A novel mathematical model describes spatial-temporal drug distribution within one or more brain units, which are cubic representations of a piece of brain tissue with brain capillaries at the... Show moreA novel mathematical model describes spatial-temporal drug distribution within one or more brain units, which are cubic representations of a piece of brain tissue with brain capillaries at the edges. The brain unit can be considered a highly representative building block of the brain in terms of drug distribution. While the focus of the model is on drug distribution within the brain ECF, the model includes descriptions of drug concentrations within the blood plasma, drug distribution via brain capillary blood flow, drug transport across the blood-brain barrier (BBB) by passive paracellular and transcellular transport as well as active transport, brain ECF diffusion, brain ECF bulk flow, non-specific binding of the drug to brain tissue, and drug target binding kinetics. We study the model with analytical methods and numerical simulations. This allows us to examine the integrated effect of the individual processes important to drug distribution and effect on the local concentration-time profiles of free and (non-)specifically bound drug. Moreover, the model allows us to generate a local distribution profile of a drug within the brain. In addition, the impact of disease-induced changes in brain-specific properties on the concentrations of drug within the brain ECF is assessed. Show less
Administration of alemtuzumab (targeting the CD52 antigen) to the patient (in-vivo) or to the graft (in-vitro) before allogeneic stem cell transplantation (alloSCT) decreases the incidence of graft... Show moreAdministration of alemtuzumab (targeting the CD52 antigen) to the patient (in-vivo) or to the graft (in-vitro) before allogeneic stem cell transplantation (alloSCT) decreases the incidence of graft-versus-host disease (GvHD). Effectiveness of this treatment relies on depletion of donor T cells. Currently, no data are available on alemtuzumab pharmacokinetics and pharmacodynamics in patients who received combined in-vivo and in-vitro alemtuzumab-based T-cell depletion. In this prospective study, we analyzed alemtuzumab pharmacokinetics and its effect on the circulating T cells in 36 patients who received an allogeneic T-cell-depleted graft by addition of 20 mg alemtuzumab "to the bag" with or without prior alemtuzumab (30 mg cumulative dose intravenously) as part of the conditioning regimen. Effective T-cell depletion was shown for all patients, even though alemtuzumab plasma levels varied considerably. Peak alemtuzumab levels were observed directly after graft infusion and were not associated with the number of circulating T cells pre-infusion, but with plasma volumes of the patients. All patients engrafted, confirming feasibility of this transplantation protocol. Only three patients with low alemtuzumab levels developed acute GvHD (grade II in 2 patients and grade III in 1 patient). Persistence of circulating alemtuzumab at 3 weeks after transplantation had prevented reconstitution of CD52-positive T cells when alemtuzumab plasma levels were above 0.7 mu g/mL. However, overall T-cell reconstitution did not correlate with the levels of alemtuzumab exposure, due to early reconstitution of CD52-negative alemtuzumab-resistant T cells. The protective effect of these cells likely explains the low incidence of Epstein-Barr-virus- and cytomegalovirus-related disease despite circulating alemtuzumab. Show less
Bury, D.; Heine, R. ter; Garde, E.M.W. van de; Nijziel, M.R.; Grouls, R.J.; Deenen, M.J. 2019
ACT-541468 is a dual orexin receptor antagonist with sleep-promoting effects in humans. Following entry-into-humans, its pharmacokinetics (PK) including dose-proportionality and accumulation,... Show moreACT-541468 is a dual orexin receptor antagonist with sleep-promoting effects in humans. Following entry-into-humans, its pharmacokinetics (PK) including dose-proportionality and accumulation, pharmacodynamics (PD), safety, and tolerability following multiple-ascending oral dose (MAD) administration in the morning, and next-day residual effects after repeated evening administration were investigated in a double-blind, placebo-controlled, randomized study. 31 healthy male and female subjects in 3 dose-groups (10, 25, and 75 mg) received study drug in the morning for 5 days (MAD part), and 20 healthy subjects received 25 mg in the evening for 1 week (evening part). PK, PD (saccadic peak velocity (SPV), adaptive tracking, body sway, Bond and Lader visual analogue scales (VAS), Karolinska Sleepiness Scale (KSS), VAS Bowdle for assessment of psychedelic effects), Digit Symbol Substitution Test (DSST), and Simple Reaction Time Test (SRTT), safety, and tolerability were assessed. ACT-541468 was absorbed with a median t(max) of 1.0-2.0 h across the 3 dose groups. The geometric mean elimination half-life (t(1/2)) on Day 5 was between 5.6 and 8.5 h, and the exposure (area under the curve (AUC)) showed dose proportionality. No accumulation and no influence of sex on the multiple-dose PK parameters of ACT-541468 was observed. No effects were observed at 10 mg. Administration of 25 and 75 mg during the day showed clear dose-dependent effects on the PD parameters, while next-day effects were absent after evening administration of 25 mg. The drug was safe and well tolerated. In conclusion, multiple-dose PK/PD of ACT-541468 were compatible with a drug designated to treat insomnia. (C) 2019 Elsevier B.V. and ECNP. All rights reserved. Show less
Donk, T. van de; Niesters, M.; Kowal, M.A.; Olofsen, E.; Dahan, A.; Velzen, M. van 2019
Zebrafish larvae are increasingly used in pharmacological and toxicological studies, but it is often overlooked that internal exposure to exogenous compounds, rather than the incubation medium... Show moreZebrafish larvae are increasingly used in pharmacological and toxicological studies, but it is often overlooked that internal exposure to exogenous compounds, rather than the incubation medium concentration, is driving observed effects. Moreover, as the zebrafish larva is a developing organism, continuous physiological changes impact pharmacokinetic or toxicokinetic processes like the absorption and elimination of exogenous compounds, influencing the interpretation of observations and conclusions drawn from experiments at different larval ages. Here, using paracetamol as paradigm compound, mathematical modelling is used to quantify absorption and elimination rates from internal exposure over time profiles after waterborne treatment, as well as changes in these parameters in post-hatching larvae of 3, 4, and 5 days post fertilisation (dpf). An increase of 106% in absorption rate was observed between 3 and 4 dpf, but no further increase at 5 dpf, and an increase of 17.5% in elimination rate for each dpf. Paracetamol clearance, determined from elimination rate constants and reported total larval volumes of 253, 263, and 300 nL at 3, 4, and 5 dpf respectively, correlates best with higher vertebrates at 5 dpf. This suggests that when studying direct effects of exogenous compounds, experiments with zebrafish larvae are best performed at 5 dpf. Show less
