Organ Toxicity in Drug Development: Biomarkers and Novel Approaches

Organizers: Supriya Jayadev, Boehringer-Ingelheim Pharmaceuticals, Inc.; Marla Weetall, PTC Therapeutics, Inc.; David Brewster, Hoffmann-La Roche Inc.

Traditional preclinical toxicology approaches are often inadequate to detect adverse events or provide insufficient understanding of the mechanism to evaluate relevance of preclinical findings to the clinical setting. Scientists are now turning to novel approaches and biomarkers to enable early identification of target-organ toxicity. Emerging methods include imaging, novel biomarkers, and in silico predictions. To better understand the value of incorporating novel approaches in preclinical toxicology assessments, this symposium will focus on three key areas of concern - cardiotoxicity, hepatotoxicity, and immunotoxicity. Sessions will focus on case studies, novel evaluation methods, regulatory perspectives, and bridging from the preclinical to the clinical setting.

Abstracts

Can altered myocardial Ca²⁺ handling be used as a biomarker for assessing cardiomyopathy and arrhythmogenesis of drug candidates?
Liang Guo, Hoffmann-La Roche Inc.

Alteration in intracellular Ca²⁺(Ca²⁺_i) regulation has been implicated in drug-induced cardiomyopathy and arrhythmogenesis. Thus, analysis of myocardial Ca²⁺_i dynamics may hold the predictive value for early identification of cardiac liabilities of new molecule entities. Ca²⁺ imaging experiments utilizing Fura-2 fluorescent dye in cultured guinea pig cardiomyocytes were conducted to characterize Ca²⁺_i perturbation, as caused by 15 marketed drugs that possess diverse cardiac liabilities through different modes of action. Results of this pilot study provide evidence, as a "proof of concept", demonstrating that altered Ca²⁺_i handling may be used as a valuable functional biomarker in early cardiac drug safety assessment.

A 28-Day Mechanistic Safety Study in Rhesus Monkeys on Hepatitis C Virus Protease Inhibitor BILN 2061:Lessons Learned
James Stoltz, Boehringer-Ingelheim Pharmaceuticals, Inc.

BILN 2061 is a potent, novel, orally bioavailable, reversible inhibitor of the hepatitis C virus NS3/NS4A serine protease required for viral replication. The early successful clinical proof of principle with BILN 2061 was offset by later preclinical safety studies in Rhesus monkeys that demonstrated a cardiotoxicity characterized by myocardial vacuolation, that corresponded to swollen mitochondria ultrastructurally. Here we describe an experiment designed to investigate the nature, onset and reversibility of the lesion, and explore biomarkers (echocardiography, electrocardiography, clinical chemistry) for the change.

Cardiotoxicity of Cancer Chemotherapy: Recent Advances in Molecular Mechanisms and Novel Strategies for its Prevention
Diwakar Jain, Drexel University College of Medicine

Cardiotoxicity is a serious complication of several groups of cancer chemotherapeutic agents such as anthracyclines, taxanes, and Erb-b2 receptor blockers (tyrokinase receptor blockers). The mechanism of cardiotoxicity of these agents is different. Doxorubicin, an anthracycle antibiotic is used quite extensively in cancer chemotherapy. This results in left ventricular dysfunction and heart failure in a significant proportion of patients receiving this medication. Serial left ventricular function monitoring with equilibrium radionuclide angiocardiography (MUGA) during the course of cancer chemotherapy is probably the most effective strategy for the prevention of overt heart failure. However, recent advances in our understanding of the molecular mechanims of cardiotoxicity of this agent offer unique new opportunities for preventing its cardiotoxicity.

Qualification of Biomarkers of Cardiovascular Toxicity for Nonclinical Regulatory Studies
James Weaver, Food and Drug Administration/CDER

The U.S. Food & Drug Administration has developed a process to qualify new biomarkers for use in studies submitted in support of a regulatory application. This process is designed to develop and evaluate data to support the use of the biomarker for a specific purpose. Biomarkers that are being developed for cardiotoxicity and for vascular injury in preclinical species will be used to illustrate this process.

Predicting Drug-Induced Liver Injury (DILI): Safer Drugs or Safer Patients?
Jinghai James Xu, Merck & Co. Inc.

The goal of responsible medical treatment has always been personalized medicine, i.e., administering the right medicine at the right dose to the right people. However, general applicability of the current genetic- or genomic-centric view of personalized medicine in drug toxicity is debatable. With regard to predicting DILI, the goal of identifying safer patients through human genetics or genomics may not be as cost-effective as identifying safer drugs earlier in the drug R&D process. Finally, recent successes in applying systems biology and cellular imaging technology towards predicting drug hepatotoxicity will be discussed.

