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Chemical probes have gained importance in the elucidation of signal transduction in biology. Insufficient selectivity and potency, lack of cellular activity and inappropriate use of chemical probes has major consequences on interpretation of biological results. The catalytic subunit of phosphoinositide 3-kinase α (PI3Kα) is one of the most frequently mutated genes in cancer, but fast-acting, high-quality probes to define PI3Kα's specific function to clearly separate it from other class I PI3K isoforms, are not available. Here, we present a series of novel covalent PI3Kα-targeting probes with optimized intracellular target access and kinetic parameters. On-target TR-FRET and off-target assays provided relevant kinetic parameters ( k chem , k inact and K i ) to validate our chemical probes. Additional intracellular nanoBRET tracer displacement measurements showed rapid diffusion across the cell membrane and extremely fast target engagement, while investigations of signaling downstream of PI3Kα via protein kinase B (PKB/Akt) and forkhead box O (FOXO) revealed blunted pathway activity in cancer cell lines with constitutively activated PI3Kα lasting for several days. In contrast, persistent PI3Kα inhibition was rapidly bypassed by other class I PI3K isoforms in cells lacking functional phosphatase and tensin homolog (PTEN). Comparing the rapidly-diffusing, fast target-engaging chemical probe 9 to clinical reversible PI3Kα-selective inhibitors alpelisib, inavolisib and 9r, a reversible analogue of 9, revealed 9's superior potency to inhibit growth (up to 600-fold) associated with sustained suppression of PI3Kα signaling in breast cancer cell lines. Finally, using a simple washout protocol, the utility of the highly-selective covalent PI3Kα probe 9 was demonstrated by the quantification of the coupling of insulin, EGF and CXCL12 receptors to distinct PI3K isoforms for signal transduction in response to ligand-dependent activation. Collectively, these findings along with the novel covalent chemical probes against PI3Kα provide insights into isoform-specific functions in cancer cells and highlight opportunities to achieve improved selectivity and long-lasting efficacy., Competing Interests: MPW is founder and shareholder of Akylox Therapeutics ApS., (This journal is © The Royal Society of Chemistry.)

The establishment of the Young Scientists Network (YSN) by the European Federation for Medicinal Chemistry (EFMC) served as a proactive response to the evolving landscape of the scientific community. The YSN aims to assist early-career medicinal chemists and chemical biologists by responding to emerging themes, such as the influence of social media, shifts in gender balance within the scientific population, and evolving educational opportunities. The YSN also ensures that the upcoming generation of scientists actively contributes to shape the EFMC's strategic direction while addressing their specific needs. Initially conceived as a general concept, YSN has evolved into a proactive and dynamic team which demonstrates a tangible impact. To boost the impact of the YSN and involve additional motivated young scientists, we have adopted a novel organization, and structured the team in seven working groups (WGs). Herein, we will discuss the tasks of the different WGs as well as the activities planned for the near future. We believe this structure will strengthen the pivotal role YSN has already played in serving medicinal chemists and chemical biologists in Europe. The YSN now has the structure and motivation to pave the way to attract young scientists across Europe and to give them the stage within EFMC., (© 2024 Wiley-VCH GmbH.)

Vector-borne parasitic diseases (VBPDs) pose a significant threat to public health on a global scale. Collectively, Human African Trypanosomiasis (HAT), Leishmaniasis, and Malaria threaten millions of people, particularly in developing countries. Climate change might alter the transmission and spread of VBPDs, leading to a global burden of these diseases. Thus, novel agents are urgently needed to expand therapeutic options and limit the spread of drug-resistant parasites. Herein, we report the development of broad-spectrum antiparasitic agents by screening a known library of antileishmanial and antimalarial compounds toward Trypanosoma brucei ( T. brucei ) and identifying a 1,3,4-oxadiazole derivative ( 19 ) as anti- T. brucei hit with predicted blood-brain barrier permeability. Subsequently, extensive structure-activity-relationship studies around the lipophilic tail of 19 led to a potent antitrypanosomal and antimalarial compound ( 27 ), with moderate potency also toward Leishmania infantum ( L. infantum ) and Leishmania tropica . In addition, we discovered a pan-active antiparasitic molecule ( 24 ), showing low-micromolar IC 50 s toward T. brucei and Leishmania spp. promastigotes and amastigotes, and nanomolar IC 50 against Plasmodium falciparum , together with high selectivity for the parasites over mammalian cells (THP-1). Early ADME-toxicity assays were used to assess the safety profile of the compounds. Overall, we characterized 24 and 27 , bearing the 1,3,4-oxadiazole privileged scaffold, as broad-spectrum low-toxicity agents for the treatment of VBPDs. An alkyne-substituted chemical probe ( 30 ) was synthesized and will be utilized in proteomics experiments aimed at deconvoluting the mechanism of action in the T. brucei parasite.

