Population Pharmacokinetics of Volasertib Administered in Patients with Acute Myeloid Leukaemia as a Single Agent or in Combination with Cytarabine.

BACKGROUND: Volasertib, a potent and selective polo-like kinase inhibitor, has shown to increase response rates and improve survival with a clinically manageable safety profile, administered alone and in combination with cytarabine in patients with acute myeloid leukaemia. OBJECTIVES: The objectives of this analysis were to describe the pharmacokinetics of volasertib and cytarabine, administered as single agents or in combination. METHODS: Three thousand, six hundred and six plasma volasertib concentrations from 501 patients receiving either volasertib alone, or in combination with cytarabine, and 826 plasma cytarabine concentrations from 650 patients receiving cytarabine as multiple subcutaneous injections per cycle either alone, or in combination with volasertib, were analysed using NONMEM Version 7.3. Covariates evaluated included demographic and disease-related parameters. RESULTS: The pharmacokinetics of volasertib were found to be dose independent from 150 to 550 mg. Body surface area and ethnicity showed significant effects in all the patients. This is reflected as an increase in drug exposure for Japanese patients, although this finding has to be interpreted with caution because only 7% of patients were part of that population group. Volasertib showed low-to-mild inter-individual variability in total clearance. For the case of cytarabine, its pharmacokinetics was affected by body surface area. Finally, volasertib and cytarabine did not influence the pharmacokinetic characteristics of each other. CONCLUSIONS: The pharmacokinetics of volasertib in patients with acute myeloid leukaemia alone or in combination with cytarabine is predictable and associated with low-to-mild patient variability with the exception of the high variability associated with the volume of distribution of the central compartment, having no effect on the area under the plasma concentration-time curve.

A semi-physiological model of amyloid-ß biosynthesis and clearance in human cerebrospinal fluid: a tool for alzheimer's disease research and drug development.

Stable isotope labeling kinetics (SILK) was successfully applied to quantify endogenous amyloid-ß (Aß) metabolism in human cerebrospinal fluid (CSF). A semi-physiological model describing Aß biosynthesis and degradation in human CSF and the impact of the γ-secretase inhibitor semagacestat should be developed and validated based on digitized data from three published SILK studies. Aß biosynthesis was adequately characterized by six transit compartments. At each transition step, a first-order degradation process was implemented. A two-compartment model best described semagacestat CSF concentration-time profiles. Semagacestat concentrations were linked to the Aß production by an inhibitory Emax model. For model validation, three individual Aß profiles from literature were successfully predicted. Model application demonstrated a 35% decreased Aß elimination rate constant in Alzheimer's disease (AD) patients. Study design optimization revealed that SILK studies could be conducted with significant less sampling points compared to the standard protocol without losing information about the Aß metabolism, if analyzed by the presented model. In conclusion, the analysis outlined the advantages and opportunities of integrating all available data and knowledge into a semi-physiological model. The model can serve as valuable tool for researchers and clinicians interested in the pathology of AD as well as in the development of new therapeutics for AD.

Pharmacokinetic evaluation of visnagin and Ammi visnaga aqueous extract after oral administration in rats.

The furanochromone visnagin is one of the main compounds of Ammi visnaga L. (syn. Khella) with potential effects on kidney stone prevention. After determination of the pharmacokinetic properties of visnagin after intravenous bolus administration in rats, the aim of the present study was to evaluate the pharmacokinetic properties of visnagin and an aqueous Ammi visnaga extract after oral administration in rats. In two separate experiments, three doses of visnagin (2.5, 5, and 10 mg/kg) solubilized in 25 % Captisol® and three doses of Ammi visnaga extract (standardized on visnagin and containing equivalent amounts of visnagin) were administered by oral gavage to male Sprague-Dawley rats, respectively. Plasma samples were extracted and subsequently analyzed using a validated LC-MS/MS method. Plasma concentration-time profiles were explored by non-compartmental analysis. Visnagin plasma exposure (median AUClast and AUCinf) was significantly increased for all three doses (more than 10-fold for the low dose) when administered as an extract compared to the pure agent. For both the Ammi visnaga extract and the pure compound, AUClast and AUCinf increased disproportionately with an increase in dose. Visnagin resided significantly longer in the body when given in the form of AVE with up to a three times longer median MRTlast and MRTinf for the low dose. Cmax values after AVE administration were elevated and occurred at later time points in comparison to equivalent doses of pure visnagin. The terminal half-life increased with the dose for both AVE and pure visnagin, reaching a maximum value of 1.94 h for the 10 mg/kg pure compound group.In conclusion, the exposure of visnagin is enhanced after extract administration and could result in a superior efficacy of AVE compared to an equivalent dose of visnagin.

