The document discusses the definitions and distinctions between adverse, adaptive, and non-adverse responses in toxicologic pathology, particularly within preclinical studies. It highlights the challenges in defining adverse responses, the criteria for establishing no observed adverse effect levels (NOAEL), and the significance of adaptive responses which may sometimes be adverse. Recommendations for evaluating and reporting toxicological findings are also provided, emphasizing a paradigm shift towards non-animal testing methodologies.

1. Adverse, Non-adverse and Adaptive
Responses in Toxicologic Pathology
International Academy of Toxicology
Pathology (IATP) Lecture
Robert R. Maronpot
Website: focusontoxpath.com32nd JSTP Annual Meeting, Takamatsu, Japan

2. Acknowledgements
• Photomicrographs
– National Toxicology Program Archives
– NTP Non-neoplastic Lesion Atlas
– Dr. Rick Hailey
– Dr. Peter Mann
– Dr. David Malarkey
• Japanese translations
– Dr. Katsuhiko Yoshizawa

3. Outline of Presentation
• Definitions
– Adverse response
– Adaptive response
– Reversible response
– Exacerbation of background lesions
• For the Toxicology Report & Regulatory
Submission
• Paradigm Shift & Determining Adversity
• Practical Examples of Adverse and Adaptive
Responses in Preclinical Studies

4. Adverse Response
There is no perfect definition of an
adverse response in a preclinical study.
前臨床試験におけるadverse（有害性）
反応の完璧な定義はない

5. Adverse Response
• A biochemical, morphological or physiological
change (in response to a stimulus) that either
singly or in combination adversely affects the
performance of the whole organism or
reduces the organism’s ability to respond to
an additional environmental challenge
Lewis et al., Toxicol Pathol 30:66-74 (2002)

6. Adverse Response
• In very broad terms, an adverse finding may be
considered to be a change (biochemical,
functional, or structural) that may impair
performance and generally has a detrimental
effect on growth, development, or life span of a
non-clinical toxicology model.
• More specifically, an adverse effect in a non-
clinical toxicology study should be an effect that
would be unacceptable if it occurred in a human
clinical trial (FDA Guidance, 2002).
Dorato & Englehardt, Reg Tox & Pharmacol 42:265-274 (2005)

7. Adverse Effect
• The judgment on the adverse nature of an
observation in a non-clinical toxicology study
is subject to discussion, challenge, and
reinterpretation.
• 前臨床試験で観察されたadverse（有害性）の判断
は、ディスカッション、チャレンジおよび解釈を必要と
する。
Dorato & Englehardt, Reg Tox & Pharmacol 2005

8. Adverse Response
• A change in morphology, physiology, growth,
development, reproduction, or life span of a cell
or organism, system, or (sub)population that
results in:
– impairment of functional capacity
– 機能的なｷｬﾊﾟｼﾃｨ‐を損なう
– impairment of the capacity to compensate for
additional stress or
– 付加的なストレスを補うｷｬﾊﾟｼﾃｨｰを損なう
– increase in susceptibility to other influences
– 他の影響に対する感受性が増加する
Keller et al., Toxicol Sci 2012

9. No Observed Adverse Effect Level
(NOAEL)
• Highest dose or exposure that does not cause a
toxicologically relevant increase in frequency or
severity of effects between exposed and control
groups based on careful biological and statistical
analysis.
• Minimum toxic or pharmacodynamic responses
may occur at the NOAEL and may not endanger
human health or be precursors to serious events
with continued duration of exposure.
Dorato & Englehardt 2005

10. NOAEL (Keller et al., 2012)
• Highest exposure level with no significant increases in
the frequency or severity of adverse effects between
exposed population and its appropriate control.
• 投与群と適切な対照群との間で、adverse effect（有害作用）
の頻度・程度に関して有意な増加がみられない最も高い暴
露量
• Significance is considered with regard to biological
significance in the test species and may also
incorporate statistical significance.
• 有意性とは、試験動物において生物学的に意味があるとい
うことであり、統計学的な有意差を含んでいることもある。

11. Two Recent Publications
• Scientific and Regulatory Policy Committee:
Recommended (“Best”) Practices for
Determining, Communicating, and Using Adverse
Effect Data from Nonclinical Studies
– Kerlin et al., 2015 Toxicologic Pathology
(DOI:10.1177.0192623315623265)
• Characterizing “Adversity” of Pathology Findings
in Nonclinical Toxicity Studies: Results from the
4th ESTP International Expert Workshop
– Palazzi et al., 2016 Toxicologic Pathology (In Press)

12. STP Recommendations
• Judgment if a test article effect in a nonclinical study is
adverse or nonadverse must be clearly stated in the study
report
• 前臨床試験において、被験物質の影響がadverse（有害性）である
かの判断は、試験報告書に明確に言及しなければならない
• Adversity in a nonclinical study should be applied only to the test
species used in that study
• 前臨床試験におけるadversity（有害性）は、その試験で使用した
動物種のみに適応すべきである
• Setting a NOAEL for a test article should be stated in an overview
document based on data from multiple studies.
• 被験物質に対するNOAELの設定は、多くの試験データに基づいた
概要書に言及されるべきである

13. STP Recommendations
• All available data from nonclinical studies must be
evaluated together to define potential toxicities and
predict human risk.
• 潜在的な毒性の明確化とヒトへのリスク予測のために、前臨床
試験の全ての利用できるデータは評価されなければならない
• Communication of adverse findings and NOAEL should include
direct participation of contributing scientific disciplines
(toxicologists, pathologists, risk assessore, etc.) in assessing and
communicating human risk.
• Adverse（有害）所見とNOAELに関するコミュニケーションは、ヒト
のリスク評価・コミュニケーションにおいて、関係した科学者（毒
性学者、病理学者、リスク評価者など）の直接的参加が含まれ
るべきだ

14. Factors to Consider in an Adversity Call
• Are there related pathological findings?
• 関連する病理所見はあるか？
• Is there a known or biologically plausible underlying
mechanism?
• 既知あるいは生物学的に妥当なメカニズムがあるか？
• What are the severity criteria?
• 重篤度のクライテリアは何か？
• What is the background incidence (historical control)?
• 背景データでの頻度はどうか（ヒストリカルコントロー
ル）？

