European Committee of Organic Surfactants and their Intermediates LRI Workshop “ Applicability of skin sensitization testing methods for regulatory purposes" Comparative CESIO study in surfactants: Inconsistent results between the LLNA and Guinea Pig sensitization tests J.-C. Carrillo ; N. Ball; S. Cagen; H. Certa; D. Eigler; H. Esch; C. Garcia; C. Graham; C. Haux; R. Kreiling; A. Mehling
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European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Comparative CESIO study in
surfactants:
Inconsistent results between the
LLNA and Guinea Pig
sensitization tests
J.-C. Carrillo; N. Ball; S. Cagen; H. Certa; D. Eigler; H. Esch; C. Garcia; C.
Graham; C. Haux; R. Kreiling; A. Mehling
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
OVERVIEW
Background
Allergy and test methods for skin sensitization
Specificity, selectivity and accuracy
Industry data
Conclusions
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
OVERVIEW
Background
Allergy and test methods for skin sensitization
Specificity, selectivity and accuracy
Industry data
Conclusions
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Background:
Skin sensitization tests (e.g. OECD 406 or 429) are performed for hazard
assessment and C&L purposes.
Under REACH LLNA (OECD 429) is the prescribed test
New LLNA-generated data led to „unexpected positive‟ results for surfactants
“Word of mouth” revealed the unexpected results were not limited to
surfactants
Past experience and weight of evidence „unexpected‟ positive results
could be „false‟ positives
The CESIO-LLNA Task Force was formed as an inter-industry effort to
investigate these findings
The CESIO-LLNA TF is currently investigating the reliability of the LLNA for
predicting skin sensitization potential of surfactants and their intermediates
Why was the CESIO-LLNA-Task Force formed?
INTRODUCTION
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
OVERVIEW
Introduction
Allergy and test methods for skin sensitization
Specificity, selectivity and accuracy
Industry data
Conclusions
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
VALIDATION in a Nutshell
The LLNA was the first regulatory test to be formally
validated.
Validation was based on comparative data (e.g. LLNA vs.
Guinea Pig Tests)
Comparative data: The same substances tested in the LLNA
and GPT systems allows comparing the methods to one
another. Are results concordant (yes/no) ?
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
DEFINITIONS (I)
Selectivity/Sensitivity: The proportion of all positive
chemicals that are correctly classified as positive in a test
Specificity: The proportion of all negative chemicals that are
correctly classified as negative in a test
Accuracy: The closeness of agreement between a test result
and an accepted reference value; (b) the proportion of correct
outcomes of a method
Dean et al., Regulatory Toxicology and Pharmacology 34, 258–273 (2001)
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
DEFINITIONS (II)
In the following (as in the ICCVAM validation):
Positive/(negative) results mean that in a regulatory
context, labeling would be required (or not)
“False” positive means that a LLNA result is positive,
the result of the guinea pig test is negative
“False” negative means that a LLNA result is
negative, the result of the guinea pig test is positive
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
CHEMICAL
IDENTIFICATION
GUINEA PIG
POSITIVES
GUINEA PIG
NEGATIVES
UNCLEAR TOTAL
LLNA Positives 86 6 0 92
LLNA Negatives 10 28 0 38
total 96 34 0 130
DATA SUBMITTED TO ICCVAM (METHOD VALIDATION)
COMPARISON OF LLNA AND GUINEA PIG CLASSIFICATIONS
Sensitivity (86 LLNA positives of 96 true positives): 90%
Specificity (28 LLNA negatives of 34 true negatives): 82%
Accuracy (correctly predicted results 86+28=114 of 130): 88%
Solvent DMF or acetone/ olive oil Dist illed water or olive oil Dist illed water
Concentrat ion At least 3 between 1.25% to
25%
1 for the induct ion between
1.25% to 10% and 2 for the
challenge between 2.5% to 100%
Concentrat ions previously
determined according to
necrosis (induct ion) or irritat ion
(challenge)
1 (use dose) for both
induct ion and challenge
between 1% to 6%
Parameter St imulat ion Index (3H
thymidine)
Ear thickness for skin irritat ion
Readings of skin react ions after
challenge
Readings of skin react ions
after challenge
Industry data: STUDY 1 – Sugarlipid surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Industry data: STUDY 1 – Sugarlipid surfactants
STUDY 1: Sugarlipid surfactants:
Irritation was assessed by:
LLNA increase in ear thickness (%)
GPMT control animals (% of positive animals)
HRIPT irritation index (induction phase)
Mostly, good overlap between concentrations in the GPMT and LLNA
In the GPMT in only one example (C8-C10 glucoside), 22% of the test
animals gave a positive response 24 hours after the first challenge,
however at 48 hours all animals were negative.
