Abstract
Introduction to Division of Anti-Infectives and Ophthalmology Products
Amy Ellis
Pharmacologist, US FDA, CDER, Silver Spring, MD
This session will introduce the FDA’s Office of Antimicrobial Products within the Office of New Drugs and its organizational structure, roles and responsibilities of the reviewing pharmacologist, and interactions of pharmacologists within and outside the divisions. The Office of Antimicrobial Products is composed of Division of Anti-Viral Products, Division of Special Pathogen and Transplant Products, and Division of Anti-Infectives and Ophthalmology. The presentation will focus on the Division of Anti-Infectives and Ophthalmology Products. Nonclinical requirements and recommendations that are unique to these divisions in consideration of the target indications and the clinical phases of drug development will be discussed.
Introduction to Division of Neurology Products and Division of Psychiatry Products
Paul L. Roney
Senior Consultant, Toxicology, Kendle International Inc, Rockville, MD
This presentation will introduce the FDA’s Office of Drug Evaluation I within the Office of New Drugs and its organizational structure, roles and responsibilities of the reviewing pharmacologist, and interactions of pharmacologists within an outside Agency. The ODE I is composed of Division of Cardiovascular and Renal Products, Division of Neurology Products, and Division of Psychiatry Products. The former Division of Neuropharmacology was divided into two separate divisions (Neurology and Psychiatry). The presentation will focus on these two new divisions, and similarities and differences between the two divisions will be discussed. Nonclinical differences and preferences that are unique and required or recommended by these two divisions will be discussed in detail.
Introduction to Division of Pulmonary and Allergy Products
Timothy Joseph McGovern
Consultant, Scilucent LLC, Herndon, VA
This session will introduce the FDA’s Office of Drug Evaluation II within the Office of New Drugs and its organizational structure, roles and responsibilities of the reviewing pharmacologist, and interactions of pharmacologists within and outside the Agency. ODE II is composed of Divisions of Metabolism and Endocrinology Products, Division of Anesthetic, Analgesia and Rheumatology Products, and Division of Pulmonary and Allergy Products. The main portion of the presentation will focus on the Division of Pulmonary and Allergy Products. Nonclinical requirements and recommendations of the division in consideration of the target indications and the clinical phases of drug development will be discussed.
Introduction to Division of Reproductive and Urologic Products
Lynnda Reid
Pharmacology/Toxicology Team Leader, US FDA, CDER, Silver Spring, MD
This presentation will introduce the FDA’s Office of Drug Evaluation III within the Office of New Drugs and its organizational structure, roles and responsibilities of the reviewing pharmacologist, and internal and external interaction and communication of pharmacologists. The ODE III is composed of Division of Gastroenterology Products, Division of Reproductive and Urologic Products, and Division of Dermatology and Dental Products. The focus of the discussion will be on the reproductive, urologic and bone products. The nonclinical differences and preferences that are unique and required or recommended by this division will be elaborated.
Introduction to Division of Drug Oncology Products and Division of Biologic Oncology Products
David Morse
Principal Consultant, Parexel Consulting, Bethesda, MD
This session will introduce the FDA’s Office of Oncology Drug Products within the Office of New Drugs and will include its organizational structure, roles and responsibilities of the reviewing pharmacologist, and interactions of pharmacologists within and outside FDA. The Office of Oncology Drug Products is composed of Division of Medical Imaging and Hematology Products, Division of Drug Oncology Products, and Division of Biologic Oncology Products. The presentation will focus on the divisions of drug and biologic products. Specific nonclinical differences and preferences that are required or recommended by the drug and biologic oncology divisions will be discussed in detail.
Asthma Epidemic: An Overview of Disease Process, Environmental and Genetic Factors
David Diaz-Sanchez
Clinical Research Branch, NHEERL, US Environmental Protection Agency
Asthma is a multifactorial disease involving a complex interplay of multiple genes interacting with the environment. A key feature of asthma is chronic airway inflammation which can be accompanied by acute attacks induced by triggers during which bronchial constriction occurs. Asthma can thus be associated with wheezing, shortness of breath, cough and chest tightness. These environmental triggers range from allergens, exercise and cold, to irritants and pollutants. An overview of the epidemiology of asthma and how this preferentially affects certain populations will be discussed along with current definitions of asthma and the underlying anatomic and physiological changes associated with the disease. Several theories have been proposed for the recent rise in asthma prevalence including changes in personal and public hygiene, diet and both indoor and ambient air quality. While the pathophysiology of asthma induction has yet to be fully elucidated, several risk factors for susceptibility to asthma have been recognized. These include at the individual level, allergic disease host immunity, personal environment and obesity; and at the population level socioeconomic status, residence and ethnicity. In addition, family history is a good predictor of development of asthma underlying the role of genetics in determining susceptibility. To date over 100 genes have been identified that are associated with asthma. Moreover several genes have recently been identified that confer susceptibility to environmental exposures that can cause or exacerbate asthma. Identification of susceptibility genes such as those associated with responses to endotoxin (a bacterial product) or antioxidant genes that protect against the pro-asthmatic effects of pollutants are now being pursued as targets of pharmaceutical inventions.
Animal Models for Asthma: Controversial Aspects and Unsolved Problems
Edward Barrett
Lovelace Respiratory Research Institute, Albuquerque, NM
There is a long history of utilizing animal models for developing our understanding of the pathogenesis of human asthma and subsequently utilizing them for the development and testing of new therapeutics for human asthma. Numerous review articles have been written over the last decade addressing the pros, cons and limitations of different animal models of human asthma. Summarizing the present models leads to several basic conclusions 1) there is no animal that naturally develops a disease that completely mimics human asthma, 2) there is no animal model available that perfectly reflects the complexity of human asthma, and 3) consequently there are numerous candidate drugs that have shown promise in these animal models but have failed in the clinical setting. The presentation will review the current state of animal models, how they are being utilized in the drug development process, and how we can move forward to improve their interpretability-predictability. A special focus will be placed on alternative animal models (eg non rodent) and how they may recapitulate features of human asthma and experimental capabilities that are not present in the commonly used rodent models
New Targets for Drug Development in Asthma
Matthew D. Reed
Lovelace Respiratory Research Institute, Albuquerque, NM
Research strategies to define asthma pathogenesis have focused on the hypothesis that this condition is a consequence of an excessive allergen-driven response. However, most new therapeutic strategies in development have focused on improving and combining beta agonists and steroids to manage symptoms and increase patient compliance. Fortunately there are new treatment paradigms and platform technologies that target the Th2-Th1 imbalance, specific combinations of cytokines and chemokines within the allergic cascade, and other pathways leading to airway hyperresponsiveness and airway remodeling. This discussion will highlight these nontraditional approaches. A specific emphasis will be placed on tol-like receptor strategies and well as RNA interference technologies.
Developing Pharmaceuticals for Use in Asthma: Test Case Inhalers
Chet L. Leach
Consultant in Pulmonary Drug Development, Tijeras, NM
Metered dose inhalers (MDIs) for use in respiratory disease were invented some 53 years ago. They have steadily evolved and remain the mainstay of asthma and COPD treatment throughout the world. The understanding of disease targets sites within the lungs as well as the phase-out of CFC MDI propellants has lead to new technologies to more efficiently deliver old and new drugs. Dry powder inhalers (DPIs) and other specialized delivery devices have also been added to the battery of inhaled products available today. Further inhaled products such as insulin have been and are being developed to deliver drugs that are not available orally or are difficult to formulate to the systemic circulation and subsequently to other target organs such as the heart and brain. An example of a paradigm change in the post CFC propellant age is that of the small particle steroids inhalers such as HFA-beclomethasone, HFA-cyclesonide and HFA-flunisolide. It was recognized in the late 1980s that asthma is a disease of all of the airways including the large, intermediate and small airways and indeed severe asthma may be predominantly a small airway disease. However the particle size of the original CFC steroid inhalers was too big at 3.5 microns to reach any but the large airways. Thus new formulations and inhaler devices were developed to meet the new particle size needs. Extensive clinical studies have shown the benefit of the newer, more optimally sized particle inhalers. For example the HFA-beclomethasone demonstrated an increase of human lung deposition from 10-20% to 50-60% with improved peripheral lung penetration. There was a concomitant three-fold decrease in oropharyngeal deposition with HFA-beclomethasone inhaler, thus reducing local side effects. Naturally all of the new HFA propellants had to undergo extensive preclinical studies similar to a New Molecular Entity program. The challenge to preclinical scientists and health authorities came in determining the preclinical program necessary to proving that old drugs reformulated with new technologies were safe. An additional complication was that of adding new excipients to the formulations. A qualification program has to be developed for each excipient depending on its history of use. Even those excipients endogenous to the lungs require a preclinical safety qualification program. This presentation will include a discussion of the topics cited above.
What Are Endocrine Disruptors and Why Are We Concerned?
Edward F. Orlando
University of Maryland, College of Agriculture and Natural Resources Animal & Avian Sciences (ANSC)
It is widely acknowledged that our environment is becoming increasingly contaminated with man-made chemicals. Mammals, as well as lower organisms, are vulnerable to exposure to these agents through a variety of different sources and routes, and there is concern that such substances may have a detrimental effect on ecological and population health. It is just over 40 years since wildlife studies first suggested that environmental chemicals could be interacting with hormone systems, a hypothesis which has since been consolidated and debated both in the popular press and in the scientific literature. This presentation will provide an overview of environmental endocrine disruption and the potential health concerns that may be associated with environmental chemicals.
Endocrine Disruption in Wildlife and Aquatic Animals
Jeffrey C. Wolf
Experimental Pathology Laboratories, Inc., Sterling, VA
It is generally acknowledged that our environment contains a variety of manmade and naturally occurring hormonally-active substances that could potentially influence the health and population dynamics of wildlife and aquatic animals. Numerous laboratory investigations have confirmed that the exposure of various animal species to endocrine disruptive compounds (EDCs) can affect elements of the hypothalamic-pituitary-gonadal or hypothalamic-pituitary-thyroidal axes, resulting in behavioral, physiologic and/or morphologic alterations. However, despite a mountain of evidence provided by controlled experiments, and abundant data generated by an assortment of survey studies, relatively few solid causative links have been established between EDC exposure in the field and effects in individual wild animals or on animal populations. Well-accepted examples of robust associations include the relationship between sewage effluent exposure and gonadal alterations in roach fish (Rutilus rutilus) that inhabit contaminated rivers in the United Kingdom, and the observation of a suite of reproductive abnormalities in American alligators (Alligator mississippiensis) subjected to municipal waste discharge, agricultural runoff, and pesticide spills in Florida lakes. Conversely, the evidence for many other proposed causal relationships is less convincing. For example, although an increased incidence of limb deformities in North American frogs has been attributed periodically to chemical contaminants, the most compelling data suggests that infection with digenetic trematode parasites is a principal cause of these malformations. The scarcity of definitive EDC response relationships in wildlife may be due to a variety of confounding issues inherent to toxicological field studies, such as potential synergistic and antagonistic effects within chemical mixtures, and the appropriate selection of uncontaminated reference sites. Conflicting interstudy outcomes are not uncommon, and in some instances, retrospective evaluations have revealed deficiencies in experimental study design and/or results interpretation. Consequently, a conservative approach to the reporting and publication of potential EDC-related phenomena appears justified.
