Simulated rat intestinal fluid improves oral exposure prediction for poorly soluble compounds over a wide dose range

Solubility can be the absorption limiting factor for drug candidates and is therefore a very important input parameter for oral exposure prediction of compounds with limited solubility. Biorelevant media of the fasted and fed state have been published for humans, as well as for dogs in the fasted state. In a drug discovery environment, rodents are the most common animal model to assess the oral exposure of drug candidates. In this study a rat simulated intestinal fluid (rSIF) is proposed as a more physiologically relevant media to describe drug solubility in rats. Equilibrium solubility in this medium was tested as input parameter for physiologically-based pharmacokinetics (PBPK) simulations of oral pharmacokinetics in the rat. Simulations were compared to those obtained using other solubility values as input parameters, like buffer at pH 6.8, human simulated intestinal fluid and a comprehensive dissolution assay based on rSIF. Our study on nine different compounds demonstrates that the incorporation of rSIF equilibrium solubility values into PBPK models of oral drug exposure can significantly improve the reliability of simulations in rats for doses up to 300 mg/kg compared to other media. The comprehensive dissolution assay may help to improve further simulation outcome, but the greater experimental effort as compared to equilibrium solubility may limit its use in a drug discovery environment. Overall, PBPK simulations based on solubility in the proposed rSIF medium can improve prioritizing compounds in drug discovery as well as planning dose escalation studies, e.g. during toxicological investigations

Ensemble modeling highlights importance of understanding parasite-host behavior in preclinical antimalarial drug development

Emerging drug resistance and high-attrition rates in early and late stage drug development necessitate accelerated development of antimalarial compounds. However, systematic and meaningful translation of drug efficacy and host-parasite dynamics between preclinical testing stages is missing. We developed an ensemble of mathematical within-host parasite growth and antimalarial action models, fitted to extensive data from four antimalarials with different modes of action, to assess host-parasite interactions in two preclinical drug testing systems of murine parasite P. berghei in mice, and human parasite P. falciparum in immune-deficient mice. We find properties of the host-parasite system, namely resource availability, parasite maturation and virulence, drive P. berghei dynamics and drug efficacy, whereas experimental constraints primarily influence P. falciparum infection and drug efficacy. Furthermore, uninvestigated parasite behavior such as dormancy influences parasite recrudescence following non-curative treatment and requires further investigation. Taken together, host-parasite interactions should be considered for meaningful translation of pharmacodynamic properties between murine systems and for predicting human efficacious treatment

The Parasite Reduction Ratio (PRR) Assay Version 2: Standardized Assessment of Plasmodium falciparum Viability after Antimalarial Treatment In Vitro

With artemisinin-resistant Plasmodium falciparum parasites emerging in Africa, the need for new antimalarial chemotypes is persistently high. The ideal pharmacodynamic parameters of a candidate drug are a rapid onset of action and a fast rate of parasite killing or clearance. To determine these parameters, it is essential to discriminate viable from nonviable parasites, which is complicated by the fact that viable parasites can be metabolically inactive, whilst dying parasites can still be metabolically active and morphologically unaffected. Standard growth inhibition assays, read out via microscopy or [3H] hypoxanthine incorporation, cannot reliably discriminate between viable and nonviable parasites. Conversely, the in vitro parasite reduction ratio (PRR) assay is able to measure viable parasites with high sensitivity. It provides valuable pharmacodynamic parameters, such as PRR, 99.9% parasite clearance time (PCT99.9%) and lag phase. Here we report the development of the PRR assay version 2 (V2), which comes with a shorter assay duration, optimized quality controls and an objective, automated analysis pipeline that systematically estimates PRR, PCT99.9% and lag time and returns meaningful secondary parameters such as the maximal killing rate of a drug (Emax) at the assayed concentration. These parameters can be fed directly into pharmacokinetic/pharmacodynamic models, hence aiding and standardizing lead selection, optimization, and dose prediction

Setting our sights on infectious diseases

In May 2019, the Wellcome Centre for Anti-Infectives Research (WCAIR) at the University of Dundee, UK, held an international conference with the aim of discussing some key questions around discovering new medicines for infectious diseases and a particular focus on diseases affecting Low and Middle Income Countries. There is an urgent need for new drugs to treat most infectious diseases. We were keen to see if there were lessons that we could learn across different disease areas and between the preclinical and clinical phases with the aim of exploring how we can improve and speed up the drug discovery, translational, and clinical development processes. We started with an introductory session on the current situation and then worked backward from clinical development to combination therapy, pharmacokinetic/pharmacodynamic (PK/PD) studies, drug discovery pathways, and new starting points and targets. This Viewpoint aims to capture some of the learnings

