ADVERSE OUTCOME PATHWAYS - APPLICATION IN CONSUMER...
Transcript of ADVERSE OUTCOME PATHWAYS - APPLICATION IN CONSUMER...
ADVERSE OUTCOME PATHWAYS - APPLICATION IN CONSUMER [AND ENVIRONMENTAL] SAFETY RISK ASSESSMENTS
CARL WESTMORELAND SAFETY & ENVIRONMENTAL ASSURANCE CENTRE (SEAC) UNILEVER R&D
AOPS
• Safety assessment of consumer products
• Exploring AOPS in consumer safety assessment
» Skin sensitisation
» Systemic toxicity
• Challenges
Can we use x% of ingredient y in product z?
CAN WE USE A NEW INGREDIENT SAFELY?
CURRENT SAFETY ASSESSMENT PROCESS FOR INGREDIENTS IN CONSUMER PRODUCTS
Consider product type and consumer habits
Determine route and amount of exposure
Identify toxicological endpoints of potential
concern
Identify critical end point(s) for risk
assessment
Identify available toxicology data
Identify supporting safety data (e.g. QSAR,
HoSU)
Evaluate required vs. available support
Conduct risk assessment for each critical endpoint
Conduct toxicology testing as required
Overall safety evaluation for product – define acceptability
and risk management measures
Source Environmental Containment
Exposure Molecular Initiating
Event
Organelle and
Molecular Assemblies
Effects
Cellular Effects
Tissue Effects
Organ Effects
Organ Systems Effects
Individual Effects
Population Effects
Community Effects
Toxicity Pathway
Mode of Action
Adverse Outcome Pathway
Source to Outcome Pathway
Adapted from Kevin Crofton 2010, OECD AOP Meeting Definitions
FROM TOXICITY PATHWAYS TO ADVERSE OUTCOME PATHWAYS (AOPS)
EXAMPLE 1: SKIN SENSITISATION
We risk assess to prevent skin sensitisation in consumers: » What risk does ingredient X at conc. Y in product Z pose to the consumer?
Focus should be on prevention of human adverse outcome, not replacing animal test(s)
1. Identify pathways driving human adverse response = allergic contact dermatitis.
2. Develop test methods to predict key toxicity pathways.
3. Will response be adverse for a relevant exposure scenario?
Risk ?
Prod
uct
X
Hazard Exposure
Historical Non-animal In Vivo
Induction of skin allergy is a multi-stage process driven by toxicity pathways:
- Mechanistic understanding is captured in Adverse Outcome Pathway (AOP)
- How can we make risk assessment decisions by integrating this evidence?
Modified from ‘Adverse Outcome Pathway (AOP) for Skin Sensitisation’, OECD report
1. Skin Penetration
2. Electrophilic substance:
directly or via auto-oxidation or metabolism
3-4. Haptenation: covalent
modification of epidermal proteins
5-6. Activation of epidermal
keratinocytes & Dendritic cells
7. Presentation of haptenated protein by Dendritic cell resulting
in activation & proliferation of specific
T cells
8-10. Allergic Contact Dermatitis: Epidermal
inflammation following re-exposure to
substance due to T cell-mediated cell death
Key Event 1 Key Event 2 + 3 Key Event 4 Adverse Outcome
OECD AOP FOR SKIN SENSITISATION
Prod
uct
hazard in vivo response
Adverse
Non-Adverse
exposure
1. Skin Penetration
2. Electrophilic substance:
directly or via auto-oxidation or metabolism
3-4. Haptenation: covalent
modification of epidermal proteins
5-6. Activation of epidermal
keratinocytes & Dendritic cells
7. Presentation of haptenated protein by Dendritic cell resulting
in activation & proliferation of specific
T cells
8-10. Allergic Contact Dermatitis: Epidermal
inflammation following re-exposure to
substance due to T cell-mediated cell death
X
OUR CHALLENGE: WHAT RISK DOES INGREDIENT X AT CONC. Y IN PRODUCT Z POSE TO CONSUMERS?
1. Generate relevant non-animal data for the chemical and the exposure scenario
2. Use data as inputs for two linked mathematical models capable of predicting magnitude of human sensitiser-specific immune response
3. Invest in clinical research to establish adverse threshold in human immune response allows model prediction(s) to underpin risk assessment decisions
Adverse
Non-Adverse
allergic immune response
time
No.