15. Calling a Finding ADVERSE Should NOT
be Based On:
• Extrapolation across species (including humans)
• 種をまたがる外挿性（ヒトを含む）
• Whether the effect is an exacerbation of a background lesion
• その変化は背景病変を増悪化させたものかどうか
• Whether the effect is a presumed supra-pharmacological effect
• その変化は薬理効果を増強させたものと予想できるかどうか
• Whether the effect is primary, secondary, tertiary, etc,.
• その変化は、直接的、二次的、三次的なもの……かどうか
• Whether the lesion is transient or reversible
• その病変は一時的なものか回復可能なものか
• Solely on statistics
• 単に統計学的なものか

16. Are some findings non-adverse?

17. Are some findings non-adverse?
• Bile duct hyperplasia
• Lymphoid hyperplasia
• Microsomal enzyme induction
• Decreased serum ALT and AST
• Extramedullary hematopoiesis in liver

18. Are some findings non-adverse?
• Bile duct hyperplasia
• Lymphoid hyperplasia
• Microsomal enzyme induction
• Decreased serum ALT and AST
• Extramedullary hematopoiesis in liver
When findings such as these do not compromise normal
tissue physiology, do not impair functional capacity, and
do not increase susceptibility to other influences, then
they may be considered non-adverse.

19. Some Examples of Non-Adverse
Findings
Thymic involution in
a chronic rat study
Congenital cyst in
a rodent study

20. Some Examples of Non-Adverse
Findings
Bile duct hyperplasia
in a chronic rat study

21. Some Examples of Non-Adverse
Findings
Bile duct hyperplasia
in a chronic rat study
However, this degree
of bile duct hyperplasia
in a 90-day rat study
would probably be
an adverse response.

22. Some Examples of Non-Adverse
Findings
Extramedullary hematopoiesis
in the liver – a secondary
response to bone marrow
suppression
Pigment in a lymph node – a
normal function in a
draining lymph node

23. Some Examples of Non-Adverse
Findings
Extramedullary hematopoiesis
in the liver – a secondary
response to bone marrow
suppression
Pigment in a lymph node – a
normal function in a
draining lymph node
These secondary responses
could be considered
adaptive responses.

24. Adaptive Response
• In the context of a toxicology study, the
process whereby a cell or organism responds
to a xenobiotic so that the cell or organism
will survive in the new environment that
contains the xenobiotic without impairment of
function.
• Adaptive responses to toxicant exposure may
be characterized by reversibility.

25. Adaptation
• Evolutionary strategy to insure survival in a new
environment where the xenobiotic is present
• 生体異物の存在する新しい環境において、生き残るた
めの進化的戦略である
• Adaptation can be adverse
• Adaptation（適応）がadverse（有害性）になりうる
• Example: Tracheal squamous metaplasia
• Adaptive changes are not always reversible
• 適応性変化は必ずしも回復性があるとは限らない
• Example: Hepatic fibrosis

26. Adaptive Responses
• Adaptive change allows organism to respond
to environmental change & is usually
beneficial but not necessarily desirable
• 生物体の環境変化への反応として適応性変化がお
こるが、通常は有益であるが、必ずしも望ましいもの
ではない
• Can result in a new functional steady state in a tissue
or organ
• 組織や器官において、新たな機能的安定状態にな
ることができる

27. Adaptive Response (cont)
• Adaptive changes are often early homeostatic
adjustments (metabolism or gene
expression/transcriptomic changes)
• 適応性変化はしばしば初期の恒常性調節機構である（代謝
あるいは遺伝子発現／トランスクリプトームな変化）
• May temporarily result in a new homeostatic steady-state
• 一次的に新たな恒常性の定常状態になるかもしれない
• Adaptive changes may ultimately result in return to a normal
homeostatic condition
• 適応性変化は最終的に正常の恒常状態に戻るかもしれない

28. Adaptive Responses
• An adaptive change can sometimes be adverse
• 適応性変化は時にadverse（有害性）となりうる

29. Adaptive Responses
• An adaptive change can sometimes be adverse
• 適応性変化は時にadverse（有害性）となりうる
Squamous metaplasia
of the trachea occurred
following inhalation
exposure to smoke.

30. Adaptive Responses
• An adaptive change can sometimes be adverse
• 適応性変化は時にadverse（有害性）となりうる
Squamous metaplasia
affects normal cilliary
function in the trachea
and is, therefore, an
adaptive response that
is adverse.

31. Adaptive Responses
• An adaptive change can sometimes be adverse
• 適応性変化は時にadverse（有害性）となりうる
Squamous metaplasia
affects normal ciliary
function in the trachea
and is, therefore, an
adaptive response that
is adverse.
Even thought it is
potentially reversible
after the cause is
removed, it is still an
adverse response.

32. Reversibility
• Disappears after treatment is stopped
• Typically determined using recovery groups in
toxicity studies

33. What Determines if a Lesion is
Reversible?
• Depends upon the regenerative capacity of
the tissue or organ
• Depends of the type of lesion
– Proliferative/non-proliferative
• Depends on the severity of the lesion
• Depends upon length of time without further
treatment
– Partial/complete reversibility

34. Reversibility
• An adverse lesion may or may not be reversible
• Adverse（有害性）な変化は回復性がある場合やない
場合がある
• If an adverse lesion is reversible, then it can be:
• もしadverse（有害性）な変化に回復性があるならば、
A key component in weight-of-evidence in study
interpretation
– 試験の解釈でのweight-of-evidenceにおけるキーポイント
である。
– May indicate a lower level of concern
– より低用量に懸念があるかもしれない
Perry et al., 2013. Toxicologic Pathology 41: 1159-1169
Sewell et al., 2014. Regulatory Toxicology & Pharmacology 70: 414-429

35. What About Exacerbation?

36. Exacerbation
Exacerbation = an increase in the incidence and/or severity of
an age-related and/or strain-specific common background
lesion seen in control animals
増悪化とは
：対照群の動物で観察される加齢性変化や系統に特異的
に観察される背景データに関して、その発現頻度や程度
が増加することである。

