High-content screening technology combined with a human granuloma model as a new approach to evaluate the activities of drugs against Mycobacterium tuberculosis.

Tuberculosis remains a major health problem due to the emergence of drug-resistant strains of Mycobacterium tuberculosis. Some models have provided valuable information about drug resistance and efficacy; however, the translation of these results into effective human treatments has mostly proven unsuccessful. In this study, we adapted high-content screening (HCS) technology to investigate the activities of antitubercular compounds in the context of an in vitro granuloma model. We observed significant shifts in the MIC50s between the activities of the compounds under extracellular and granuloma conditions.

Testing tuberculosis drug efficacy in a zebrafish high-throughput translational medicine screen.

The translational value of zebrafish high-throughput screens can be improved when more knowledge is available on uptake characteristics of potential drugs. We investigated reference antibiotics and 15 preclinical compounds in a translational zebrafish-rodent screening system for tuberculosis. As a major advance, we have developed a new tool for testing drug uptake in the zebrafish model. This is important, because despite the many applications of assessing drug efficacy in zebrafish research, the current methods for measuring uptake using mass spectrometry do not take into account the possible adherence of drugs to the larval surface. Our approach combines nanoliter sampling from the yolk using a microneedle, followed by mass spectrometric analysis. To date, no single physicochemical property has been identified to accurately predict compound uptake; our method offers a great possibility to monitor how any novel compound behaves within the system. We have correlated the uptake data with high-throughput drug-screening data from Mycobacterium marinum-infected zebrafish larvae. As a result, we present an improved zebrafish larva drug-screening platform which offers new insights into drug efficacy and identifies potential false negatives and drugs that are effective in zebrafish and rodents. We demonstrate that this improved zebrafish drug-screening platform can complement conventional models of in vivo Mycobacterium tuberculosis-infected rodent assays. The detailed comparison of two vertebrate systems, fish and rodent, may give more predictive value for efficacy of drugs in humans.

The repurposing of Tebipenem pivoxil as alternative therapy for severe gastrointestinal infections caused by extensively drug-resistant Shigella spp.

Background: Diarrhoea remains one of the leading causes of childhood mortality globally. Recent epidemiological studies conducted in low-middle income countries (LMICs) identified Shigella spp. as the first and second most predominant agent of dysentery and moderate diarrhoea, respectively. Antimicrobial therapy is often necessary for Shigella infections; however, we are reaching a crisis point with efficacious antimicrobials. The rapid emergence of resistance against existing antimicrobials in Shigella spp. poses a serious global health problem. Methods: Aiming to identify alternative antimicrobial chemicals with activity against antimicrobial resistant Shigella, we initiated a collaborative academia-industry drug discovery project, applying high-throughput phenotypic screening across broad chemical diversity and followed a lead compound through in vitro and in vivo characterisation. Results: We identified several known antimicrobial compound classes with antibacterial activity against Shigella. These compounds included the oral carbapenem Tebipenem, which was found to be highly potent against broadly susceptible Shigella and contemporary MDR variants for which we perform detailed pre-clinical testing. Additional in vitro screening demonstrated that Tebipenem had activity against a wide range of other non-Shigella enteric bacteria. Cognisant of the risk for the development of resistance against monotherapy, we identified synergistic behaviour of two different drug combinations incorporating Tebipenem. We found the orally bioavailable prodrug (Tebipenem pivoxil) had ideal pharmacokinetic properties for treating enteric pathogens and was effective in clearing the gut of infecting organisms when administered to Shigella-infected mice and gnotobiotic piglets. Conclusions: Our data highlight the emerging antimicrobial resistance crisis and shows that Tebipenem pivoxil (licenced for paediatric respiratory tract infections in Japan) should be accelerated into human trials and could be repurposed as an effective treatment for severe diarrhoea caused by MDR Shigella and other enteric pathogens in LMICs. Funding: Tres Cantos Open Lab Foundation (projects TC239 and TC246), the Bill and Melinda Gates Foundation (grant OPP1172483) and Wellcome (215515/Z/19/Z).