Pharmacokinetics of valerenic acid in rats after intravenous and oral administrations.

Valerenic acid (VA), a sesquiterpenoid, is one of the major secondary bioactive metabolites of VALERIANA OFFICINALIS L. Until now IN VIVO studies on the absorption, bioavailability, disposition, and metabolism of VA are limited. We established and validated an LC-MS/MS assay for the determination of VA in rat plasma and successfully used this method for pharmacokinetic studies in rats after intravenous (i. v.) and oral administrations. The plasma concentration-time data was analyzed by both non-compartmental and compartmental approaches using WinNonlin software. Following i. v. administration, the disposition of VA in rat plasma was biphasic, subdivided into a fast distribution and a slow elimination phase. The half-life of the distribution phase was 6-12 min, and that of the terminal elimination phase 6-46 h, indicating a possible large tissue binding. Disposition PK of valerenic acid after oral treatment was also described by a two-compartment model with a clearance (CL/F) of 2-5 L · h (-1) · kg (-1) and volume of distribution of (V (d)) 17-20 L · kg (-1). The extent of absorption (F) after oral administration was estimated to be 33.70 % with a half-life of 2.7-5 h. Dose proportionality was observed in terms of dose and AUCs, suggesting linear pharmacokinetics at the dose levels studied in rats.

Nonlinear pharmacokinetics of visnagin in rats after intravenous bolus administration.

Ammi visnaga L. (syn. Khella, Apiaceae) preparations have traditionally been used in the Middle East for the treatment of kidney stone disease. Visnagin, a furanocoumarin derivative, is one of the main compounds of Ammi visnaga with potential effects on kidney stone prevention. To date, no information is available about the pharmacokinetic (PK) properties of visnagin. It was the aim of the study to characterize the PK properties of visnagin after intravenous (i.v.) bolus administration in rats and to develop an adequate model for the description of the observed data, including model parameter estimates. Therefore, three doses of visnagin (1.25, 2.5, and 5mg/kg) solubilized in 25% Captisol® were administered by i.v. bolus injection to male Sprague-Dawley rats. Plasma samples were extracted and subsequently analyzed using a validated LC-MS/MS method. Both non-compartmental and compartmental PK analyses were performed. A stepwise model building approach was applied including nonlinear mixed effect modeling for final model selection and to obtain final model estimates in NONMEM VI. The average areas under the curve (AUC(0-last)) after doses of 1.25, 2.5, and 5mg/kg were 1.03, 3.61, and 12.6 mg *h/l, respectively. The shape of the plasma concentration-time profiles and the observed disproportionate increase in AUC(0-last) with increasing dose suggested nonlinearity in the elimination of visnagin. A two-compartment Michaelis-Menten model provided the best fit with following typical values of the parameter estimates: 2.09 mg/(l*h) (V(max)), 0.08 mg/l (K(M)), 0.175 l (V(C)), 1.0 h⁻¹ (k12), and 1.22 h⁻¹ (k21). Associated inter-subject variability estimates (% CV) for V(max), K(M) and V(C) were 21.8, 70.9, and 9.2, respectively. Intra-subject variability (constant CV error model) was estimated to be 7.0%. The results suggest the involvement of a saturable process in the elimination of visnagin, possibly an enzyme or transporter system.