From Diagnosis to Conclusion

1. From Diagnosis to Conclusion Jeffery A. Engelhardt, DVM, PhD, DACVP Amgen Inc. Thousand Oaks, CA

2. Pathologist’s narrative Written pathology interpretation • Detailed description of findings • Clear interpretation and best judgment of importance of findings • Provide assurance that a thorough evaluation was conducted • Concise and explicit wording • Analysis is based on the treatment cohort rather than effects on individual animals • Need to consider individual effects in non-rodent species

3. Pathologist’s narrative A clear well written pathology report is not always what is produced Influenced by a variety of factors • Experience of the pathologist • Experience or perceptions of the sponsor

4. What does the Sponsor want from the narrative? Sponsors will vary in expectations of the pathology reports from • Data tabulation of what occurred • Identification of compound-induced changes • Integrated assessment of effects in the test groups • Correlative presentation of effects in relation to exposure

5. What does the Reviewer need from the narrative? Assessors need to know what was seen and what the pathologist thought of the findings • Clear indication of how data was assessed Do not need • Obtuse or verbose presentation where significant findings are buried within the narrative • Data dump lacking interpretation • Broad sweeping assessments lacking rationale • Vague diagnoses

6. How are data sets integrated? Varies among pathologists based upon training, experience, and conventions of employer Generally need to evaluate data in terms of population pathology

7. How are data sets integrated? Many ways to look at data sets • Statistical basis • Diagnosis basis • Incidence basis • Incidence and severity • Trends • Cut-off values for percentage increase in a parameter • Dose responsive or not • Spectrum of findings for a organ or system

8. Correlation of animal toxicity to man Up to 71% correlation when similar organ systems are affected in both rodent and non-rodent species 63% correlation when only non-rodent affected 43% correlation when only rodent affected Olson H, et al. 2000. Reg Toxicol Pharmacol. 32:56-67.

9. Correlation of animal toxicity to man Greatest correlation in predicting human adverse effects in • Hematological system • Gastrointestinal system • Cardiovascular system Least predictive for effects on skin and hepatobiliary system Olson H, et al. 2000. Reg Toxicol Pharmacol. 32:56-67.

10. Special areas of interpretation Systemic effects in animals in toxicology studies may have multi-factorial pathogenesis • Predominant pathway may be the most obvious or expedient, but others should be considered More than one way to look at a particular finding

11. Special areas of interpretation Stress • Multiple organs affected with correlative organ weight, morphologic, and clinical pathology effects • i.e., adrenal weights with hypertrophy, lymphocyte counts • Sometimes correlates are incomplete or inconclusive, so this may become a catch-all diagnosis • “All other effects on organ weights, etc., could be attributed to stress” • Need to present clear evidence to support this diagnosis

12. Special areas of interpretation Dehydration • Multiple clinical pathology parameters support this diagnosis • Systemic effects on clinical pathology parameters • Present the correlative evidence in the narrative • Need to sort out primary and secondary effects on organs • What is really due to the test article? • Need to determine cause of dehydration • Often attributed to mechanical defect in watering system

13. Special areas of interpretation Body weight loss • What is the cause • Decreased food consumption • Decreased body weight gain • EFU • Effects on organ weights and anatomic pathology • “Pattern of organ weight effects most consistent with effects on body weight” • Loss of body weight can lead to sweeping statements • Need to look closely for correlates in affected animals

14. Issues open to multiple interpretations Evaluation of data sets is always influenced by training and experience • “I’ve seen this before” syndrome Transferability of findings across species is not always correct or appropriate Influence of internal review • Stand-alone pathology report • Combined toxicology report

15. Cause of death The pathologist is responsible for identification of the cause of death as part of the interpretation of compound-induced effects If cause of death is not apparent, this should be recorded as undetermined Causes of death may include neoplasms, cardiomyopathy, chronic renal disease, trauma, or infectious diseases G. Long Toxicol. Pathol. 32:269-270, 2004

16. Cause of death Cause of death for each animal should be determined qualitatively and utilize professional judgment • An interpretive diagnosis Determination of cause of death is not always clear • Proximate cause may be difficult to identify • Diagnosis should be the overall process leading to the proximate cause • Contributory changes in organs may be integrated G. Long Toxicol. Pathol. 32:269-270, 2004

17. Pathologist’s narrative – What should be In-depth discussion with perspective to support safety assessment • Statistical versus biological importance • Clear explanation of cause of death • Was mortality due to test compound? Perspective on similar lesions induced by other compounds, a common mechanism of action, or spontaneous disease • At least list critical references • Historical data

18. Pathologist’s narrative – What should be Correlation to other changes in the animals • Clinical observations • Aid in identifying target organs and potential mechanisms of action/toxicity • Body and organ weights • Primary and secondary effects on tissues • Hematology, clinical chemistry, and urinalysis data • Potential markers to monitor in patients • Metabolism and toxicokinetic data • Margins of exposure

19. Pathologist’s narrative – What should be Large doses are used to assure measurable effects will occur in small populations of animals • Highest dose should cause overt toxicity • Lowest dose should not cause any toxic effects (NOEL) • NOAEL • Clear indication of criteria used to determine “adverse” Perspective needs to be discussed by the pathologist • Work with the Study Director to provide a balanced integration and interpretation of the overall study

20. Pathology peer review Quality control mechanism • Ensure accuracy and completeness in recording histopathological findings • Control observational bias by the histopathologist • Standardize terminology and diagnostic criteria • Confirm target organs • Confirm NOEL and NOAEL

21. Pathology peer review A second evaluation of a subset of animals and tissues • All tissues from 10% or minimum of 3/sex in high dose and control groups • Target tissues and equivocal alterations • Verification of cause of death Ensures accuracy and consistency of terminology and severity grades for compound-related findings • Necessary to determine NOEL and NOAEL Reviews the validity of the interpretation

22. Pathology peer review Differences of opinion • Consensus • Literature, consultation, pathology working group • Non-substantive • Minor differences in terminology or grading that have no bearing on the overall interpretation of a study • Substantive • Identification of important new pathologic changes or differences of a least two severity grades

23. Pathology peer review Document peer review with a signed Peer Review Certificate • Study Identification • Purpose and process of the review • Results of the review • How any differences in opinion were resolved Worksheets and all other records made during review are not retained

24. Summary Pathology data are qualitative, subjective, and descriptive rather than quantitative and objective • Causes interpretation differences and misunderstanding by regulatory assessors and sponsor toxicologists Pathologists need to provide a detailed description of compound-induced effects and ensure that important findings are understood • Use standard and meaningful terminology to aid understanding by non-pathologist

25. Summary - The pathologist’s narrative Describes potential pathogenesis of important findings for the regulatory assessor to understand what has occurred in animals Facilitates appropriate evaluation of toxicity and risk assessment of a new drug Allows clinical investigators to understand potential adverse effects in humans

26. Conclusion The pathology evaluation should ensure that compound-induced alterations are presented • Clearly • Consistently • Accurately • Understandably Importance of the findings for safety is explicitly identified for inclusion in the various regulatory documents

27. Questions

28. Panel Discussion Toxicologic Pathology: From Diagnosis to Interpretive Narrative What Pathologists Supply Versus What Reviewers Need