Translating slow-binding inhibition kinetics into cellular and in vivo effects.

Many drug candidates fail in clinical trials owing to a lack of efficacy from limited target engagement or an insufficient therapeutic index. Minimizing off-target effects while retaining the desired pharmacodynamic (PD) response can be achieved by reduced exposure for drugs that display kinetic selectivity in which the drug-target complex has a longer half-life than off-target-drug complexes. However, though slow-binding inhibition kinetics are a key feature of many marketed drugs, prospective tools that integrate drug-target residence time into predictions of drug efficacy are lacking, hindering the integration of drug-target kinetics into the drug discovery cascade. Here we describe a mechanistic PD model that includes drug-target kinetic parameters, including the on- and off-rates for the formation and breakdown of the drug-target complex. We demonstrate the utility of this model by using it to predict dose response curves for inhibitors of the LpxC enzyme from Pseudomonas aeruginosa in an animal model of infection.

Translational Population-Pharmacodynamic Modeling of a Novel Long-Acting siRNA Therapy, Inclisiran, for the Treatment of Hypercholesterolemia.

Inclisiran is a novel N-acetylgalactosamine (GalNAc) conjugated small-interfering ribonucleic acid (siRNA) therapy designed to specifically target proprotein convertase subtilisin/kexin type 9 (PCSK9) mRNA in the liver for the treatment of hypercholesterolemia. Inclisiran's GalNAc attachment results in a rapid uptake into the liver, and thus a short plasma half-life, but long duration of effects on PCSK9 inhibition and low-density lipoprotein cholesterol (LDL-C) lowering. The effects on PCSK9 inhibition and consequent LDL-C reduction are sustained for more than 6 months following a single subcutaneous (s.c.) dose, despite inclisiran being detectable in the plasma only for up to 48 hours. A kinetic-pharmacodynamic (K-PD) model was developed to characterize inclisiran's dose-related LDL-C lowering effects and to evaluate the impact of intrinsic and extrinsic factors on LDL-C lowering. To accommodate the long duration of action, the K-PD model incorporated an effect compartment which represents the liver. Inclisiran concentration in the liver leads to decreased production of the PCSK9 protein and allow recycling of more LDL-C receptors on the hepatocyte cell surface, which results in a reduction of circulating LDL-C. The analysis of covariates identified PCSK9 and LDL-C baseline levels as important factors for the effects of LDL-C lowering. Observations and modeling and simulation results demonstrated that PCSK9 and LDL-C reductions are achieved rapidly after dosing and sustained when patients are treated with a 300 mg s.c. dose once every 6 months.

Responding to the challenge of untreatable gonorrhea: ETX0914, a first-in-class agent with a distinct mechanism-of-action against bacterial Type II topoisomerases.

With the diminishing effectiveness of current antibacterial therapies, it is critically important to discover agents that operate by a mechanism that circumvents existing resistance. ETX0914, the first of a new class of antibacterial agent targeted for the treatment of gonorrhea, operates by a novel mode-of-inhibition against bacterial type II topoisomerases. Incorporating an oxazolidinone on the scaffold mitigated toxicological issues often seen with topoisomerase inhibitors. Organisms resistant to other topoisomerase inhibitors were not cross-resistant with ETX0914 nor were spontaneous resistant mutants to ETX0914 cross-resistant with other topoisomerase inhibitor classes, including the widely used fluoroquinolone class. Preclinical evaluation of ETX0914 pharmacokinetics and pharmacodynamics showed distribution into vascular tissues and efficacy in a murine Staphylococcus aureus infection model that served as a surrogate for predicting efficacious exposures for the treatment of Neisseria gonorrhoeae infections. A wide safety margin to the efficacious exposure in toxicological evaluations supported progression to Phase 1. Dosing ETX0914 in human volunteers showed sufficient exposure and minimal adverse effects to expect a highly efficacious anti-gonorrhea therapy.