37. Exacerbation
Can exacerbated background lesions be adverse?
Exacerbation = an increase in the incidence and/or severity of
an age-related and/or strain-specific common background
lesion seen in control animals
増悪化とは
：対照群の動物で観察される加齢性変化や系統に特異的
に観察される背景データに関して、その発現頻度や程度
が増加することである。

38. Exacerbation
Can exacerbated background lesions be adverse?
Yes, if –
• the exacerbation is a biologically plausible primary effect of
the test agent
• the exacerbation shows a clear dose-response
• the exacerbation exceeds historical control
Exacerbation = an increase in the incidence and/or severity of
an age-related and/or strain-specific common background
lesion seen in control animals
増悪化とは
：対照群の動物で観察される加齢性変化や系統に特異的
に観察される背景データに関して、その発現頻度や程度
が増加することである。

39. • Definitions
– Adverse response
– Adaptive response
– Reversible response
– Exacerbation of background lesions
• For the Toxicology Report & Regulatory
Submission
• Paradigm Shift & Determining Adversity
• Practical Examples of Adverse and Adaptive
Responses in Preclinical Studies
Outline of Presentation

40. What is needed in the toxicology report
for submission to regulatory
authorities?
規制当局に提出する毒性レポートで何
が必要とされるか？

41. For the Toxicology Report and
Regulatory Submission
• Need detailed description of what is adverse for
each health-related endpoint
• どの健康に関連するエンドポイントに対しても、何が
adverse（有害性）であるかについて詳細な記載が必要で
ある
• Provide details on pathogenesis & mechanism
• 病因とメカニズムを詳細に提供すること
• Explain morphological criteria for diagnoses and severity
scoring
• 診断の形態学的クライテリアと病変程度のスコアーにつ
いて説明すること

42. For the Toxicology Report and
Regulatory Submission
• Clearly characterize relevant changes &
explain judgments regarding why a change is
adverse or non-adverse
• 関連のある変化を明確に特徴付けることと、変化が
adverse（有害性）かどうかの判断した根拠について
説明すること
• Consider use of outside peer review & expert reports
• 外部のピアレビューや専門家の報告を利用すること
を考慮すること

43. For the Toxicology Report and Regulatory Submission
• Cite relevant literature
• For example : using alveolar histiocytosis
Control Treated

44. For the Toxicology Report and Regulatory Submission
• Cite relevant literature
• For example : using alveolar histiocytosis
Treated
• Inhalation study
• Serum enzymes are normal
• Minimal to mild increase in alveolar
histiocytes
• No evidence of inflammation
• No epithelial hyperplasia
Sponsor considered the alveolar
histiocytosis to be adaptive and
non-adverse because…

45. For the Toxicology Report and Regulatory Submission
• Cite relevant literature
• For example : using alveolar histiocytosis
Treated
• Inhalation study
• Serum enzymes are normal
• Minimal to mild increase in alveolar
histiocytes
• No evidence of inflammation
• No epithelial hyperplasia
Sponsor considered the alveolar
histiocytosis to be adaptive and
non-adverse because…
In submitting their report to a regulatory
authority, the sponsor cited some
relevant literature

46. For the Toxicology Report and Regulatory Submission
• Citing relevant literature for histiocytosis example
Nikula et al., 2014.
Toxicologic Pathology 42:472-486.
“An STP working group focused
on distinguishing adaptive versus
adverse responses in rodents and
concluded that increases in
alveolar macrophage number
and/or size are not adverse if
there are no other lung changes
such as inflammation and/or
hyperplastic epithelial
responses.”

47. What about the paradigm shift?
• What is the paradigm shift?
– In accordance with Tox21 and related global opinion,
there is the recommendation to move away from
animal testing and to rely on new molecular
measurements and molecular pathways
• High throughput screening
• Toxicity pathways
• Adversity outcome pathways
• In vitro testing using human cells
• Computational systems biology
Ankley et al., (2010) Environ Toxicol Chem 29:730-41

48. What about the paradigm shift?
Now there is an interest in defining adversity at
the molecular level using new molecular biology
and related methods.

49. What about the paradigm shift?
Now there is an interest in defining adversity at the
molecular level using new molecular biology and
related methods.
The question is:
Can adverse effects be defined
at the molecular level?

50. What about the paradigm shift
• Development of new molecular methods to replace animal
testing
• 動物実験に置き換わる新たな分子学的手法の開発
• Tox21, high throughput screening, toxicogenomics, toxicity
pathways, altered gene expression, adverse outcome pathways
• Use of these new molecular methods to identify adversity
will require establishing scientific validation
• Adversity（有害性）を見つけ出すこれらの新たな分子学的手法の
利用には、科学的なバリデーションの確立が必要となる
• Until new methods are validated, we continue to rely on classical
toxicity testing to identify adverse data for risk assessment
• リスク評価のためのadverse（有害性）のデータを明らかにするため
に、新たな手法がバリデートされるまで、我々はクラシカルな毒性
試験に頼り続けざるを得ない

51. What about the paradigm shift?
Can adverse effects be
defined at the molecular
level?
Answer: Not yet.

52. A Final Definition of Adverse
• ‘…change in the morphology, physiology, growth,
development, reproduction, or life span of an
organism, system, or (sub) population that results
in an impairment of functional capacity, an
impairment of the capacity to compensate for
additional stress, or an increase in susceptibility
to other influences’ (IPCS, 2004).
• Based on “apical responses”
– Clinical signs, lesions, traditional biomarkers
– And always within the context of the specific study

53. • Definitions
– Adverse response
– Adaptive response
– Reversible response
– Exacerbation of background lesions
• For the Toxicology Report & Regulatory
Submission
• Paradigm Shift & Determining Adversity
• Practical Examples of Adverse and Adaptive
Responses in Preclinical Studies
Outline of Presentation

54. Practical Examples
• Restricted to one sex for purposes of
demonstrating potential adverse responses
• However, an effect seen in both genders
would be of more concern
• Examples are based on reasonably expected
study outcomes

55. Dr. John Seely’s car

56. Sprague-Dawley 12-Month Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 20 n= 20 n= 20 n= 20
Chronic Progressive
Nephropathy
% Incidence 10 15 25 30
Minimal 2 2 1 0
Mild 0 0 2 2
Moderate 0 0 2 4
Severity Average 1.0 1.0 2.2 2.7
Treatment associated exacerbation
of chronic progressive nephropathy

57. Sprague-Dawley 12-Month Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 20 n= 20 n= 20 n= 20
Chronic Progressive
Nephropathy
% Incidence 10 15 25 30
Minimal 2 2 1 0
Mild 0 0 2 2
Moderate 0 0 2 4
Severity Average 1.0 1.0 2.2 2.7
Treatment associated exacerbation
of chronic progressive nephropathy
Is this an adverse response?

