Klarissa D. Jackson

Venetoclax is a first‐in‐class orally administered B‐cell lymphoma‐2 inhibitor used to treat chronic lymphocytic leukemia (CLL). Venetoclax is primarily metabolized in the liver by cytochrome P450 (CYP) 3A4 to its major metabolite M27, via M5, and M2, M3, and M4 via oxidation. Although venetoclax is a breakthrough in CLL treatment, managing drug safety and toxicity remains a clinical challenge. The objectives of this study were to investigate how individual CYP3A activity and protein expression affect hepatic venetoclax metabolism in vitro and examine whether plasma 4β‐hydroxycholesterol (4β‐HC)/cholesterol ratio can predict venetoclax metabolism in vitro and in vivo. In human liver microsomes (n = 20) and primary human hepatocytes (n = 15), venetoclax metabolite formation varied widely between donors and significantly correlated with CYP3A activity (midazolam 1′‐hydroxylation) and CYP3A4 protein expression. Venetoclax metabolite formation positively correlated with 4β‐HC/cholesterol ratio in plasma samples from the matched non‐infant donors (n = 14, ages 3–63 years). In an observational pilot study of real‐world patients with CLL (n = 12, ages 56–84 years) treated with venetoclax, the plasma M3/venetoclax metabolic ratio negatively correlated with plasma 4β‐HC/cholesterol ratio and positively correlated with patient age. Plasma 4β‐HC/cholesterol ratio negatively correlated with patient age. Differences between the in vitro data, which showed a positive association between venetoclax metabolism, hepatic CYP3A markers, and plasma 4β‐HC/cholesterol ratio, and the in vivo findings in patients with CLL could be due to age or other factors regulating plasma 4β‐HC/cholesterol and/or venetoclax disposition. Future studies with larger sample sizes are needed to investigate age‐related changes in venetoclax metabolism and plasma 4β‐HC/cholesterol ratio.

Cannabinoid use has surged in the past decade, with a growing interest in expanding cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) applications into special populations. Consequently, the increased use of CBD and THC raises the risk of drug–drug interactions (DDIs). Nevertheless, DDIs for cannabinoids, especially in special populations, remain inadequately investigated. While some clinical trials have explored DDIs between therapeutic drugs like antiepileptic drugs and CBD/THC, more potential interactions remain to be examined. This review summarizes the published studies on CBD and THC–drug interactions, outlines the mechanisms involved, discusses the physiological considerations in pharmacokinetics (PK) and DDI studies in special populations (including pregnant and lactating women, pediatrics, older adults, patients with hepatic or renal impairments, and others), and presents modeling approaches that can describe the DDIs associated with CBD and THC in special populations. The PK of CBD and THC in special populations remain poorly characterized, with limited studies investigating DDIs involving CBD/THC in these populations. Therefore, it is critical to evaluate potential DDIs between CBD/THC and medications that are commonly used in special populations. Modeling approaches can aid in understanding these interactions.

Cannabidiol (CBD) is a pharmacologically active metabolite of cannabis that is FDA-approved to treat seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex in children aged one year and older. During clinical trials, CBD caused dose-dependent hepatocellular toxicity at therapeutic doses. The risk for toxicity was increased in patients taking valproate (VPA), another hepatotoxic antiepileptic drug, through an unknown mechanism. With the growing popularity of CBD in the consumer market, an improved understanding of the safety risks associated with CBD is needed to ensure public health. This review details current efforts to describe CBD pharmacokinetics and mechanisms of hepatotoxicity using both pharmacokinetic models and in vitro models of the liver. In addition, current evidence and knowledge gaps related to intracellular mechanisms of CBD-induced hepatotoxicity are described. The authors propose future directions that combine systems-based models with markers of CBD-induced hepatotoxicity to understand how CBD pharmacokinetics may influence the adverse effect profile and risk of liver injury for those taking CBD. Significance Statement This review describes current pharmacokinetic modeling approaches to capture the metabolic clearance and safety profile of cannabidiol (CBD). CBD is an increasingly popular natural product and FDA-approved antiepileptic drug known to cause clinically significant enzyme-mediated drug interactions and hepatotoxicity at therapeutic doses. CBD metabolism, pharmacokinetics, and putative mechanisms of CBD-induced liver injury are summarized from available preclinical data to inform future modeling efforts for understanding CBD toxicity.

Small molecule kinase inhibitors are one of the fastest growing classes of drugs, which are approved by the US Food and Drug Administration (FDA) for cancer and non-cancer indications. As of September 2023, there were over 70 FDA-approved small molecule kinase inhibitors on the market, 42 of which were approved in the past five years (2018-2023). This minireview discusses recent advances in our understanding of the pharmacology, metabolism, and toxicity profiles of recently approved kinase inhibitors with a central focus on tyrosine kinase inhibitors (TKIs). In this minireview we discuss the most common therapeutic indications and molecular target(s) of kinase inhibitors FDA-approved 2018-2023. We also describe unique aspects of the metabolism, bioactivation, and drug-drug interaction (DDI) potential of kinase inhibitors; discuss drug toxicity concerns related to kinase inhibitors, such as drug-induced liver injury; and highlight clinical outcomes and challenges relevant to TKI therapy. Case examples are provided for common TKI targets, metabolism pathways, DDI potential, and risks for serious adverse drug reactions. The minireview concludes with a discussion of perspectives on future research to optimize TKI therapy to maximize efficacy and minimize drug toxicity. Significance Statement This minireview highlights important aspects of the clinical pharmacology and toxicology of small molecule kinase inhibitors FDA-approved 2018-2023. We describe key advances in the therapeutic indications and molecular targets of tyrosine kinase inhibitors (TKIs). The major metabolism pathways and toxicity profiles of recently approved TKIs are discussed. Clinically relevant case examples are provided that demonstrate the risk for hepatotoxic drug interactions involving TKIs and co-administered drugs.