Development of Mammalian Endocrine Disruptor Screening and Testing
Rochelle W. Tyl
Distinguished Fellow, DART, RTI International, Research Triangle Park, NC
The concerns that man-made persistent pesticides were poisoning our environment (by Rachel Carson in Silent Spring, 1966) and subsequently, that endocrine-active chemicals in the environment are affecting humans, other mammals, other vertebrates and invertebrates, including effects on fertility, reproduction, development, our intelligence, and even our very survival (by Theo Colborn et al. in Our Stolen Future, 1996, and Dr. Colborn’s Wingspread Conferences in the early 1990s) set the stage for the US EPA charge to convene the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC, of which I was the only CRO member) in 1996. The purpose of EDSTAC was to develop an Endocrine Disruptors Screening Program (EDSP) in two years. The EDSTAC did so in a two-volume report in 1998. The report detailed the background, conceptual framework and principles, priority setting, screening and testing protocols across taxa and communication and outreach. The screening assays included in vitro cell-free and cell line assays, and in vivo screens in rodents, frogs and fish. The Tier 2 Tests included mammalian multigeneration (or one-generation) test in rodents, full life cycle tests in birds, fish, mysids (an invertebrate), and a developmental and reproductive test in amphibians. I will focus on the US EPA EDSP with original, current and alternative screens and tests, their strengths and weaknesses, validation and standardization, alternatives and progress. The activities of the Organization for Economic Cooperation and Development (OECD) will also be mentioned.
Trust Me—I’m a Pathologist
Peter C. Mann, DVM, DACVP
Experimental Pathology Laboratories, Inc., Seattle, WA
Pathology is an arcane and complicated art. In this talk, I will attempt to explain how a pathologist makes some of his most basic decisions – what is normal, what should be diagnosed and when. In order to successfully evaluate a study, a pathologist needs a combination of knowledge, experience, context and judgment. I will also discuss thresholds, lumping versus splitting, study arithmetic and diagnostic drift. This is a rare chance to spend a few minutes inside a pathologist’s brain (The good news is that you get to leave when it’s over!).
Rodent Diets and Nutrition as a Study Variable
Graham Tobin
Harlan Laboratories, Indianapolis, IN
Surprisingly few toxicologists fully appreciate the extent to which diet can impact on their studies. It can contribute to study variation through its nutrient levels, the presence and form of organic and inorganic contaminants, and non-nutrients that are inherent constituents of specific ingredients. And despite a desire for stable background data, toxicologists often use variable formula diets in which there may be undeclared changes to both ingredients and their inclusion.
Nutrient levels in diets for toxicology are often not optimal, with little regard to published requirements. A common example is the excessive protein level of many diets, resulting in adverse pathology.
There is also a need to consider the presence of ingredients in diet that contain non-nutrients and that contribute to study variation. Historically, the most well-recognized, undesirable non-nutrients are highly carcinogenic nitrosamines that may be present at high levels in meat and fish meals. Recently soybean meal and alfalfa, previously thought to be safe and commonly used in laboratory diets, have been identified as major study variables because of their content of a class of non-nutrients termed phytoestrogens. Phytoestrogens act as both estrogen agonists and antagonists, and interact with physiological and pathological processes influenced by endogenous estrogens (eg mammary tumors, neurodegeneration). They may confound the effects of drugs such as Tamoxifen that act on estrogen receptors.
It is important that toxicologists and other investigators understand the way in which diet affects their studies and are willing to select diets that are more appropriate and provide more reliable data.
Use of Placebo, Vehicle, and Positive Controls and Recovery Groups to Aid in Study Interpretation
Klaus Weber, PhD, Dr. rer.nat., Dipl.Biol.,Vet.-Ing
RCC, Ltd., Harlan, Inc.
The performance of preclinical studies requires team work, thorough discussion prior to study start and careful monitoring during the course of the study. Many variables may influence the study outcome. Often they may be foreseeable and can be limited or even avoided, eg: study design such as insufficient duration, absence or insufficient duration of recovery period, insuffient group size, continuous versus cyclic administration, incorrect dose selection and omission of data from protein binding and similar testing; incorrect positive or negative control treatments; selection of inappropriate metabolising species, unhealthy strains, irrelevant sex, inappropriate age; misinformation or no information on the nature of the test item by sponsor leading to inadequate basic knowledge of test item-related lesions; poor knowledge of test system; analytical errors or development of inadequate methods; selection of established vs. new vehicles or inadequate knowledge on possible hazard by known vehicles. Others may occur accidentally during the study, eg: technical errors and artifacts;
Independently, the report design and conclusions taken from the results obtained from the study may be a source of variability, eg ‘shopping lists' instead of summaries or conclusions, use of different nomenclature during the execution of a number of studies with the same test item, misinformation and miscommunication.
Optimizing the Design of Toxicity Studies for Pharmaceutical Safety Testing
David L. Hopper, DVM, PhD, DABT
Bioanalytical Systems, Inc., Mount Vernon, IN
This presentation focuses on considerations for optimizing the design of toxicity studies for pharmaceutical safety testing. The concept of safety testing and the need for presenting clear and relevant information to regulatory agencies for determining dosages for exposures of human patients will be discussed. Design of studies to maximize resources of time and money, and minimize delays and excessive costs are presented. Designs of safety studies for pharmaceuticals can vary widely based on animal model, route and regimen of administration, duration of administration and recovery, and endpoints examined.
Two categories of studies are frequently conducted and can, under some circumstances, be conducted together in some parts. One category is that which actually is intended to support safety and is submitted to regulatory agencies for that purpose. This type of study is required to be conducted in compliance with USFDA GLPs. The second type of study frequently conducted may encompass any of a number of purposes and are not generally required to comply with GLPs. These studies include such supporting efforts as dose-range-finding, pilot, investigative, mechanistic, method-development, and pharmacokinetic studies.
Considerations for optimizing study designs should be geared toward how best to answer the seminal question for which the study is being considered. An equally important question for design of studies, in addition to how best to answer the primary question, is how to design it most efficiently with respect to time and cost. Discussion of the various study types, model, dosing regimen, endpoints, duration, etc., will be discussed with the goal to answering these questions.
History of Drug-Induced Phospholipidosis
Mark J. Reasor, PhD, DABT
Department of Physiology and Pharmacology, Robert C. Byrd Health Sciences Center of West Virginia University, Morgantown, WV
Numerous experimental and marketed cationic, amphiphilic drugs (CADs) are capable of inducing a phospholipidosis in cells of humans and laboratory animals under conditions of in vivo administration or ex vivo incubation. The principal characteristics of this condition include the reversible accumulation of polar phospholipids in association with the development of unicentric or multicentric lamellated bodies of lysosomal origin within cells. The induction of phospholipidosis is a dose/concentration-dependent process with its development often being directly proportional to the accumulation of the CAD in the cell. Virtually every tissue and species is susceptible to the induction of this condition. The ability of a CAD to induce phospholipidosis is not a function of its pharmacologic activity but rather of its cationic, amphiphilic structure. There is consistent evidence that CADs inhibit lysosomal phospholipase activity resulting in the accumulation of several classes of phospholipids within the altered organelle. While other mechanisms have been proposed, they have not been studied as extensively. The functional consequences and clinical implications of the presence of this condition on cellular or tissue function are not understood. The general consensus is that the condition is an adaptive response rather than a toxicological manifestation; however, additional studies to examine this question are needed. The uncertainty about the consequences of phospholipidosis raises questions about drug safety since this condition is not an uncommon observation during drug development. Until this issue is resolved, concerns about phospholipidosis will continue to exist at regulatory agencies. Procedures for the screening of potential phospholipidogenic candidate compounds are available. In contrast, a clear need exists for the identification of valid biomarkers to assess the development of phospholipidosis in preclinical and clinical studies.
Morphologic Evidence of Phospholipidosis and Potential Biomarkers for Clinical Application
Richard A. Peterson II, DVM, PhD, Diplomate ACVP
GlaxoSmithKline, Safety Assessment, Investigative Pathology Laboratory, Research Triangle Park, NC
Phospholipidosis (PLD) is a reversible test article-induced morphologic change in preclinical species and clinical patients characterized by an excessive accumulation of intralysosomal phospholipid. PLD is induced by cationic amphiphilic drugs. PLD may develop through a single pathway or a combination of the following pathways: inhibition of lysosomal phospho-lipase, drug binding to phospholipid making substrate indigestible, or increased phospholipid synthesis. PLD in H&E stained sections is characterized by “foamy” cytoplasmic vacuolization that can contain central eosinophilic inclusions. Cell types most affected in PLD include: macrophages, hepatocytes, biliary epithelium, pneumocytes, lymphocytes, renal tubular epithelium, and endothelial cells. “Foamy” macrophages accumulate in the lung, intestinal villus lamina propria, spleen, thymus, liver, and lymph node. PLD-associated cytotoxicity should be considered adverse. Immunohistochemistry for lysosome-associated membrane protein (LAMP)-2 has shown utility in highlighting intracellular phospholipid accumulation. Transmission electron microscopy (TEM) is the “gold standard” for PLD diagnosis. Lysosomes contain prominent highly electron-dense multilamellar concentric to amorphous phospholipid profiles. Ultrastructural changes such as prominent phagocytosis, delayed fixation, photoreceptor phagocytosis by retinal pigmented epithelial cells, surfactant within type 2 pneumocytes, and autophagy can appear similar to PLD, but are normal or a distinct pathologic change. The search for a robust translational PLD biomarker continues. PLD biomarker research has evaluated peripheral blood mononuclear cells by flow cytometry (Nile Red fluorescence), TEM, cytology (blood smears), and transcriptomics. Lymphocytes and macrophages are affected by most drugs associated with PLD and flow cytometry correlates with TEM. Metabolomics (small volume of serum, plasma, urine, etc. needed) is a powerful approach to identify potential PLD biomarkers using nuclear magnetic resonance and/or liquid chromatography-mass spectrometry [eg, Lyso-Bis-Phosphatidic Acid (LBPA), BMP, urine Phenylacetylglycine (PAG), etc.].
The Impact of Phospholipidosis on Drug Development; Illustrating Human Risk Assessment With a Case History
James S. MacDonald, PhD, DABT
Chrysalis Pharma Consulting, LLC
Phospholipidosis is a morphologic abnormality seen in a variety of tissues with many chemicals. With some of these chemicals, significant organ system pathology and dysfunction is also observed although the association between the observation of phospholipidosis and the cellular toxicity is not always clear. Experience with this finding has shown, however, that it occurs in most cases with no apparent other morphologic or functional impact on the cell or tissue. As with all findings in preclinical toxicology, the challenge with phospholipidosis is to understand the implications of the observation for human risk. One approach to this important process will be illustrated with a case history of the development of an azole anti-fungal posaconazole (now marketed as Noxafil). In addition to the appearance of phospholipidosis in monocytes, histiocytes of lympho-reticular organs, and hepatocytes, the characteristic morphologic features were observed in neurons of the central nervous system, dorsal root ganglia of the spinal cord and mysenteric plexus in chronic toxicity studies in dogs. This finding was not associated with any degenerative changes in any region of the nervous system. The significance of this unusual distribution of phospholipidosis was assessed in a comprehensive series of studies designed to detect functional changes in the affected species. The absence of any adverse effect in these studies or of any similar morphological findings in monkeys led to the conclusion that the appearance of phospholipidosis did not predict human toxicity and led to the availability of this important anti-fungal.
