Potential applicability and challenges of using in pp y g g vitro - - PowerPoint PPT Presentation

Potential applicability and challenges of using in pp y g g vitro and in silico methodologies in food ingredient safety assessment

S Fit t i k PhD DABT ERT Suzanne Fitzpatrick, PhD, DABT, ERT CFSAN/FDA SOT Food Safety Specialty Section Webinar August 18 2016 August 18, 2016

Topics of Discussions for this Talk Topics of Discussions for this Talk

• Vision of the NRC Report on Toxicity Testing in the 21

p y g Century

• Tox 21 Partnership between FDA, EPA, NIEHS, and

NCATS NCATS

• Other Emerging “Tox 21” Methods

– SAR/QSAR – SAR/QSAR – Read Across – AOPs – Organs of a Chip

• New ICCVAM Activities
• New NRC Report

2007 NRC - Toxicity Testing in the 21 t C t A Vi i & St t 21st Century: A Vision & Strategy

• Sponsored by EPA
• Use cell-based (high throughput) assays to

understand how chemicals perturb normal cellular functions (i.e., toxicity pathway) ( , y p y)

– Establish relationships of perturbations with “adverse

• utcomes”
• Develop in vitro to in vivo extrapolation

p p methods

• Integrate results to predict hazard/risk

Broader coverage of chemicals & endpoints Reduce cost & time of testing Reduce cost & time of testing Use fewer animals

Vision of the NRC report Vision of the NRC report

• The NRC report laid out a roadmap for

The NRC report laid out a roadmap for revamping toxicity testing

• Focus should shift away from identification of

y toxicant-induced apical endpoint effects towards an identification of a sequence of key t / d f ti th i i events/modes of action as the organizing principle for risk assessment

• The use of mechanistic data will help risk
• The use of mechanistic data will help risk

assessors gain a better understanding of how chemicals exert their toxic effects

Vision of the NRC report Vision of the NRC report

 NRC also advocated the use of adverse NRC also advocated the use of adverse

• utcome pathways (AOPs)as a critical aspect of

predictive toxicity testing.  The AOP Framework was established to systematically collect, organize and evaluate mechanistic data and causally link them to adverse effects.

Memorandum of Understanding for Tox 21

• 5-year Memorandum of Understanding (MoU) on “High-Throughput

S i T i it P th P fili d Bi l i l I t t ti f Screening, Toxicity Pathway Profiling, and Biological Interpretation of Findings” released on Feb 14, 2008 signed by NHGRI (F.S. Collins), NIEHS/NTP (S.H. Wilson), and EPA (G.M. Gray).

• Revised 5-year MoU to add FDA signed on July 19, 2010 by

NHGRI (E.D. Green), NIEHS/NTP (L.S. Birnbaum), EPA (P.T. Anastas) and FDA (J Woodcock) Anastas), and FDA (J. Woodcock).

• Known informally as Tox21 for Toxicology in the 21st Century
• MOU revised July 2015. Dr. Susan Mayne, Director of the Center

for Food Safety & Applied Nutrition, signed for FDA.

6

Tox21 Goals

• Identify patterns of compound-

induced biological response in d t

• rder to:

− characterize toxicity/disease pathways − facilitate cross-species extrapolation − model low-dose extrapolation

• Prioritize compounds for more

Prioritize compounds for more extensive toxicological evaluation

• Develop predictive models for

biological response in humans

7

Agency Points of Contact FDA Suzanne Fitzpatrick Ph D FDA – Suzanne Fitzpatrick Ph.D. NCGC/NCATS –Anton Simeonov, Ph.D. EPA/NCCT –Russell Thomas, Ph.D. NIEHS/NTP – Rick Paules, Ph.D.

Informatics Working Group Chemical Selection Working Group Targeted Testing Working Group Assays & Pathways Working Group Working Group Co-Chairs Ruili Huang, Ph.D. (NCGC) Richard Judson, Ph.D. (EPA) Nisha Sipes, Ph.D. (NIEHS) Weida Tong Ph D (FDA) Working Group Co-Chairs William Leister, Ph.D. (NCGC) Donna Mendrick, Ph.D. (FDA) Ann Richard, Ph.D. (EPA) Suramya Waidanatha Ph D (NTP) Working Group Co-Chairs Michael DeVito, Ph.D. (NTP) David Gerhold, Ph.D. (NCGC) Timothy Shafer, Ph.D. (EPA) Robert Sprando Ph D (FDA) Working Group Co-Chairs Kevin Gaido, Ph.D. (FDA) Keith Houck, Ph.D. (EPA) Kristine Witt, M.S. (NTP) Menghang Xia Ph D (NCGC)