Synthesis and structure-activity relationships of gamma-carboline derivatives as potent and selective cysLT(1) antagonists.

A gamma-carboline series of cysLT(1) receptor antagonists has been prepared. Some of the compounds show good potencies both, in vitro and in vivo, compared to the standard compounds.

Discovery of a Novel Inhaled PI3Kδ Inhibitor for the Treatment of Respiratory Diseases.

Oral PI3Kδ inhibitors such as Idelalisib and Duvelisib have shown efficacy as anticancer agents and Idelalisib has been approved for the treatment of three B-cell cancers. However, Idelalisib has a black box warning on its product label regarding the risks of fatal and serious toxicities including hepatic toxicity, severe diarrhea, colitis, pneumonitis, infections, and intestinal perforation. Some of these side effects are mechanism-related and could hinder the development of Idelalisib for less severe conditions. For respiratory diseases, compounds administered by inhalation are delivered directly to the site of action and may improve the therapeutic index of a drug, minimizing undesired side effects. This work describes the discovery and optimization of inhaled PI3Kδ inhibitors intended for the treatment of severe asthma and COPD. Once the potency was in the desired range, efforts were focused on identifying the particular physicochemical properties that could translate into better lung retention. This medicinal chemistry exercise led to the identification of LAS195319 as a candidate for clinical development.

Design, synthesis and structure-activity relationship study of wollamide B; a new potential anti TB agent.

Wollamide B is a cationic antimycobacterial cyclohexapeptide that exhibits activity against Mycobacterium bovis (M. bovis) (IC50 of 3.1 µM). Aiming to define its structural activity relationship (SAR), optimizing potency and pharmacokinetic properties, libraries of analogues were synthesized following a standard Fmoc-based solid phase peptide synthesis approach. The antimycobacterial activities of wollamide B and all the synthesized analogues were tested against Mycobacterium tuberculosis (Mtb) H37Rv. Parallely, in vitro drug metabolism and pharmacokinetic (ADME) profiling was done for the synthesized compounds to evaluate their drug likeness. Among the 25 synthesized wollamides five of them showed potent activities with MICs ≤ 3.1 µM and found to be nontoxic against human HepG2 cells up to 100 µM. The results of the in vitro ADME profiling revealed the remarkable plasma stability and very good aqueous solubility of the class in general while the metabolic stability was found to be moderate to low. Of particular note, compounds 7c (MIC = 1.1 µM) and 13c (0.6 µM) that exhibited good balance of antimycobacterial activity vs. optimal pharmacokinetic properties could be used as a new lead for further development.

Biphenyl Pyridazinone Derivatives as Inhaled PDE4 Inhibitors: Structural Biology and Structure-Activity Relationships.

Cyclic nucleotide cAMP is a ubiquitous secondary messenger involved in a plethora of cellular responses to biological agents involving activation of adenylyl cyclase. Its intracellular levels are tightly controlled by a family of cyclic nucleotide degrading enzymes, the PDEs. In recent years, cyclic nucleotide phosphodiesterase type 4 (PDE4) has aroused scientific attention as a suitable target for anti-inflammatory therapy in respiratory diseases, particularly in the management of asthma and COPD. Here we describe our efforts to discover novel, highly potent inhaled inhibitors of PDE4. Through structure based design, with the inclusion of a variety of functional groups and physicochemical profiles in order to occupy the solvent-filled pocket of the PDE4 enzyme, we modified the structure of our oral PDE4 inhibitors to reach compounds down to picomolar enzymatic potencies while at the same time tackling successfully an uncovered selectivity issue with the adenosine receptors. In vitro potencies were demonstrated in a rat lung neutrophilia model by administration of a suspension with a Penn-Century MicroSprayer Aerosolizer.