The Slippery Slope: Experiences of the CDER Phospholipidosis Working Group
James M. Willard, PhD
Division of Cardiovascular and Renal Products/CDER/FDA
Phospholipidosis is presently a confounding factor in new drug development, with a diversity of opinion as to whether it is a normal, adaptive response, or a sign that cellular defense mechanisms are being overwhelmed.
In the regulation of new drug candidates, the issue of phospholipidosis arises frequently. At the FDA, how to consistently interpret these findings has generally been informed by the review Division’s past experience. In 2004, the FDA began a working group to study phospholipidosis as part of the Critical Path Initiative. The Phospholipidosis Working Group has created a database of over 250 compounds causing phospholipidosis (117 confirmed by electron microscopy) that have been submitted to the FDA, with data being obtained from published literature, FDA submissions and industry.
Resulting from this effort, in conjunction with the Computational Toxicology Group at the FDA, a combined physico-chemical characteristics – QSAR model has been produced along with the development of predictive tools for phospholipidosis. At the same time, toxicogenomic research identifying early biomarkers of phospholipidosis is also being pursued. A further effort in this direction is attempting to uncouple phospholipidosis from toxicological manifestations. The database work is presently being utilized to examine the dose relationship between the appearance of phospholipidosis and general toxicity signs in animal studies, and the relationship of phospholipidosis to QT prolongation, myopathy and neuropathy. Preliminary ideas on a scheme for determining the level of concern generated by a finding of phospholipidosis are presented.
Microscopic Evaluation of Combination Products in Nonclinical Studies – Challenges, Methods, and Examples
Daniel J. Patrick, DVM, DACVP
Principal Pathologist, MPI Research Inc, Mattawan, Michigan
The nonclinical evaluation of combination products (comprised of two or more regulated components, drug/device, biologic/device, drug/biologic, or drug/device/biologic) is challenging for both the toxicologist and pathologist due to the almost limitless constituent possibilities and intents of these products. Paramount to a successful evaluation is an early and active line of communication between the sponsor, study director, and pathologist so that the study objective is well understood. Ideally, the pathologist should be involved in the construction of the study design or protocol, be familiar with the test and control materials, and assist in the determination of the optimal histological procedure (orientation, processing, embedding media, and sectioning), necropsy implant retrieval, and recording of macroscopic observations. The pathologist must evaluate and interpret microscopic endpoints (qualitative and/or semiquantitative/quantitative) which best reflect and assess the biocompatibility and efficacy of the combination product, and which also fulfill the standards and requirements of the applicable regulatory agency. A brief overview of some microscopic evaluation methods and photomicrographs for various combination products, including drug-eluting stents, will be provided.
Nonclinical Testing Strategies for Combination Products
Tracey Zoetis, MS
Managing Consultant, SciLucent, Herndon, Virginia
The nonclinical testing paradigm for combination products is not as straightforward as one would hope. Testing strategies must meet requirements specific to individual components and their combination to support the safety of clinical trials. The “golden rule” for combination products in the clinic is the combination provides greater benefit than individual components alone. This rule does not hold true for the nonclinical product development scheme, in that the combination is not necessarily safer than individual components. Nonclinical testing strategies for various combinations of drugs, devices and biologics will be presented. Dose selection for drug/drug combinations will be discussed. Drug/device combinations will also be considered. In particular, a comparison between biocompatibility (device) and toxicology (drug) studies will be presented, followed by a proposed testing strategy for a drug/device combination. Finally, testing strategies for combinations using biologic products will be presented. Participants should gain an understanding of the rationale for designing a nonclinical testing program to support the development of a combination product.
A Case Study: Safety Evaluation of Ophthalmic Drug-Device Combination Products
Alan P. Brown, PhD, DABT
Senior Toxicologist, NAMSA, Northwood, OH
The combination of medical devices, polymers/coatings, and pharmacologic agents is occurring, due to the integration of various technologies. In the field of ophthalmology, this is resulting in combination products for treating infectious disease, retinal disorders, glaucoma, inflammation, etc. As an example, intraocular implantation of drug-device combination products can deliver pharmacologically active compounds to the posterior portion of the eye. By doing so, this product may provide therapeutic concentrations of the active compound to ocular substructures, with minimal systemic exposure. Contact lenses impregnated with a drug may afford greater efficacy for treating conditions of the anterior portion of the eye, while correcting vision. This session will provide an overview of points to consider when conducting nonclinical safety evaluation of ophthalmic drug-device combination products, with examples provided. Topics to be presented will include toxicokinetics, ocular safety assessment, and biocompatibility of devices.
Review and Approval Process for Combination Products in the U.S.
Brian E. Harvey, MD, PhD
Vice President Regulatory Policy, Sanofi-Aventis, Bethesda, MD
The U.S. regulatory history of drugs, biologics and medical devices has many examples where a health crisis has led to congressional action creating laws that resulted in an inconsistent patchwork of regulations based upon these diverse threats to public health. The difference in the various regulatory pathways has become clear with the increase in number of combination products. Initially, many combination products consisted of a device that was a drug or biologic delivery system. Later, products consisting of drug-device and biologic-device combinations, where the drug or biologic served as the active component, and their action was facilitated by the device. Recently, there is a growing trend for in vitro diagnostic devices being paired with either a drug or biologic product, in order to help select appropriate patients for treatment, to maximize efficacy and/or minimize risk. Currently in the U.S., there are multiple potential regulatory pathways for each of these types of combination products, each of which has their own set of advantages and disadvantages. The FDA Office of Combination Products (OCP) was established in light of these regulatory complexities, and works with the FDA Center for Biologics Evaluation and Research (CBER), the Center for Drug Evaluation and Research (CDER), and the Center for Devices and Radiological Health (CDRH). The OCP serves as a focal point for combination product issues for agency reviewers and industry, develops guidance and regulations for combination products, assigns an FDA center to have primary jurisdiction for review, ensures consistency and appropriateness of postmarket regulation of combination products, resolves disputes regarding the timeliness of premarket review of combination products and updates agreements, guidance documents, or practices specific to the assignment of combination products.
REACH Implementation: Early Lessons for Health Data Requirements
Richard Phillips
ExxonMobil, Belgium
REACH entered into force in Europe in June 2007. This regulation requires that manufacturers and importers obtain health, safety and environmental information on their chemical substances and to register this information with the European Chemicals Agency (ECHA). The administrative and technical requirements for REACH are significant and complex. This presentation will focus on the technical requirements and issues associated with data requirements for health hazard end points. There is concern that REACH could lead to a high volume of testing which may use a large number of vertebrate animals and be very costly while providing little added value to achieving the intended goals of REACH. The legislation (Annex XI) and guidance calls for “Integrated Testing Strategies” (ITS). ITS involves the use of multiple approaches for obtaining information necessary for a regulatory decision. Ideally, ITS should remain flexible, be science-based and avoid unnecessary “check-the-box” approaches to animal testing. Approaches such as chemical grouping/categories, read-across, use of existing information, exposure-based waiving, in vitro tools and QSAR’s have been the basis for ITS. A systematic weight-of-evidence approach and discussion is essential to transparency and optimizing the benefits of ITS. Finally, new developments and initiatives such as human biomonitoring and “mode of action” frameworks should be incorporated into informing testing strategies and requirements. This presentation will discuss the practical implementation of ITS, review the present state of tools for developing ITS and look to the future for improvement in the process.
Requiring Greater Accountability for Chemical Use in Canada
Fe de Leon,
Researcher, Canadian Environmental Law Association (deleonf@cela.ca)
The production, use, release and disposal of toxic substances are impacting the quality of the environment and human health. Toxic substances are used or released from various industrial processes but they are also found in various consumer products. Increasingly, toxic substances are being detected in water, land and air threatening the quality of drinking water, food sources and the air we breathe. Some toxic substances have been linked to various cancers, reproductive and developmental impairments, neurological toxicity and endocrine disruption in humans and wildlife. The efforts to reduce or eliminate the impacts of toxic substances have been slow and reactive, taking decades for governments to act on toxic substances. The ability to consider management measures quickly and efficiently has been hampered by the absence of toxicity data on most of the substances found in the market today and the risk based approach applied by Canada and other countries around the world.
Based on the revised Canadian Environmental Protection Act, 1999 (CEPA 1999), the Canadian government acknowledged that the process for assessing and managing toxic substances was slow and reactive. In response to this gap, Canada was the first country to make a legal commitment to identify substances that require further assessment and management activities. Canada completed the categorization of 23,000 substances listed under its Domestic Substances List (DSL) in September 2006 as required under CEPA 1999. Categorization identified the substances which present the greatest potential for exposure or are persistent or bioaccumulative and inherently toxic to human beings or to non-human organisms.
The results of the categorization process identified over 4,000 substances that required further government assessment. This presentation will discuss the government’s approach to categorization and its limitations; the Chemicals Management Plan (CMP) and its contributions to the reduction or elimination of toxic substances; and the contributions of environmental and health non-governmental organizations throughout categorization and CMP in promoting better accountability by industry and government on chemical use in Canada.
Improving the Chemical Regulatory System in the US
Charles M. Auer
Charles Auer & Associates, LLC, (Poolesville, MD)
A series of converging developments point to the likelihood of legislative overhaul of the current US chemicals law, the 1976 Toxic Substances Control Act (TSCA), over the coming years. The presentation will outline these developments and discuss key issues, needs, and approaches that should be considered in developing new legislation. These include, among others, the need for: periodic reporting/updating of hazard and exposure information by companies throughout the chain of commerce; more effective and flexible authorities to manage - and prevent – risks; greater public access to risk information while protecting trade secrets; timely and informed decision-making which applies current scientific and socioeconomic understanding; recognition of the crucial role of and the need to encourage innovation in development and commercialization of sustainable products and technologies; and the use of fee-based approaches in conjunction with appropriated funds to ensure adequate EPA resources.
ICCA Global Product Strategy: Building Public Confidence in Chemicals
Gregory G. Bond
The Dow Chemical Company, Midland, MI.
The Global Product Strategy (GPS) was launched by the International Council of Chemical Associations (ICCA) at the first International Conference on Chemical Management (ICCM-1) held in Dubai in 2006. GPS is intended to improve the product stewardship components of the industry’s flagship Responsible Care program. These two complementary initiatives are dedicated to the responsible handling of chemicals throughout the world and contribute to achieving the vision of UNEP’s Strategic Approach to International Chemicals Management (SAICM). SAICM is a policy framework to foster the safe handling of chemicals so that, by 2020, chemicals are produced and used in ways that minimize significant adverse impacts on human health and the environment. Through practicing GPS and complying with existing regulatory requirements, companies and associations that belong to ICCA work to improve risk characterization and risk management procedures. Over the past 18 months, the industry has made significant strides toward implementing GPS and these were well-received by all stakeholders at the ICCM-2 meeting held this past May in Geneva. ICCA believes effective chemicals management is best accomplished through a combination of government regulatory initiatives and meaningful voluntary industry programs. Under the GPS, by 2020, ICCA aims to: Establish a base set of hazard and exposure information adequate to conduct safety assessments for chemicals in commerce globally. Provide global capacity building to implement best assessment practices and management procedures, especially with small and medium sized companies and those operating in developing countries. Share relevant product safety information with co-producers, governments and with the public. Work across the value chain so suppliers and customers can effectively evaluate the risks and successfully manage chemicals through their life-cycles. Make information on chemicals publicly available through a GPS IT-portal via http://www.icca-chem.org/.
This presentation will illustrate the significant progress that has been made on each of these objectives and future plans to achieve the promise of GPS.
