Amy L. Roe

The Conduct of In Vitro and In Vivo Drug‐Drug Interaction Studies: A PhRMA Perspective

Current regulatory guidances do not address specific study designs for in vitro and in vivo drug‐drug interaction studies. There is a common desire by regulatory authorities and by industry sponsors to harmonize approaches to allow for a better assessment of the significance of findings across different studies and drugs. There is also a growing consensus for the standardization of cytochrome P450 (CYP) probe substrates, inhibitors, and inducers and for the development of classification systems to improve the communication of risk to health care providers and patients. While existing guidances cover mainly CYP‐mediated drug interactions, the importance of other mechanisms, such as transporters, has been recognized more recently and should also be addressed. This paper was prepared by the Pharmaceutical Research and Manufacturers of America (PhRMA) Drug Metabolism and Clinical Pharmacology Technical Working Groups and represents the current industry position. The intent is to define a minimal best practice for in vitro and in vivo pharmacokinetic drug‐drug interaction studies targeted to development (not discovery support) and to define a data package that can be expected by regulatory agencies in compound registration dossiers.

NAD(P)H: quinone oxidoreductase (NQO1) polymorphism, exposure to benzene, and predisposition to disease: A HuGE review

NAD(P)H:quinone oxidoreductase (NQO1) catalyzes the two- or four-electron reduction of numerous endogenous and environmental quinones (e.g., the vitamin E α-tocopherol quinone, menadione, benzene quinones). In laboratory animals treated with various environmental chemicals, inhibition of NQO1 metabolism has long been known to increase the risk of toxicity or cancer. Currently, there are 22 reported single-nucleotide polymorphisms (SNPs) in the NQO1 gene. Compared with the human consensus (reference, “wild-type”) NQO1*1 allele coding for normal NQO1 enzyme and activity, the NQO1*2 allele encodes a nonsynonymous mutation (P187S) that has negligible NQO1 activity. The NQO1*2 allelic frequency ranges between 0.22 (Caucasian) and 0.45 (Asian) in various ethnic populations. A large epidemiologic investigation of a benzene-exposed population has shown that NQO1*2 homozygotes exhibit as much as a 7-fold greater risk of bone marrow toxicity, leading to diseases such as aplastic anemia and leukemia. The extent of the contribution of polymorphisms in other genes involved in the metabolism of benzene and related compounds—such as the P450 2E1 (CYP2E1), myeloperoxidase (MPO), glutathione-S-transferase (GSTM1, GSTT1), microsomal epoxide hydrolase (EPHX1), and other genes—should also be considered. However, it now seems clear that a lowered or absent NQO1 activity can increase ones risk of bone marrow toxicity, after environmental exposure to benzene and benzene-like compounds. In cancer patients, the NQO1*2 allele appears to be associated with increased risk of chemotherapy-related myeloid leukemia. Many other epidemiological studies, attempting to find an association between the NQO1 polymorphism and one or another human disease, have now begun to appear in the medical literature.

The effect of endotoxin on hepatocyte nuclear factor 1 nuclear protein binding: potential implications on CYP2E1 expression in the rat.

The purpose of this study was to determine if changes in nuclear protein binding of hepatocyte nuclear factor 1 (HNF‐1) occur after lipopolysaccharide (LPS) administration. In addition, the time‐course of alterations in CYP2E1 regulation were evaluated. Rats were injected with 2.0 mg LPS and euthanized over a 72‐h period. Nuclear protein binding to a consensus HNF‐1 oligonucleotide was assessed by the electrophoretic mobility shift assay. CYP2E1 activity was analysed using chlorzoxazone as a substrate (6OH‐CLZ), and CYP2E1 protein concentration was determined by enzyme‐linked immunosorbent assay. Endotoxin treatment resulted in decreased nuclear protein binding to an HNF‐1 element as early as 1 h after treatment and returned to control levels by 72 h. This reduced binding persisted for 24 h and returned to control values 48 h after LPS administration. In addition, the reduction in binding was primarily attributable to a HNF‐1α immunoreactive protein. The observed reduction in HNF‐1 binding was followed in the time‐course by decreases in CYP2E1 activity and protein content with maximal decreases to 50 and 67% of control, respectively, at 48 h after LPS administration. Endotoxin is a potent inducer of the acute phase response (APR). The APR stimulation by endotoxin administration reduced HNF‐1α binding and decreased the expression of CYP2E1 in the rat liver. The time‐course of alterations in HNF‐1 and CYP2E1 lend support to the possibility that HNF‐1α may play a role in the down‐regulation of genes that require HNF‐1α for their constitutive expression. These data serve as an important precedent for future studies evaluating the direct association of decreased HNF‐1α binding and reduced gene expression after LPS administration.