The antimalarial MMV688533 provides potential for single-dose cures with a high barrier to

The emergence and spread of Plasmodium falciparum resistance to first-line antimalarials creates an imperative to identify and develop potent preclinical candidates with distinct modes of action. Here, we report the identification of MMV688533, an acylguanidine that was developed following a whole-cell screen with compounds known to hit high-value targets in human cells. MMV688533 displays fast parasite clearance in vitro and is not cross-resistant with known antimalarials. In a P. falciparum NSG mouse model, MMV688533 displays a long-lasting pharmacokinetic profile and excellent safety. Selection studies reveal a low propensity for resistance, with modest loss of potency mediated by point mutations in PfACG1 and PfEHD. These proteins are implicated in intracellular trafficking, lipid utilization, and endocytosis, suggesting interference with these pathways as a potential mode of action. This preclinical candidate may offer the potential for a single low-dose cure for malaria

The antimalarial MMV688533 provides potential for single-dose cures with a high barrier to

The emergence and spread of Plasmodium falciparum resistance to first-line antimalarials creates an imperative to identify and develop potent preclinical candidates with distinct modes of action. Here, we report the identification of MMV688533, an acylguanidine that was developed following a whole-cell screen with compounds known to hit high-value targets in human cells. MMV688533 displays fast parasite clearance in vitro and is not cross-resistant with known antimalarials. In a P. falciparum NSG mouse model, MMV688533 displays a long-lasting pharmacokinetic profile and excellent safety. Selection studies reveal a low propensity for resistance, with modest loss of potency mediated by point mutations in PfACG1 and PfEHD. These proteins are implicated in intracellular trafficking, lipid utilization, and endocytosis, suggesting interference with these pathways as a potential mode of action. This preclinical candidate may offer the potential for a single low-dose cure for malaria

Medium-scale experiments of fire warehouses

International audienceThis study, funded by AFILOG, focuses on the threat caused by the large heat releases from warehouse fires. The objective is to improve the understanding of the propagation of the fire inside the warehouse and to quantify the heat fluxes experienced in the vicinity of the warehouse. This will ultimately help refine the modelling tool presently employed by INERIS [1] to evaluate the thermal effects from warehouse fires on nearby populations and/or other industrial installations. Such an evaluation is important, for example, to help land-use planning. Medium-scale experiments of warehouse fires (see Figures 1 and 2) were conducted in a purposedly built 3 metres high building with a section of 4.3 4 m2. One side of the building was open and the top was covered with a plywood. This roof was meant to help the propagation of the fire and then disappear so as to be representative of a fully-developed fire in a large warehouse. Four steel racks were set up inside the building on which were stacked 40 cm 40 cm 50 cm high wood cribs made of pine sticks. To monitor the fire propagation, 52 measurements of temperature were undertaken with thermocouples throughout the storage area. Outside the building, heat fluxes were measured at a total of 20 locations in front of the building and on the two sides. The heat flux metres were located at different distances from the building and different heights. Videos were recorded from 4 cameras around the building and an infrared camera. The images allowed to time events such as the appearance and propagation of smoke, the collapse of the roof and stacks and to determine the shape and size of the flames. The fire was set by a burner located beneath the third rack towards the rear of the building. The heat release rate from the fire was deduced from the measurement of the total mass loss. The influence of a number of parameters on the longitudinal fire propagation along the racks, the lateral propagation from one rack to another and the shape and height of the flame once the roof collapsed was investigated. These parameters were the stockage compacity, the thickness of the roof and the number of rack shelves. The most important results will be presented and compared where appropriate to previous work, in particular to studies on fire propagation in warehouses [eg. 2] Thermal effects of fire warehouses on their surroundings have been less studied and will be analysed here in some details. In particular, the measured heat fluxes will be compared with the values predicted by the in-house tool FNAP. The limitations of FNAP which assumes a solid parallelepipedic flame will be discussed in the light of the observations of the shapes and heights of the flames. Future steps aimed to improve FNAP and to carry out full-scale experiments will be briefly presented

