Catherine Piveteau

Ethionamide Boosters: Synthesis, Biological Activity, and Structure−Activity Relationships of a Series of 1,2,4-Oxadiazole EthR Inhibitors

We report in this article an extensive structure-activity relationships (SAR) study with 58 thiophen-2-yl-1,2,4-oxadiazoles as inhibitors of EthR, a transcriptional regulator controling ethionamide bioactivation in Mycobacterium tuberculosis. We explored the replacement of two key fragments of the starting lead BDM31343. We investigated the potency of all analogues to boost subactive doses of ethionamide on a phenotypic assay involving M. tuberculosis infected macrophages and then ascertained the mode of action of the most active compounds using a functional target-based surface plasmon resonance assay. This process revealed that introduction of 4,4,4-trifluorobutyryl chain instead of cyanoacetyl group was crucial for intracellular activity. Replacement of 1,4-piperidyl by (R)-1,3-pyrrolidyl scaffold did not enhance activity but led to improved pharmacokinetic properties. Furthermore, the crystal structures of ligand-EthR complexes were consistent with the observed SAR. In conclusion, we identified EthR inhibitors that boost antibacterial activity of ethionamide with nanomolar potency while improving solubility and metabolic stability.

Ethionamide Boosters. 2. Combining Bioisosteric Replacement and Structure-Based Drug Design To Solve Pharmacokinetic Issues in a Series of Potent 1,2,4-Oxadiazole EthR Inhibitors

Mycobacterial transcriptional repressor EthR controls the expression of EthA, the bacterial monooxygenase activating ethionamide, and is thus largely responsible for the low sensitivity of the human pathogen Mycobacterium tuberculosis to this antibiotic. We recently reported structure-activity relationships of a series of 1,2,4-oxadiazole EthR inhibitors leading to the discovery of potent ethionamide boosters. Despite high metabolic stability, pharmacokinetic evaluation revealed poor mice exposure; therefore, a second phase of optimization was required. Herein a structure-property relationship study is reported according to the replacement of the two aromatic heterocycles: 2-thienyl and 1,2,4-oxadiazolyl moieties. This work was done using a combination of structure-based drug design and in vitro/ex vivo evaluations of ethionamide boosters on the targeted protein EthR and on the human pathogen Mycobacterium tuberculosis. Thanks to this process, we identified compound 42 (BDM41906), which displays improved efficacy in addition to high exposure to mice after oral administration.

Daytime variation of perioperative myocardial injury in cardiac surgery and its prevention by Rev-Erbα antagonism: a single-centre propensity-matched cohort study and a randomised study

BACKGROUND On-pump cardiac surgery provokes a predictable perioperative myocardial ischaemia-reperfusion injury which is associated with poor clinical outcomes. We determined the occurrence of time-of-the-day variation in perioperative myocardial injury in patients undergoing aortic valve replacement and its molecular mechanisms. METHODS We studied the incidence of major adverse cardiac events in a prospective observational single-centre cohort study of patients with severe aortic stenosis and preserved left ventricular ejection fraction (>50%) who were referred to our cardiovascular surgery department at Lille University Hospital (Lille, France) for aortic valve replacement and underwent surgery in the morning or afternoon. Patients were matched into pairs by propensity score. We also did a randomised study, in which we evaluated perioperative myocardial injury and myocardial samples of patients randomly assigned (1:1) via permuted block randomisation (block size of eight) to undergo isolated aortic valve replacement surgery either in the morning or afternoon. We also evaluated human and rodent myocardium in ex-vivo hypoxia-reoxygenation models and did a transcriptomic analysis in myocardial samples from the randomised patients to identify the signalling pathway(s) involved. The primary objective of the study was to assess whether myocardial tolerance of ischaemia-reperfusion differed depending on the timing of aortic valve replacement surgery (morning vs afternoon), as measured by the occurrence of major adverse cardiovascular events (cardiovascular death, myocardial infarction, and admission to hospital for acute heart failure). The randomised study is registered with ClinicalTrials.gov, number NCT02812901. FINDINGS In the cohort study (n=596 patients in matched pairs who underwent either morning surgery [n=298] or afternoon surgery [n=298]), during the 500 days following aortic valve replacement, the incidence of major adverse cardiac events was lower in the afternoon surgery group than in the morning group: hazard ratio 0·50 (95% CI 0·32-0·77; p=0·0021). In the randomised study, 88 patients were randomly assigned to undergo surgery in the morning (n=44) or afternoon (n=44); perioperative myocardial injury assessed with the geometric mean of perioperative cardiac troponin T release was significantly lower in the afternoon group than in the morning group (estimated ratio of geometric means for afternoon to morning of 0·79 [95% CI 0·68-0·93; p=0·0045]). Ex-vivo analysis of human myocardium revealed an intrinsic morning-afternoon variation in hypoxia-reoxygenation tolerance, concomitant with transcriptional alterations in circadian gene expression with the nuclear receptor Rev-Erbα being highest in the morning. In a mouse Langendorff model of hypoxia-reoxygenation myocardial injury, Rev-Erbα gene deletion or antagonist treatment reduced injury at the time of sleep-to-wake transition, through an increase in the expression of the ischaemia-reperfusion injury modulator CDKN1a/p21. INTERPRETATION Perioperative myocardial injury is transcriptionally orchestrated by the circadian clock in patients undergoing aortic valve replacement, and Rev-Erbα antagonism seems to be a pharmacological strategy for cardioprotection. Afternoon surgery might provide perioperative myocardial protection and lead to improved patient outcomes compared with morning surgery. FUNDING Fondation de France, Fédération Française de Cardiologie, EU-FP7-Eurhythdia, Agence Nationale pour la Recherche ANR-10-LABX-46, and CPER-Centre Transdisciplinaire de Recherche sur la Longévité.