58. Sprague-Dawley 12-Month Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 20 n= 20 n= 20 n= 20
Chronic Progressive
Nephropathy
% Incidence 10 15 25 30
Minimal 2 2 1 0
Mild 0 0 2 2
Moderate 0 0 2 4
Severity Average 1.0 1.0 2.2 2.7
Treatment associated exacerbation
of chronic progressive nephropathy
Is this an adverse response?
Yes, it is adverse

59. Sprague-Dawley 12-Month Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 20 n= 20 n= 20 n= 20
Chronic Progressive
Nephropathy
% Incidence 10 15 25 30
Minimal 2 2 1 0
Mild 0 0 2 2
Moderate 0 0 2 4
Severity Average 1.0 1.0 2.2 2.7
Treatment associated exacerbation
of chronic progressive nephropathy
Is this an adverse response?
Yes, it is adverse
Dose-related
increase incidence
and increased
severity

60. Sprague-Dawley 12-Month Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 20 n= 20 n= 20 n= 20
Chronic Progressive
Nephropathy
% Incidence 10 15 25 30
Minimal 2 2 1 0
Mild 0 0 2 2
Moderate 0 0 2 4
Severity Average 1.0 1.0 2.2 2.7
Treatment associated exacerbation
of chronic progressive nephropathy
Is this an adverse response?
NOAEL

61. 9-Month Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
KIDNEY n= 15 n= 15 n= 15 n= 15
Karyomegaly 0 0 15 15
Tubular hyperplasia 0 0 1 0
Tubular adenoma 0 0 0 0
Renal Tubular
Karyomegaly

62. 9-Month Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
KIDNEY n= 15 n= 15 n= 15 n= 15
Karyomegaly 0 0 15 15
Tubular hyperplasia 0 0 1 0
Tubular adenoma 0 0 0 0
Renal Tubular
Karyomegaly
Boorman et al., 1992. Toxicologic Pathology 20:236-245
Frazier et al., 2012. Toxicologic Pathology 40: 7S-86S
• The toxicological
significance of this change
is unknown
• There is no evidence that
it progresses to neoplasia
• Not considered adverse by
subject matter experts

63. 9-Month Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
KIDNEY n= 15 n= 15 n= 15 n= 15
Karyomegaly 0 0 15 15
Tubular hyperplasia 0 0 1 0
Tubular adenoma 0 0 0 0
Renal Tubular
Karyomegaly
Boorman et al., 1992. Toxicologic Pathology 20:236-245
Frazier et al., 2012. Toxicologic Pathology 40: 7S-86S
• The toxicological
significance of this change
is unknown
• There is no evidence that
it progresses to neoplasia
• Not considered adverse by
subject matter experts
Non-adverse

64. Renal Tubular
Karyomegaly
Boorman et al., 1992. Toxicologic Pathology 20:236-245
Frazier et al., 2012. Toxicologic Pathology 40: 7S-86S
• The toxicological
significance of this change
is unknown
• There is no evidence that
it progresses to neoplasia
• Not considered adverse by
subject matter experts

65. Renal Tubular
Karyomegaly
Boorman et al., 1992. Toxicologic Pathology 20:236-245
Frazier et al., 2012. Toxicologic Pathology 40: 7S-86S
• The toxicological
significance of this change
is unknown
• There is no evidence that
it progresses to neoplasia
• Not considered adverse
but subject matter experts
9-Month Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
KIDNEY n= 15 n= 15 n= 15 n= 15
Karyomegaly 0 0 15 15
Tubular hyperplasia 0 0 3 6
Tubular adenoma 0 0 0 1
Everything is the
same except

66. Renal Tubular
Karyomegaly
Boorman et al., 1992. Toxicologic Pathology 20:236-245
Frazier et al., 2012. Toxicologic Pathology 40: 7S-86S
• The toxicological
significance of this change
is unknown
• There is no evidence that
it progresses to neoplasia
• Not considered adverse by
subject matter experts
Probably adverse
because of tubular
hyperplasia and
adenoma

67. Renal Papillary Mineralization

68. 90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Kidney - Mineralization
Minimal 1 2 1 3
Mild 0 0 1 1
Moderate 0 0 1 1
Total 1 2 3 5
Kidney – Mineralization
• Treatment may exacerbate
this background lesion
• May not be a direct effect of
the test agent
• Mechanism is usually
unknown

69. 90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Kidney - Mineralization
Minimal 1 2 1 3
Mild 0 0 1 1
Moderate 0 0 1 1
Total 1 2 3 5
Kidney – Mineralization
• Treatment may exacerbate
this background lesion
• May not be a direct effect of
the test agent
• Mechanism is usually
unknown
Presumption – a perturbation
of calcium homeostasis

70. 90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Kidney - Mineralization
Minimal 1 2 1 3
Mild 0 0 1 1
Moderate 0 0 1 1
Total 1 2 3 5
Kidney – Mineralization
• Treatment may exacerbate
this background lesion
• May not be a direct effect of
the test agent
• Mechanism is usually
unknown
Presumption – a perturbation
of calcium homeostasis
Conservative
NOAEL is the
low dose

71. Adrenal Cortical Necrosis

72. Adrenal
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Adrenal
Necrosis, diffuse, severe 0 0 2 8
Hemorrhage, cortex, focal 0 0 1 6

73. Adrenal
• Adrenal cortical necrosis is adverse
• The 2/10 incidence at the medium
exposure is a severe response
• The NOAEL is the low exposure

74. Alveolar Histiocytosis
Control Exposed

75. Lung – Alveolar histiocytosis
• Inhalation study
• Serum enzymes are normal
• Minimal to mild increase in
alveolar histiocytes

76. Lung – Alveolar histiocytosis
• Inhalation study
• Serum enzymes are normal
• Minimal to mild increase in
alveolar histiocytes
Is this adverse?