CD
8+ T
cel
ls
dose Y
dose X
haptenated skin protein prediction
1. Skin Penetration
3-4. Haptenation: covalent
modification of epidermal proteins
5-6. Activation of epidermal
keratinocytes & Dendritic cells
7. Presentation of haptenated protein by Dendritic cell resulting
in activation & proliferation of specific
T cells
8-10. Allergic Contact Dermatitis: Epidermal
inflammation following re-exposure to
substance due to T cell-mediated cell death
2. Electrophilic substance:
directly or via auto-oxidation or metabolism
Maxwell et al (http://axlr8.eu/assets/axlr8-progress-report-2012.pdf) pp219-226
APPLYING THE AOP TO RISK ASSESSMENT
SEAC
For foreseeable
future
Traditional
Toxicology
Our Unilever
stated aim
No Unilever animal tests
Tox pathway activation in vitro
Modelling networks & exposure
Applying TT21C principles
NEW TOXICOLOGY PATHS
WHICH PATHWAYS?
• Pro-oxidant + Free-radical based • Mitochondrial targets + energy production disruption • Specific receptor agonist/antagonist targets » Functional receptors + cell surface receptors » Nuclear receptor mediated + promoter regions » Hormonal including ED • Electrophiles covalently binding » DNA and protein dysfunction (incl. haptens) • Immuno-specific mechanisms + cytokine effects • Disruption of calcium homeostasis + signalling • Direct necrosis or apoptosis induction • Impairment of cell proliferation and tissue repair • Interfering with ion transporters + metabolism
Exposure & Consumer Use Assessment
High-content information in vitro assays in human cells & models
Dose-response assessments
Computational models of the circuitry of the relevant toxicity pathways
PBPK models supporting in vitro to in vivo extrapolations
Risk assessment based on exposures below the levels of significant pathway perturbations
Chemistry-led alerts & in vitro screening
CHARACTERISING THE CELLULAR RESPONSE TO DNA DAMAGE
0.5
1
1.5
2
2.5
3
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0.001 0.201 0.401 0.601 0.801 1.001 1.201 1.401 1.601 1.801 2.001
PP53 TK6
Total p53
H2AX
pp53 RC
HT Total P53
HT H2AX
Mn data
FACs MN data HT1080
INTEGRATE DATA INTO MODELS/NETWORKS
Basal function
Response to small perturbations
Response to larger perturbations
Assessing mechanism of underlying threshold giving rise to increased mutation
Computational modeling of dose response for DNA damage pathway activation
IN VITRO IN VIVO (HUMAN EXPOSURE) EXTRAPOLATION
Exposure mg/kg/day
Target site concentration (µM)
Acceptable in vitro concentration (µM)
THOUGHTS/CHALLENGES (1)
Case Studies » Encourage pragmatism
» What is the key information to allow decision-making?
Multidisciplinary teams » Key importance of modelling in the process
» Interactions between modellers, chemists, biologists and toxicologists accelerates pathway characterisation.
» Multi-disciplinary teams are difficult to steer but necessary.
THOUGHTS/CHALLENGES (2)
Risk Assessment: Source to Outcome Pathway » Full integration of exposure to develop quantitative AOPs to go from hazard
identification to risk assessment for both human health and the environment
» Effective integration of expertise.
Relevance of in vitro concentrations to in vivo » MEASURING free concentrations vs nominal
» Importance of understanding kinetics
Defining adversity » What are we trying to prevent in our consumers / environment?
» Need to consider up-front how adversity will manifest: • Is there a defined clinical outcome (eg skin allergy)? • Can we define ‘adversity’ in the pathway in vitro? (e.g. DNA damage) • Irreversible disruption of homeostasis ?
THANK YOU
Yeyejide Adeleye, Maja Aleksic, Nora Aptula, Mahesh Batakurki, Emma Butler, Paul Carmichael, Kristina Castle, Catherine Clapp,
Richard Cubberley, Claire Davies, Michael Davies, Eliot Deag, Matthew Dent, Sue Edwards, Julia Fentem, Paul Fowler, Antonio
Franco, Nichola Gellatly, Nicola Gilmour, Stephen Glavin, Dave Gore, Todd Gouin, Steve Gutsell, Colin Hastie, Juliette Hodges, Geoff Hodges, Sandrine Jacquoilleot, Gaurav Jain, Penny Jones, Kevin
Lam, Heidi Langley, Yvan Le Marc, Moira Ledbetter, Jin Li, Cameron MacKay, Ian Malcomber, Sophie Malcomber, Stuart Marshall, David
Mason, Gavin Maxwell, Claire Moore, Craig Moore, Beate Nicol, Sean O’Connor, Ruth Pendlington, Juliette Pickles, Oliver Price,
Fiona Reynolds, Jayne Roberts, Nicola Roche, Paul Russell, Ouarda Saib, David Sanders, Andrew Scott, Sharon Scott, David Sheffield,
Wendy Simpson, Ilias Soumpasis, Chris Sparham, Vicki Summerfield, Dawei Tang, Sivaram TK, Roger van Egmond, Andrew
White, Sam Windebank