 Identify toxicity pathways & corresponding  Evaluate assay performance  Develop

 Evaluate relevance

• f prioritization

schemes &

 Establish compound

libraries for qHTS (10K, mixtures, water-

Weida Tong, Ph.D. (FDA) Suramya Waidanatha,Ph.D.(NTP) Robert Sprando, Ph.D. (FDA) Menghang Xia, Ph.D. (NCGC)

assays  Review nominated assays and i iti f t prioritization schemes and prediction models  Make all data prediction models

 Extrapolate in vitro

concentration to in i o dose soluble)

 Establish QC

procedures for compound identity prioritize for use at the NCGC Make all data publicly accessible vivo dose compound identity, purity, concentration, and stability 8

Exposure

Tox Tox 21: Outcome Pathways of NAS 21: Outcome Pathways of NAS

Exposure Uptake-Delivery to Target Tissues Perturbation

Biologic inputs

“Normal” Biological Function

Cellular response pathway

Adaptive Responses

Early cellular changes Adverse Outcomes (e.g., mortality, Reproductive Impairment)

Cell injury, Inability to regulate

Responses

Impairment)

Molecular initiating event Perturbed cellular response pathway Adverse outcome relevant to risk assessment risk assessment

Toxicity Pathway Adverse Outcome Pathway

NAS, 2007

Tox Cast Inventories Tox Cast Inventories

• ToxCast Phase I (293 unique cmpds)

– EPA pesticidal actives w/ rich in vivo data PFOA BPA 12 t b lit / t i – PFOAs, BPA, approx 12 metabolite/parent pairs

• ToxCast Phase II (767 unique new cmpds)

– EPA pesticides, high interest EPA and stakeholder inventories, data rich h i l (EDSP OPPT ti i bi l i t lt ti f chemicals (EDSP, OPPT, antimicrobials, inerts, green alternatives, fragrances, water …) – FDA CFSAN data rich, NCTR LTKB Priority 1 drugs Toxicity reference chemicals data rich chemicals NTP immunotox – Toxicity reference chemicals, data‐rich chemicals, NTP immunotox – 135 Donated pharma cmpds ‐‐ failed drugs w/ pre‐clinical or clinical tox data

• ToxCast E1K (800 unique new cmpds)

E d i ti f d SAR di t d ER ti /i ti EDSP – Endocrine active reference cmpds, SAR predicted ER‐active/inactives, EDSP cmpds

• EPA’s Tox21 library (3727 unique cmpds out of current 8599 total)

C l t h d EPA l lib d t b ild T C t i t i – Complete on‐hand EPA sample library used to build ToxCast inventories

Tox21 Robot System

NCGC d 1408 d (1353 i ) f NTP NCGC screened 1408 compounds (1353 unique) from NTP and 1462 compounds (1384 unique) from EPA in 140 qHTS assays representing 77 predominantly cell‐based reporter gene endpoints.

11 http://www.youtube.com/watch?v=ECloTsdD-xo

Current Limitations of Data for Regulatory Use

• Lack of xenobiotic metabolism
• Inability to screen volatile or highly hydrophillic

chemicals

• Limited coverage of biological targets
• Lack of a pragmatic path forward for validation
• Inability to confidently translate perturbations at

molecular level to likely tissue and organ‐level effects

• These are all the challenges/goals for all four

agencies going forward with this program

SAR/QSAR /Q

• Structure-Activity Relationships (SAR) are

relationships between a compound’s chemical relationships between a compound s chemical structure and physiochemical properties and biological effects on living systems g g y

• Complex computer software modeling programs

have been and are being developed to predict carcinogenic and mutagenic potential using quantitative SAR or QSAR.

• QSAR analysis – could be useful tool for

complementing and possibly reducing the battery of genetic toxicity testing requested for battery of genetic toxicity testing requested for food contact substances

Read‐Across Read Across

• Read-across is when the already available data of a

y data-rich substance (the source) is used for a data-poor substance (the target), which is considered similar enough to the source substance to use the same data as enough to the source substance to use the same data as a basis for the safety assessment

• Uses of read Across

– To avoid additional animal testing – To save time and cost – To use human data if available for one compound but not – To use human data, if available for one compound but not possible to produce for another – To cover more substances with one safety assessment

Opportunities for incorporating in it /i ili d t i t d vitro/in silico data into read-across

Reducing uncertainty in a read-across argument in a regulatory submission: g y

• Using in vitro/in silico data to confirm the similarity

in the mechanism of action within a category d/ b t th “t t” d “ ” and/or between the “target” and “source” compounds

