cancer cell lines including colon, breast, and prostate. Two complexes displayed significant anti‐inflammatory effect, while one displayed a pro‐inflammatory behaviour ‐ highlighting the impact of the position of the fluorophore on the caffeine scaffold. Additionnally, the three coumarin derivatives could be vizualized in vitro by two‐photons microscopy.
>> Read More

Chemotherapy for Fighting Schistosomiasis: Past, Present and Future ()
Chemotherapy based on repeated doses of Praziquantel (PZQ) is still the most effective control strategy against schistosomiasis, a neglected tropical disease caused by platyhelminths of the genus Schistosoma spp.. Its long‐term use, however, raises serious concerns about drug resistance against PZQ. Therefore, it is generally acknowledged that alternative treatment options are urgently needed. This review intends to summarize data on relinquished drugs as well as recent advances in the area of antischistosomal compounds from a medicinal chemistry point of view. Furthermore, insights into the structure‐activity relationships of each class of compounds are presented including in vitro and in vivo data, if available. Although many compounds demonstrated good antischistosomal activity in vitro, they offer little promise to replace PZQ. Nevertheless, the race for novel antischistosomal agents is ongoing.
>> Read More

Injectable Hydrogel of Vitamin B9 for Controlled Release of Both Hydrophilic and Hydrophobic Anticancer Drugs ()
Folic acid (FA), vitamin‐B9, is a good receptor of drugs triggering cellular uptake via endocytosis. FA is sparingly soluble in water and here a new approach for formation of FA hydrogel at physiological condition is reported using hydrolysis of glucono‐δ‐lactone in PBS buffer. The gel has fibrillar network morphology arising from intermolecular H‐bonding and π‐stacking interaction. Thixotropic property of gel is utilized for encapsulation of both hydrophilic (doxorubicin, DOX) and hydrophobic (camptothecin, CPT) drugs. The loading of DOX and CPT in the gel is attributed to H‐bonding interaction between FA and drugs. The release of DOX, is sustainable at both pHs and Peppas model indicate that at pH7 diffusion of drug is Fickian but, non Fickian at pH4. The release of CPT is documented from fluorescence study which also corroborates combined release of both the drugs. MTT assay of hydrogel shows nontoxic behaviour and cytotoxicity of DOX loaded FA hydrogel is higher than that of pure DOX with a minimal effect to the normal cell.
>> Read More

Site Search