PK/PD modeling of a clazosentan thorough QT study with hysteresis in concentration-QT and RR-QT

Modeling time-delayed concentration-QT effects with ACT-1014-6470, a novel oral complement factor 5a receptor 1 (C5a1 receptor) antagonist

The novel oral complement factor 5a receptor 1 antagonist ACT-1014-6470 was well tolerated in single- and multiple-ascending dose studies, including 24 h Holter electrocardiogram (ECG) recordings evaluating its cardiodynamics based on data from single doses of 30-200 mg and twice-daily (b.i.d.) dosing of 30-120 mg for 4.5 days. By-time point, categorical, and morphological analyses as well as concentration-QT modeling and simulations were performed. No relevant effect of ACT-1014-6470 on ECG parameters was observed in the categorical and morphological analyses. After single-dose administration, the by-time point analysis indicated a delayed dose-dependent increase in placebo-corrected change from baseline in QT interval corrected with Fridericia's formula (ΔΔQTcF) at >6 h postdose. After b.i.d. dosing, ΔΔQTcF remained elevated during the 24-h recording period, suggesting that the effect was not directly related to ACT-1014-6470 plasma concentration. The concentration-QT model described change from baseline in QTcF (ΔQTcF)-time profiles best with a 1-oscillator model of 24 h for circadian rhythm, an effect compartment, and a sigmoidal maximum effect model. Model-predicted ΔΔQTcF was derived for lower doses and less-frequent dosing than assessed clinically. Median and 90% prediction intervals of ΔΔQTcF for once-daily doses of 30 mg and b.i.d. doses of 10 mg did not exceed the regulatory threshold of 10 ms but would achieve ACT-1014-6470 plasma concentrations enabling adequate target engagement. Results from cardiodynamic assessments identified dose levels and dosing regimens that could be considered for future clinical trials, attempting to reduce QT liability.

A validated LC-MS/MS method for the determination of hederasaponin C: Application to Pharmacokinetic-pharmacodynamic studies in the therapeutic area of acetic acid-induced ulcerative colitis in rats

Hederasaponin C (HSC), one of the main components of pulsatilla chinensis, is considered as a potential drug for the treatment of inflammatory bowel disease. In the present research, we developed a PK-PD model to describe the concentration-effect course of drug action following intraperitoneal injection of HSC in colitis rats. A sensitive UPLC-MS/MS method was firstly established for the the determination of HSC in rat plasma to explore the pharmacokinetics properties. The separation was performed on an Accucore C₁₈ column (2.1mm×100mm, 2.6μm) with the flow phase consisted of acetonitrile and 0.1% formic acid water. The assay method was validated and demonstrated good adaptability for application in the pharmacokinetic study. Then the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in colon tissues were measured by ELISA assay. The levels of TNF-α, IL-1β and IL-6 was decreased after HSC administration, suggesting that HSC can significantly improve the level of inflammatory syndrome factor. The pharmacokinetics study showed that the T_max of HSC was 1 h. The concentration-effect curves showed hysteresis loop. And there has a hysteresis between the peaked concentration and the maximum effect of HSC. The present study established in vivo PK/PD models and the result showed a great potential of HSC for treating ulcerative colitis.

Intracellular uptake of agents that block the hERG channel can confound the assessment of QT interval prolongation and arrhythmic risk

BACKGROUND

Oliceridine is a biased ligand at the μ-opioid receptor recently approved for the treatment of acute pain. In a thorough QT study, corrected QT (QTc) prolongation displayed peaks at 2.5 and 60 minutes after a supratherapeutic dose. The mean plasma concentration peaked at 5 minutes, declining rapidly thereafter.

OBJECTIVE

The purpose of this study was to examine the basis for the delayed effect of oliceridine to prolong the QTc interval.

METHODS

Repolarization parameters and tissue accumulation of oliceridine were evaluated in rabbit left ventricular wedge preparations over a period of 5 hours. The effects of oliceridine on ion channel currents were evaluated in human embryonic kidney and Chinese hamster ovary cells. Quinidine was used as a control.

RESULTS

Oliceridine and quinidine produced a progressive prolongation of the QTc interval and action potential duration over a period of 5 hours, paralleling slow progressive tissue uptake of the drugs. Oliceridine caused modest prolongation of these parameters, whereas quinidine produced a prominent prolongation of action potential duration and QTc interval as well as development of early afterdepolarization (after 2 hours), resulting in a high torsades de pointes score. The 50% inhibitory concentration values for the oliceridine inhibition of the rapidly activating delayed rectifier current (human ether a-go-go current) and late sodium channel current were 2.2 and 3.45 μM when assessed after traditional acute exposure but much lower after 3 hours of drug exposure.

CONCLUSION

Our findings suggest that a gradual increase of intracellular access of drugs to the hERG channels as a result of their intracellular uptake and accumulation can significantly delay effects on repolarization, thus confounding the assessment of QT interval prolongation and arrhythmic risk when studied acutely. The multi-ion channel effects of oliceridine, late sodium channel current inhibition in particular, point to a low risk of devloping torsades de pointes.