Deborah A. Nicoll-Griffith

Bio: Deborah A. Nicoll-Griffith is an academic researcher from Merck & Co.. The author has contributed to research in topics: Metabolite & Microsome. The author has an hindex of 26, co-authored 65 publications receiving 3786 citations.

Drug-protein adducts: an industry perspective on minimizing the potential for drug bioactivation in drug discovery and development.

Abstract: It is generally accepted that there is neither a well-defined nor a consistent link between the formation of drug-protein adducts and organ toxicity. Because the potential does exist, however, for these processes to be causally related, the general strategy at Merck Research Laboratories has been to minimize reactive metabolite formation to the extent possible by appropriate structural modification during the lead optimization stage. This requires a flexible approach to defining bioactivation issues in a variety of metabolism vectors and typically involves the initial use of small molecule trapping agents to define the potential for bioactivation. At some point, however, there is a requirement to synthesize a radiolabeled tracer and to undertake covalent binding studies in vitro, usually in liver microsomal (and sometimes hepatocyte) preparations from preclinical species and human, and also in vivo, typically in the rat. This paper serves to provide one pragmatic approach to addressing the issue of bioactivation from an industry viewpoint based on protocols adopted by Merck Research Laboratories. The availability of a dedicated Labeled Compound Synthesis group, coupled to a close working relationship between Drug Metabolism and Medicinal Chemistry, represents a framework within which this perspective becomes viable; the overall aim is to bring safer drugs to patients.

Managing the challenge of chemically reactive metabolites in drug development

Abstract: The normal metabolism of drugs can generate metabolites that have intrinsic chemical reactivity towards cellular molecules, and therefore have the potential to alter biological function and initiate serious adverse drug reactions. Here, we present an assessment of the current approaches used for the evaluation of chemically reactive metabolites. We also describe how these approaches are being used within the pharmaceutical industry to assess and minimize the potential of drug candidates to cause toxicity. At early stages of drug discovery, iteration between medicinal chemistry and drug metabolism can eliminate perceived reactive metabolite-mediated chemical liabilities without compromising pharmacological activity or the need for extensive safety evaluation beyond standard practices. In the future, reactive metabolite evaluation may also be useful during clinical development for improving clinical risk assessment and risk management. Currently, there remains a huge gap in our understanding of the basic mechanisms that underlie chemical stress-mediated adverse reactions in humans. This Review summarizes our views on this complex topic, and includes insights into practices considered by the pharmaceutical industry.

Effect of common organic solvents on in vitro cytochrome P450-mediated metabolic activities in human liver microsomes

Abstract: Rare fully penetrant mutations in AKT2 are an established cause of monogenic disorders of glucose metabolism. Recently, a novel partial loss-of-function AKT2 coding variant (p.Pro50Thr) was identified that is nearly specific to Finns (frequency 1.1%), with the low-frequency allele associated with an increase in fasting plasma insulin level and risk of type 2 diabetes. The effects of p.Pro50Thr on insulin-stimulated glucose uptake (GU) in the whole body and in different tissues have not previously been investigated. We identified carriers (N=20) and matched non-carriers (N=25) for this allele in the population-based METSIM study and invited these individuals back for positron emission tomography study with [18F]-fluorodeoxyglucose during euglycemic hyperinsulinemia. When we compared p.P50T/AKT2 carriers to non-carriers, we found a 39.4% reduction in whole body GU (P=0.006) and a 55.6% increase in the rate of endogenous glucose production (P=0.038). We found significant reductions in GU in multiple tissues: skeletal muscle (36.4%), liver (16.1%), brown adipose (29.7%), and bone marrow (32.9%), and increases of 16.8-19.1% in 7 tested brain regions. These data demonstrate that the P50T substitution of AKT2 influences insulin-mediated GU in multiple insulin sensitive tissues, and may explain, at least in part, the increased risk of type 2 diabetes in p.P50T/AKT2 carriers.

Fluorine in medicinal chemistry.

Abstract: It has become evident that fluorinated compounds have a remarkable record in medicinal chemistry and will play a continuing role in providing lead compounds for therapeutic applications. This tutorial review provides a sampling of renowned fluorinated drugs and their mode of action with a discussion clarifying the role and impact of fluorine substitution on drug potency.