N-Benzyl-4-((heteroaryl)methyl)benzamides: A New Class of Direct NADH-Dependent 2-trans Enoyl-Acyl Carrier Protein Reductase (InhA) Inhibitors with Antitubercular Activity.

Isoniazid (INH) remains one of the cornerstones of antitubercular chemotherapy for drug-sensitive strains of M. tuberculosis bacteria. However, the increasing prevalence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains containing mutations in the KatG enzyme, which is responsible for the activation of INH into its antitubercular form, have rendered this drug of little or no use in many cases of drug-resistant tuberculosis. Presented herein is a novel family of antitubercular direct NADH-dependent 2-trans enoyl-acyl carrier protein reductase (InhA) inhibitors based on an N-benzyl-4-((heteroaryl)methyl)benzamide template; unlike INH, these do not require prior activation by KatG. Given their direct InhA target engagement, these compounds should be able to circumvent KatG-related resistance in the clinic. The lead molecules were shown to be potent inhibitors of InhA and showed activity against M. tuberculosis bacteria. This new family of inhibitors was found to be chemically tractable, as exemplified by the facile synthesis of analogues and the establishment of structure-activity relationships. Furthermore, a co-crystal structure of the initial hit with the enzyme is disclosed, providing valuable information toward the design of new InhA inhibitors for the treatment of MDR/XDR tuberculosis.

New direct inhibitors of InhA with antimycobacterial activity based on a tetrahydropyran scaffold.

Tetrahydropyran derivative 1 was discovered in a high-throughput screening campaign to find new inhibitors of mycobacterial InhA. Following initial in-vitro profiling, a structure-activity relationship study was initiated and a focused library of analogs was synthesized and evaluated. This yielded compound 42 with improved antimycobacterial activity and low cytotoxicity. Additionally, the crystal structure of InhA in complex with inhibitor 1 was resolved, to reveal the binding mode and provide hints for further optimization.

Design, synthesis, and evaluation of new thiadiazole-based direct inhibitors of enoyl acyl carrier protein reductase (InhA) for the treatment of tuberculosis.

Mycobacterial enoyl acyl carrier protein reductase (InhA) is a clinically validated target for the treatment of tuberculosis infections, a disease that still causes the death of at least a million people annually. A known class of potent, direct, and competitive InhA inhibitors based on a tetracyclic thiadiazole structure has been shown to have in vivo activity in murine models of tuberculosis infection. On the basis of this template, we have here explored the medicinal chemistry of truncated analogues that have only three aromatic rings. In particular, compounds 8b, 8d, 8f, 8l, and 8n show interesting features, including low nanomolar InhA IC50, submicromolar antimycobacterial potency, and improved physicochemical profiles in comparison with the tetracyclic analogues. From this series, 8d is identified as having the best balance of potency and properties, whereby the resolved 8d S-enatiomer shows encouraging in vivo efficacy.

Carbamoyl Triazoles, Known Serine Protease Inhibitors, Are a Potent New Class of Antimalarials.

Screening of the GSK corporate collection, some 1.9 million compounds, against Plasmodium falciparum (Pf), revealed almost 14000 active hits that are now known as the Tres Cantos Antimalarial Set (TCAMS). Followup work by Calderon et al. clustered and computationally filtered the TCAMS through a variety of criteria and reported 47 series containing a total of 522 compounds. From this enhanced set, we identified the carbamoyl triazole TCMDC-134379 (1), a known serine protease inhibitor, as an excellent starting point for SAR profiling. Lead optimization of 1 led to several molecules with improved antimalarial potency, metabolic stabilities in mouse and human liver microsomes, along with acceptable cytotoxicity profiles. Analogue 44 displayed potent in vitro activity (IC50 = 10 nM) and oral activity in a SCID mouse model of Pf infection with an ED50 of 100 and ED90 of between 100 and 150 mg kg(-1), respectively. The results presented encourage further investigations to identify the target of these highly active compounds.

