Estimation of AUC from 0 to Infinity in Serial Sacrifice Designs.

Nonclinical in vivo animal studies have to be completed before starting clinical studies of the pharmacokinetic behavior of a drug in humans. The drug exposure in animal studies is often measured by the area under the concentration time curve (AUC). The classical complete data design where each animal is sampled for analysis once per time point is usually only applicable for large animals. In the case of rats and mice, where blood sampling is restricted, the batch design or the serial sacrifice design need to be considered. In batch designs samples are taken more than once from each animal, but not at all time points. In serial sacrifice designs only one sample is taken from each animal. This paper presents an estimator for AUC from 0 to infinity in serial sacrifice designs, the corresponding variance and its asymptotic distribution

Establishing bioequivalence in complete and incomplete data designs using AUCs.

Nonclinical in vivo animal studies have to be completed before starting clinical studies of the pharmacokinetic behavior of a drug in humans. The drug exposure in animal studies is often measured by the area under the concentration versus time curve (AUC). The classical complete data design where each animal is sampled for analysis at every time point is applicable for large animals only. In the case of small animals, where blood sampling is restricted, the batch design or the serial sampling design need to be considered. In batch designs, samples are taken more than once from each animal, but not at all time points. In serial sampling designs, only one sample is taken from each animal. In this article we derive the asymptotic distribution for the ratio of two AUCs and construct different confidence intervals, which are frequently used to assess bioequivalence. The performance of these intervals is then evaluated between the different designs in a simulation study. Additionally, the sample sizes required for the different designs are compared

Non-compartmental estimation of pharmacokinetic parameters in serial sampling designs.

Pharmacokinetic studies are commonly analyzed using a two-stage approach where the first stage involves estimation of pharmacokinetic parameters for each subject separately and the second stage uses the individual parameter estimates for statistical inference. This two-stage approach is not applicable in sparse sampling situations where only one sample is available per subject. Nonlinear models are often applied to analyze pharmacokinetic data assessed in such serial sampling designs. Modelling approaches are suitable provided that the form of the true model is known, which is rarely the case in early stages of drug development. This paper presents an alternative approach to estimate pharmacokinetic parameters based on non-compartmental and asymptotic theory in the case of serial sampling when a drug is given as an intravenous bolus. The statistical properties of the estimators of the pharmacokinetic parameters are investigated and evaluated using Monte Carlo simulations

Recombinant ADAMTS13 normalizes von Willebrand factor-cleaving activity in plasma of acquired TTP patients by overriding inhibitory antibodies

Severe deficiency of the von Willebrand factor (VWF)-cleaving protease ADAMTS13 as observed in acquired thrombotic thrombocytopenic purpura (TTP) is caused by inhibitory and non-inhibitory autoantibodies directed against the protease. Current treatment with plasma exchange is considered to remove circulating antibodies and to concurrently replenish the deficient enzyme

Pharmacokinetics, disease-modifying activity, and safety of an experimental therapeutic targeting an immunological isoform of macrophage migration inhibitory factor, in rat glomerulonephritis

New therapeutic agents are needed to overcome the toxicity and suboptimal efficacy observed in current treatment of glomerulonephritis (GN). BaxB01 is a fully human monoclonal antibody targeting a disease-related immunologically distinct isoform of Macrophage migration Inhibitory Factor (MIF), designated oxidized MIF (oxMIF) and locally expressed in inflammatory conditions. We report the pharmacokinetic profile of BaxB01, and its dose and exposure-related disease-modifying activity in experimentally induced rat GN. BaxB01 bound to rat oxMIF with high affinity and reduced rat macrophage migration in vitro. After intravenous administration in rats, BaxB01 demonstrated favorable pharmacokinetics, with a half-life of up to nine days. Disease modification was dose-related (≥10 mg/kg) as demonstrated by significantly reduced proteinuria and diminished histopathological glomerular crescent formation. Importantly, a single dose was sufficient to establish an exposure-related, anti-inflammatory milieu via amelioration of glomerular cellular inflammation. Pharmacodynamic modeling corroborated these findings, consistently predicting plasma exposures that were effective in attenuating both anti-inflammatory activity and reducing loss of kidney function. This pharmacologic benefit on glomerular function and structure was sustained during established disease, while correlation analyses confirmed a link between the antibody's anti-inflammatory activity and reduced crescent formation in individual rats. Finally, safety assessment in rats showed that the experimental therapeutic was well tolerated without signs of systemic toxicity or negative impact on kidney function. These data define therapeutically relevant exposures correlated with mechanism-based activity in GN, while toxicological evaluation suggests a large therapeutic index and provides evidence for achieving safe and effective exposure to a MIF isoform-directed therapeutic in nephritis-associated disease

Optimization, refinement and reduction of murine in vivo experiments to assess therapeutic approaches for hemophilia A.

The tail cut bleeding model (CUT) is routinely used in factor VIII-deficient mice to assess pharmacodynamic effects of therapeutic strategies for haemophilia A. Results from this model are highly variable, many modifications to the model are reported and at times the animals' wellbeing may be compromised by recording survival as an endpoint. We therefore investigated if the ferric chloride carotid occlusion model (COM) used for thrombosis research can be applied to enhance data quality and animal welfare in haemophilia A research. Relative dose effects and relative dose variations were calculated for the CUT and COM. The requisite sample sizes were estimated and the importance of survival rates to assess rebleeds during recovery was evaluated by correlating initial blood loss to mortality. Relative dose effects increased with higher doses in both models. The COM was more sensitive at lower doses than the CUT, had up to 82% less variation across doses and clearly showed superior accuracy. Only 5% of the sample size required for the CUT would be needed to establish non-inferiority between a specific therapeutic dose in haemophilia A mice and healthy wild-type animals. A strong statistically significant correlation was found between initial blood loss and mortality within 24 h. Our findings clearly suggest that the COM is a valid tool for assessing haemophilia A treatment in vivo. The highly reproducible data means that significantly fewer animals are required and a more humane endpoint can be used by directly assessing clot stability instead of survival rate

Duration of the Snow Cover and the Need for Artificial Snow—A Challenge for Management in Ski-Centres of Serbia

The production and use of artificial snow has become necessary in most ski centres in Europe. The lack of snow creates problems in ski centres that were built without the prior valuation of natural factors. The survey covered winter tourist centres in Serbia, which are facing problems due to the shortening of the tourist season caused by the lack of snow cover on the ski slopes. The duration of the snow cover is the result of several factors. Air temperature changes were analysed in mountain tourist centres in Serbia, as well as at undeveloped destinations with a potential for snow sports. On the basis of the quantitative indicators of the air temperature and the methodology by means of which snowmaking is carried out, the time periods during the year for making artificial snow are presented. Due to the forecast rise in air temperature, the issue of profitability of artificial snow in the ski centres of Serbia remains open