Class I phosphoinositide 3-kinases (PI3Ks) control cellular growth, but are also essential in insulin signaling and glucose homeostasis. Pan-PI3K inhibitors thus generate substantial adverse effects, a reality that has plagued drug development against this target class. We present here evidence that a high affinity binding module with the capacity to target all class I PI3K isoforms can facilitate selective degradation of the most frequently mutated class I isoform, PI3Kα, when incorporated into a cereblon-targeted (CRBN) degrader. A systematic proteomics study guided the fine tuning of molecular features to optimize degrader selectivity and potency. Our work resulted in the creation of WJ112-14, a PI3Kα-specific nanomolar degrader that should serve as an important research tool for studying PI3K biology. Given the toxicities observed in the clinic with unselective PI3Kα inhibitors, the results here offer a new approach toward selectively targeting this frequently mutated oncogenic driver., Competing Interests: WJ, MS, MW, and DG have filed for patent protection of the work described herein., (This journal is © The Royal Society of Chemistry.)

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key glycolytic enzyme, plays a crucial role in the energy metabolism of cancer cells and has been proposed as a valuable target for the development of anticancer agents. Among a series of 5-substituted 3-bromo-4,5-dihydroisoxazole (BDHI) derivatives, we identified the spirocyclic compound 11, which is able to covalently inactivate recombinant human GAPDH (hGAPDH) with a faster reactivity than koningic acid, one of the most potent hGAPDH inhibitors known to date. Computational studies confirmed that conformational rigidification is crucial to stabilize the interaction of the inhibitor with the binding site, thus favoring the subsequent covalent bond formation. Investigation of intrinsic warhead reactivity at different pH disclosed the negligible reactivity of 11 with free thiols, highlighting its ability to selectively react with the activated cysteine of hGAPDH with respect to other sulfhydryl groups. Compound 11 strongly reduced cancer cell growth in four different pancreatic cancer cell lines and its antiproliferative activity correlated well with the intracellular inhibition of hGAPDH. Overall, our results qualify 11 as a potent hGAPDH covalent inhibitor with a moderate drug-like reactivity that could be further exploited to develop anticancer agents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Chiral natural compounds are often biosynthesized in an enantiomerically pure fashion, and stereochemistry plays a pivotal role in biological activity. Herein, we investigated the significance of chirality for nature-inspired 3-Br-acivicin (3-BA) and its derivatives. The three unnatural isomers of 3-BA and its ester and amide derivatives were prepared and characterized for their antimalarial activity. Only the (5 S , α S ) isomers displayed significant antiplasmodial activity, revealing that their uptake might be mediated by the L-amino acid transport system, which is known to mediate the acivicin membrane's permeability. In addition, we investigated the inhibitory activity towards Plasmodium falciparum glyceraldehyde 3-phosphate dehydrogenase ( Pf GAPDH) since it is involved in the multitarget mechanism of action of 3-BA. Molecular modeling has shed light on the structural and stereochemical requirements for an efficient interaction with Pf GAPDH, leading to covalent irreversible binding and enzyme inactivation. While stereochemistry affects the target binding only for two subclasses ( 1a - d and 4a - d ), it leads to significant differences in the antimalarial activity for all subclasses, suggesting that a stereoselective uptake might be responsible for the enhanced biological activity of the (5 S , α S ) isomers.