In vitro microdialysis sampling of docetaxel.

Microdialysis is a technique that allows sampling compounds from the extracellular fluid in different tissues, such as muscle, lung, and brain. However, the feasibility of using this technique with lipopohilic and high molecular weight compounds has been questioned, since these compounds are less likely to diffuse through the dialysis membrane. Therefore, it was the objective of this study to investigate the feasibility of doing microdialysis of docetaxel by determining its recovery by the microdialysis probe. Three different methods were investigated: extraction efficiency, retrodialysis, and no-net-flux. For the first two methods, three different concentrations were tested: 2.5, 5, and 9 mg/l. The recovery obtained for each concentration was 49.3 +/- 6.7 (n = 4), 44.6 +/- 5.4 (n = 3), and 34.7 +/- 2.1 (n = 4) by extraction efficiency, and 53.4 +/- 7.9 (n = 3), 61.4 +/- 7.6 (n = 3), and 64.2 +/- 1.9 (n = 3) by retrodialysis, respectively. The average recovery obtained by no-net-flux was 68.7 +/- 9.6 (n = 5). Although it has been reported that microdialysis cannot be applied to lipophilic compounds, the results here show the opposite. The high recoveries obtained for docetaxel in all methods applied show that the compound can diffuse through the probe membrane. Overall, docetaxel seems to be very suitable for microdialysis despite its lipophilicity and high molecular weight.

Novel DNA gyrase inhibiting spiropyrimidinetriones with a benzisoxazole scaffold: SAR and in vivo characterization.

The compounds described herein with a spirocyclic architecture fused to a benzisoxazole ring represent a new class of antibacterial agents that operate by inhibition of DNA gyrase as corroborated in an enzyme assay and by the inhibition of precursor thymidine into DNA during cell growth. Activity resided in the configurationally lowest energy (2S,4R,4aR) diastereomer. Highly active compounds against Staphylococcus aureus had sufficiently high solubility, high plasma protein free fraction, and favorable pharmacokinetics to suggest that in vivo efficacy could be demonstrated, which was realized with compound (-)-1 in S. aureus mouse infection models. A high drug exposure NOEL on oral dosing in the rat suggested that a high therapeutic margin could be achieved. Importantly, (-)-1 was not cross-resistant with other DNA gyrase inhibitors such as fluoroquinolone and aminocoumarin antibacterials. Hence, this class shows considerable promise for the treatment of infections caused by multidrug resistant bacteria, including S. aureus.

Model-based drug discovery: implementation and impact.

Model-based drug discovery (MBDDx) aims to build and continuously improve the quantitative understanding of the relation between drug exposure (target engagement) efficacy and safety, to support target validation; to define compound property criteria for lead optimization and safety margins; to set the starting dose; and to predict human dose and scheduling for clinical candidates alone, or in combination with other medicines. AstraZeneca has systematically implemented MBDDx within all drug discovery programs, with a focused investment to build a preclinical modeling and simulation capability and an in vivo information platform and architecture, the implementation, impact and learning of which are discussed here.

Avaliação da atividade antimicrobiana de Cymbopogon citratus / Evaluation of the antimicrobial activity of Cymbopogon citratus

Cymbopogon citratus (DC) Stapf. é uma gramínea, conhecida popularmente como capim-cidró, capim-cheiroso, erva-cidreira, entre outros, e, em inglês, "lemon grass". A população utiliza o chá ou abafado, preparado a partir de suas folhas, como calmante, digestivo, estomáquico, em dores de cabeça, antiespasmódico, entre outras aplicações. Devido às propriedades antimicrobianas apresentadas pelo óleo volátil de capim-cidró, este trabalho tem por objetivo avaliar a atividade antibacteriana e antifúngica do óleo volátil, extratos aquosos e hidroetanólico, obtidos a partir das folhas frescas e secas da planta. A atividade antimicrobiana foi avaliada pelo método de difusão em ágar, frente aos microrganismos...