No Effect of Levothyroxine and Levothyroxine-Induced Subclinical Thyrotoxicosis on the Pharmacokinetics of Sorafenib in Healthy Male Subjects

Pharmacokinetic Simulation and Area under the Curve Estimation of Drugs Subject to Enterohepatic Circulation

Enterohepatic circulation (EHC) is a complex process where drugs undergo secretion and reabsorption from the intestinal lumen multiple times, resulting in pharmacokinetic profiles with multiple peaks. The impact of EHC on area under the curve (AUC) has been a topic of extensive debate, questioning the suitability of conventional AUC estimation methods. Moreover, a universal model for accurately estimating AUC in EHC scenarios is lacking. To address this gap, we conducted a simulation study evaluating five empirical models under various sampling strategies to assess their performance in AUC estimation. Our results identify the most suitable model for EHC scenarios and underscore the critical role of meal-based sampling strategies in accurate AUC estimation. Additionally, we demonstrate that while the trapezoidal method performs comparably to other models with a large number of samples, alternative models are essential when sample numbers are limited. These findings not only illuminate how EHC influences AUC but also pave the way for the application of empirical models in real-world drug studies.

In vivo assessment of potential for UGT-inhibition-based drug-drug interaction between sorafenib and tapentadol

Sorafenib (SR) is one of the most potent UGT (1A1, 1A9) inhibitors (in in vitro tests). The inhibition of UGT1A1 may cause hyperbilirubinaemia, whereas the inhibition of UGT1A9 and 1A1 may result in drug-drug interactions (DDIs). Tapentadol (TAP) is a synthetic μ-opioid agonist and is used to treat moderate to severe acute pain. Tapentadol is highly glucuronidated by the UGT1A9 and UGT2B7 isoenzymes. The aim of the study was to assess the DDI between SR and TAP. Wistar rats were divided into three groups, with eight animals in each. The rats were orally treated with SR (100 mg/kg) or TAP (4.64 mg/kg) or in combination with 100 mg/kg SOR and 4.64 TAP mg/kg. The concentrations of SR and sorafenib N-oxide, TAP and tapentadol glucuronide were respectively measured by means of high-performance liquid chromatography (HPLC) with ultraviolet detection and by means of ultra-performance liquid chromatography-tandem mass spectrometry. The co-administration of TAP with SR caused TAP maximum plasma concentration (C_max) to increase 5.3-fold whereas its area under the plasma concentration-time curve (AUC_0-∞) increased 1.5-fold. The tapentadol glucuronide C_max increased 5.3-fold and whereas its AUC_0-∞ increased 2.0-fold. The tapentadol glucuronide/TAP AUC_0-∞ ratio increased 1.4-fold (p = 0.0118). TAP also increased SR C_max 1.9-fold, whereas its AUC_0-∞ increased 1.3-fold. The sorafenib N-oxide C_max increased 1.9-fold whereas its AUC_0-∞ increased 1.3-fold. The sorafenib N-oxide/SR AUC_0-t ratio increased 1.4-fold (p = 0.0127). The results show that the co-administration of sorafenib and tapentadol increases the exposure to both drugs and changes their metabolism. In consequence, the pharmacological effect may be intensified, but the toxicity may increases, too.

Pivotal Considerations for Optimal Deployment of Healthy Volunteers in Oncology Drug Development

Oncology drug development is among the most challenging of any therapeutic area, with first-in-human trials expected to deliver information on both safety and activity. Until recently, therapeutic approaches in oncology focused on cytotoxic chemotherapy agents, ruling out even the possibility of enrolling normal healthy volunteers (NHVs) in clinical trials due to safety considerations. The emergence of noncytotoxic modalities, including molecularly targeted agents with more favorable safety profiles, however, has led to increasing numbers of clinical pharmacology studies of these agents being conducted in NHVs. Beyond rapid enrollment and cost savings, there are other advantages of conducting specific types of studies in NHVs with the goal of more appropriate dosing decisions in certain subsets of the intended patient populations, allowing for enrollment of such patients in therapeutic trials from which they might otherwise have been excluded. Nevertheless, the decision must be carefully weighed against potential disadvantages, and although the considerations surrounding conduct of clinical trials using NHVs are generally well-defined in most other therapeutic areas, they are less well-defined in oncology.