QT prolongation is recognized as a risk factor for car- diac arrhythmia and torsades de *** QT cor- rection is essential for unbiased estimation of drug effect. However,evaluation of drug effect on QTc is challenging ...
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QT prolongation is recognized as a risk factor for car- diac arrhythmia and torsades de *** QT cor- rection is essential for unbiased estimation of drug effect. However,evaluation of drug effect on QTc is challenging due to multiple source of variability and low precision of QT measures resulting in low signal to noise ratio,high between individual and between occasion variabilities,the presence of circadian rhythm and inadequacy of fixed cor- rection methods such as Bezette's and Fredericia's. “Standard”QT analytical methods include 1)largest time- matched mean difference between the drug and placebo (baseline subtracted)over the collection period,2)time- averaged QT/QTc intervals for each individual,3)analysis for changes occurring at Cfor each ***- er,the“standard”methods have limitations:1)do not provide quantitative information on QT prolongation,po- tency & activity,2)unable to simulate most critical situ- ation ***-therapeutic concentration,and 3)time averaging substantially reduces the .sensitivity of the test. Quantitative PK/PD analysis could reduce the risk of false-positive or false-negative signals,and could differen- tiate drug effect from the multiple source of *** allows for splitting the overall variability into components and estimate them with sufficient precision in order to pro- vide more reliable assessment of the drug induced QT pro- *** addition,quantitative PK/PD analysis allows for determining the model-based correction factor α.With adequate data per individual per study day(10-15), mixed effect modeling allows for the determination of sub- ject-specific αi,QTc for a j-th measurement for an i-th in- dividual :QTc=QT ij/*** the QTc data are limited for individuals,a population corrector factor could be de- *** rate and QT could be subject to circadian rhythm,and can be modeled by 1 or more cosine function with different periods:QT=QT*RR*(1+CIR- C)*(1+ε),where QTcmi is an indi
AIM:The purpose of this analysis was to construct approp- riate models to characterise population pharmacokinetics (PK)for PHA-794428 and PK/pharmacodynamics(PD) for the efficacy biomarker Insulin-like Growth fact...
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AIM:The purpose of this analysis was to construct approp- riate models to characterise population pharmacokinetics (PK)for PHA-794428 and PK/pharmacodynamics(PD) for the efficacy biomarker Insulin-like Growth factor-1 (IGF-1). METHODS:Fifty-six male healthy volunteers were en- rolled into a clinical *** received in a random- ised manner 3 subcutaneous injections over 3 periods:i) 3.6 mg recombinant human growth hormone(rhGH),ii) PHA-794428 0,3,10,30,60,100,300 or 500μg/kg, and iii)PHA-794428 0,10,or 30μg/*** PK and IGF-1 data were collected up to 336 h *** PK and PK/PD models were constructed in 3 stages:i)the PK model was developed,ii)the PK parameters were fixed during IGF-1 model building,iii)PK and IGF-1 da- ta were analysed simultaneously. RESULTS:PHA-794428 exhibited non-linearity with re- spect to dose.A one-compartment disposition model with parallel linear and non-linear elimination most appropriate- ly described the PHA-794428 serum concentrations versus time *** absorption of PHA-794428 was character- ised as a first-order process involving two absorption rate *** nonlinear elimination,characterised in terms of the maximal elimination capacity(V=91.5 μg/h for 70 kg)and Michaelis-Menten constant(K= 73.9μg/L)describing the concentration at which elimina- tion is at half *** non-linear elimination pathway is approximately 10 times higher than the linear route(0.129 L/h).PHA-794428 has a limited distribution in the blood (V=4.4 L),due to its large molecular *** IGF-1 concentrations versus time data were best described by an indirect response model with PEG-hGH stimulating IGF-1 production *** effect was appropriately char- acterised by a maximum effect(E)*** maxi- mal IGF-1 production rate could increase up to 8-fold across the dose range *** PHA-794428 concen- tration at half Emax(EC)is 56.5 ng/mL.A negative feedback loop was incorporated into the PK/IGF-1 model. The maximal inhibition(I)
Contemporary pharmacological research has two pro- nounced trends:one trend is from the “macro” to the “micro”.The frontier of medical research is on the cellu- lar,molecular,and genetic level,which allow people t...
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Contemporary pharmacological research has two pro- nounced trends:one trend is from the “macro” to the “micro”.The frontier of medical research is on the cellu- lar,molecular,and genetic level,which allow people to access the pharmacological arcanum more and more exact- *** important trend is from the “qualitative” to the “quantitative”.With the development of research,the
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