77. Lung – Alveolar histiocytosis
• Inhalation study
• Serum enzymes are normal
• Minimal to mild increase in
alveolar histiocytes
Is this adverse?
This degree of
histiocytosis
is not considered
adverse by lung
experts.

78. Lung – Alveolar histiocytosis
14-Day Recovery

79. Lung – Alveolar histiocytosis
14-Day Recovery
Not considered adverse, even
without recovery

80. Minimal to mild alveolar histiocytosis
reflects a macrophage response to changes in
the local environment & represents a tissue
adaptation to maintain normal lung function

81. Minimal to mild alveolar histiocytosis
reflects a macrophage response to changes in
the local environment & represents a tissue
adaptation to maintain normal lung function
But severe alveolar histiocytosis as in this
example represents an adverse response,
even if it is reversible.

82. Lesion severity is
important in defining
an adverse effect

83. Lymph Node Histiocytic Infiltrate

84. Lymph Node
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Infiltrates, histiocytic
Minimal 2 3 5 4
Mild 1 1 3 3
Moderate 0 0 1 3
Total 3 4 9 10
Necrotic foci
Minimal 0 0 1 0

85. 90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Infiltrates, histiocytic
Minimal 2 3 5 4
Mild 1 1 3 3
Moderate 0 0 1 3
Total 3 4 9 10
Necrotic foci
Minimal 0 0 1 0
Lymph Node
• Clearance via lymph node drainage is a part of
normal lymph node physiology
• Not adverse unless severe and associated with
necrosis in the affected lymph node

86. Lymph Node
Although there is a dose response and increased severity, this change
may be non-adverse. A recovery study would help clarify this issue.
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Infiltrates, histiocytic
Minimal 2 3 5 4
Mild 1 1 3 3
Moderate 0 0 1 3
Total 3 4 9 10
Necrotic foci
Minimal 0 0 1 0
• Clearance via lymph node drainage is a part of
normal lymph node physiology
• Not adverse unless severe and associated with
necrosis in the affected lymph node

87. Lymph Node
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10
Infiltrates, histiocytic
Minimal 2 3 5 4
Mild 1 1 3 3
Moderate 0 0 1 3
Total 3 4 9 10
Necrotic foci
Minimal 0 0 1 0
• Clearance via lymph node drainage is a part of
normal lymph node physiology

88. Progressive Cardiomyopathy in Rats

89. Progressive Cardiomyopathy - Rat
Slide courtesy of Dr. Rick Hailey

90. Progressive Cardiomyopathy - Rat
• Background lesion in rats in prechronic
studies
• Especially common in Sprague Dawley
rats
• Difficult to find at low magnification
• Typically very mild in severity unless
exacerbated by treatment
• Randomly distributed in the
myocardium
Slide courtesy of Dr. Rick Hailey

91. Progressive Cardiomyopathy - Rat
• Background lesion in rats in prechronic
studies
• Especially common in Sprague Dawley
rats
• Difficult to find at low magnification
• Typically very mild in severity unless
exacerbated by treatment
• Randomly distributed in the
myocardium
Pathogenesis: myocardial fiber degenerationmononuclear inflammatory
responsephagocytosis of degenerating myofibersfocal fibrosis
Slide courtesy of Dr. Rick Hailey

92. Examples of Progressive Cardiomyopathy
Slide courtesy of Dr. Rick Hailey

93. Slide 1 of 3
Cardiomyopathy in a 13-Week Study
Slide courtesy of Dr. Rick Hailey

94. Slide 2 of 3
Medium Magnification
Slide courtesy of Dr. Rick Hailey

95. Slide 3 of 3
High Magnification
Slide courtesy of Dr. Rick Hailey

96. Progressive Cardiomyopathy
Adverse or Non-adverse?

97. Progressive Cardiomyopathy
Non-Adverse
No dose-response
All lesions are of minimal
severity

98. Progressive Cardiomyopathy
Adverse or Non-adverse?

99. Progressive Cardiomyopathy
Non-Adverse
No convincing dose-response
All lesions are of minimal
severity

100. Progressive Cardiomyopathy
13-Week Rat Study
Progressive Cardiomyopathy
Control Low-Dose Medium-Dose High-Dose
1/10 3/10 3/10 4/10
(1) (1) (1.5) (2)
( ) = Severity score: 1= minimal, 2= mild, 3 = moderate,
4 = marked
Same lesion but different incidence !!

101. Progressive Cardiomyopathy
13-Week Rat Study
Progressive Cardiomyopathy
Control Low-Dose Medium-Dose High-Dose
1/10 3/10 3/10 4/10
(1) (1) (1.5) (2)
( ) = Severity score: 1= minimal, 2= mild, 3 = moderate,
4 = marked
Adverse or Non-adverse?
Same lesion but different incidence !!

102. Progressive Cardiomyopathy
13-Week Rat Study
Progressive Cardiomyopathy
Control Low-Dose Medium-Dose High-Dose
1/10 3/10 3/10 4/10
(1) (1) (1.5) (2)
( ) = Severity score: 1= minimal, 2= mild, 3 = moderate,
4 = marked
Adverse
Dose-response - yes
Increased severity - yes
NOAEL

104. Acute Centrilobular Necrosis
(Prechronic Mouse Study)
Liver enzymes
increased
> 5-fold

105. Acute Centrilobular Necrosis
(Prechronic Mouse Study)
This change is adverse
Liver enzymes
increased
> 5-fold

106. Acute Periportal Necrosis
Liver enzymes
increased
> 5-fold

107. Acute Periportal Necrosis
This change is adverse
Liver enzymes
increased
> 5-fold

108. Acute Liver Response
Return to normal in 3 to 7 days
This represents an example
of reversibility

109. Acute Liver Response
Return to normal in 3 to 7 days
Liver enzyme levels may or may not
still be elevated when the liver
structure has returned to normal
depending upon their half-life in the
circulation.
This represents an example
of reversibility

110. Acute Liver Response
Return to normal in 3 to 7 days
Liver enzyme levels may or may not
still be elevated when the liver
structure has returned to normal
depending upon their half-life in the
circulation.What is adverse or what is
non-adverse may depend on
when you take the sample.
This represents an example
of reversibility

111. Acute Liver Response
Return to normal in 3 to 7 days
What is adverse or what is
non-adverse may depend on
when you take the sample.
This represents an example
of reversibility The fact that a lesion is reversible
is an important piece of information
that should be considered in a
weight-of-evidence approach.