Upregulation of mechanistic target of rapamycin (mTOR) signaling drives various types of cancers and neurological diseases. Rapamycin and its analogues (rapalogs) are first generation mTOR inhibitors, and selectively block mTOR complex 1 (TORC1) by an allosteric mechanism. In contrast, second generation ATP-binding site inhibitors of mTOR kinase (TORKi) target both TORC1 and TORC2. Here, we explore 3,6-dihydro-2H-pyran (DHP) and tetrahydro-2H-pyran (THP) as isosteres of the morpholine moiety to unlock a novel chemical space for TORKi generation. A library of DHP- and THP-substituted triazines was prepared, and molecular modelling provided a rational for a structure activity relationship study. Finally, compound 11b [5-(4-(3-oxa-8-azabicyclo[3.2.1]octan-8-yl)-6-(tetrahydro-2H-pyran-4-yl)-1,3,5-triazin-2-yl)-4-(difluoromethyl)pyridin-2-amine] was selected due its potency and selectivity for mTOR kinase over the structurally related class I phosphoinositide 3-kinases (PI3Ks) isoforms. 11b displayed high metabolic stability towards CYP1A1 degradation, which is of advantage in drug development. After oral administration to male Sprague Dawley rats, 11b reached high concentrations both in plasma and brain, revealing an excellent oral bioavailability. In a metabolic stability assay using human hepatocytes, 11b was more stable than PQR620, the first-in-class brain penetrant TORKi. Compound 11b also displayed dose-dependent anti-proliferative activity in splenic marginal zone lymphoma (SMZL) cell lines as single agent and when combined with BCL2 inhibition (venetoclax). Our results identify the THP-substituted triazine core as a novel scaffold for the development of metabolically stable TORKi for the treatment of chronic diseases and cancers driven by mTOR deregulation and requiring drug distribution also to the central nervous system., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Matthias P. Wymann reports financial support was provided by Swiss National Science Foundation and by Swiss Cancer Research Foundation. Matthias P. Wymann, Martina De Pascale and Chiara Borsari have a patent on dihydropyran- and tetrahydropyran-substituted triazines pending to University of Basel, Tech. Transfer Office, Unitectra., (Copyright © 2022 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Covalent protein kinase inhibitors exploit currently noncatalytic cysteines in the adenosine 5'-triphosphate (ATP)-binding site via electrophiles directly appended to a reversible-inhibitor scaffold. Here, we delineate a path to target solvent-exposed cysteines at a distance >10 Å from an ATP-site-directed core module and produce potent covalent phosphoinositide 3-kinase α (PI3Kα) inhibitors. First, reactive warheads are used to reach out to Cys862 on PI3Kα, and second, enones are replaced with druglike warheads while linkers are optimized. The systematic investigation of intrinsic warhead reactivity ( k chem ), rate of covalent bond formation and proximity ( k inact and reaction space volume V r ), and integration of structure data, kinetic and structural modeling, led to the guided identification of high-quality, covalent chemical probes. A novel stochastic approach provided direct access to the calculation of overall reaction rates as a function of k chem , k inact , K i , and V r , which was validated with compounds with varied linker lengths. X-ray crystallography, protein mass spectrometry (MS), and NanoBRET assays confirmed covalent bond formation of the acrylamide warhead and Cys862. In rat liver microsomes, compounds 19 and 22 outperformed the rapidly metabolized CNX-1351, the only known PI3Kα irreversible inhibitor. Washout experiments in cancer cell lines with mutated, constitutively activated PI3Kα showed a long-lasting inhibition of PI3Kα. In SKOV3 cells, compounds 19 and 22 revealed PI3Kβ-dependent signaling, which was sensitive to TGX221. Compounds 19 and 22 thus qualify as specific chemical probes to explore PI3Kα-selective signaling branches. The proposed approach is generally suited to develop covalent tools targeting distal, unexplored Cys residues in biologically active enzymes.

Phosphoinositide 3-kinase (PI3K) plays a key role in a plethora of physiologic processes and controls cell growth, metabolism, immunity, cardiovascular and neurological function, and more. The discovery of wort-mannin as the first potent PI3K inhibitor (PI3Ki) in the 1990s provided rapid identification of PI3K-dependent processes, which drove the discovery of the PI3K/protein kinase B (PKB/Akt)/target of rapamycin (mTOR) pathway. Genetic mouse models and first PI3K isoform-specific inhibitors pinpointed putative therapeutic applications. The recognition of PI3K as target for cancer therapy drove subsequently drug development. Here we provide a brief journey through the emerging roles of PI3K to the development of preclinical and clinical PI3Ki candidates.