• Confirming or refuting a hypothesis that proposed
• Confirming or refuting a hypothesis that proposed

analogues may have “other” effects

• Assessing the relative “potency” of the analogues

g p y g

Understanding an AOP Provides A Basis to Inform The Use of Data for

Structure Activity R l i hi In vitro di In vivo di

Risk Assessment & Decision Making

Relationships studies studies

Molecular initiating event Key events or predictive relationships spanning levels of biological

• rganization

Adverse outcome relevant to risk assessment

Greater Toxicological Greater Risk

g

Understanding Relevance

(Qualitative AOP) (Quantitative AOP)

FDA FDA‐DARPA DARPA‐NIH NIH Microphysiological Microphysiological Systems Systems Program Program Program Program

• Started in 2011 to support the development of human microsystems, or
• rgan “chips,” to screen for safe and effective drugs swiftly and efficiently
• rgan chips, to screen for safe and effective drugs swiftly and efficiently

(before human testing)

• Collaboration through coordination of independent programs

Engineering platforms and biological proof-of-concept (DARPA-BAA-11- 73: Microphysiological Systems) Underlying biology/pathology and mechanistic understanding (RFA-RM-12-001 and RFA RM-11-022) Advise on regulatory requirements, validation and qualification

Base period DARPA bioengineering DARPA bioengineering Platform + 2 systems Platform + 2 systems & & U18 generated cell resources U18 generated cell resources UH2 generated organ systems UH2 generated organ systems 24 months ntegration ntegration validation validation Period 1 4 systems 4 systems 7 systems 7 systems UH3 phase: UH3 phase: ‐ Incorporation of differentiated Incorporation of differentiated P i d 2 In In 10 systems 10 systems p stem stem‐ and progenitor and progenitor‐derived cells derived cells ‐ Integration of various organ systems Integration of various organ systems Period 2

• Cell viability for 4 weeks
• Integrated system predicts

human in vivo efficacy, toxicity and

• Multicellular architecture
• Vascularization, innervation,

hormonal, humoral and

toxicity, and pharmacokinetics:

• safe and effective
• safe and ineffective

f b t ff ti immunological signaling

• Genetic diversity and

pharmacogenomic capacity

• Representation of normal

60 months Period 3

• unsafe, but effective
• unsafe and ineffective

Representation of normal and disease phenotypes

The Tissue Chip Program

GOAL: Develop an in vitro platform that uses human tissues to evaluate the efficacy safety GOAL: Develop an in vitro platform that uses human tissues to evaluate the efficacy, safety and toxicity of promising therapies.

2012‐13 2013‐14 2014‐15 2015‐16 2016‐17 Phase 1: Phase 1: De Develo lopme pment Phase 2: Phase 2: Cell incorporation & Cell incorporation &

• rgan int
• rgan integration

gration 2012 13 2013 14 2014 15 2015 16 2016 17 DARP RPA base periods: Organ int A base periods: Organ integration gration Liver **FD **FDA pr provides ides insight insight and e and exper pertise ise thr throughout the ughout the pr program

• gram

Current Goals:

• Integration
• Compound testing

V lid ti

• Validation
• Partnerships
• Adoptions of the tech to

the community

The Tissue Chip…Diversity a Good Thing

ICCVAM Activities ICCVAM Activities

• Developing a Strategy and Roadmap to

Developing a Strategy and Roadmap to Replace the Use of Animals for Toxicity Testing

• Very similar to the EU ToxRisk Plan
• Focus on the following:

– Repeat Dose Toxicity – Pharmacokinetics and Metabolism C i i it – Carcinogenicity – Reproductive and Developmental Toxicity Neurotoxicity – Neurotoxicity

NATIONAL RESEARCH COUNCIL SECOND MEETING OF THE COMMITTEE ON INCORPORATING 21ST CENTURY CENTURY SCIENCE INTO RISK-BASED EVALUATIONS

• Combining the recommendations of the two reports:

– Toxicity Testing in the 21st Century – Exposure Testing in the 21st Century

• This new report will focus on 21st Century Science-based Risk

St t i i t Ri k A t Strategies into Risk Assessment

• FDA was not part of committee for either of these two

previous reports B t FDA recogni es the importance of this ne ision for

• But FDA recognizes the importance of this new vision for

toxicology

• FDA has made two presentations to the committee on FDA’s

Risk Assessment Challenges Risk Assessment Challenges

• Report due end of 2016

Thank You for Inviting Me to Talk Thank You for Inviting Me to Talk

• Questions

Questions

• You can contact me at:

S C Fit t i k PhD DABT ERT Suzanne C. Fitzpatrick, PhD, DABT, ERT Senior Advisor for Toxicology Senior Science Advisory Staff Office of the Center Director CFSAN/FDA suzanne.fitzpatrick@fda.hhs.gov 240‐402‐3042