Transcript Slide 1

IQF Framework for QSAR
Speciation
Parent
Chemical
Molecular
Initiating
Events
and
Measurable
System
Effects
Adverse
Outcomes
Metabolism
Chemistry/
Biochemistry
QSAR
Systems
Biology
1. Identify Plausible Molecular Initiating Events
2. Design Database for Abiotic Binding Affinity/Rates
3. Explore Linkages in Pathways to Downstream Effects
4. Develop QSARs to Predict Initiating Event from Structure
Estrogen Receptor (ER) Toxicity Pathway
Chemical interacts with Receptor at Molecular Level,
Initiates a Series of events, and leads to Adverse Outcome
QSAR
In vitro Assays
In vivo Assays
Inert/Antimicrobial
Chemical
MOLECULAR
Initiating Event
ER
Binding
Toxicological
Understanding
CELLULAR
Response
TISSUE/ORGAN
Altered
Protein
Expression
Altered
proteins,
hormones;
Ova-testis
INDIVIDUAL
POPULATION
Sex
reversal;
Altered
behavior;
Repro.
Skewed
Sex
Ratios;
Yr Class
Risk Assessment
Relevance
ER Toxicity Pathway
MOLECULAR
Initiating Event
ER
Binding
In vitro
Assay
Endpts
In vivo
Assay
Endpts
Trout
cyto rtER
Binding
TISSUE/ORGAN
Response
CELLULAR
Respopse
Altered
Protein
Expression
Altered
proteins
(VTG),
Ova-testis
INDIVIDUAL
Response
Chg 2ndry
Sex Char
MaleTrout
Liver Slice
Vtg Induction
Altered
Repro.
POPULATION
Response
Skewed
Sex
Ratios,
Altered
Repro.
Male Medaka
Liver
Vtg Induction
Male Medaka
Chg in 2ndary sex
characteristic; behavior?
Papillary Processes
Female Medaka
Liver
Vtg decr.
Sex Reversal
Genetic Males to
Phenotypic Females
Male Medaka
Gonad
Complete
conversion to ovary
Female Medaka
Fecundity
Hatch
Yes
Chemical
Universe
Contains Cycle
Non binder
(RBA<0.00001)
Log Kow <1.3
• Alkylbenzsulfonic Acids
• Sulfonic Acid Dyes
• p-Alkyl Fluorobenzenes
• Bis–anilines
• Oxazoles
• Alkoxy Anilines • Benzamide
• Imidazolidines • Furans
• Isothiazolines • Sorbitans
• Alkyl Benzthiols • Triazines
• Pyrrolidiones
Possible Low Affinity
Binder
No
Type “A” II
Contains Phenol
Fragment
Yes
No
Belongs to
known Active
class
Yes
No
Type “B” III Yes
Contains identif. Type B
Fragment
No
Belongs to
known Inactive
III
class
• DDT-Like
• Tamoxifen-Like
• Multi-Cyclohydrocarbons
• Alkyl Chlorobenzenes
Yes
Yes
• Alkyl Anilines
• Phthalates
• Branched Phenones
• Cyclo Phenones
• p-subst Cyclohexanols
• p-subst Cyclohexanones
• ring subst (o-CH3,
tri-CH3) Benzoates
Belongs to
known Active
class
Belongs to
known Inactive
class
No
Potency
Rules / Equations
Belongs to class
with possible
Type B low affinity
under investigation
Yes
IV
Non binder
(RBA<0.00001)
Yes
• N-alkyl Phenones
• Non ring subst Benzoates
• ring subst p-CH3 Benzoates
•Thiophosphate Esters
• Mixed Organics
• Cyclic Alcohols (not
p-subst hexanols)
• Cyclic Pentanones/Others
• Br, I halobenzenes
No
Contains some
Yes
attenuating feature
steric?; other?
No
High Binding Affinity
“A-B”;“A-C” or “A-B-C” type
Special Rule Classes
• Fully-hindered Alkyl Phenols
No
Possible High Affinity,
“A-B”; “A-C”; or
“A-B-C” type binder
V
Contains
at least
one
possible
Hbonding
site
Potency
Rules / Equations
Belong to untested class
with possible
Type A low affinity
Yes
No
• Alkyl Phenols
• Alkoxy Phenols
• Parabens
• Salicylates
Belong to untested class
Needs testing
Contains 2 OH,
or OH and =0, at
Spec. Dist
Yes
No
No
No
Yes
No
Yes
Belongs to
known Inactive
class
Some
Assess strength
of attenuation steric?;
other?