Challenges and Opportunities for Assessing and Regulating Chemicals With Genomics and High Throughput Molecular Screening Techniques
Richard A. Becker
American Chemistry Council, Arlington, VA
Within a modern integrated testing and assessment framework for commodity chemicals, both relevant toxicity data and surrogate toxicity information derived from computational models are used to develop initial hazard profiles. Computational models such as QSAR and read across have been extensively used to date, and now high throughput screening (HTS), genomics and related methods for biological profiling have emerged. But to forecast toxicity will require extensive collaborative research to forge the solid scientific foundation for developing genomics profiling and HTS prediction models. This research must include developing key science-based interpretation tools so that results from these advanced technologies can be translated into meaningful information that can be used effectively in decisions about priority setting and chemical safety and thereby reduce or replace classical toxicity testing methods. There is also a pressing need to better understand exposures and to ultimately develop approaches that integrate biological measurements of response with exposure information, and to relate concentrations eliciting responses in HTS and genomic methods to real world exposure levels. In addition, it will always be necessary to evaluate relevance, reliability, sensitivity and specificity of advanced high throughput molecular screening, genomics and computational profiling methods prior to regulatory acceptance so that regulatory agencies, the regulated community and the public have sufficient confidence in the decisions based on such methods. While traditional structures for conducting method validation and demonstrating model predictivity may not be practical, approaches such as discussed by the NRC with respect to validation of toxicogenomic technologies as well as practices embodied in the OECD principles and guidance for the validation of QSARs and evidence based toxicology should be considered.
Introduction, Mechanisms of Action, Historical Perspective, and Changes in Drug Development Paradigms
Jeffrey Murray, MD
US Food and Drug Administration.
Drug development for the treatment of HIV/AIDS is a remarkable modern success story that can serve as a model for the development of treatments of other diseases. Within 25 years from the first diagnostic for HIV infection, 26 unique drugs from 6 drug classes have been approved for treatment, changing a fatal and profoundly devastating disease into a chronic manageable infection. Community activism; collaborative research among industry, government, and academia; and promulgation of new FDA regulations and policy were some of the factors that promoted successful drug development. Accelerated approval using a surrogate marker, validation of viral load measurements as an endpoint that predicted clinical progression, expanded access programs, and use of advances in laboratory technologies are a few of the tools that made HIV drug development efficient and productive. These tools as well as lessons learned from some of the pitfalls of HIV drug development may be applied to other therapeutic areas, such as hepatitis C. The future of HIV drug development holds challenges particularly in maintaining high success rates in the setting of drug resistance, scaling up products for developing nations, and making progress in the field of HIV prevention.
Nonclinical Safety Assessment of Anti-HIV Therapeutics—A Regulatory Perspective
L. Peyton Myers
US Food and Drug Administration.
HIV-specific therapeutics have advanced during the two decades of HIV drug development from 1 class to now 6 approved classes of anti-HIV drugs. These six approved classes of drugs include Nucleoside Reverse Transcriptase Inhibitors, Non-Nucleoside Reverse Transcriptase Inhibitors, an Integrase Strand Transfer Inhibitor, Protease Inhibitors, a CCR5 Co-receptor Antagonist, and a Fusion Inibitor. These different classes of medications have varying toxicities, which may be either drug specific toxicities or potentially class effects. FDA has developed Guidances to assist Sponsors in the drug development process. For nonclinical risk assessment, Guidances for anti-HIV therapeutics are similar to other therapeutics. However, drugs for life threatening indications such as HIV infection has historically been allowed to progress more quickly through the regulatory pathway. This usually allowed for quicker access to life-saving medications. As drug development advances to treat this chronic disease, drug development issues have changed as the treatment of HIV has changed. Some of the recent issues that appear to be confounding Sponsors are: timing for carcinogenicity testing, relating juvenile toxicity studies to a pediatric indication, and when/if combination studies are necessary. It is often helpful for Sponsors to work with the Division to get feedback, when necessary, for the particular drug development issue. This presentation will address the available guidance documents that define a scientifically sound pathway for the development of anti-HIV therapeutics.
Nonclinical Safety Assessment of Anti-HIV Therapeutics—An Industry Perspective
Grushenka H. I. Wolfgang
Gilead Sciences, Inc
Considerations when designing a nonclinical program to meet US and European guidelines include timing of studies (including carcinogenicity), whether to conduct combination toxicity or juvenile toxicity studies, and what regional differences may exist (eg mitochondrial toxicity screening, environmental risk assessment). Despite targeting viral replication (no host target), current anti-HIV therapeutics display a wide range of toxicities. For nucleoside reverse transcriptase inhibitors (NRTIs), which are the current backbone of combination antiviral therapy, the class has been associated with mitochondrial toxicity. In vitro screens have proven effective in assessing the mitochondrial toxicity of nucleosides with good correlation to clinical outcomes. Favored agents have fewer side effects and are not associated with mitochondrial toxicity. For non-nucleoside reverse transcriptase inhibitors (NNRTIs), the toxicities observed clinically, such as rash and neuropsychiatric side effects, are not readily determined by nonclinical testing. Protease inhibitors (PIs) are often the third agent in a regimen and of interest from a regulatory point of view as they are often poorly bioavailable and as such are developed with a boosting agent such as ritonavir to increase exposure. Adverse effects of PIs include metabolic complications, gastrointestinal disturbances and drug-drug interactions. In vitro screens have been able to detect the metabolic disturbances of PIs and initial data indicates these data correlate with in vivo data. As anti-HIV agents are given in combination, the spectrum of toxicities for the planned clinical regimens should be considered. Fixed dose combinations of NRTIs and NNRTIs have been developed to simplify regimens in order to improve treatment response. These products can come to market rapidly if companies and regulators work together. While the field of HIV treatment has progressed rapidly there are still improvements to be made to ensure patients have regimens available with long-term efficacy and safety.
Clinical Perspective of the Toxicology of Anti-HIV Therapeutics
Richard Haubrich, MD
University of California, San Diego
Since the approval of Zidovudine as the first anti-HIV monotherapy, there have been great advances in the treatment of HIV infection. Although evaluation of the nonclinical data did adequately provide safety information to support the initiation of clinical trials, many adverse effects must still be monitored in clinical practice. Some of these long term effects (eg, lipid disorders, renal toxicity, cardiovascular disorders, or potential for increased carcinogenicity) require active monitoring and adjustment of clinical care over time. Due to the nature of the infection, these medications must be used in higher risk populations (eg, patients with underlying liver and cardiovascular disease) which can present unique challenges. This session will discuss these various toxicological issues/adverse effects in anti-HIV clinical trials as well as the strategies utilized to successfully treat HIV infection in different patient populations.
Current Perspective on Comparability Issues Summary of DIA Meeting
Mary Ellen Cosenza, PhD, DABT
Executive Director, Regulatory Affairs, Amgen Inc., Thousand Oaks, CA
Comparability is the process of demonstrating that a product has highly similar attributes before and after process, production, or manufacturing changes. These changes can be minor or can be as major as cell line changes or site changes. The assessment of comparability may require a multidisciplinary approach that includes process development, manufacturing, quality, clinical, preclinical, and regulatory affairs. We are striving for alignment and greater understanding of the requirements between industry and regulatory agencies on a global basis. The desire would be an approach to comparability assessment which would incorporate risk management principles.
Preclinical Comparability Assessments of a Biologic Product
Laura Andrews, PhD, DABT, Fellow ATS
Vice President–Pharmacology and Toxicology, Genzyme, Framingham, MA
Product comparability assessments can be a daunting and very new arena to many toxicologists in the field of biologic development. This introduction to comparability assessment of biotherapeutics will review briefly the terminology associated with the idea of comparability, touch on the impact of changes in the manufacturing processes and how these decisions impact the potential assessments and set the stage for the specific discussions and regulatory considerations that will follow.
CDER Perspective on Comparability of a Biologic Product
M. Stacey Ricci, ScD
Toxicologist, US FDA, CDER, Office Oncology Drug Products, Office of New Drugs, Silver Spring, MD
A brief review of the current perspective and relevant documents within CDER with respect to comparability.
Gene Therapy Comparability
Timothy MacLachlan, PhD
Genzyme Corporation, Framingham, MA
Gene therapies can typically be broken down into two separate components – the transgene that will produce the therapeutic and the packaging system (i.e., viral-based, lipid based, etc). The viral component of a gene therapy is central to the body’s initial reaction to dosing, the biodistribution of the therapeutic and long-term immune reaction to the viral coat. With the ever evolving manufacturing technologies in this area, process changes are inevitable, and are likely to result in differences in viral portion of the material, some of which have potential for affecting the safety profile of the therapy. This discussion will outline some of the changes that can take place and what kind of preclinical assessments may be necessary to characterize the impact of these changes.
CBER Perspective on Comparability
Ramjay Vatsan, PhD
GTB/Division of Cellular & Gene Therapies, US FDA, OCTCT/CBER, Rockville, MD
A brief review of the current perspective and relevant documents within CBER with respect to comparability.
Introduction
Chris DeMerlis
Manager, Regulatory Affairs, Colorcon, Inc. West Point, PA
Excipients have many uses in the development of drug product dosage forms. The oral route of administration continues to be the preferred method for product development with tablets and capsules as the leading approved dosage form. The use of extended release matrices and delivery systems has increased due to the potential to improve patient compliance and manage product life cycles. However, new polymers for hydrophilic matrices have not been developed due to the regulatory and safety constraints and high cost of development. Consequently, efforts have focused on combining existing polymers of different viscosity and chemistry to achieve optimal drug release characteristics.
Excipients in New and Specialized Areas of Drug Delivery
David W. Hobson PhD, DABT
LoneStar PharmTox LLC, Boerne, Texas
The challenges created by new and specialized areas of drug delivery bring with them the need to incorporate and utilize known excipients as well as the necessity to develop new and specialized excipients. Examples of new and specialized forms of drug delivery that will be discussed in this presentation include, but are not limited to the following, drug coated medical devices, novel topical drug delivery systems, wound healing products, drugs for medical imaging and nanoparticulate drug delivery systems. The uses of excipients in such areas include typical uses such as preservatives, colorants, binding and thickening agents, stabilizers, etc., but specialized areas of drug delivery may also require new forms for typical excipient uses or sometimes create new categories of excipients relatively unique to the delivery mode. New delivery systems can necessitate excipient development to address novel requirements for packaging, preserving and stabilizing drug substances. For example, drug-incorporated nanoparticles may have surface charged particle requirements measured as zeta potentials that must be maintained within specified limits for optimal drug stability and coated cardiovascular stents often require the use of specialized bioerodable polymer systems that provide controlled release of drugs into the bloodstream. This discussion will provide examples of excipient uses of a novel and specialized nature as well as outline and describe the toxicologic needs for establishing and demonstrating their safety for practical and regulatory purposes.
Current and Future Methods For the Safety Assessment of Excipients
Robert E. Osterberg RPh, PhD Fellow-ATS
Drug products may contain several excipients that are used for a variety of purposes. Some are essential to manufacture the drug product and others are necessary to make the product acceptable to the patient. Some excipients might make a topical drug product more efficacious such as the use of penetration enhancers. Most drug products are formulated with commonly used and allowed excipients that are mostly included in FDA’s Inactive Ingredients Guide as well as those listed in other countries compendia. Some new formulations may require novel excipients that offer benefits not provided by commonly used excipients. New excipients must be evaluated for safety before they can be used legally. The International Pharmaceutical Excipients Council (IPEC), the US Food and Drug Administration, OECD and JPMA have written their own guidelines and guidances for the safety testing of excipients. FDA’s guideline as well as the other guidelines essentially requests the same data as derived from those tests for a new drug as mentioned in the ICH M3 guideline because of the concern for known excipient toxicities. However, in the FDA guidance there is a suggestion to possibly omit the need for carcinogenicity testing. A similar suggestion is also found in the ICH S1A guideline entitled “The Need for Long-Term Rodent Carcinogenicity Studies for Pharmaceuticals.” Ways of implementing these suggestions will be described for discussion.