Characterizing Idiosyncratic Drug-Induced Liver Injury in Individual Laboratory Animals for Application to Study of Human Drug-Induced Liver Injuries
John R. Senior, Food and Drug Administration/CDER

Drug-induced liver injury (DILI) is a serious and growing problem, accounting for more acute liver failure in the United States than all other causes combined, and is a leading reason for failure of drugs in development and withdrawal of approved drugs from the market. Conventional preclinical toxicology studies have been successful in preventing many overt toxicants from being investigated or approved, but discordance between animal and human responses has been substantial. We offer, for consideration and debate, a proposal that prospective studies of idiosyncratic DILI responses in modest numbers of conventional laboratory animals be explored as a pathway to instruct clinicians and investigators how to identify truly susceptible individuals to exclude them from exposure to a drug they cannot tolerate or adapt to, while allowing the great majority of others to use the drug safely.

Using Clinical Trials to Identify Biomarkers of Hepatotoxicity
Paul Watkins, University of North Carolina, Chapel Hill

The current FDA draft guidance for evaluating liver safety in clinical trials suggests continuing treatment of patients with signs of mild liver injury to determine whether the liver injury will subside (adaptation) or advance to a "Hy's Law Case". This is because there are currently no biomarkers capable to identifying severe liver injury potential before a subject develops severe liver injury. A draft report for the Institute of Medicine (Oct-08) has recommended standardized collection of clinical data, genomic DNA, and serial serum and urine collections in phase 3 clinical trials once a liver safety signal appears. This recommendation is based on the hypothesis that application of genetic, transcriptomic, proteomic and metabolomic technologies will identify more sensitive and biomarkers of serious liver injury potential. Data obtained in healthy volunteers treated with acetaminophen support this hypothesis.

Non-Clinical Drug Hypersensitivity Testing: Challenges and Future Approaches
Thomas T. Kawabata, Pfizer Global Research and Development

Standard non-clinical toxicity testing methods are not predictive of hypersensitivity (allergic) reactions in humans. For many years, investigators have been trying to develop animal models to investigate mechanisms and risk factors of hypersensitivity reactions with low MW drugs with limited success. Recent advances in immunology, a greater understanding of mechanisms of reactions in humans and re-evaluation of methods developed in the past, may lead to the development of predictive methods. Methods being explored include a combination of in vivo and in vitro methods that may help rank order compounds for potential allergenicity during the discovery phase before the selection of a clinical candidate.

Case Study: CXCR2 Antagonist
Ellen Evans, Schering-Plough Corporation

SCH 527123 is a small molecule which antagonizes the CXC2 receptor, responsible for neutrophil chemotaxis to sites of inflammation. It is currently under development for Chronic Obstructive Pulmonary Disease. A comprehensive and on-going assessment of immune function has been an important aspect of the development program, and has included assays and endpoints in Discovery, nonclinical drug safety studies, and clinical trials.

Biomarkers of Immunotoxicology in the Regulatory Realm: A Reviewer's Perspective
Sally Hargus, Food and Drug Administration/CDER

Detection and management of toxicity to the immune system during the discovery and development of drug- and biologic-based therapies is an important issue for regulators, pharmaceutical companies, and the public. Immunotoxicity-related concerns may be raised for many product types that are under the regulatory purview of the US FDA, and FDA Regulatory Scientists recognize that there would be a potential benefit in developing biomarkers of immunotoxicity in animal models and/or humans, provided they are reliably predictive. However, the complexity of the immune system and immune responses to various stimuli, and the inter-individual and inter-species variability in responses, makes for challenging discovery and development programs for these biomarkers. Dr. Hargus will present a CDER Pharmacology/Toxicology Regulatory Reviewer's perspective on various aspects of biomarkers in the context of "regulatory immunotoxicology".

Translational Toxicology and the Work of the Predictive Safety Testing Consortium
William B. Mattes, The Critical Path Institute

Safety Assessment has always been a "translational" science in that results in animal models were used to anticipate adverse responses in humans. However, many problematic drug-induced adverse events in humans are not well predicted in animal or early clinical studies. In some cases the tools (e.g., histopathology) relied upon in preclinical studies do not have truly translational, non-invasive correlative biomarkers that could be measured in, for example, blood or urine. The Predictive Safety Testing Consortium, made up of regulatory authorities, pharmaceutical companies, and coordinated by the Critical Path Institute, is developing data sets that support the use of sensitive and specific novel safety biomarkers in translational toxicology, where the biomarker allows the assessment of safety in animal models and in humans. As an example, current developments in biomarkers of renal injury will be discussed.