Abstract:One of the most important quantitative outputs from toxicity studies is identi cation of the highest exposure level (dose or concentration) that does not cause treatment related effects that could be considered relevant to human health risk assessment. A review of regulatory and other scienti c literature and of current practices has revealed a lack of consistency in de nition and application of frequently used terms such as No Observed Effect Level (NOEL), No Observed Adverse Effect Level (NOAEL), adverse eff… Show more
“…To help address this issue, a European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) initiative, reporting in 2002, organized a task force for addressing adversity in toxicology studies. This effort resulted in a publication by Lewis et al in (2002) that provided the following definitions, which were more specific to findings in toxicologic pathology:…”
Section: Past Definitions Of Adversitymentioning
confidence: 99%
“…Conversely, extremely rare or unfamiliar findings may increase uncertainty regarding adversity and result in a higher degree of conservatism. Factors indicating that an intergroup difference is probably not a test item-related effect include lack of a clear dose-response or pairwise differences between groups, high variability or imprecision of the end point, incidence values within the normal range of biological variation, and/or lack of biological plausibility taking into account preexisting knowledge of the test item (adapted from Lewis et al 2002).…”
Section: Exacerbation Of Spontaneous/background Findingsmentioning
The identification of adverse health effects has a central role in the development and risk/safety assessment of chemical entities and pharmaceuticals. There is currently a need for better alignment regarding how nonclinical adversity is determined and characterized. The European Society of Toxicologic Pathology (ESTP) therefore coordinated a workshop to review available definitions of adversity, weigh determining and qualifying factors of adversity based on case examples, and recommend a practical approach to define and characterize adversity in toxicology reports, to serve as a valuable prerequisite for future organ-or lesion-specific workshops planned by the ESTP.
“…To help address this issue, a European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) initiative, reporting in 2002, organized a task force for addressing adversity in toxicology studies. This effort resulted in a publication by Lewis et al in (2002) that provided the following definitions, which were more specific to findings in toxicologic pathology:…”
Section: Past Definitions Of Adversitymentioning
confidence: 99%
“…Conversely, extremely rare or unfamiliar findings may increase uncertainty regarding adversity and result in a higher degree of conservatism. Factors indicating that an intergroup difference is probably not a test item-related effect include lack of a clear dose-response or pairwise differences between groups, high variability or imprecision of the end point, incidence values within the normal range of biological variation, and/or lack of biological plausibility taking into account preexisting knowledge of the test item (adapted from Lewis et al 2002).…”
Section: Exacerbation Of Spontaneous/background Findingsmentioning
The identification of adverse health effects has a central role in the development and risk/safety assessment of chemical entities and pharmaceuticals. There is currently a need for better alignment regarding how nonclinical adversity is determined and characterized. The European Society of Toxicologic Pathology (ESTP) therefore coordinated a workshop to review available definitions of adversity, weigh determining and qualifying factors of adversity based on case examples, and recommend a practical approach to define and characterize adversity in toxicology reports, to serve as a valuable prerequisite for future organ-or lesion-specific workshops planned by the ESTP.
“…. affects the performance of the whole organism's ability to respond to an additional environmental challenge'' (Lewis et al 2002). Another widely accepted definition is that an adverse effect is ''a change in morphology, physiology, growth, reproduction, development, or life span of an organism which results in impairment of functional capacity or impairment of capacity to compensate for additional stress or increased susceptibility to the harmful effects of other environmental influences'' (WHO/IPCS [International Programme on Chemical Safety] 2004).…”
Section: Hepatic Hypertrophy: Adverse Versus Non-adversementioning
Preclinical toxicity studies have demonstrated that exposure of laboratory animals to liver enzyme inducers during preclinical safety assessment results in a signature of toxicological changes characterized by an increase in liver weight, hepatocellular hypertrophy, cell proliferation, and, frequently in long-term (life-time) studies, hepatocarcinogenesis. Recent advances over the last decade have revealed that for many xenobiotics, these changes may be induced through a common mechanism of action involving activation of the nuclear hormone receptors CAR, PXR, or PPARa. The generation of genetically engineered mice that express altered versions of these nuclear hormone receptors, together with other avenues of investigation, have now demonstrated that sensitivity to many of these effects is rodent-specific. These data are consistent with the available epidemiological and empirical human evidence and lend support to the scientific opinion that these changes have little relevance to man. The ESTP therefore convened an international panel of experts to debate the evidence in order to more clearly define for toxicologic pathologists what is considered adverse in the context of hepatocellular hypertrophy. The results of this workshop concluded that hepatomegaly as a consequence of hepatocellular hypertrophy without histologic or clinical pathology alterations indicative of liver toxicity was considered an adaptive and a non-adverse reaction. This conclusion should normally be reached by an integrative weight of evidence approach.
“…The standard benchmarks typically used in toxicology studies-including the no-observed-effect level (NOEL), no-observed-adverse-effect level (NOAEL), and lowestobserved-adverse-effect level (LOAEL)-are usually not applicable with cytotoxic oncology molecules (Dorato and Englehardt 2005;Lewis et al 2002). Rather, benchmarking in rat and dog studies with oncology therapeutics includes the dose that results in 10% mortality over the duration of the study (STD 10 ) in rats, and the highest non-severely toxic dose (HNSTD), which is defined as a dose that does not produce death or moribundity during a study in rats or dogs.…”
Section: Definitions Of Benchmark Doses In Oncology Testingmentioning
A daunting, unmet medical need exists for effective oncology chemotherapies, with cancer deaths in 2009 to exceed 560,000 in the United States alone. Because of the rapid demise of the majority of cancer patients with metastatic disease, oncology drug development must follow a much different paradigm than therapeutic candidates for less onerous diseases. The majority of drug candidates in development today are targeted at cancer therapy. Many of these candidate chemotherapeutic agents are active against novel targets, often presenting unique toxicological profiles. Since many of these novel targets are not unique to cancer cells, therapeutic margins may not exist. Decision making, in this event, is among the most challenging that any pharmaceutical toxicologist/pathologist or regulator will face. Nonclinical development scientists must compress timelines to present therapeutic options for cancer patients who have failed conventional therapy. In support of this goal, the U. S. Food and Drug Administration has created an oncology-specific paradigm for nonclinical testing and has introduced strategies to accelerate development and approval of successful candidates. Pharmaceutical toxicology testing strategies must not only satisfy regulation as the minimal expectation, but also attempt to reduce the current high attrition rates for oncologic candidates. A successful toxicology testing strategy represents the substance of this treatise.
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