Dysregulation of the mechanistic target of rapamycin (mTOR) pathway is implicated in cancer and neurological disorder, which identifies mTOR inhibition as promising strategy for the treatment of a variety of human disorders. First-generation mTOR inhibitors include rapamycin and its analogues (rapalogs) which act as allosteric inhibitors of TORC1. Structurally unrelated, ATP-competitive inhibitors that directly target the mTOR catalytic site inhibit both TORC1 and TORC2. Here, we review investigations of chemical scaffolds explored for the development of highly selective ATP-competitive mTOR kinase inhibitors (TORKi). Extensive medicinal chemistry campaigns allowed to overcome challenges related to structural similarity between mTOR and the phosphoinositide 3-kinase (PI3K) family. A broad region of chemical space is covered by TORKi. Here, the investigation of chemical substitutions and physicochemical properties has shed light on the compounds' ability to cross the blood brain barrier (BBB). This work provides insights supporting the optimization of TORKi for the treatment of cancer and central nervous system disorders., (© 2021 The Authors. ChemMedChem published by Wiley-VCH GmbH.)

A library of seventeen novel ether phospholipid analogues, containing 5-membered heterocyclic rings (1,2,3-triazolyl, isoxazolyl, 1,3,4-oxadiazolyl and 1,2,4-oxadiazolyl) in the lipid portion were designed and synthesized aiming to identify optimised miltefosine analogues. The compounds were evaluated for their in vitro antiparasitic activity against Leishmania infantum and Leishmania donovani intracellular amastigotes, against Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi . The nature of the substituents of the heterocyclic ring (tail) and the oligomethylene spacer between the head group and the heterocyclic ring was found to affect the activity and toxicity of these compounds leading to a significantly improved understanding of their structure-activity relationships. The early ADMET profile of the new derivatives did not reveal major liabilities for the potent compounds. The 1,2,3-triazole derivative 27 substituted by a decyl tail, an undecyl spacer and a choline head group exhibited broad spectrum antiparasitic activity. It possessed low micromolar activity against the intracellular amastigotes of two L. infantum strains and T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes, while its cytotoxicity concentration (CC 50 ) against THP-1 macrophages ranged between 50 and 100 μM. Altogether, our work paves the way for the development of improved ether phospholipid derivatives to control neglected tropical diseases.

Class I Phosphoinositide 3-kinases (PI3Ks) are master regulators of cellular functions, with the class IB PI3K catalytic subunit (p110γ) playing key roles in immune signalling. p110γ is a key factor in inflammatory diseases and has been identified as a therapeutic target for cancers due to its immunomodulatory role. Using a combined biochemical/biophysical approach, we have revealed insight into regulation of kinase activity, specifically defining how immunodeficiency and oncogenic mutations of R1021 in the C-terminus can inactivate or activate enzyme activity. Screening of inhibitors using HDX-MS revealed that activation loop-binding inhibitors induce allosteric conformational changes that mimic those in the R1021C mutant. Structural analysis of advanced PI3K inhibitors in clinical development revealed novel binding pockets that can be exploited for further therapeutic development. Overall, this work provides unique insights into regulatory mechanisms that control PI3Kγ kinase activity and shows a framework for the design of PI3K isoform and mutant selective inhibitors., Competing Interests: MR, ZG, KF, CB, NH, BM, MW, RA, JB No competing interests declared, (© 2021, Rathinaswamy et al.)

Highly selective mTOR inhibitors have been discovered through the exploration of the heteroaromatic ring engaging the binding affinity region in mTOR kinase. Compound 11 showed predicted BBB permeability in a MDCK-MDR1 permeability in vitro assay, being the first pyrimido-pyrrolo-oxazine with potential application in the treatment of neurological disorders., Competing Interests: PH is a past employee of PIQUR Therapeutics AG, Basel; and PH and MPW are shareholders of PIQUR Therapeutics AG., (This journal is © The Royal Society of Chemistry.)

The mechanistic target of rapamycin (mTOR) pathway is hyperactivated in cancer and neurological disorders. Rapalogs and mTOR kinase inhibitors (TORKi) have recently been applied to alleviate epileptic seizures in tuberous sclerosis complex (TSC). Herein, we describe a pharmacophore exploration to identify a highly potent, selective, brain penetrant TORKi. An extensive investigation of the morpholine ring engaging the mTOR solvent exposed region led to the discovery of PQR626 ( 8 ). 8 displayed excellent brain penetration and was well-tolerated in mice. In mice with a conditionally inactivated Tsc1 gene in glia, 8 significantly reduced the loss of Tsc1 -induced mortality at 50 mg/kg p.o. twice a day. 8 overcomes the metabolic liabilities of PQR620 ( 52 ), the first-in-class brain penetrant TORKi showing efficacy in a TSC mouse model. The improved stability in human hepatocytes, excellent brain penetration, and efficacy in Tsc1 GFAP CKO mice qualify 8 as a potential therapeutic candidate for the treatment of neurological disorders.