Existing Procedures for Ingredient Safety Evaluations With Applications to Excipients: PCPC, GRAS, FDA and FEMA
Chemical S&T Manager, Chemical Medical Countermeasures, Chemical and Biological Technologies Directorate, Defense Threat Reduction Agency, Fort Belvoir, VA
According to FDA, an inactive ingredient is any component of a drug product other than the active ingredient. An excipient is an inactive ingredient often used in a final drug product as a carrier for the active ingredient(s). It is a requirement that excipients are safe and do not contain toxic contaminants when added to the final product. Therefore, human exposure to excipients must be evaluated and the safety substantiated. The scope of safety information required for an excipient will depend upon the intended use of the final drug/product. There are many ways to assure inclusion of safe excipients in products that will ultimately meet FDA requirements. This presentation will discuss potential excipient safety evaluation approaches that could be used to extract existing safety information previously reviewed by expert panels and typically published in the open literature. For example, acceptable daily intake values may be derived from safety assessments previously done for food additive approvals. These approaches may expedite the compilation of safety databases for old or new excipients. An introduction will be given for several existing ingredient safety assessment sources, such as the FDA, CIR, RIFM, FEMA, and GRAS substances that could be used to derive safety data relevant to excipient use.
Toxicological Concern for Impurity Safety
Timothy J. McGovern, PhD
SciLucent, LLC, Herndon, VA
The requirements regarding the safety characterization of impurities in drug substances and products are more formalized and better understood than those for excipient-related impurities even though excipients can often comprise the majority of the overall drug product formulation. Impurities in drug substances and products have been regulated over the previous decade and a half through the International Conference for Harmonization (ICH) Guidances Q3A(R2) and Q3B(R2). More recently, the Committee for Medicinal Products for Human Use (CHMP) of the EMEA and the Center for Drug Evaluation and Research (CDER) of the US FDA released guidance (final and draft, respectively) on how best to deal with genotoxic impurities in drug products. Although ICH Guidance Q3B addresses impurities in new drug products classified as reaction products of the drug substance with an excipient, the guidances currently available specifically exclude impurities arising from excipients. The control of excipient-related impurities is often managed by the manufacturer of the excipient. This session will discuss the regulatory aspects of safety characterization of impurities in drug substances and products and contrast them with the regulations regarding impurities in excipients.
Current Approaches to Assess Risk to the Developing Immune System: Some Practical Considerations
Michael P. Holsapple
ILSI Health and Environmental Sciences Institute, Washington, DC.
It is known that common infectious diseases can occur more often and are usually more severe in the very young when compared to adolescents and adults, and that infants are more susceptible to immune toxicities and immune manipulations. Interest in developmental immunotoxicology (DIT) has been based on the possibility that the developing immune system may be more sensitive than the adult system to chemical exposures. From a regulatory or risk assessment context, interest in DIT has centered on the possibility that a well-designed and well-executed study in young adult animals could miss this ‘window’ of increased susceptibility. While data comparing the developing and adult immune systems are still quite limited, a number of recent workshops have shed considerable light on the best approaches to address the potential for DIT. This presentation will provide some practical considerations of a DIT testing framework as an introduction to this session on the DIT testing of biopharmaceuticals. Assessment of DIT should be incorporated into existing protocols (eg, developmental and reproductive toxicity (DART) protocols), to the extent possible, rather than ‘stand alone’ tests. There is no consensus about which species is best suited to extrapolate to humans for the potential risk of DIT. In general, the rat is the preferred animal model for DIT, because it is the species of choice for DART studies. However, it is unlikely that rats will be the preferred species for testing biopharmaceuticals where non-human primates will be required. It is important to recognize that there is considerable variability in the state of development of the immune system across species at birth, and that the immune system in all species undergoes some postnatal development. Known developmental differences with humans must be factored into the interpretation. Animals should be exposed throughout the treatment protocol, and all critical windows of development—from gestation to the postnatal period, and perhaps extending to the juvenile / young adult stage—should be included. Currently, a compound-specific evaluation (eg, case-by-case) is anticipated, and the “triggers” for assessing DIT may include SAR information, results from other toxicity studies, and the intended use of the drug or chemical. Ultimately, the most important consideration is that flexibility is key, and that “one size doesn’t fit all.” It is important to understand the question being addressed.
Critical Windows in Development of the Rodent and Primate Immune System
Kenneth S. Landreth
Department of Microbiology, Immunology, and Cell Biology, West Virginia University School of Medicine, Morgantown, WV 26506
The immune system of mammals develops as an integral part of the hematopoietic system in both fetal and postnatal life. Much of what we now understand about development of immune responsive cells has come from studies of murine species and this detailed understanding of immune system development will be compared to our current understanding of primate species, including humans. In the developing murine embryo, hematopoietic cells that will give rise to circulating leukocytes are known to originate from lateral plate mesoderm surrounding the developing heart (aortogondomesonephros). These progenitor cells for the immune system migrate through a predicable series of embryonic tissues and initiate exclusive residence in the bone marrow space only at the time of birth. Because of this sequential change in anatomic residence of cells destined to populate the postnatal immune system, short-term and long-term effects of immunotoxic insult may differ significantly throughout gestation. This has led to the postulate that the developing immune system passes through a predictable sequence of critical embryonic developmental windows that must be considered in establishing a testing framework for immunotoxicology assessment. As mammals enter postnatal life, the immune system continues to undergo temporal change and continues to progress through a predictable series of critical post-natal developmental windows that may substantially differ in response to immunotoxic insult. Postnatal immune system development also involves establishment of functional lymphoid tissues and demands better differentiation of the impact of immunotoxic compounds on primary and secondary lymphoid tissues as they mature and senesce following birth. The developing prenatal and postnatal mammalian immune system is a renewing cell system and capacity for full reconstitution of that system following inmmunotoxic insult must also be considered in any testing paradigm.
Comparative Development of the Immune System in Primates
Eberhard Buse
Covance Lab.GmbH, Kesselfeld 29, 48163Muenster, Germany
The nature of the immune system (IS) derives from its complex tasks (protection from potentially pathogenic agents), its numerous elements with peculiar functions (organs, cells, mediators etc.), and the inhomogeneous origin of the different elements. In view of molecularly based toxicological research, sound knowledge about model animals is essential to recognize the closest proximity to the human IS. This also applies to non-human primates (NHP) with fetal and juvenile stages which have become increasingly popular in toxicological research in recent years.
Ontogenetically, the
The cynomolgus monkey
Draft OECD Recommendations for DIT Testing.
Michael Woolhiser
The Dow Chemical Company, Midland, MI
In the context of human safety for both industrial chemicals and pharmaceuticals, rodent models have been used for decades as a reliable indication of immunotoxicity potential. Knowledge regarding immunological similarities between mammalian species has allowed for the identification of some dependable measures of immune function for purposes of human hazard assessment. However, as heightened concern for children’s health has led to an increased interest in evaluating immune function during development. Since components of the immune system develop sequentially, it is being recognized that opportunities for immunotoxicological insult may differ throughout developmental life stages (eg, embryonic, fetus, pup, weanling, young adult). This has served as the basis for a testing framework by several organizations, but currently, formal DIT guidance by the OECD is taking shape in the form of an extended one-generation reproductive toxicity guideline. In short, the approach evaluates immune responsiveness following xenobiotic exposure across all developmental stages (e.g, pregnancy, post natal, and maturation). The cornerstone of the testing framework includes the assessment of an antibody response to a T-cell dependent antigen, at or around PND 70. Additional insight into the immune response would come from bone marrow cellularity, lymphoid tissue weight and histopathology, and splenic cellular analysis (i.e., flow cytometry for CD4+ and CD8+ T-cells, B-cells and NK cells). While such endpoints have been evaluated in and of themselves, this more complex approach brings additional challenges, many of which are only now beginning to be evaluated in preliminary test plans.
A Rose Is a Rose Is [Not] a Rose: Why the Approach to DIT Evaluation of (Bio)Pharmaceuticals Is Unique
Leigh Ann Burns Naas
Drug Safety Research and Development, Pfizer Inc., San Diego, CA
Several workshops and reviews over the past few years have described consensus approaches to address evaluation of the developing immune system after xenobiotic exposure. These approaches are based on the rat as the model system, primarily because it is a general toxicology and immunotoxicology model for drugs and chemicals. What has not generally been considered in depth in prior discussions around DIT testing, is the specific difference between therapeutic chemicals (intentional human exposure) and environmental chemicals (unintentional human exposure), as well as the difference between small molecules and macromolecular entities such as monoclonal antibodies (size, species specificity, etc.). As the state of the science of DIT has evolved, it is clear that philosophical, physiological, and physical differences necessitate modifications in the original consensus approach so that the safety profile of new molecular entities for the intended population can be most appropriately addressed. These differences will be discussed, and in light of the information provided by the prior presenters, study designs will be proposed for consideration as a starting point for the development of a consensus approach to DIT testing of (bio)pharmaceuticals.
Practical Approaches for Ototoxicity Testing Intended for Regulatory Submission
Leslie Lemke, PhD, DABT
Assistant Director Pharmaceutical Toxicology, Alcon Laboratories, Fort Worth, TX
The relatively recent advent of topical treatments for middle ear disease presents a challenge for the classically trained toxicologist. Utilizing a local approach to therapy decreases the probability for off target systemic effects. However, the advantageous increase in local tissue exposure requires a more comprehensive assessment of ototoxic potential than that typically undertaken in a general toxicity study. While ototoxicity is classically defined as damage to the sensory neuronal tissue of the inner ear, adverse effects on the tympanic membrane and middle ear cavity are also of toxicological concern. Ototoxicity studies can be carried out in a variety of species depending on stage of product development, clinical indication sought and specific area of concern. In life evaluations may include special attention to clinical signs of auditory or vestibular toxicity, otoscopic evaluations of the external auditory canal, and electrophysiologic evaluations of the auditory brainstem response. While histological evaluation of the hair cells of the organ of Corti is of particular importance, microscopic analysis of the external auditory canal, tympanic membrane and middle ear can also be considered part of a comprehensive assessment. The specific advantages and disadvantages associated with the use of rabbits, guinea pigs and chinchillas in these studies will be discussed in conjunction with study design modifications which can be employed to facilitate the conduct of these studies in the drug development paradigm.
Histopathologic Evaluation of the Ear
Kenneth A. Schafer, DVM, PhD, DACVP
Senior Pathologist, Vet Path Services, Mason, OH
When the special senses are evaluated in toxicology studies, the eye is routinely included, but the ear is not. This presentation will focus on the challenges of evaluating the ear as an organ of special sense histopathologically in toxicology studies. It will discuss some of the techniques used in preparation of otic specimens for histopathologic evaluation, with advantages and disadvantages of each. The microscopic anatomy and the toxicologic responses of the ear to various administered xenobiotics will be reviewed. Also to be addressed are rationales for histopathologic assessment of the ear.