112. Cholangitis
Control Treated
Treatment-associated exacerbation of
cholangitis
Common background change
in older rats
Adverse?

113. Cholangitis
Control Treated
Adverse?
In general, minimal treatment-associated exacerbations of background lesions
are non-adverse but mild, moderate, and marked changes are adverse.

114. Cholangitis
Control Treated
Increase in inflammatory cells; some are
neutrophils; there is necrosis of
adjacent hepatocytes (arrows)
Common background change
in older rats
Slide courtesy of R. Hailey
Adverse?

115. Cholangitis
Control Treated
Increase in inflammatory cells; some are
neutrophils; there is necrosis of
adjacent hepatocytes (arrows)
Common background change
in older rats
Slide courtesy of R. Hailey
Adverse-YES

116. Biliary epithelial hyperplasia:
Adverse?
Are These Examples of Bile Duct
Hyperplasia Adverse?
Slide courtesy of R. Hailey

117. Biliary epithelial hyperplasia:
Adverse?
Mitotic figures Proliferation outside the portal triad
Are These Examples of Bile Duct
Hyperplasia Adverse?
Slide courtesy of R. Hailey

118. Biliary epithelial hyperplasia:
Adverse?
Mitotic figures
Hepatocellular necrosis
Proliferation outside the portal triad
Are These Examples of Bile Duct
Hyperplasia Adverse?
Slide courtesy of R. Hailey

119. Biliary epithelial hyperplasia:
Adverse?
Mitotic figures
Hepatocellular necrosis
Proliferation outside the portal triad
Yes, They Are Adverse!
Slide courtesy of R. Hailey

120. Is this adverse?
Proliferation outside the portal triad and cellular atypia
Increases in ALT and AST (up to 20X)
and ALP (1.4X) and bilirubin (13X)
Another Example of An Adverse
Response Affecting Bile Ducts

121. Can Occur Spontaneously
Control- no change
Control- spontaneous biliary
epithelial hyperplasia
Bile ducts
In Contrast This Degree of Bile Duct
Hyperplasia is Non-Adverse

122. Hepatic Foci of Cellular Alteration

123. Hepatic Foci of Cellular Alteration
• Occur spontaneous in older rodents
• May be induced by treatment in younger rodents
• Can be present with or without hepatotoxicity
• 1 Hepatocellular tumor per 10,000 foci
Kaufmann et al., Am J Pathol 119:171-174 (1985)

124. Are Foci Predictors of Liver Tumor
Response? Are foci adverse?

125. Hepatic Foci of Cellular Alteration
* p< 0.05 ** p< 0.01

126. Hepatic Foci of Cellular Alteration
* p< 0.05 ** p< 0.01
• A treatment-related increase in foci at the
medium & high exposures per se may not be
considered adverse, but this is controversial
• 中間並びに高用量群で投与に関連した変異
細胞巣の増加が認められ、本質的にadverse
（有害性）とは考えられないかもしれないが、
これは議論の余地があるだろう
• A single hepatocellular adenoma can occur by
chance, even in a 90-day study
• 90日試験でさえも、肝細胞腺腫が1例に偶発
所見としてみられている

127. Hepatic Foci of Cellular Alteration
* p< 0.05 ** p< 0.01
• This incidence of foci in a 12-month study is
of some concern since it may predict a
potential hepatocarcinogenic response in a
long-term study.
• The concern may be sufficient to stop
development of a new drug or pesticide
• However, aside from its predictive potential,
a liver focus response by itself does not
compromise liver function sufficiently to be
classified as adverse.

128. Hepatic Foci of Cellular Alteration
* p< 0.05 ** p< 0.01
• This incidence of foci in a 12-month study is
of some concern since it may predict a
potential hepatocarcinogenic response in a
long-term study.
• The concern may be sufficient to stop
development of a new drug or pesticide
• However, aside from its predictive potential,
a liver focus response by itself does not
compromise liver function sufficiently to be
classified as adverse.
It is OK to
disagree with
my opinion on
this.

129. Hepatic Foci of Cellular Alteration
* p< 0.05 ** p< 0.01
• This incidence of foci in a 12-month study is
of some concern since it may predict a
potential hepatocarcinogenic response in a
long-term study.
• The concern may be sufficient to stop
development of a new drug or pesticide
• However, aside from its predictive potential,
a liver focus response by itself does not
compromise liver function sufficiently to be
classified as adverse.
It is OK to
disagree with
my opinion on
this.
You may feel that development of foci is part
of a continuum known to progress to adversity.