Sigma receptors (SRs) are recognized as valuable targets for the treatment of neurodegenerative disorders. A series of novel SRs ligands were designed by combining key pharmacophoric amines (i.e., benzylpiperidine or benzylpiperazine) with new 1,3-dithiolane-based heterocycles and their bioisosters. The new compounds exhibited a low nanomolar affinity for sigma-1 and sigma-2 receptors. Five selected compounds were evaluated for their neuroprotective capacity on SH-SY5Y neuroblastoma cell line. They were able to counteract the neurotoxicity induced by rotenone, oligomycin and NMDA. Competition studies with PB212, a S1R antagonist, confirmed the involvement of S1R in neuroprotection from the oxidative stress induced by rotenone. Electrophysiological experiments performed on cortical neurons in culture highlighted the compounds ability to reduce NMDA-evoked currents, suggesting a negative allosteric modulator activity toward the NMDA receptor. Altogether these results qualify our novel dithiolane derivatives as potential agents for fighting neurodegeneration., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

After the first seed concept introduced in the 18th century, different disciplines have attributed different names to dual-functional molecules depending on their application, including bioconjugates, bifunctional compounds, multitargeting molecules, chimeras, hybrids, engineered compounds. However, these engineered constructs share a general structure: a first component that targets a specific cell and a second component that exerts the pharmacological activity. A stable or cleavable linker connects the two modules of a chimera. Herein, we discuss the recent advances in the rapidly expanding field of chimeric molecules leveraging chemical biology concepts. This Perspective is focused on bifunctional compounds in which one component is a lead compound or a drug. In detail, we discuss chemical features of chimeric molecules and their use for targeted delivery and for target engagement studies.

The LIBRA compound library is a collection of 522 non-commercial molecules contributed by various Italian academic laboratories. These compounds have been designed and synthesized during different medicinal chemistry programs and are hosted by the Italian Institute of Technology. We report the screening of the LIBRA compound library against Trypanosoma brucei and Leishmania major pteridine reductase 1, TbPTR1 and LmPTR1. Nine compounds were active against parasitic PTR1 and were selected for cell-based parasite screening, as single agents and in combination with methotrexate (MTX). The most interesting TbPTR1 inhibitor identified was 4-(benzyloxy)pyrimidine-2,6-diamine (LIB_66). Subsequently, six new LIB_66 derivatives were synthesized to explore its Structure-Activity-Relationship (SAR) and absorption, distribution, metabolism, excretion and toxicity (ADMET) properties. The results indicate that PTR1 has a preference to bind inhibitors, which resemble its biopterin/folic acid substrates, such as the 2,4-diaminopyrimidine derivatives., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Leishmaniasis, a major health problem worldwide, has a limited arsenal of drugs for its control. The appearance of resistance to first- and second-line anti-leishmanial drugs confirms the need to develop new and less toxic drugs that overcome spontaneous resistance. In the present study, we report the design and synthesis of a novel library of 38 flavonol-like compounds and their evaluation in a panel of assays encompassing parasite killing, pharmacokinetics, genomics and ADME-Toxicity resulting in the progression of a compound in the drug discovery value chain. Compound 19, 2-(benzo[b]thiophen-3-yl)-3-hydroxy-6-methoxy-4H-chromen-4-one, exhibited a broad-spectrum activity against Leishmania spp. (EC 50 1.9 μM for Leishmania infantum, 3.4 μM for L. donovani, 6.7 μM for L. major), Trypanosoma cruzi (EC 50 7.5 μM) and T. brucei (EC 50 0.8 μM). Focusing on anti-Leishmania activity, compound 19 challenge in vitro did not select for resistance markers in L. donovani, while a Cos-Seq screening for dominant resistance genes identified a gene locus on chromosome 36 that became ineffective at concentrations beyond EC 50 . Thus, compound 19 is a promising scaffold to tackle drug resistance in Leishmania infection. In vivo pharmacokinetic studies indicated that compound 19 has a long half-life (intravenous (IV): 63.2 h; per os (PO): 46.9 h) with an acceptable ADME-Toxicity profile. When tested in Leishmania infected hamsters, no toxicity and limited efficacy were observed. Low solubility and degradation were investigated spectroscopically as possible causes for the sub-optimal pharmacokinetic properties. Compound 19 resulted a specific compound based on the screening against a protein set, following the intrinsic fluorescence changes., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