Except for C8-C10 glucoside, irritancy in GPMT was not consistent with
that observed in the LLNA.
Tested concentrations in the LLNA associated with increases over 10% in
ear thickness did not appear to cause an irritant response in the GPMT.
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
- 5/10 are classified
according to LLNA
- 0/10 are classified
according to GPMT
- 0/8 are positive
according to HRIPT
-50% are discordant (LLNA vs. GPMT)
- HRIPT suggest discordances in classification
are related to overestimation by the LLNA
- Positive reactions with LLNA are well correlated
with skin irritation (R2=0.71).
- LLNA able to sufficiently distinguish skin
sensitization from skin irritation?
Industry data: STUDY 1 – Sugarlipid surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
STUDY 2: Surfactants
Industry data: CESIO surfactant comparative testing
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
STUDY 2: First attempt to use alternative endpoints to distinguish irritation from
sensitization
Seven model substances representing surfactant like compounds where
investigated in a comparative setting (GPMT and LLNA).
In the LLNA, additional to thymidine incorporation, alternative endpoints were
evaluated which would help assess the irritation potential of these substances.
Assessment included (but not limited to): ear weights and thickness, B220+.
Increase in ear weights and thickness can be indicators of the irritation properties
of the substance.
B220+ has been proposed as an alternative marker to differentiate sensitizers from
irritants.
The SI cut off for these endpoints has been suggested at SI >1.25* to be
considered biologically and statistically relevant.
Industry data: STUDY 2 – Surfactants
*. OECD, Draft proposal for an update to the test guideline 429. Skin Sensitisation: Local Lymph Node Assay. 2009.
* Gerberick, G.F., et al., Use of a B cell marker (B220) to discriminate between allergens and irritants in the local lymph node assay. Toxicol Sci, 2002. 68(2): p. 420-8.
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Industry data: STUDY 2 – Surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Industry data: STUDY 2 – Surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Industry data: STUDY 2 – Surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Industry data: STUDY 2 – Surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Industry data: STUDY 2 – Surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
Based on SI thymidine incorporation alone the following is true:
The alternative endpoints assessed in this study did not help explain the role of
irritation in obtaining discordant results.
Irritation might have been a factor but not always.
A clear dose response was not always observed
Both OECD methods are equally accepted but in these cases which ones are
correct?
5/7 are discordant
Industry data: STUDY 2 – Surfactants
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
OVERVIEW
Introduction
Allergy and test methods for skin sensitization
Specificity, selectivity and accuracy
Industry data: CESIO surfactant comparative testing
Conclusions
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for
regulatory purposes"
CONCLUSIONS
No test is without limitations.
The LLNA is suitable for many substance classes, but for surfactants:
Comparative data on GPMT and LLNA point to a possible false positives in
the LLNA.
Based on data collected and generated, accuracy is 47%
Is the LLNA the method of choice for these chemistries?
Alternative endpoints are available but are probably not suited for all type of
substances. More data needs to be generated to assess applicability
A clear need exists to better understand the underlying mechanisms for the
nature of false positives/negatives to further develop alternative endpoints in the
LLNA.
We need reliable data base in order to develop reliable non-animal tests.
European Committee of
Organic Surfactants and
their Intermediates
LRI Workshop
“ Applicability of skin sensitization testing methods for