Chemical Interactions in the Auditory System
Thais C. Morata
NIOSH, Cincinnati, OH
Although noise is the predominant source of work-related hearing loss, recent evidence has demonstrated that chemical toxicants can also cause hearing loss and enhance sensitivity to noise. The adverse auditory effects of chemical toxicants have been investigated more systematically during the past two decades, both in animal and human field and clinical studies. Existing evidence has prompted the proposal of new guidelines and standards on hearing loss prevention. In the U.S., the National Institute for Occupational Safety and Health has discussed specific research needs regarding the ototoxicity of chemicals used at work. The American Conference of Governmental Industrial Hygienists and the U.S. Army have proposed preliminary practical steps that employers and occupational health professionals can take to improve hearing loss prevention. Australia and New Zealand have developed standard AS/NZS 1269:2005, recommending hearing tests for workers exposed to ototoxic agents. In the legislative arena, the European Parliament published a new noise directive (2003/10/EC), to be adopted by all participants' countries. This Directive requires employers to give attention to any effects on workers' health and safety resulting from interactions between noise and work-related ototoxic substances, when performing risk assessment of workplaces. Legislation regarding compensation has also changed in Australia (Workcover Guides for the Evaluation of Hearing Impaired, June 2002) and Brazil (Decree 3048, May 6, 1999). A new concept of creating an ototoxicity notation has been proposed. This presentation will examine the recent guidelines and legislative developments and discuss alternative strategies for preventing auditory effects of exposure to ototoxic chemicals.
Disclaimer: The findings and conclusions in this abstract have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.
Development of a Drug to Treat Hearing Loss
Josef Miller1,2, Colleen LePrell3, Jeannie Hernandez-Reyes1, Yehoash Raphael1 and Richard Alschuler1
1 Kresge Hearing Research Institute, University of Michigan, USA, 2 Center for Hearing & Communication Research, Karolinska Institute, Sweden, 3 Department of Communication Disorders, University of Florida, USA
Thirty-seven million in the USA have hearing impairment. The number is higher in Europe. WHO estimates that 600M world wide have hearing impairment, costing approximately 2% of the world GNP, and are now considering data that may double those estimates. Approximately half of hearing loss is heredity and half acquired; of the acquired hearing loss the vast majority is due to intense noise exposure, ototoxic drugs (primarily aminoglycosides), and aging (presbycusis). Pathology of the inner ear is the cause of hearing impairment in almost all cases.
Until recently prevention and treatment has been limited to hearing aids for mild hearing loss and cochlear implants for profound hearing loss, both with remarkable but limited success. No medical or drug treatment has been available. However over the last decade with new insights into the biochemistry of cell death pathways and interventions to modulate them, new understanding of the mechanisms of major factors causing hearing loss (noise and drugs), and new techniques that allow direct and selective delivery of genes and drugs to the inner ear, the development of medical interventions to prevent and reverse hearing loss are now possible.
Research is focused on two strategies: regeneration of sensorineural tissues of the inner ear following damage and interventions to prevent major causes of acquired hearing loss (primarily noise and drugs).
Regeneration research follows one of three approaches: 1) Gene therapy: Induce transdifferentiation of support cells to new sensory/neural cells, 2) Induction of endogenous stem cells to differentiate to hair cells or neurons or 3) Xenograph of exogenous stem cells to survive and differentiate to hair cells or neurons.
Research to prevent noise- and drug-induced hearing loss has grown from understanding the key role of free radical formation to evoke necrotic and apoptotic cell death and interventions to prevent and scavange radicals.
We will review the success and challenges facing translation of these strategies to clinical application and describe the successful development of a micronutrient formulation of antioxidants and vasodilators (Auraquell) that robustly prevents noise-induced hearing loss.
This work supported in part by NIH grants DC008423, DC04058, P30 DC05188 and the Ruth and Lynn Townsend Professorship.
Disclosure: The principal author (JM) is CSO of company (OtoMedicine, Inc) currently developing the micronutrient formulation (Auraquell) to prevent noise-induced hearing loss. His conflict of interest is under University of Michigan COI plan.
Bisphenol A: Ghost or Villain?
Calvin C. Willhite and Clifton J. McLellan,
NSF International, Ann Arbor, Michigan.
Bisphenol A is a monomer used in synthesis of polycarbonate plastics and epoxy resins. Although changes in reproductive tract tissues can be induced in rodents after parenteral injection, multigeneration feeding studies conducted in rats and mice at doses spanning five orders of magnitude failed to identify any sign of developmental or reproductive toxicity. Ingestion of d 16-BPA by healthy volunteers resulted in 100% recovery of administered dose as the urinary glucuronide, with no free BPA detected in plasma. The extensive glucuronidation of BPA by enterocytes and hepatocytes after ingestion to yield the inactive BPA-glucuronide is not seen after injection and it is only the parent (free) BPA that binds ERα and ERβ. The lack of carcinogenic activity in lifetime feeding studies in rats and mice suggests BPA is not likely to pose a carcinogenic risk to humans. As the multigeneration studies identified oral NOAELs for systemic toxicity that were less than those for reproductive endpoints, it is the systemic toxicity of ingested BPA that represents the most appropriate point-of-departure for human health risk assessment. Application of 10-fold inter- and intraspecies uncertainty factors and a 3-fold database uncertainty factor (to account for lack of comprehensive neurobehavioral and immunologic evaluations) to the 5 mg/kg NOAEL results in an oral reference dose of 0.016 mg/kg-day. Based on aggregate dietary BPA consumption estimates, the mean margin of exposure ranges from 10 to 53,000. Comparing geometric mean (47 ng/kg-day) and 95th percentile (274 ng/kg-day) BPA exposures calculated from the NHANES 1988, 2000 and 2003 urinary surveys to the oral RfD results in margins of exposure between 58 and 550. Based on the (total) urinary BPA concentrations from German, U.S. and Japanese studies (Toxicol. Lett. 179: 155-162, 2008; Anal. Bioanal. Chem 383: 638-644, 2005; J. Environ. Chem. 14: 57-63, 2004), minimum margins of exposure range from 260 to 2200.
Dermal Risk Assessment of Fragrance Allergens
Jon F. Lalko
Research Institute for Fragrance Materials, Inc.; Woodcliff Lake, New Jersey, USA
Dermal sensitization resulting in allergic contact dermatitis is an important issue for both occupational/environmental health and consumer product development. Over the past decade, there have been significant advances in our understanding of the underlying mechanisms of dermal sensitization. These advances have lead directly to the application of a dermal sensitization Quantitative Risk Assessment (QRA) approach being applied to fragrance ingredients identified as potential contact allergens. This methodology utilizes the general toxicological principles of QRA by adapting them to the exposure conditions and biology associated with the induction of dermal sensitization. This focus on induction provides for primary prevention (decreasing/eliminating de novo allergy) to fragrances used in consumer products. The methodology is currently being implemented by the fragrance industry as part of its product management practices for potentially sensitizing fragrance ingredients. Significantly, this takes the form of International Fragrance Association (IFRA) Standards that limit the use of these materials based on 11 product categories. This new schema provides for a more refined assessment, than was previously possible, that is based on relevant consumer exposure.
Food Allergy Update
Felicia B. Billingslea
DHHS, Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Nutrition, Labeling, and Dietary Supplements, HFS-820, 5100 Paint Branch Parkway, College Park, MD 20740, USA; Phone: 301-436-2371, Email: felicia.billingslea@hhs.fda.gov
Accurate food allergen labeling is a major priority for the US FDA. As early as 1996, FDA issued a Dear Manufacturer’s Letter advising that certain allergens could not be considered incidental ingredients and, therefore, exempt from ingredient labeling. The Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA) amended the Federal Food, Drug and Cosmetic Act to require food products marketed in the US to disclose the source of major food allergens. Major food allergens as defined by FALCPA are responsible for 90 percent of food allergies in the US and include 8 foods or food groups. FALCPA also directed FDA to study the industry use and consumer understanding of advisory (may contain) labeling. Based on our study and other information, there appears to be no uniform industry standard that establishes when advisory labeling is appropriate or what particular statement is appropriate. This presentation will discuss several activities that FDA has completed over the last several years to implement the requirements of FALCPA, its current activities to ensure that firms are accurately interpreting the requirements of FALCPA and properly labeling their food products, as well as FDA’s ongoing efforts to develop a long-range strategy to ensure that advisory labeling effectively communicates potential risk to allergic consumers.
Alternatives to Animal Testing: State of Play for EU Cosmetics 7th Amendment 2009 Endpoints
Pauline M. McNamee
The Procter & Gamble Company, U.K.
The 7th Amendment to the EU Cosmetics Directive (2003/15/EC) introduces a progressive ban on animal testing and a marketing ban on cosmetics products and their ingredients that are tested on animals that involves: 1) immediate ban on any test for which a validated alternative is available; 2) ban on testing of finished products from Sept. 2004; ban on testing of ingredients from March 2009 after which date no animal testing on ingredients for the purpose of the Cosmetics Directive is allowed in the EU; 3) marketing ban as soon as validated alternatives are available effective from Sept. 2004 for finished products and from March 2009 for cosmetic ingredients with the exception of 3 specific types of tests (repeated dose toxicity, reproductive toxicity and toxicokinetics) for which the marketing ban will come into effect no later than March 2013.
For human health effects subject to the March 2009 deadline, to date in vitro test methods for skin corrosion, phototoxicity and skin irritation have been validated by the European Centre for the Validation of Alternative Methods (ECVAM) with skin corrosion, phototoxicity and also dermal absorption/penetration already globally accepted by OECD. In vitro skin irritation test methods are in the process of gaining OECD acceptance. For other health effects also subject to this deadline (acute toxicity, eye irritation and genotoxicity) work is ongoing to achieve full replacement of the in vivo assays. Acute toxicity is being addressed within the EU 6th Framework program. Eye irritation and genotoxcity are core focus areas within the cosmetic industry’s alternatives to animal testing program. Following a brief introduction to the 7th Amendment deadlines, this presentation will provide information relevant to the 2009 deadlines on the methods available and their use, their status in terms of validation and regulatory acceptance, and for relevant endpoints, discussion of ongoing research programs for continued development of in vitro methods to address the needs of the cosmetics industry.
Root Causes of Overdose With OTC Cough and Cold Medicines in Children
Edwin Kuffner, MD
McNeil Consumer Healthcare.
