Investigation of CYP3A induction by PF-05251749 in early clinical development: comparison of linear slope physiologically based pharmacokinetic prediction and biomarker response

Role of Clinical Pharmacology in Diversity and Inclusion in Global Drug Development: Current Practices and Industry Perspectives: White Paper

The 2022 United States Food and Drug Administration (US FDA) draft guidance on diversity plan (DP), which will be implemented through the Diversity Action Plans by December 2025, under the 21st Century Cures Act, marks a pivotal effort by the FDA to ensure that registrational studies adequately reflect the target patient populations based on diversity in demographics and baseline characteristics. This white paper represents the culminated efforts of the International Consortium of Quality and Innovation (IQ) Diversity and Inclusion (D&I) Working Group (WG) to assess the implementation of the draft FDA guidance by members of the IQ consortium in the discipline of clinical pharmacology (CP). This article describes current practices in the industry and emphasizes the tools and techniques of quantitative pharmacology that can be applied to support the inclusion of a diverse population during global drug development, to support diversity and inclusion of underrepresented patient populations, in multiregional clinical trials (MRCTs). It outlines strategic and technical recommendations to integrate demographics, including age, sex/gender, race/ethnicity, and comorbidities, in multiregional phase III registrational studies, through the application of quantitative pharmacology. Finally, this article discusses the challenges faced during global drug development, which may otherwise limit the enrollment of a broader, potentially diverse population in registrational trials. Based on the outcomes of the IQ survey that provided the current awareness of diversity planning, it is envisioned that in the future, industry efforts in the inclusion of previously underrepresented populations during global drug development will culminate in drug labels that apply to the intended patient populations at the time of new drug application or biologics license application rather than through post-marketing requirements.

Applications of the Cholesterol Metabolite, 4β-Hydroxycholesterol, as a Sensitive Endogenous Biomarker for Hepatic CYP3A Activity Evaluated within a PBPK Framework

Background/Objectives: Plasma levels of 4β-hydroxycholesterol (4β-OHC), a CYP3A-specific metabolite of cholesterol, are elevated after administration of CYP3A inducers like rifampicin and carbamazepine. To simulate such plasma 4β-OHC increase, we developed a physiologically based pharmacokinetic (PBPK) model of cholesterol and 4β-OHC in the Simcyp PBPK Simulator (Version 23, Certara UK Ltd.) using a middle-out approach. Methods: Relevant physicochemical properties and metabolic pathway data for CYP3A and CYP27A1 was incorporated in the model. Results: The PBPK model recovered the observed baseline plasma 4β-OHC levels in Caucasian, Japanese, and Korean populations. The model also captured the higher baseline 4β-OHC levels in females compared to males, indicative of sex-specific differences in CYP3A abundance. More importantly, the model recapitulated the increased 4β-OHC plasma levels after multiple-dose rifampicin treatment in six independent studies, indicative of hepatic CYP3A induction. The verified model also captured the altered 4β-OHC levels in CYP3A4/5 polymorphic populations and with other CYP3A inducers. The model is limited by scant data on relative contributions of CYP3A and CYP27A1 pathways and does not account for regulatory mechanisms that control plasma cholesterol and 4β-OHC levels. Conclusion: This study provides a quantitative fit-for-purpose and framed-for-future modelling framework for an endogenous biomarker to evaluate the DDI risk with hepatic CYP3A induction.

Enzyme-mediated drug-drug interactions: a review of in vivo and in vitro methodologies, regulatory guidance, and translation to the clinic

Enzyme-mediated pharmacokinetic drug-drug interactions can be caused by altered activity of drug metabolizing enzymes in the presence of a perpetrator drug, mostly via inhibition or induction. We identified a gap in the literature for a state-of-the art detailed overview assessing this type of DDI risk in the context of drug development. This manuscript discusses in vitro and in vivo methodologies employed during the drug discovery and development process to predict clinical enzyme-mediated DDIs, including the determination of clearance pathways, metabolic enzyme contribution, and the mechanisms and kinetics of enzyme inhibition and induction. We discuss regulatory guidance and highlight the utility of in silico physiologically-based pharmacokinetic modeling, an approach that continues to gain application and traction in support of regulatory filings. Looking to the future, we consider DDI risk assessment for targeted protein degraders, an emerging small molecule modality, which does not have recommended guidelines for DDI evaluation. Our goal in writing this report was to provide early-career researchers with a comprehensive view of the enzyme-mediated pharmacokinetic DDI landscape to aid their drug development efforts.

Evaluation of the usefulness of plasma 4β-hydroxycholesterol concentration normalized by 4α-hydroxycholesterol for accurate CYP3A phenotyping

Plasma 4β-hydroxycholesterol (OHC) has drawn attention as an endogenous substrate indicating CYP3A activity. Plasma 4β-OHC is produced by hydroxylation by CYP3A4 and CYP3A5 and by cholesterol autoxidation. Plasma 4α-OHC is produced by cholesterol autoxidation and not affected by CYP3A activity. This study aimed to evaluate the usefulness of plasma 4β-OHC concentration minus plasma 4α-OHC concentration (4β-OHC-4α-OHC) compared with plasma 4β-OHC concentration and 4β-OHC/total cholesterol (TC) ratio in cross-sectional evaluation of CYP3A activity. Four hundred sixteen general adults were divided into 191 CYP3A5*1 carriers and 225 non-carriers. Twenty-six patients with chronic kidney disease (CKD) with CYP3A5*1 allele were divided into 14 with CKD stage 3 and 12 with stage 4-5D. Area under the receiver operating characteristic curve (AUC) for the three indices were evaluated for predicting presence or absence of CYP3A5*1 allele in general adults, and for predicting CKD stage 3 or stage 4-5D in patients with CKD. There was no significant difference between AUC of 4β-OHC-4α-OHC and AUC of plasma 4β-OHC concentration in general adults and in patients with CKD. AUC of 4β-OHC-4α-OHC was significantly smaller than that of 4β-OHC/TC ratio in general adults (p = 0.025), but the two indices did not differ in patients with CKD. In conclusion, in the present cross-sectional evaluation of CYP3A activity in general adults and in patients with CKD with CYP3A5*1 allele, the usefulness of 4β-OHC-4α-OHC was not different from plasma 4β-OHC concentration or 4β-OHC/TC ratio. However, because of the limitations in study design and subject selection of this research, these findings require verification in further studies.