Prediction of Clinically Relevant Herb-Drug Clearance Interactions Using Sandwich-Cultured Human Hepatocytes: Schisandra spp. Case Study

The Schisandraceae family is reported to have a range of pharmacological activities, including anti-inflammatory effects. As with all herbal preparations, extracts of Schisandra species are mixtures composed of >50 lignans, especially schizandrins, deoxyschizandrins, and gomisins. In China, Schisandra sphenanthera extract (SSE) is often coadministered with immunosuppressant treatment of transplant recipients. In cases of coadministration, the potential for herb-drug interactions (HDIs) increases. Clinical studies have been used to assess HDI potential of SSE. Results demonstrated that chronic SSE administration reduced midazolam (MDZ) clearance by 52% in healthy volunteers. Although clinical studies are definitive and considered the “gold standard,” these studies are impractical for routine HDI assessments. Alternatively, in vitro strategies can be used to reduce the need for clinical studies. Transporter-certified sandwich-cultured human hepatocytes (SCHHs) provide a fully integrated hepatic cell system that maintains drug clearance pathways (metabolism and transport) and key regulatory pathways constitutive active/androstane receptor and pregnane X receptor (CAR/PXR) necessary for quantitative assessment of HDI potential. Mechanistic studies conducted in SCHHs demonstrated that SSE and the more commonly used dietary supplement Schisandra chinensis extract (SCE) inhibited CYP3A4/5-mediated metabolism and induced CYP3A4 mRNA in a dose-dependent manner. SSE and SCE reduced MDZ clearance to 0.577- and 0.599-fold of solvent control, respectively, in chronically exposed SCHHs. These in vitro results agreed with SSE clinical findings and predicted a similar in vivo HDI effect with SCE exposure. These findings support the use of an SCHH system that maintains transport, metabolic, and regulatory functionality for routine HDI assessments to predict clinically relevant clearance interactions.

Therapeutic Perspectives on Chia Seed and Its Oil: A Review

The attraction of novel foods proceeds alongside epidemic cardiovascular disease, diabetes, obesity, and related risk factors. Dieticians have identified chia (Salvia hispanica) as a product with a catalog of potential health benefits relating to these detriments. Chia is currently consumed not only as seeds, but also as oil, which brings about similar effects. Chia seeds and chia seed oil are used mainly as a food commodity and the oil is also used popularly as a dietary ingredient used in various dietary supplements available in the U. S. market. Chia seed is rich in α-linolenic acid, the biological precursor to eicosapentaenoic acid, a polyunsaturated fatty acid, and docosahexaenoic acid. Because the body cannot synthesize α-linolenic acid, chia has a newfound and instrumental role in diet. However, the inconclusive nature of the scientific communitys understanding of its safety warrants further research and appropriate testing. The focus of this work is to summarize dietary health benefits of S. hispanica seed and oil to acknowledge concerns of adverse events from its ingestion, to assess current research in the field, and to highlight the importance of quality compendial standards to support safe use. To achieve this end, a large-scale literature search was partaken on the two well-known databases, PubMed and SciFinder. Hundreds of articles detailing such benefits as decreased blood glucose, decreased waist circumference and weight in overweight adults, and improvements in pruritic skin and endurance in distance runners have been recorded. These benefits must be considered within the appropriate circumstances.

A strategy for systemic toxicity assessment based on non-animal approaches: The cosmetics Europe Long Range Science Strategy programme.

When performing safety assessment of chemicals, the evaluation of their systemic toxicity based only on non-animal approaches is a challenging objective. The Safety Evaluation Ultimately Replacing Animal Test programme (SEURAT-1) addressed this question from 2011 to 2015 and showed that further research and development of adequate tools in toxicokinetic and toxicodynamic are required for performing non-animal safety assessments. It also showed how to implement tools like thresholds of toxicological concern (TTCs) and read-across in this context. This paper shows a tiered scientific workflow and how each tier addresses the four steps of the risk assessment paradigm. Cosmetics Europe established its Long Range Science Strategy (LRSS) programme, running from 2016 to 2020, based on the outcomes of SEURAT-1 to implement this workflow. Dedicated specific projects address each step of this workflow, which is introduced here. It tackles the question of evaluating the internal dose when systemic exposure happens. The applicability of the workflow will be shown through a series of case studies, which will be published separately. Even if the LRSS puts the emphasis on safety assessment of cosmetic relevant chemicals, it remains applicable to any type of chemical.