When used as directed, children’s OTC cough and cold medicines are generally recognized as safe with adverse events (AEs) being reported very rarely. Root cause analysis of AEs reported prior to recent labeling changes reveals, in addition to accidental unsupervised ingestions, rare reports of misuse leading to overdose, particularly in infants. Identified root causes of overdose included both incorrect dosing (exceeding recommended single or daily doses or dosing too frequently) and administration errors (giving adult medicines to children, using multiple products with same/similar ingredients). Analysis of parental knowledge of correct dosing was complicated because FDA did not allow dosing information for small children on the label. In 2007 manufacturers voluntarily withdrew oral cough and cold medicines that referred to “infants” and in 2008 after consultation with the FDA dosing directions on oral OTC cough and cold medicines were changed from “Consult a doctor” for children < 2 years to “Do not use” for children < 4 years. An educational campaign designed to address root causes of overdose and inappropriate dosing behaviors is underway. Enhanced safety surveillance continues to support the safety of OTC cough and cold medicines when used at recommended doses. In addition to stressing the importance of preventing accidental unsupervised ingestions, healthcare providers can help ensure safe use of OTC cough and cold medicines by knowing the information on the OTC label and counseling caregivers and patients to: Always read the OTC package label and follow directions Not use OTC cough and cold medicines in children < 4 yrs Know the active ingredients Not give more than recommended dose Use the measuring device that comes with product Not give adult medicines to children Not use antihistamines to sedate children Stop using the medicine and immediately be evaluated if their condition does not improve or worsens
A Systems Biology Approach to Developing Targeted Therapies
Matt Onsum, Brian Harms, Sasha Huhalov, Sharlene Adams, Jinming Gu, Emily Pace, Jonathan Fitzgerald, Charlotte McDonagh, Gabriela Garcia, Birgit Schoeberl, Ulrik Nielsen
Merrimack Pharmaceuticals, Cambridge, MA
Quantitative, data-driven computational modeling of signal transduction networks can be used to identify targets, to design better therapeutics and to help guide the selection of indications or biomarkers. Using the ErbB signaling network as an example, we will discuss how this systems approach helped to identify ErbB3 as a critical node in the pathway. We will present simulations suggesting that an anti-ErbB3 monoclonal antibody can effectively inhibit signaling in the ligand dependent setting and a bispecific antibody using ErbB2 (a.k.a. HER2) as a targeting arm and ErbB3 as a therapeutic arm can effectively inhibit signaling in the ErbB2 amplified setting.
We will present data consistent with simulations showing that MM-121, an anti-ErbB3 monoclonal antibody, and MM-111, a bispecific antibody to ErbB2/3, inhibit the ErbB pathway and prevent the outgrowth of tumors in xenografted mice in either the ligand dependent or ErbB2 amplified setting.
Taken together, we show how a systems approach helped us to identify the critical role of ErbB3, a previously under appreciated target, and allowed us to develop two different therapeutics showing efficacy in different disease settings.
Data- and Simulation-Driven Systems for Predictive Toxicology
Scott Siler1, Alison Harrill2, Ananth Kadambi1 and Alan H. Roter1
1 Entelos, Inc., 2 The Hamner Institutes for Health Sciences.
Toxicogenomics has delivered predictive transcriptomic signatures for renal tubular injury, non-genotoxic carcinogenicity and numerous other pathological phenotypes. The quality and performance of transcriptomic signatures are proportional to the size of the training data set. Larger training data give less overestimation of performance in data-split-validation simulations, and therefore closer estimates to actual forward validation results. But transcriptomic models can only predict pathology for the species they are evaluated in. Better ways of translating toxic mechanisms in animal models to human biology is key to predictive toxicology.
The Entelos Drug Induced Liver Injury model is a top-down, physiological model of mechanisms of liver injury in human, mouse and rat built in collaboration with the Hamner Institutes and the FDA. Modeling in Physiolab allows focus on known toxicological mechanisms and elucidation of known species differences. The initial mechanisms modeled include hepatocellular necrosis, apoptosis, cholestasis, steatosis and mitochondrial dysfunction. The use of a mechanistic dynamic model of mechanisms of liver toxicity enables simulation of effects of drugs on liver physiology, expressing the quantitative differences between species, and predictive testing of new drug candidates.
Integrating Experimental, Text Mining and Analytical Prediction Methods in Drug Discovery
Carolyn R. Cho
Pfizer Research Technology Center, 620 Memorial Dr., Cambridge MA 02139, USA
Understanding and applying context specificity to intracellular signaling is crucial to not only the design of therapeutic interventions for a specific disease, but in the prediction of susceptible patient populations. Tissue specificity arises due to differential tissue functions, it also varies due to quantitative variations in the molecular players. In cancer, different tissues carry different frequencies of mutations. Although one pathway may be more frequently effected, the impact of cross-talk among other pathways is not well understood. Here, we report an integrated approach to analyzing pathway cross-talk in the context of the genetics of hepatocellular carcinoma.
We identify three key pathways using genetic and therapeutic considerations. Interactions among the approximately 25 molecular players are generated using text mining and verified by consideration of phosphoproteomic data. The interactions are then analyzed using logic-based modeling to predict the best pair wise combination of targets that increase cell apoptosis. Hypotheses are tested in vitro. This analysis demonstrates the effective integration of methods that improve our ability to consolidate our current knowledge and increase the effectiveness of therapeutic programs.
Using Systems Biology and Personal Genomes to Deliver Personalized Drug Combinations
Hamid Bolouri
Division of Biology, California Institute of Technology, Pasadena, CA
Over the past decade, systems biology analyses of high-throughput whole-genome assays have dramatically changed our understanding of cellular organization and function. In particular, common disorders are increasingly seen as the outcome of widespread interactions among large numbers of gene products and molecular pathways. At the sametime, studies of genetic and epigenetic variability within and across populations have revealed enormous inter-individual variability. One impact of these findings has been the development of population-specific drugs such as Herceptin. Stratified medicine is an excellent step in the right direction, but it is only one step. We already know that there is as much variability within ‘genetic populations' as between population averages. Medical diagnosis and treatment will ultimately need to be individualized. Within the next few years, we will be able to sequence the entire genome of any individual for a few (perhaps one) thousand dollars. Using systems biology to combine personal genomes with biomarker data, we will be to identify specific - and multiple - dysregulated pathways and systems in the patient. Instead of addressing a disorder as a single complex phenomenon, individual drugs and devices can be designed to target very specific sub-processes associated with a disorder. Drug combinations can then be tuned to the specific needs of each patient. In this talk, I will review the attractions and challenges ahead.
FDA-CDER Use of Modeling and Simulation with an Emphasis on Systems Biology and Safety
Bob Powell, PharmD
Office of Translational Science, Center for Drug Evaluation and Research (CDER), FDA White Oak, MD
CDER scientists employ modeling and simulation (M&S) to predict/anticipate drug toxicity, evaluate and compare trial designs, and assess the safety and efficacy of new drug submission requests for marketing. Scientists are using three types of M&S based on structure activity relationships, systems biology mechanistic modeling, and empirical efficacy and safety data modeling using pharmacokinetic-pharmacodynamic principles. The presentation will present a basic framework for these applications along with the bioinformatic systems being built. Emphasis will be placed on two systems biology projects designed to help CDER scientists anticipate both cardiovascular toxicity and hepatotoxicity. Safety science in the clinical domain is generally focused on signal detection in large numbers of patients followed by confirmation. Our interest in these systems is based on a desire to understand the individual patient characteristics that place some, but not all patients at risk in a given scenario. We are also interested to use tools such as these for knowledge management and sharing. Modeling and simulation can also be used to contrast drugs in class to estimate relative risk based on pharmacology, disease and patient characteristics.
Application of Threshold of Toxicological Concern in Food Safety Decisions
Ian C. Munro, PhD, FATS, FRCPath
Executive Vice President, Senior Scientific Consultant, Cantox Health Sciences International, 2233 Argentia Road, Suite 308, Mississauga, ON, Canada L5N 2X7, Barbara Danielewska-Nikiel, B.Sc., M.Sc., Scientist, Cantox Health Sciences International, 2233 Argentia Road, Suite 308, Mississauga, ON, Canada L5N 2X7
The Threshold of Toxicological Concern (TTC) concept is based on the premise that for all chemicals, with the possible exception of genotoxic carcinogens, a threshold of exposure exists below which there is no significant risk of adverse effects regardless of the duration of exposure. TTC values have been developed for the three structural classes of chemicals elaborated by Cramer et al. (1978) based on dose-response/no-observed adverse effect levels for over 600 chemicals. These TTC values, along with data on metabolism and exposure, have been used by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) for the safety evaluation of flavoring substances. The TTC can be applied in the safety evaluation of food additives and flavors, even in the absence of chemical-specific toxicity data, provided the structure and exposure to the substance are well established. The TTC procedure used by JECFA for the safety evaluation of flavouring agents has been validated by conducting parallel safety evaluations using conventional approaches. It is recommended that the TTC approach be expanded to include other chemicals to which humans are exposed.
Management of Genotoxic Impurities in Pharmaceuticals With the Threshold of Toxicological Concern
Timothy J. McGovern, PhD
SciLucent, LLC, Herndon, VA
Safety concerns regarding known or suspected genotoxic impurities in pharmaceutical products have become more prominent in the last decade. When regulators identified concerns, delays often occurred in pharmaceutical development programs, at least partially due to the lack of consistent regulatory guidance. The Committee for Medicinal Products for Human Use (CHMP) of the EMEA and the Center for Drug Evaluation and Research (CDER) of the US FDA subsequently released guidance (final and draft, respectively) on how best to deal with these impurities in 2006 and 2008. The recommendations include the use of toxicological thresholds as one acceptable approach for setting acceptable daily exposure levels. The recommended thresholds are based on a previous Threshold of Regulation approach developed by US FDA’s Center for Food Safety and Nutrition for food contact materials set on the determination of a virtually safe dose derived from a carcinogenic potency data base. This session will discuss the derivation of the TTC by the CHMP and CDER and will describe how the TTC is applied to the regulation of genotoxic impurites in pharmaceutical products.
Use of Threshold of Toxicological Concern in the Risk Assessment of Personal Care Products
Susan P. Felter
Procter & Gamble
In the absence of chemical-specific data, TTC provides a method to determine a conservative estimate of a chronic oral exposure below which there is a very low probability of risk. The utility of TTC as a pragmatic risk assessment tool has been well-established and accepted by regulatory bodies in a number of areas (eg, indirect food additives, flavor chemicals, genotoxic impurities in pharmaceuticals). Another area for which TTC has received extensive consideration is in the area of cosmetics and personal and household care products. In extending the applicability of TTC to these areas, a number of factors have been considered including the chemical domain of the databases supporting the TTC exposure limits, how relative bioavailability can be addressed for dermal exposures, and how less-than-lifetime exposures might be considered. In addition, recent work has focused on how TTC might be used to support complex mixtures such as botanical extracts, and how the principles of TTC might be extended to address local effects such as allergic contact dermatitis and effects in the respiratory tract following inhalation. This talk will provide an overview of how these issues have been addressed and what opportunities remain for further expansion of TTC as a first-tier risk assessment tool to evaluate and substantiate human safety of low-level exposures and appropriately focus societal resources to avoid unnecessary animal testing.
Use of the Threshold of Toxicological Concern (TTC) for Extractables/Leachables Evaluation Strategies Relevant to Pharmaceutical Container / Closure Systems
Courtney Callis
Lilly Research Laboratories, Health/Safety/Environmental, Eli Lilly and Company
Plastics, elastomers, and protective coatings are components of container closure systems used to store and dispense pharmaceutical products. Since drug products will come into contact with these polymeric materials, a thorough evaluation is integral to understanding leachables as potential contaminants. Toxicology consultation is important in the early development of analytical strategies when extractables information is used as a surrogate for potential leachables. The toxicologist conducts a risk assessment to develop safe limits for each identified extractable and then quantifies margins of safety relative to maximum potential patient exposures. Extractables limits are subsequently used in the risk management of leachables. Analytical protocols are developed for leachables testing from container/closures into drug product based on the identified extractables. The corresponding safe limits can influence method development and the degree of validation. Sometimes, data are not available and chemical-specific risk assessments are not possible. This presentation will describe how the threshold of toxicological concern (TTC) can be used as part of an overall strategy for extractables assessment when toxicology data are limited. The TTC can also be used to support as-low-as-reasonably practicable (ALARP) analytical evaluation thresholds for unknown peaks in leachables studies. Case examples will be highlighted to illustrate the application.