Complete
• Mixed Phenols
Needs testing
Non binder
Ex: Progesterone
Corticossterone
(RBA<0.00001)
No
Non binder
(RBA<0.00001)
Low Affinity Binder
“A-B”,“A-C” or “A-B-C” type
Needs testing
Speciation
Parent
Chemical
Molecular
Initiating
Events
and
Measurable
System
Effects
Adverse
Outcomes
Metabolism
Chemistry/
Biochemistry
Chemical
Universe
Y
Log Kow <1.3
e
s
N
Type “A” II
o
Contains Phenol
Fragment
Type “B”N III
Contains identif.oType B
Fragment
Possible Low Affinity
Binder
Y
e
s
Y
e
N class s
Belong to untested
o
Y
Needs
testing
• Alkyl
Anilines
e
• Phthalates
Y
s
• Branched Phenones
e
• Cyclo Phenones
s
• p-subst Cyclohexanols
• p-subst Cyclohexanones
• ring subst (o-CH3,
tri-CH3)
Benzoates
Potency
Rules / Equations
Belongs to
known Active
class
Belongs N
to
No
known Inactive
o III
class
N
Belongsoto
known Active
class
N
Belongs to
o
known Inactive
class
Belongs to class
N
with possible
o
Type B low affinity
under investigation
Y
e
s
Y
e
s
Y
e
s
Systems
Biology
N
Yes
N
Non binder
o
(RBA<0.00001)
QSAR
Contai
• Alkylbenzsulfonic Acids o
ns atN
• Sulfonic AcidYDyes
e
leasto
• p-Alkyl Fluorobenzenes
one
• Bis–anilines s
possibl
• Alkoxy Anilines•
e H• Imidazolidines Oxazoles
• Isothiazolines •
Ye bondin
g site
Alkyl BenzthiolsBenzami
s
•••DDT-Like
Pyrrolidiones de
IV
• Tamoxifen-Like
• Furans
Special Rule Classes
• Multi-Cyclohydrocarbons
•
Chlorobenzenes
• Alkyl Phenols
Sorbitan
• Alkoxy Phenols
Potency
s
• Parabens
Rules / Equations
•
• Salicylates
Non binder
Triazines
• Fully-hindered Alkyl
Phenols
(RBA<0.00001)
Belong to untested class
with possible
• Mixed Phenols
Type A low affinity
Needs testing
• N-alkyl Phenones
•• Non
ring subst
Benzoates
ring subst
p-CH3
Benzoates
•Thiophosphate Esters
• Mixed Organics
• Cyclic Alcohols (not
p-subst hexanols)
• Cyclic Pentanones/Others
• Br, I halobenzenes
MOLECULAR
Initiating Event
ER
Binding
Non binder
(RBA<0.00001)
Needs testing
CELLULAR
Respopse
Altered
Protein
Expression
TISSUE/ORGAN
Response
Altered
proteins
(VTG),
Ova-testis
INDIVIDUAL
Response
Chg 2ndry
Sex Char
Altered
Repro.
POPULATION
Response
Skewed
Sex
Ratios,
Altered
Repro.
Speciation
Parent
Chemical
Molecular
Initiating
Events
and
Measurable
System
Effects
Adverse
Outcomes
Metabolism
Chemistry/
Biochemistry
Systems
Biology
QSAR
Circulating LH,
FSH FSH
LH
LDL
R
Parent
Chemical
Molecular
Initiating
Events
Speciation
and
Metabolism
Outer mitochondrial
HDL
membrane
R
Inner mitochondrial
membrane
R
R
Choleste
rol
Activi
n
Inhib
in
StAR
P450sc
c
VTG
3bHS
pregnenolo
D
17αne
progester
P450c17
hydroxyprogesteron
one
20βHSD
androstened
e
ione17βHS
17α,20β-P
P450aro
testosteroD
(MIS)
P4501
m
ne1β
(steroidogenic cells)
11βHS
11- D
ketotestosterone
estradiol
Circulating Sex Steroids /
Steroid Hormone Binding
Globlulin
Vtg
Fecundity
Population
AR
Estradi
olE
R
+
Fenarimol
17β-trenbolone
Fadrozole
Prochloraz
17α-trenbolone
ER ( -)
VTG
Fecundity
Population
AR (+)
VTG
Fecundity
Population
VTG
Fecundity
Population
Aromatase (CYP 19)
CYP17
Risk Assessment Applications
1) Prioritization
-Systematic testing with a “well-defined” endpoint
-QSAR Decision Support System for ER molecular initiating event
- diverse chemical structures
Same approach can be taken for other molecular initiating events
AR – diverse structures – extent may be same of less than ER
systematic testing needed to develop model for defined chemical list
- assays available; may need to be optimized for anticipated
low affinity chemicals (EPA problem); EU application?
aromatase – diversity of structures causing enz inhib?
systematic testing needed to develop model for defined chemical list
- assays available; need optimization??
other steroidogenic enzymes – (same approach as above)
2) Higher Tier Assessment
HPG Systems Models assist data interpretation?
Developmental Endpoints
HPT Systems Model
Identify molecular initiating events
NIS
TPO ( in vitro assays optimized for QSAR approach)
CYP induction – T4 kinetics (gluc)