130. Hepatomegaly
Control Treated

131. Liver Weight Increases Without Other
Changes
• < 10% liver weight - non-adverse
• >40-50% increase liver at 12-months – leads
to cancer (it is predictive but not necessarily
adverse)
Carmichael et al., Environ Hlth Perspectives 105: 1196-1203 (1997)
Haseman et al., Toxicol Pathol 25:256-263(1997)
Maronpot et al., Toxicol Pathol 38: 7786-795 (2010

132. Liver Weight Increases Without Other
Changes
• < 10% liver weight - non-adverse
• >20% liver weight increase =
adverse
– According to some regulatory
authorities
• >40-50% increase liver at 12-
months – leads to cancer
(predictive)
• This is controversial!!
• 20% liver weight increases
are common responses to
xenobiotic exposures
• In the absence of any
other changes, a 20%
increase should not be
considered adverse
Carmichael et al., Environ Hlth Perspectives 105: 1196-1203 (1997)
Haseman et al., Toxicol Pathol 25:256-263(1997)
Maronpot et al., Toxicol Pathol 38: 7786-795 (2010

133. Chemicals That Cause Liver Enlargement
• Chemicals that cause liver enlargement
(hypertrophy/hyperplasia) at low doses often will cause
degeneration at higher doses
• 低用量で肝腫大（肥大／過形成）を引き起こす化学物質は、より
高用量では変性をしばしば誘発する
• Saturation of normal clearance mechanisms
– Alternate metabolic routes can damage cellular macromolecules
• Presence of degeneration is adverse
• 変性の存在はadverse（有害性）である
• Resulting functional loss may not be completely reversed (e.g.,
heptic fibrosis)
• 結果としてみられる機能消失は完全に回復しないかもしれない
（例えば肝線維化）

134. Hepatomegaly in Prechronic Studies is a
Frequent Reflection of Microsomal Enzyme
Induction
Control Treated

135. Hepatic Enzyme Induction
• Centrilobular hepatocyte hypertrophy

136. Microsomal Enzyme Induction

137. N
N
Smooth Endoplasmic Reticulum (SER) Proliferation
Control Treated
Arrows = smooth endoplasmic reticulum

138. Microsomal Enzyme Induction
Evidence of enzyme
induction without any
other changes is typically
an adaptive change that
is not adverse.

139. Hepatic Enzyme Induction
• Centrilobular hepatocyte hypertrophy
Adaptive and non-adverse when there
is only hepatocellular hypertrophy
Typically reversible when exposure
is stopped

140. Enzyme Induction with other changes should be considered an
adverse response
Cytoplasmic vacuolation & bile duct hyperplasia Single cell necrosis

141. 1. extreme hypertrophy
leading to reduced
sinusoidal blood circulation,
hypoxia, and necrosis and/or
2. metabolic activation
forming more toxic active
metabolites
Proposed Mechanisms for Hepatocyte
Necrosis
Adverse

142. Extreme Hepatocyte Hypertrophy
• Enlarged hepatocytes
• Increased cytoplasm
• Multiple nuclei
• Karyomegaly
Adverse

143. Liver Case #1
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Low Medium
Exposure
High Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10 n=10
Liver –Centrilobular hypertrophy 0 4
(1)
7
(1.5)
9
(1.5)
9
(2)
Hepatocyte fatty change 6
(1.5)
9
(2)
10
(3)
9
(3)
8
(3)
( ) = Severity: 1 – minimal 2 – mild 3 = marked

144. Liver Case #1
This is very similar to an actual case that
was considered by a regulatory agency.
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Low Medium
Exposure
High Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10 n=10
Liver –Centrilobular hypertrophy 0 4
(1)
7
(1.5)
9
(1.5)
9
(2)
Hepatocyte fatty change 6
(1.5)
9
(2)
10
(3)
9
(3)
8
(3)
( ) = Severity: 1 – minimal 2 – mild 3 = marked

145. Liver Case #1
• Generally low severity centrilobular hepatocyte hypertrophy
• No cytotoxicity or hepatocellular degeneration
• Liver weight increased up to 35%
• ALT & AST increased 2.6 to 4.5 at 2 highest exposures
• Plasma cholesterol increased 25 to 40% at 3 highest doses
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Low Medium
Exposure
High Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10 n=10
Liver –Centrilobular hypertrophy 0 4
(1)
7
(1.5)
9
(1.5)
9
(2)
Hepatocyte fatty change 6
(1.5)
9
(2)
10
(3)
9
(3)
8
(3)
( ) = Severity: 1 – minimal 2 – mild 3 = marked

146. Liver Case #1
HYPERTROPHY CONSIDERED ADAPTIVE
• Typical low severity centrilobular hepatocyte hypertrophy &
no cytotoxicity or hepatocellular degeneration
• Liver weight increased up to 35%
FATTY CHANGE CONSIDERED ADVERSE (Alteration in lipid metabolism)
• ALT & AST increased 2.6 to 4.5 at 2 highest exposures
• Plasma cholesterol increased 25 to 40% at 3 highest doses
( ) = Severity: 1 – minimal 2 – mild 3 = marked
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Low Medium
Exposure
High Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10 n=10
Liver –Centrilobular hypertrophy 0 4
(1)
7
(1.5)
9
(1.5)
9
(2)
Hepatocyte fatty change 6
(1.5)
9
(2)
10
(3)
9
(3)
8
(3)

147. Liver Case #1
NOAEL
HYPERTROPHY CONSIDERED ADAPTIVE
• Typical low severity centrilobular hepatocyte hypertrophy &
no cytotoxicity or hepatocellular degeneration
• Liver weight increased up to 35%
FATTY CHANGE CONSIDERED ADVERSE (Alteration in lipid metabolism)
• ALT & AST increased 2.6 to 4.5 at 2 highest exposures
• Plasma cholesterol increased 25 to 40% at 3 highest doses
90-Day Rat Study
Microscopic Findings
Control Low
Exposure
Low Medium
Exposure
High Medium
Exposure
High
Exposure
n= 10 n= 10 n= 10 n= 10 n=10
Liver –Centrilobular hypertrophy 0 4
(1)
7
(1.5)
9
(1.5)
9
(2)
Hepatocyte fatty change 6
(1.5)
9
(2)
10
(3)
9
(3)
8
(3)

148. Liver Case #2
• Increased liver weight up to 30%
• Increased liver enzymes in 3 of the high exposure rats
28-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
LIVER n= 10 n= 10 n= 10 n= 10
Centrilobular hypertrophy 0 0 5 (1) 7(1)
Hepatocyte vacuolation 2(1) 1(1) 1(1) 2(1)
Degeneration/necrosis 0 0 0 3(1.5)
Increased mitoses 0 0 0 4 (1)
( ) = Severity: 1 – minimal 2 – mild 3 = marked
SIMILAR TO DATA SUBMITTED FOR REGULATORY REVIEW