Applications of Fluorine in Medicinal Chemistry

Abstract: The role of fluorine in drug design and development is expanding rapidly as we learn more about the unique properties associated with this unusual element and how to deploy it with greater sophistication. The judicious introduction of fluorine into a molecule can productively influence conformation, pKa, intrinsic potency, membrane permeability, metabolic pathways, and pharmacokinetic properties. In addition, 18F has been established as a useful positron emitting isotope for use with in vivo imaging technology that potentially has extensive application in drug discovery and development, often limited only by convenient synthetic accessibility to labeled compounds. The wide ranging applications of fluorine in drug design are providing a strong stimulus for the development of new synthetic methodologies that allow more facile access to a wide range of fluorinated compounds. In this review, we provide an update on the effects of the strategic incorporation of fluorine in drug molecules and applications in po...

Synopsis of some recent tactical application of bioisosteres in drug design.

Abstract: The concept of isosterism between relatively simple chemical entities was originally contemplated by James Moir in 1909, a notion further refined by H. G. Grimm’s hydride displacement law and captured more effectively in the ideas advanced by Irving Langmuir based on experimental observations. Langmuir coined the term “isostere” and, 18 years in advance of its actual isolation and characterization, predicted that the physical properties of the then unknown ketene would resemble those of diazomethane. The emergence of bioisosteres as structurally distinct compounds recognized similarly by biological systems has its origins in a series of studies published byHans Erlenmeyer in the 1930s, who extended earlier work conducted by Karl Landsteiner. Erlenmeyer showed that antibodies were unable to discriminate between phenyl and thienyl rings or O, NH, and CH2 in the context of artificial antigens derived by reacting diazonium ions with proteins, a process that derivatized the ortho position of tyrosine, as summarized in Figure 1 The term “bioisostere” was introduced by Harris Friedman in 1950 who defined it as compounds eliciting a similar biological effect while recognizing that compounds may be isosteric but not necessarily bioisosteric. This notion anticipates that the application of bioisosterism will depend on context, relying much less on physicochemical properties as the underlying principle for biochemical mimicry. Bioisosteres are typically less than exact structural mimetics and are often more alike in biological rather than physical properties. Thus, an effective bioisostere for one biochemical application may not translate to another setting, necessitating the careful selection and tailoring of an isostere for a specific circumstance. Consequently, the design of bioisosteres frequently introduces structural changes that can be beneficial or deleterious depending on the context, with size, shape, electronic distribution, polarizability, dipole, polarity, lipophilicity, and pKa potentially playing key contributing roles in molecular recognition and mimicry. In the contemporary practice of medicinal chemistry, the development and application of bioisosteres have been adopted as a fundamental tactical approach useful to address a number of aspects associated with the design and development of drug candidates. The established utility of bioisosteres is broad in nature, extending to improving potency, enhancing selectivity, altering physical properties, reducing or redirecting metabolism, eliminating or modifying toxicophores, and acquiring novel intellectual property. In this Perspective, some contemporary themes exploring the role of isosteres in drug design are sampled, with an emphasis placed on tactical applications designed to solve the kinds of problems that impinge on compound optimization and the long-term success of drug candidates. Interesting concepts that may have been poorly effective in the context examined are captured, since the ideas may have merit in alternative circumstances. A comprehensive cataloging of bioisosteres is beyond the scope of what will be provided, although a synopsis of relevant isosteres of a particular functionality is summarized in a succinct fashion in several sections. Isosterism has also found productive application in the design and optimization of organocatalysts, and there are several examples in which functional mimicry established initially in a medicinal chemistry setting has been adopted by this community.

Tobacco Smoke Carcinogens and Lung Cancer

Abstract: The complexity of tobacco smoke leads to some confusion about the mechanisms by which it causes lung cancer. Among the multiple components of tobacco smoke, 20 carcinogens convincingly cause lung tumors in laboratory animals or humans and are, therefore, likely to be involved in lung cancer induction. Of these, polycyclic aromatic hydrocarbons and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone are likely to play major roles. This review focuses on carcinogens in tobacco smoke as a means of simplifying and clarifying the relevant information that provides a mechanistic framework linking nicotine addiction with lung cancer through exposure to such compounds. Included is a discussion of the mechanisms by which tobacco smoke carcinogens interact with DNA and cause genetic changes--mechanisms that are reasonably well understood--and the less well defined relationship between exposure to specific tobacco smoke carcinogens and mutations in oncogenes and tumor suppressor genes. Molecular epidemiologic studies of gene-carcinogen interactions and lung cancer--an approach that has not yet reached its full potential--are also discussed, as are inhalation studies of tobacco smoke in laboratory animals and the potential role of free radicals and oxidative damage in tobacco-associated carcinogenesis. By focusing in this review on several important carcinogens in tobacco smoke, the complexities in understanding tobacco-induced cancer can be reduced, and new approaches for lung cancer prevention can be envisioned.