Ligand Efficiency Driven Design of New Inhibitors of Mycobacterium tuberculosis Transcriptional Repressor EthR Using Fragment Growing, Merging, and Linking Approaches.

Tuberculosis remains a major cause of mortality and morbidity, killing each year more than one million people. Although the combined use of first line antibiotics (isoniazid, rifampicin, pyrazinamide, and ethambutol) is efficient to treat most patients, the rapid emergence of multidrug resistant strains of Mycobacterium tuberculosis stresses the need for alternative therapies. Mycobacterial transcriptional repressor EthR is a key player in the control of second-line drugs bioactivation such as ethionamide and has been shown to impair the sensitivity of the human pathogen Mycobacterium tuberculosis to this antibiotic. As a way to identify new potent ligands of this protein, we have developed fragment-based approaches. In the current study, we combined surface plasmon resonance assay, X-ray crystallography, and ligand efficiency driven design for the rapid discovery and optimization of new chemotypes of EthR ligands starting from a fragment. The design, synthesis, and in vitro and ex vivo activities of these compounds will be discussed.

Catalytic site inhibition of insulin-degrading enzyme by a small molecule induces glucose intolerance in mice

Insulin-degrading enzyme (IDE) is a protease that cleaves insulin and other bioactive peptides such as amyloid-β. Knockout and genetic studies have linked IDE to Alzheimers disease and type-2 diabetes. As the major insulin-degrading protease, IDE is a candidate drug target in diabetes. Here we have used kinetic target-guided synthesis to design the first catalytic site inhibitor of IDE suitable for in vivo studies (BDM44768). Crystallographic and small angle X-ray scattering analyses show that it locks IDE in a closed conformation. Among a panel of metalloproteases, BDM44768 selectively inhibits IDE. Acute treatment of mice with BDM44768 increases insulin signalling and surprisingly impairs glucose tolerance in an IDE-dependent manner. These results confirm that IDE is involved in pathways that modulate short-term glucose homeostasis, but casts doubt on the general usefulness of the inhibition of IDE catalytic activity to treat diabetes.