The mechanistic target of rapamycin (mTOR) plays a pivotal role in growth and tumor progression and is an attractive target for cancer treatment. ATP-competitive mTOR kinase inhibitors (TORKi) have the potential to overcome limitations of rapamycin derivatives in a wide range of malignancies. Herein, we exploit a conformational restriction approach to explore a novel chemical space for the generation of TORKi. Structure-activity relationship (SAR) studies led to the identification of compound 12b with a ∼450-fold selectivity for mTOR over class I PI3K isoforms. Pharmacokinetic studies in male Sprague Dawley rats highlighted a good exposure after oral dosing and a minimum brain penetration. CYP450 reactive phenotyping pointed out the high metabolic stability of 12b . These results identify the tricyclic pyrimido-pyrrolo-oxazine moiety as a novel scaffold for the development of highly selective mTOR inhibitors for cancer treatment.

The phosphoinositide 3-kinase (PI3K)/mechanistic target of rapamycin (mTOR) pathway is a critical regulator of cell growth and is frequently hyperactivated in cancer. Therefore, PI3K inhibitors represent a valuable asset in cancer therapy. Herein we have developed a novel anticancer agent, the potent pan-PI3K inhibitor PQR514 ( 4 ), which is a follow-up compound for the phase-II clinical compound PQR309 ( 1 ). Compound 4 has an improved potency both in vitro and in cellular assays with respect to its predecessor compounds. It shows superiority in the suppression of cancer cell proliferation and demonstrates significant antitumor activity in an OVCAR-3 xenograft model at concentrations approximately eight times lower than PQR309 ( 1 ). The favorable pharmacokinetic profile and a minimal brain penetration promote PQR514 ( 4 ) as an optimized candidate for the treatment of systemic tumors., Competing Interests: The authors declare the following competing financial interest(s): F.B., P.He., P.Hi., and D.F. are current or past employees of PIQUR Therapeutics AG, Basel, and P.He., D.F., and M.P.W. are shareholders of PIQUR Therapeutics AG., (Copyright © 2019 American Chemical Society.)

A benzothiophene-substituted chromenone with promising activity against Leishmania and Trypanosoma species exhibits peculiar fluorescence properties useful for identifying its complexes with target proteins in the microorganism proteomes. The emission spectra, anisotropy and time profiles of this flavonoid strongly change when moving from the free to the protein-bound forms. The same two types of emission are observed in organic solvents and their mixtures with water, with the relative band intensities depending on the solvent ability to establish hydrogen bonds with the solute. The regular emission prevails in protic solvents, while in aprotic solvents the anomalously red-shifted emission occurs from a zwitterionic tautomeric form, produced in the excited state by proton transfer within the intramolecularly H-bonded form. This interpretation finds support from an experimental and theoretical investigation of the conformational preferences of this compound in the ground and lowest excited state, with a focus on the relative twisting about the chromenone-benzothiophene interconnecting bond. An analysis of the absorption and emission spectra and of the photophysical properties of the two emitting tautomers highlights the relevance of the local microenvironment, particularly of the intra- and intermolecular hydrogen bonds in which this bioactive compound is involved, in determining both its steady-state and time-resolved fluorescence behaviour.

Cycloguanil is a known dihydrofolate-reductase (DHFR) inhibitor, but there is no evidence of its activity on pteridine reductase (PTR), the main metabolic bypass to DHFR inhibition in trypanosomatid parasites. Here, we provide experimental evidence of cycloguanil as an inhibitor of Trypanosoma brucei PTR1 ( Tb PTR1). A small library of cycloguanil derivatives was developed, resulting in 1 and 2a having IC 50 values of 692 and 186 nM, respectively, toward Tb PTR1. Structural analysis revealed that the increased potency of 1 and 2a is due to the combined contributions of hydrophobic interactions, H-bonds, and halogen bonds. Moreover, in vitro cell-growth-inhibition tests indicated that 2a is also effective on T. brucei . The simultaneous inhibition of DHFR and PTR1 activity in T. brucei is a promising new strategy for the treatment of human African trypanosomiasis. For this purpose, 1,6-dihydrotriazines represent new molecular tools to develop potent dual PTR and DHFR inhibitors.

