# Presentation: 233003

## Choosing core chemicals to use in pre-validation studies

- Endocrine Disruptor Screening Program
- March 2002

## What do we mean by“core chemicals”?

-   Chemicals that would be tested in all assays during the prevalidation stage.
-    Exceptions:
- “special studies” (one-gen, avian dosing, etc.)
- “for cause” (for example, no need to test thyroid chemicals in aromatase assay)
- 	Does not preclude testing additional chemicals

## Purposes of having a set of core chemicals

- Compare the same chemicals across assays
- Do different assays provide consistent results?
- Establish the ability of (apical) assays to respond to different modes of action

## Two-part discussion

- Today: Establish candidates
- Establish criteria for choosing a core set
- Review current candidates
- Modify the handout if necessary
-   (“Chemicals used in prevalidation of EDSP-related studies”)
- Tomorrow: Choose a core set
- EPA proposal for core chemicals
- Discussion
-     (The distinction between establishing candidates and choosing a core set is artificial; the discussions may overlap.)

## Criteria to consider when choosing a set of core chemicals

- Coverage of E/A/T
- Mode of action
- Potency
- Applicability to both human and eco
- Other
- Solubility
- Availability in pure form
- Stability
- Negative controls?

## See handout“Chemicals used in prevalidation of EDSP-related studies”

- Notes:
- The table covers what’s being tested in EDSP, not all studies in the literature
- Some “mode” columns were created to accommodate chemicals already in testing; the level of detail does not necessarily reflect need for core coverage

## Questions about the handout

- Are the modes of action appropriate?
- All important modes listed?
- Appropriate level of detail?
- Which modes need not be considered in core?
- Other candidates?
- Table correctly filled out?

## Tomorrow

- EPA proposal for core chemicals
- Discussion

## Slide 9

## EPA Proposal 1: “Full set”

- Receptor binding and thyroid (12)
- E+/-,  A+/-,  T+/-
- Strong and weak of each
- Aromatase inhibitor (1? Female assays only)
- Other steroidogenesis inhibitor (1?)
- CNS/pituitary (1?)
- “Negative toxic” (1?)
-    Total: 16 chemicals

## Review: Candidate assays in Tier 1

- Receptor binding/reporter gene, E & A
- Uterotrophic
- Hershberger
- Steroidogenesis
- Pubertal female
- Frog metamorphosis
- Fish screen
- Pubertal male
- Aromatase
- Adult male
- In utero through lactation

## Review:  Assays in Tier 2

- Mammalian 2-generation
- Fish life cycle
- Mysid life cycle
- Avian 2-generation reproduction
- Amphibian development and repro

## EPA Proposal 2: “Limited set”

- Receptor binding and thyroid (3)
- E+, A-, T- only
- Weak only
- Aromatase inhibitor (1? Female assays only)
- Other steroidogenesis inhibitor (1?)
- CNS/pituitary (1?)
- “Negative toxic” (1?)
- Total: 7 chemicals

## “Limited set”

- E+				Methoxychlor
- A-				p,p’-DDE
- T-				Phenobarbital
- Aromatase		Fenarimol
- Other st’genesis	Ketoconazole
- CNS/pituitary		Atrazine
- “Negative toxic”	?

## Slide 15

## “Negative toxics”?cause decrease in body weight gain but toxicity is not related to ED

- 1. methoxyacetic acid
- 2. cadmium chloride
- 3. alpha-2u-globulin inhibitors
- 4. bromobenzene, phenacetin, or acetaminophen
- 5. eugenol
- 6. chloroform
- 7. acetaldehyde
- 8. inhibitors of oxidative phosphorylation
-    e.g., pentachlorophenol or 2,4-dinitrophenol
- 9. cyanide

## EPA Proposal 1: specifics

- E+ strong:			Ethinyl estradiol
- E+ weak:			Methoxychlor
- E- strong:			ICI 182,780
- E- weak:			?
- A+ strong:			Methyl testosterone
- A+ weak:			Androstene-3,17-dione, 4-
- A- strong:			Vinclozolin (M1 if *in vitro*)
- A- weak:			p,p’-DDE
- T+ strong:			Thyroxine
- T+ weak:			?
- T- strong:			Propylthiouracil
- T- weak:			Phenobarbital

## EPA Proposal 1: specifics (cont’d)

- Aromatase:		Fenarimol
- Other St’genesis:	Ketoconazole
- CNS/pituitary:		Atrazine
- Negative:		?

## Other questions to consider#1 of 4

- Should assays already in prevalidation be run again to include the core chemicals?

## Other questions to consider#2 of 4

- Is the core set of chemicals sufficient to establish relevance of an assay?
- 	If not, how should additional chemicals be chosen, and how many are needed?

## Other questions to consider#3 of 4

- Should the core chemicals be used in the interlaboratory validation stage?(All / some / none)

## Other questions to consider#4 of 4

- Should the core chemicals be used for Tier 2 assays?