A Developability-Focused Optimization Approach Allows Identification of in Vivo Fast-Acting Antimalarials: N-[3-[(Benzimidazol-2-yl)amino]propyl]amides.

Malaria continues to be a major global health problem, being particularly devastating in the African population under the age of five. Artemisinin-based combination therapies (ACTs) are the first-line treatment recommended by the WHO to treat Plasmodium falciparum malaria, but clinical resistance against them has already been reported. As a consequence, novel chemotypes are urgently needed. Herein we report a novel, in vivo active, fast-acting antimalarial chemotype based on a benzimidazole core. This discovery is the result of a medicinal chemistry plan focused on improving the developability profile of an antichlamydial chemical class previously reported by our group.

Synthesis and structure-activity relationships of novel histamine H1 antagonists: indolylpiperidinyl benzoic acid derivatives.

A series of indolylpiperidinyl derivatives were prepared and evaluated for their activity as histamine H(1) antagonists. Structure-activity relationship studies were directed toward improving in vivo activity and pharmacokinetic profile of our first lead (1). Substitution of fluorine in position 6 on the indolyl ring led to higher in vivo activity in the inhibition of histamine-induced cutaneous vascular permeability assay but lower selectivity toward 5HT(2) receptor. Extensive optimization was carried out within this series and a number of histamine H(1) antagonists showing potency and long duration of action in vivo and low brain penetration or cardiotoxic potential were identified. Within this novel series, indolylpiperidines 15, 20, 48,51 and 52 exhibited a long half-life in rat and have been selected for further preclinical evaluation.

Encoded library technology as a source of hits for the discovery and lead optimization of a potent and selective class of bactericidal direct inhibitors of Mycobacterium tuberculosis InhA.

Tuberculosis (TB) is one of the world's oldest and deadliest diseases, killing a person every 20 s. InhA, the enoyl-ACP reductase from Mycobacterium tuberculosis, is the target of the frontline antitubercular drug isoniazid (INH). Compounds that directly target InhA and do not require activation by mycobacterial catalase peroxidase KatG are promising candidates for treating infections caused by INH resistant strains. The application of the encoded library technology (ELT) to the discovery of direct InhA inhibitors yielded compound 7 endowed with good enzymatic potency but with low antitubercular potency. This work reports the hit identification, the selected strategy for potency optimization, the structure-activity relationships of a hundred analogues synthesized, and the results of the in vivo efficacy studies performed with the lead compound 65.

α2,3-Sialyltransferase ST3Gal IV promotes migration and metastasis in pancreatic adenocarcinoma cells and tends to be highly expressed in pancreatic adenocarcinoma tissues.

Sialyltransferases have received much attention recently as they are frequently up-regulated in cancer cells. However, the role played by each sialyltransferase in tumour progression is still unknown. α2,3-Sialyltransferases ST3Gal III and ST3Gal IV are involved in sialyl-Lewis(x) (SLe(x)) synthesis. Given that the role of ST3Gal III in pancreatic adenocarcinoma cells has been previously reported, in this study we have focused on investigating the role of ST3Gal IV in the acquisition of adhesive, migratory and metastatic capabilities and, secondly, in analyzing the expression of ST3Gal III and ST3Gal IV in pancreatic adenocarcinoma tissues versus control tissues. ST3Gal IV overexpressing pancreatic adenocarcinoma MDAPanc-28 cell lines were generated. They showed a heterogeneous increase in SLe(x), and enhanced E-selectin adhesion and migration. Furthermore, when injected into nude mice, increased metastasis and decreased survival were found in comparison with controls. The behaviour of MDAPanc-28 ST3Gal IV overexpressing cells in these processes was similar to the already reported MDAPanc-28 ST3Gal III overexpressing cells. Furthermore, pancreatic adenocarcinoma tissues tended to express high levels of ST3Gal III and ST3Gal IV together with other fucosyltransferase genes FUT3 and FUT6, all involved in the last steps of sialyl-Lewis(x) biosynthesis. In conclusion, both α2,3-sialyltransferases are involved in key steps of pancreatic tumour progression processes and are highly expressed in most pancreatic adenocarcinoma tissues.