The phosphoinositide 3-kinase (PI3K)/mechanistic target of rapamycin (mTOR) pathway is frequently overactivated in cancer, and drives cell growth, proliferation, survival, and metastasis. Here, we report a structure-activity relationship study, which led to the discovery of a drug-like adenosine 5'-triphosphate-site PI3K/mTOR kinase inhibitor: ( S )-4-(difluoromethyl)-5-(4-(3-methylmorpholino)-6-morpholino-1,3,5-triazin-2-yl)pyridin-2-amine (PQR530, compound 6 ), which qualifies as a clinical candidate due to its potency and specificity for PI3K and mTOR kinases, and its pharmacokinetic properties, including brain penetration. Compound 6 showed excellent selectivity over a wide panel of kinases and an excellent selectivity against unrelated receptor enzymes and ion channels. Moreover, compound 6 prevented cell growth in a cancer cell line panel. The preclinical in vivo characterization of compound 6 in an OVCAR-3 xenograft model demonstrated good oral bioavailability, excellent brain penetration, and efficacy. Initial toxicity studies in rats and dogs qualify 6 for further development as a therapeutic agent in oncology.

According to the World Health Organization, more than 1 billion people are at risk of or are affected by neglected tropical diseases. Examples of such diseases include trypanosomiasis, which causes sleeping sickness; leishmaniasis; and Chagas disease, all of which are prevalent in Africa, South America, and India. Our aim within the New Medicines for Trypanosomatidic Infections project was to use (1) synthetic and natural product libraries, (2) screening, and (3) a preclinical absorption, distribution, metabolism, and excretion-toxicity (ADME-Tox) profiling platform to identify compounds that can enter the trypanosomatidic drug discovery value chain. The synthetic compound libraries originated from multiple scaffolds with known antiparasitic activity and natural products from the Hypha Discovery MycoDiverse natural products library. Our focus was first to employ target-based screening to identify inhibitors of the protozoan Trypanosoma brucei pteridine reductase 1 ( TbPTR1) and second to use a Trypanosoma brucei phenotypic assay that made use of the T. brucei brucei parasite to identify compounds that inhibited cell growth and caused death. Some of the compounds underwent structure-activity relationship expansion and, when appropriate, were evaluated in a preclinical ADME-Tox assay panel. This preclinical platform has led to the identification of lead-like compounds as well as validated hits in the trypanosomatidic drug discovery value chain.

Chemical modulation of the flavonol 2-(benzo[d][1,3]dioxol-5-yl)-chromen-4-one ( 1 ), a promising anti-Trypanosomatid agent previously identified, was evaluated through a phenotypic screening approach. Herein, we have performed structure-activity relationship studies around hit compound 1 . The pivaloyl derivative ( 13 ) showed significant anti- T. brucei activity (EC 50 = 1.1 μM) together with a selectivity index higher than 92. The early in vitro ADME-tox properties (cytotoxicity, mitochondrial toxicity, cytochrome P450 and h ERG inhibition) were determined for compound 1 and its derivatives, and these led to the identification of some liabilities. The 1,3-benzodioxole moiety in the presented compounds confers better in vivo pharmacokinetic properties than those of classical flavonols. Further studies using different delivery systems could lead to an increase of compound blood levels., Competing Interests: The authors declare no competing financial interest.

Mechanistic target of rapamycin (mTOR) promotes cell proliferation, growth, and survival and is overactivated in many tumors and central nervous system disorders. PQR620 (3) is a novel, potent, selective, and brain penetrable inhibitor of mTORC1/2 kinase. PQR620 (3) showed excellent selectivity for mTOR over PI3K and protein kinases and efficiently prevented cancer cell growth in a 66 cancer cell line panel. In C57BL/6J and Sprague-Dawley mice, maximum concentration ( C max ) in plasma and brain was reached after 30 min, with a half-life ( t 1/2 ) > 5 h. In an ovarian carcinoma mouse xenograft model (OVCAR-3), daily dosing of PQR620 (3) inhibited tumor growth significantly. Moreover, PQR620 (3) attenuated epileptic seizures in a tuberous sclerosis complex (TSC) mouse model. In conclusion, PQR620 (3) inhibits mTOR kinase potently and selectively, shows antitumor effects in vitro and in vivo, and promises advantages in CNS indications due to its brain/plasma distribution ratio.