History of Spaceflight Toxicology
John T. James, PhD
NASA Chief Toxicologist, Space Tox Office-Space Life Sciences, Houston TX
After a half-century of human spaceflight, the community of space-faring nations has accumulated a diverse and sometimes harrowing history of toxicological events that have plagued space endeavors almost from the very beginning. Lessons have been learned in ground-based test beds and others were discovered the hard way - when human lives were at stake in space. We, of course, are aware that many propellants are highly toxic compounds, yet we have not always been able to thoroughly isolate the crew from exposure to these toxicants. Leakage of fluids from systems has resulted in hazardous conditions at times, and the behavior of such compounds inside a spacecraft has taught us how to manage potentially harmful escapes should they occur. Combustion events are an ever-present threat to the wellbeing of the crew. Such events have been sufficiently common that we have learned that one cannot judge the health threat of a given fire by the apparent seriousness of the event. Management of such risks demands monitoring of combustion products. In the category of unpredictable toxic events, if one assumes that fires are predictable, we can place experience with toxic microbial metabolites, upsets during repair operations, and discharges from filters that have accumulated a substantial load of pollutants in their absorption beds. We have learned that relatively harmless compounds can be converted by air revitalization systems into compounds that cause serious harm to the crew. Our toxic risk management strategy now includes an assessment of the fate of any compound that might be released into the atmosphere, and in addition, the environmental engineers determine if a compound could poison the air purification filter beds and thereby reduce their ability to protect crew health. We recognize that mistakes are an integral part of any human activity, and the space-faring community must learn as much as possible from mistakes that result in toxic exposures to crews and from mistakes that were near misses.
Spacecraft Maximum Allowable Concentrations (SMACS)
Rochelle W. Tyl, PhD, DABT, Distinguished Fellow
RTI International, Res Triangle Pk, NC
In the early 1990s NASA began to work with a subcommittee of the National Research Council Committee on Toxicology to set and formally document exposure standards for astronauts. The standards were initially applied to continuous exposure lengths from 1 hour to 180 days, which was the longest expected stay on the International Space Station. More recently, many of the standards have been extended to exposure times up to 1000 days in anticipation of long-duration missions to Mars or one of its moons. The scientific interplay during the setting of SMACs has embraced a number of novel approaches to setting limits for astronaut exposure.
Spacecraft Water Exposure Guidelines (SWEGS)
Kenneth E. Thummel, PhD
Professor, Dept Pharmaceutics, University of Washington, Department Physics Health Sci Bldg., Seattle, WA
In the later 1990s as NASA anticipated more thorough recovery of water aboard the International Space Station from humidity condensate and urine, the need for unique water quality standards was recognized. NASA engaged a subcommittee of the National Research Council Committee on Toxicology to assist in developing and thoroughly documenting SWEGs for periods of recovered water consumption from 1 day to 1000 days. During the process of developing SWEGs a number of novel approaches were employed to support the guidelines, including benchmark dose modeling and ten Berge time-dose extrapolations. Application of these approaches will be discussed.
Risk-Based Monitoring of Spacecraft Pollutant
Noreen Nicole Khan-Mayberry, PhD
Space Toxicologist, NASA, Houston, TX
As air and water quality standards became available specifically for human spaceflight, the need to perform real-time, onboard monitoring of some of the riskiest compounds became evident. NASA has developed and used various instruments to monitor selected combustion products since the early 1990s. We have targeted other pollutants for monitoring including carbon dioxide, propellants, and formaldehyde. NASA has also developed broad-spectrum trace organic analyzers for air quality monitoring aboard the International Space Station. In addition, a total organic carbon analyzer has been flown to monitor water quality as we begin to recover water from urine.
Lunar Dust Pulmonary Toxicity
Chiu-wing Lam, PhD
Senior Toxicologist, Wyle Labs - Space Life Sciences, Houston, TX
During the Apollo era of spaceflight astronauts were exposed briefly to lunar dust, and a few had relatively minor respiratory symptoms. As NASA embarks on much longer mission to the moon, the possibility of repeated and prolonged exposures to lunar dust must be considered. We are in the process of developing a database by intratracheal instillation and nose-only inhalation in rodents to support an evidence-based exposure standard for a lunar habitat. This is made challenging by the expectation that lunar dust has reactive surfaces caused by the harsh radiation environment of the moon’s surface and the total absence of compounds with which dust surface reactions can occur. Because of the extreme limitations in the availability of authentic lunar dust and the challenges in “reactivating” it, we have devised novel approaches to developing a suitable toxicological database.
Respiratory Tract Lining Fluids (RTLFS): First Reactants With Cigarette Smoke (CS)
Carroll E. Cross, MD
School of Medicine, University of California, Davis
Airway and parenchymal RTLFs contain significant amounts of antioxidant substances including low molecular weight compounds such as glutathione (GSH), antioxidant micronutrients including vitamins C and E and uric acid, high molecular weight protein thiols and glycoconjugates including mucus glycoproteins, and small amounts of antioxidant enzymes and iron chelating proteins. CS contains a large group of chemical species, many of which will interact with RTLFs, importantly including the aforementioned protective RTLF antioxidant constituents, thus ameliorating the overall impact of oxidative CS toxicants on RT cellular constituents. Unneutralized CS constituents, including both gaseous and particulate fractions, remain to damage the underlying RT epithelium and to activate RT inflammatory-immune processes. These latter processes constitute a considerable additional oxidative stress to RTLFs and to the underlying RT epithelial cells. Abundant supporting evidences document that CS-related oxidative stress exists at RT surfaces and that this stress contributes to the RT injury and dysfunctional reparative responses in CS-related chronic obstructive pulmonary diseases (COPD). The challenge is to further develop approaches that could specifically address this oxidative stress.
Ultrafine Particles, Inflammation, and Human Health
Mark W. Frampton MD
University of Rochester Medical Center, Rochester, NY
Research conducted over the past 15 years has established that exposure to particulate matter (PM) air pollution is a major public health issue. Exposure to PM is associated with increased risk for both respiratory and cardiovascular morbidity and mortality. Understanding the mechanisms involved, and the PM characteristics that confer the greatest risks, are important priorities. Ultrafine particles (UFP, size less than 100 nm) may contribute to the respiratory and cardiovascular health effects associated with exposure to PM. UFP behave differently than larger particles because they have a very large surface area, but very little mass. They tend to evade typical airway clearance mechanisms, and have the ability to diffuse across cell membranes and enter cell organelles. It is possible that they have direct effects on vascular structures, and may enter the circulation via the pulmonary capillaries.
Our studies suggest that inhalation of carbon ultrafine particles, at concentrations that can be experienced on a busy highway, induce subtle acute changes in both the pulmonary and systemic vascular beds, possibly induced by injury or activation of vascular endothelial cells. These effects occur without inducing significant airway inflammation. In adults with type 2 diabetes, inhalation of carbon UFP activates blood platelets. We have now extended our studies using the Harvard Ultrafine Concentrated Ambient Particle System (HUCAPS), which concentrates outdoor UFP for use in human clinical studies. Preliminary findings indicate that outdoor concentrated ultrafine particles transiently increase the blood pressure, and cause small reductions in lung function, in healthy subjects. These human studies provide insights into mechanisms by which PM may contribute to the burden of pulmonary and cardiovascular disease, and provide data to inform efforts in improving air quality.
Assessing the Role of Surface Characteristics in Nanoparticle-Related Pulmonary Toxicity and Inflammation
David B. Warheit1, Kenneth L. Reed1, Christie M. Sayes2
1 DuPont Haskell Global Centers for Health and Environmental Sciences, Newark, DE
2 Texas A&M University, College Station, TX
A variety of pulmonary hazard studies in rats have demonstrated that exposures to ultrafine or nanoparticles (generally defined as particles in the size range < 100 nm) produce more intensive inflammatory responses when compared with bulk-sized particle-types of similar chemical composition. However, this common perception of greater nanoparticle toxicity is based on a limited number of studies with titanium dioxide and carbon black particle-types. Apart from variables such as particle size and surface area, it is conceivable that several other physicochemical characteristics could play more significant roles in facilitating the development of nanoparticle-related toxicity. These include but are not limited to: 1) Surface reactivity of particle-types 2) surface coatings; 3) aggregation/disaggregation potential; and 4) the method of nanoparticle synthesis. Results of pulmonary bioassay hazard/safety studies with quartz particles of varying sizes/surface areas demonstrated that intratracheal instillation exposures to fine-sized, Min-U-Sil quartz particles (0.5 µm – 5 m2/g (surface area)) produced (persistent) enhanced pulmonary toxicity (inflammation, cytotoxicity, cell proliferation and/or histopathology) in rats when compared to nanoscale quartz particles (50 nm-31 m2/g), but not when compared to smaller nanoquartz sizes (eg, 12 nm- 91 m2/g). The toxicity results correlated with red blood cell hemolytic potency. In a second pulmonary bioassay study in rats, no measurable differences in pulmonary effects were evident when comparing impact of exposures to either 1) fine-sized TiO2 particles (300 nm – 6 m2/g (surface area); 2) TiO2 nanodots (6-10 nm–169 m2/g); or 3) TiO2 nanorods (25 m2/g). In a third study, pulmonary hazard effects were measured following exposures to three different nano TiO2 particle-types, each with similar particle size distributions. The various TiO2 particles differed in their crystal structures and surface reactivity endpoints as measured by the Vitamin C yellowing assay. Moreover, the surface characteristics correlated with potency of hazard endpoints as described above, in these dose/response, time-course studies. It is concluded that particle surface reactivity, rather than particle size/surface area endpoints correlated best with lung inflammatory potency following exposures to particles.
Development of Chronic Bronchitis and Emphysema in Beta-Epithelial Na+ Channel-Overexpressing Mice: Role of Airway Surface Dehydration in the Pathogenesis of COPD
Jack R. Harkema
Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, MI, USA
Chronic obstructive pulmonary disease (COPD) is a leading cause of death, but its pathogenesis is not fully known. Airway surface dehydration is a key feature in cystic fibrosis and other forms of COPD. Recent studies have shown that dehydration of airway surface fluid in beta-epithelial Na+ channel (βENaC)-overexpressing mice cause a chronic lung disease with high neonatal mortality due to mucus obstruction of airways and the development chronic bronchitis and emphysema in surviving adult mice (Mall et al., Am J Respir Crit Care Med 177: 730, 2008). The current presentation will review the development of this transgenic animal model and how it has contributed to our understanding of the role of airway surface hydration in respiratory health and disease. βENaC-overexpressing mice develop tracheal mucus obstruction in the first days of life with associated hypoxia, airway epithelial necrosis, and death. Surviving βENaC-overexpressing mice develop bronchial mucus obstruction accompanied by mucous cell metaplasia, increased mucin expression, and airway inflammation with transient increases in tumor necrosis factor-α and macrophages, IL-13 and eosinophils, and persistent increases in keratinocyte-derived cytokine, neutrophils and chitinases in the lung. βENaC-overexpressing mice also develop emphysema with increased lung volumes, distal airspace enlargement, and increased lung compliance. These results demonstrate that airway surface dehydration in mice is sufficient to cause key pathologic features of COPD that includes persistent pulmonary inflammation, airway mucus obstruction, and emphysema. This suggests that deficient airway surface hydration may play a critical role in the pathogenesis of COPD of different etiologies and serve as a target for novel therapies.