Identification of Small Inhibitory Molecules Targeting the Bfl-1 Anti-Apoptotic Protein That Alleviates Resistance to ABT-737

One approach currently being developed in anticancer drug discovery is to search for small compounds capable of occupying and blocking the hydrophobic pocket of anti-apoptotic Bcl-2 family members necessary for interacting with pro-apoptotic proteins. Such an approach led to the discovery of several compounds, such as ABT-737 (which interacts with Bcl-2, Bcl-xl, and Bcl-w) or the latest one, ABT-199, that selectively targets Bcl-2 protein. The efficacy of those compounds is, however, limited by the expression of two other anti-apoptotic Bcl-2 members, Mcl-1 and Bfl-1. Based on the role of Bfl-1 in cancer, especially in chemoresistance associated with its overexpression in B-cell malignancies, we searched for modulators of protein–protein interaction through a high-throughput screening of a designed chemical library with relaxed drug-like properties to identify small molecules targeting Bfl-1 anti-apoptotic protein. We found two compounds that display electrophilic functions, interact with Bfl-1, inhibit Bfl-1 protective activity, and promote cell death of malignant B cells. Of particular interest, we observed a synergistic effect of those compounds with ABT-737 in Bfl-1 overexpressing lymphoma cell lines. Our results provide the basis for the development of Bfl-1 specific antagonists for antitumor therapies.

Combination therapy for tuberculosis treatment: pulmonary administration of ethionamide and booster co-loaded nanoparticles

Tuberculosis (TB) is a leading infectious cause of death worldwide. The use of ethionamide (ETH), a main second line anti-TB drug, is hampered by its severe side effects. Recently discovered “booster” molecules strongly increase the ETH efficacy, opening new perspectives to improve the current clinical outcome of drug-resistant TB. To investigate the simultaneous delivery of ETH and its booster BDM41906 in the lungs, we co-encapsulated these compounds in biodegradable polymeric nanoparticles (NPs), overcoming the bottlenecks inherent to the strong tendency of ETH to crystallize and the limited water solubility of this Booster. The efficacy of the designed formulations was evaluated in TB infected macrophages using an automated confocal high-content screening platform, showing that the drugs maintained their activity after incorporation in NPs. Among tested formulations, “green” β-cyclodextrin (pCD) based NPs displayed the best physico-chemical characteristics and were selected for in vivo studies. The NPs suspension, administered directly into mouse lungs using a Microsprayer®, was proved to be well-tolerated and led to a 3-log decrease of the pulmonary mycobacterial load after 6 administrations as compared to untreated mice. This study paves the way for a future use of pCD NPs for the pulmonary delivery of the [ETH:Booster] pair in TB chemotherapy.

Topical Intestinal Aminoimidazole Agonists of G-Protein-Coupled Bile Acid Receptor 1 Promote Glucagon Like Peptide-1 Secretion and Improve Glucose Tolerance

The role of the G-protein-coupled bile acid receptor TGR5 in various organs, tissues, and cell types, specifically in intestinal endocrine L-cells and brown adipose tissue, has made it a promising therapeutical target in several diseases, especially type-2 diabetes and metabolic syndrome. However, recent studies have shown deleterious on-target effects of systemic TGR5 agonists. To avoid these systemic effects while stimulating glucagon-like peptide-1 (GLP-1) secreting enteroendocrine L-cells, we have designed TGR5 agonists with low intestinal permeability. In this article, we describe their synthesis, characterization, and biological evaluation. Among them, compound 24 is a potent GLP-1 secretagogue, has low effect on gallbladder volume, and improves glucose homeostasis in a preclinical murine model of diet-induced obesity and insulin resistance, making the proof of concept of the potential of topical intestinal TGR5 agonists as therapeutic agents in type-2 diabetes.

Controlling Plasma Stability of Hydroxamic Acids: A MedChem Toolbox

Hydroxamic acids are outstanding zinc chelating groups that can be used to design potent and selective metalloenzyme inhibitors in various therapeutic areas. Some hydroxamic acids display a high plasma clearance resulting in poor in vivo activity, though they may be very potent compounds in vitro. We designed a 57-member library of hydroxamic acids to explore the structure-plasma stability relationships in these series and to identify which enzyme(s) and which pharmacophores are critical for plasma stability. Arylesterases and carboxylesterases were identified as the main metabolic enzymes for hydroxamic acids. Finally, we suggest structural features to be introduced or removed to improve stability. This work thus provides the first medicinal chemistry toolbox (experimental procedures and structural guidance) to assess and control the plasma stability of hydroxamic acids and realize their full potential as in vivo pharmacological probes and therapeutic agents. This study is particularly relevant to preclinical development as it allows obtaining compounds equally stable in human and rodent models.

Publisher Correction: Combination therapy for tuberculosis treatment: pulmonary administration of ethionamide and booster co-loaded nanoparticles

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