Synthesis and biological activity of pyrido[3',2':4,5]furo[3,2-d]pyrimidine derivatives as novel and potent phosphodiesterase type 4 inhibitors.

A series of pyrido[3',2':4,5]furo[3,2-d]pyrimidines (PFP) were synthesized and tested for phosphodiesterase type 4 (PDE4) inhibitory activity, with the potential to treat asthma and chronic obstructive pulmonary disease (COPD). Structure-activity relationships within this series, leading to an increase of potency on the enzyme, is presented. Both gem-dimethylcyclohexyl moieties fused to the pyridine ring and the substitution at the 5 position of the PFP scaffold, proved to be key elements in order to get a high affinity in the enzyme.

alpha2,3-sialyltransferase ST3Gal III modulates pancreatic cancer cell motility and adhesion in vitro and enhances its metastatic potential in vivo.

BACKGROUND: Cell surface sialylation is emerging as an important feature of cancer cell metastasis. Sialyltransferase expression has been reported to be altered in tumours and may account for the formation of sialylated tumour antigens. We have focused on the influence of alpha-2,3-sialyltransferase ST3Gal III in key steps of the pancreatic tumorigenic process. METHODOLOGY/PRINCIPAL FINDINGS: ST3Gal III overexpressing pancreatic adenocarcinoma cell lines Capan-1 and MDAPanc-28 were generated. They showed an increase of the tumour associated antigen sialyl-Lewis(x). The transfectants' E-selectin binding capacity was proportional to cell surface sialyl-Lewis(x) levels. Cellular migration positively correlated with ST3Gal III and sialyl-Lewis(x) levels. Moreover, intrasplenic injection of the ST3Gal III transfected cells into athymic nude mice showed a decrease in survival and higher metastasis formation when compared to the mock cells. CONCLUSION: In summary, the overexpression of ST3Gal III in these pancreatic adenocarcinoma cell lines underlines the role of this enzyme and its product in key steps of tumour progression such as adhesion, migration and metastasis formation.

Synthesis and biological activity of pyrido[3',2':4,5]thieno[3,2-d]pyrimidines as phosphodiesterase type 4 inhibitors.

A series of pyrido[3',2':4,5]thieno[3,2-d]pyrimidines (PTP) has been synthesized and tested as phosphodiesterase IV inhibitors (PDE4), a target for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Structure-activity relationships within this series, leading to an increase of potency on the enzyme, are presented. The gem-dimethylcycloalkyl moiety fused to the pyridine ring proved to be a key element of the scaffold in order to get a higher affinity in the enzyme.

PDE4 inhibitors: a review of current developments (2005 - 2009).

BACKGROUND: Despite the sound preclinical database and some promising data from clinical trials, development of PDE4 inhibitors for the treatment of inflammatory or neurological diseases has been hampered by dose-limiting class-related side effects. OBJECTIVE: In the past years, companies opted for different approaches to improve the therapeutic window of their compounds including topical administration of PDE4 inhibitors with the goal of minimizing systemic exposure. This change in strategy is reflected by the disclosure of novel and chemically diverse molecules that demonstrate the continued interest of pharmaceutical industry in developing PDE4 inhibitors. CONCLUSION: This review summarizes the clinical development of PDE4 inhibitors since 2005 and the associated patent literature with a focus on strategies applied to minimize systemic adverse effects. In sum, although a significant number of new drugs designed for improved tolerability entered clinical trials, so far none of them fulfilled expectations and best progress has been achieved recently with the oral, non-isoform selective PDE4 inhibitor roflumilast.