Evaluation of the GastroPlus™ Advanced Compartmental and Transit (ACAT) Model in Early Discovery

Purpose: The aim of this study was to evaluate the oral exposure predictions obtained early in drug discovery with a generic GastroPlus Advanced Compartmental And Transit (ACAT) model based on the in vivo intravenous blood concentration-time profile, in silico properties (lipophilicity, pKa) and in vitro high-throughput absorption-distribution-metabolism-excretion (ADME) data (as determined by PAMPA, solubility, liver microsomal stability assays). Methods: The model was applied to a total of 623 discovery molecules and their oral exposure was predicted in rats and/or dogs. The predictions of Cmax, AUClast and Tmax were compared against the observations. Results: The generic model proved to make predictions of oral Cmax, AUClast and Tmax within 3-fold of the observations for rats in respectively 65%, 68% and 57% of the 537 cases. For dogs, it was respectively 77%, 79% and 85% of the 124 cases. Statistically, the model was most successful at predicting oral exposure of Biopharmaceutical Classification System (BCS) class 1 compounds compared to classes 2 and 3, and was worst at predicting class 4 compounds oral exposure. Conclusion: The generic GastroPlus ACAT model provided reasonable predictions especially for BCS class 1 compounds. For compounds of other classes, the model may be refined by obtaining more information on solubility and permeability in secondary assays. This increases confidence that such a model can be used in discovery projects to understand the parameters limiting absorption and extrapolate predictions across species. Also, when predictions disagree with the observations, the model can be updated to test hypotheses and understand oral absorption

Modelling the effect of an occupant on displacement ventilation with computational fluid dynamics

International audienceDisplacement ventilation of a room with an occupant is modelled using computational fluid dynamics (CFD) and compared against experimental data. The geometry of the experimental manikin is accurately represented in the CFD model to minimise potential errors from using a simplified form. Modelling thermal radiation from the manikin is found to be important and calculations using a radiation model show good agreement with experimental data. The influence of turbulence modelling is considered and a comparative study is made between an unsteady Reynolds-averaged approach (URANS) and detached-eddy simulation (DES). The results show that the URANS and DES give similar predictions with the DES results in slightly better agreement with the experimental data. The realistic manikin geometry is required to give accurate heat transfer and contaminant exposure predictions; such geometries can be handled with relative ease using current grid generation tools and CFD solvers

A phase 1, placebo controlled, randomised, single ascending dose study and a volunteer infection study to characterize the safety, pharmacokinetics and antimalarial activity of the Plasmodium phosphatidylinositol 4-kinase inhibitor MMV390048

MMV390048 is the first Plasmodium phosphatidylinositol 4-kinase inhibitor to reach clinical development as a new antimalarial. We aimed to characterize the safety, pharmacokinetics and antimalarial activity of a tablet formulation of MMV390048.A two-part, phase 1 trial was conducted in healthy adults. Part one was a double-blind, randomised, placebo-controlled, single ascending dose study consisting of three cohorts (40, 80, 120 mg MMV390048). Part two was an open-label volunteer infection study using the Plasmodium falciparum induced blood-stage malaria model consisting of two cohorts (40, 80 mg MMV390048).Twenty four subjects were enrolled in part one (n=8 per cohort, randomised 3:1 MMV390048:placebo) and 15 subjects were enrolled in part two (n=7 and n=8; 40 and 80 mg cohort respectively). One subject was withdrawn from part 2 (80 mg cohort) before dosing and was not included in analyses. No serious or severe adverse events were attributed to MMV390048. The rate of parasite clearance was greater in subjects administered 80 mg compared to those administered 40 mg (clearance half-life 5·5 h [95% CI: 5·2-6·0] vs 6·4 h [95% CI: 6·0-6·9]; P=0·005). Pharmacokinetic/pharmacodynamic modeling estimated a minimal inhibitory concentration of 83 ng/mL, a minimal parasiticidal concentration that would achieve 90% of the maximum effect of 238 ng/mL, and predicted a single 120 mg dose would achieve an adequate clinical and parasitological response with 92% certainty.The safety, pharmacokinetics, and pharmacodynamics of MMV390048 support its further development as a partner drug of a single-dose combination therapy for malaria