Protozoan infections caused by Plasmodium, Leishmania, and Trypanosoma spp. contribute significantly to the burden of infectious diseases worldwide, causing severe morbidity and mortality. The inadequacy of available treatments calls for cost- and time-effective drug discovery endeavors. To this end, we envisaged the triazole linkage of privileged structures as an effective drug design strategy to generate a focused library of high-quality compounds. The versatility of this approach was combined with the feasibility of a phenotypic assay, integrated with early ADME-tox profiling. Thus, an 18-membered library was efficiently assembled via Huisgen cycloaddition of phenothiazine, biphenyl, and phenylpiperazine scaffolds. The resulting 18 compounds were then tested against seven parasite strains, and counter-screened for selectivity against two mammalian cell lines. In parallel, hERG and cytochrome P450 (CYP) inhibition, and mitochondrial toxicity were assessed. Remarkably, 10-((1-(3-([1,1'-biphenyl]-3-yloxy)propyl)-1H-1,2,3-triazol-5-yl)methyl)-10H-phenothiazine (7) and 10-(3-(1-(3-([1,1'-biphenyl]-3-yloxy)propyl)-1H-1,2,3-triazol-4-yl)propyl)-10H-phenothiazine (12) showed respective IC 50 values of 1.8 and 1.9 μg mL -1 against T. cruzi, together with optimal selectivity. In particular, compound 7 showed a promising ADME-tox profile. Thus, hit 7 might be progressed as an antichagasic lead., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Crassiflorone is a natural product with anti-mycobacterial and anti-gonorrhoeal properties, isolated from the stem bark of the African ebony tree Diospyros crassiflora. We noticed that its pentacyclic core possesses structural resemblance to the quinone-coumarin hybrid 3, which we reported to exhibit a dual-targeted inhibitory profile towards Trypanosoma brucei glyceraldehyde-3-phosphate dehydrogenase (TbGAPDH) and Trypanosoma cruzi trypanothione reductase (TcTR). Following this basic idea, we synthesized a small library of crassiflorone derivatives 15-23 and investigated their potential as anti-trypanosomatid agents. 19 is the only compound of the series showing a balanced dual profile at 10 μM (% inhibition TbGAPDH  = 64% and % inhibition TcTR  = 65%). In phenotypic assay, the most active compounds were 18 and 21, which at 5 μM inhibited Tb bloodstream-form growth by 29% and 38%, respectively. Notably, all the newly synthesized compounds at 10 μM did not affect viability and the status of mitochondria in human A549 and 786-O cell lines, respectively. However, further optimization that addresses metabolic liabilities including solubility, as well as cytochromes P450 (CYP1A2, CYP2C9, CYP2C19, and CYP2D6) inhibition, is required before this class of natural product-derived compounds can be further progressed., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Phosphoinositide 3-kinase (PI3K) is deregulated in a wide variety of human tumors and triggers activation of protein kinase B (PKB/Akt) and mammalian target of rapamycin (mTOR). Here we describe the preclinical characterization of compound 1 (PQR309, bimiralisib), a potent 4,6-dimorpholino-1,3,5-triazine-based pan-class I PI3K inhibitor, which targets mTOR kinase in a balanced fashion at higher concentrations. No off-target interactions were detected for 1 in a wide panel of protein kinase, enzyme, and receptor ligand assays. Moreover, 1 did not bind tubulin, which was observed for the structurally related 4 (BKM120, buparlisib). Compound 1 is orally available, crosses the blood-brain barrier, and displayed favorable pharmacokinetic parameters in mice, rats, and dogs. Compound 1 demonstrated efficiency in inhibiting proliferation in tumor cell lines and a rat xenograft model. This, together with the compound's safety profile, identifies 1 as a clinical candidate with a broad application range in oncology, including treatment of brain tumors or CNS metastasis. Compound 1 is currently in phase II clinical trials for advanced solid tumors and refractory lymphoma.