Follow that botanical: Challenges and recommendations for assessing absorption, distribution, metabolism and excretion of botanical dietary supplements

Botanical dietary supplements are complex mixtures containing one or more botanical ingredient(s), each containing numerous constituents potentially responsible for its purported biological activity. Absorption, distribution, metabolism, and excretion (ADME) data are critical to understand the safety of botanical dietary supplements, including their potential for pharmacokinetic botanical-drug or botanical-botanical interactions. However, ADME data for botanical dietary supplements are rarely available and frequently inadequate to characterize their fate in vivo. Based on an assessment of the current status of botanical dietary supplements ADME research, the following key areas are identified that require robust data for human safety assessment: 1) phytochemical characterization including contaminant analysis and botanical authentication; 2) in vitro and/or in vivo data for identifying potential botanical-botanical or botanical-drug interactions and active/marker constituents; 3) robust ADME study design to include systemic exposure data on active/marker constituents using traditional or novel analytical chemistry and statistical approaches such as poly-pharmacokinetics; and 4) investigation of human relevance. A case study with Ginkgo biloba extract is used to highlight the challenges and proposed approaches in using ADME data for human safety assessment of botanical dietary supplements.

A Tiered Approach for the Evaluation of the Safety of Botanicals Used as Dietary Supplements: An Industry Strategy

Exposure to botanicals in dietary supplements is increasing across many geographies; with increased expectations from consumers, regulators, and industry stewards centered on quality and safety of these products. We present a tiered approach to assess the safety of botanicals, and an in silico decision tree to address toxicity data gaps. Tier 1 describes a Threshold of Toxicologic Concern (TTC) approach that can be used to assess the safety of conceptual levels of botanicals. Tier 2 is an approach to document a history of safe human use for botanical exposures higher than the TTC. An assessment of botanical‐drug interaction (BDI) may also be necessary at this stage. Tier 3 involves botanical chemical constituent identification and safety assessment and the in silico approach as needed. Our novel approaches to identify potential hazards and establish safe human use levels for botanicals is cost and time efficient and minimizes reliance on animal testing.

A practice analysis of toxicology

In 2015, the American Board of Toxicology (ABT), with collaboration from the Society of Toxicology (SOT), in consultation with Professional Examination Service, performed a practice analysis study of the knowledge required for general toxicology. The purpose of this study is to help assure that the examination and requirements for attainment of Diplomate status are relevant to modern toxicology and based upon an empirical foundation of knowledge. A profile of the domains and tasks used in toxicology practice was developed by subject-matter experts representing a broad range of experiences and perspectives. An on-line survey of toxicologists, including Diplomates of the ABT and SOT members, confirmed the delineation. Results of the study can be used to improve understanding of toxicology practice, to better serve all toxicologists, and to present the role of toxicologists to those outside the profession. Survey results may also be used by the ABT Board of Directors to develop test specifications for the certifying examination and will be useful for evaluating and updating the content of professional preparation, development, and continuing education programs.

A Review of the Toxicity of Compounds Found in Herbal Dietary Supplements

Use of herbal dietary supplements by the public is common and has been happening for centuries. In the United States, the Food and Drug Administration has a limited scope of regulation over marketed herbal dietary supplements, which may contain toxic botanical compounds that pose a public health risk. While the Food and Drug Administration has made efforts to prohibit the sale of unsafe herbal dietary supplements, numerous reports have proliferated of adverse events due to these supplements. This literature review investigates bioactive plant compounds commonly used in herbal dietary supplements and their relative toxicities. Using primarily the National Library of Medicine journal database and SciFinder for current reports, 47 toxic compounds in 55 species from 46 plant families were found to demonstrate harmful effects due to hepatic, cardiovascular, central nervous system, and digestive system toxicity. This review further contributes a novel and comprehensive view of toxicity across the botanical dietary market, and investigates the toxicity of the top ten botanical dietary supplements purchased in the United States of America to gauge the exposure risk of toxicity to the public. The criteria of measuring toxicity in this review (plant compound, family, quantity, and toxicity effects) across the entire market in the United States, with special attention to those supplements whose exposure to the consumer is maximal, provides a unique contribution to the investigation of botanical supplements.