149. Liver Case #2
• Hypertrophy and vacuolation considered adaptive
• Degeneration/necrosis and increased mitoses considered adverse
28-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
LIVER n= 10 n= 10 n= 10 n= 10
Centrilobular hypertrophy 0 0 5 (1) 7(1)
Hepatocyte vacuolation 2(1) 1(1) 1(1) 2(1)
Degeneration/necrosis 0 0 0 3(1.5)
Increased mitoses 0 0 0 4 (1)
( ) = Severity: 1 – minimal 2 – mild 3 = marked
• Increased liver weight up to 30%
• Increased liver enzymes in 3 of the high exposure rats

150. Liver Case #2
• Hypertrophy and vacuolation considered adaptive
• Degeneration/necrosis and increased mitoses considered adverse
28-Day Rat Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
LIVER n= 10 n= 10 n= 10 n= 10
Centrilobular hypertrophy 0 0 5 (1) 7(1)
Hepatocyte vacuolation 2(1) 1(1) 1(1) 2(1)
Degeneration/necrosis 0 0 0 3(1.5)
Increased mitoses 0 0 0 4 (1)
( ) = Severity: 1 – minimal 2 – mild 3 = marked
NOAEL identified as medium exposure
• Increased liver weight up to 30%
• Increased liver enzymes in 3 of the high exposure rats

151. Three Other Practical Examples

152. Epididymis – Tunica
vaginalis mesothelioma
Male 2-Year F344 Study
Microscopic
Findings
Control Low
Exposure
Low
Medium
Exposure
High
Medium
Exposure
High
Exposure
Tunica vaginalis
mesothelioma
2/48
4%
2/48
4%
1/48
2%
3/48
6%
8/48
17%
Historical control range = 3.3% to 6.4%

153. Epididymis – Tunica
vaginalis mesothelioma
Male 2-Year F344 Study
Microscopic
Findings
Control Low
Exposure
Low
Medium
Exposure
High
Medium
Exposure
High
Exposure
Tunica vaginalis
mesothelioma
2/48
4%
2/48
4%
1/48
2%
3/48
6%
8/48
17%
Historical control range = 3.3% to 6.4%
Adverse

154. 14-Day Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 3 n= 3 n= 3 n= 3
BRAIN
Inflammation, acute 1 0 0 1
Inflammation, subacute 0 0 0 1
Dog Study
No clinical signs or
gross lesions
Slide courtesy of Dr. Peter Mann

155. 14-Day Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
n= 3 n= 3 n= 3 n= 3
BRAIN
Inflammation, acute 1 0 0 1
Inflammation, subacute 0 0 0 1
Dog Study
No clinical signs or
gross lesions
Slide courtesy of Dr. Peter Mann
A difficult call because
of the small number of
study animals but
probably not adverse.

156. Female 2-Year F344 Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
Mononuclear cell Leukemia 8/50
16%
7/50
14%
19/51*
37%
16/50
32%
* p < 0.05 Fischer’s Exact Test; p < 0.05 Life Table test
Mononuclear cell
leukemia
• No tumors in males
• No other tumors in
females in this study
Historical Control
14% to 36%

157. Female 2-Year F344 Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
Mononuclear Cell Leukemia 8/50
16%
7/50
14%
19/51*
37%
16/50
32%
* p < 0.05 Fischer’s Exact Test; p < 0.05 Life Table test
Mononuclear cell
leukemia
• No tumors in males
• No other tumors in
females in this study
Historical Control
14% to 36%
NTP considered this
response was
equivocal evidence
of carcinogenicity

158. Female 2-Year F344 Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
Mononuclear Cell Leukemia 8/50
16%
7/50
14%
19/51*
37%
16/50
32%
* p < 0.05 Fischer’s Exact Test; p < 0.05 Life Table test
Historical Control Range = 14% to 36%
Is this an exacerbation of
leukemia and is it an adverse
response?

159. Female 2-Year F344 Study
Microscopic Findings
Control Low
Exposure
Medium
Exposure
High
Exposure
Mononuclear Cell Leukemia 8/50
16%
7/50
14%
19/51*
37%
16/50
32%
* p < 0.05 Fischer’s Exact Test; p < 0.05 Life Table test
Historical Control Range = 14% to 36%
Is this an exacerbation of
leukemia and is it an adverse
response?
Because of its high &
variable background
incidence, a positive
mononuclear cell leukemia
response should take the
historical control range
into account in determining
if there is a real treatment-
related increased incidence.

160. • Definitions
– Adverse response
– Adaptive response
– Reversible response
– Exacerbation of background lesions
• For the Toxicology Report & Regulatory
Submission
• Paradigm Shift & Determining Adversity
• Practical Examples of Adverse and Adaptive
Responses in Preclinical Studies
Outline of Presentation

161. Adverse Response
There is no perfect definition of an
adverse response in a preclinical study.
前臨床試験におけるadverse反応の完
璧な定義はない

162. Criteria for Defining an Adverse
Response
• ‘…change in the morphology, physiology, growth,
development, reproduction, or life span of an
organism, system, or (sub) population that results
in an impairment of functional capacity, an
impairment of the capacity to compensate for
additional stress, or an increase in susceptibility
to other influences’ (IPCS, 2004).
• At the present time based on “apical responses”
– Clinical signs, lesions, traditional biomarkers
– And always within the context of the specific study

163. If a finding fulfills the criteria for an
adverse effect, then it is considered
adverse even if:
• it is transient (disappears during treatment)
• 一過性の変化（投与期間中に消失）
• it is reversible (disappears after treatment is stopped)
• 回復性がある（投与中止後に消失）
• it is caused by exaggerated pharmacology
• 薬理作用が増強されたことによって発現
• It is secondary to some other change or secondary to stress
• 他の所見に対する二次的な変化、あるいはストレスに対す
る二次的な変化
もし、ある所見がadverse effect（有害性作用）のクライテリアを満た
すならば、たとえ下記の件が該当するとしても、adverseであると考
えられる

164. Thanks to Dr. Katsuhiko Yoshizawa
for Japanese translations
And
Thanks to you for your kind attention

165. You can view this presentation at focusontoxpath.com/adverse-responses