Reproductive Toxicology: History and State of Regulatory Science

Joseph F. Holson, Ph.D.WIL Research Laboratories, Inc.

Where We Are and How We Got There…Introductory Lecture on Reproductive

Toxicology

CTE/CDER

October 17, 2002

Experimental and Epidemiologic Vigilance are our only Safeguards

When I thought I was dying and my hands were numb and wouldn't work-- and my father was dying too--when the villagers turned against us--it was to the sea I would go to cry. No one can understand why I love the sea so much. The sea has never abandoned me. The sea is the blood of my veins.

Tomoko Uemura

“Chrontogeny” of Reproductive Toxicology

1891

1979

1998

Return of Thalidomide

Effects on Eggs(Dareste)

1855

1997

FDAMA

1996

FQPASWDA

1959

1962

Thalidomide Epidemic

1982

Isotretinoin Approved

1967

First Pregnancy Registry (Atlanta)

1974

First National Pregnancy Registry

1966

1940 First FDA Laboratory Animal Safety Studies

Rubella Epidemic(Gregg)

1941

1981

First ACE-Fetopathy

Case Report

1993

“ACE-Fetopathy”

Coined

Goldenthal Guidelines

1971

DES (Herbst & Scully)

Wilson’s Principles 1963

Conference on Prenatal Drug

Effects

NCTR Collaborative Behavioral

Study

NCTR Collaborative

Study Reported

1985

NCTR Concordance

Study (Teratology vs. Developmental

Toxicology)

Ongoing Methylmercury

and DES Exposures

1973

DBCP

1975

Red Dye No. 2

1906

USDA Bureau of Chemistry

International Concern on Decreasing

Fertility

1992

Agent Orange/2,4,5-T

& TCDD

Karnofsky

1950

Litigation continues - Involves forseeability

Medical community believed DES promoted

progesterone synthesis by FPU

First randomized control study with

placebo: safe but no efficacy

Present

(Walker - Mouse) Numerous experimental

studies to develop a good animal model

Litigation

Karnaby Clinical Studies Apparent safety at high doses

Green, et al., Intersexuality

in mice

SYNTHESISfirst orally

active estrogen mimic

DES-Vaginal CCA link in 8 young women (15-22 years)

Debate about DES use in cattle and residues in meat

1971Herbst & Scully

Not considered a teratogenKalter & Warkany

Prescribed to prevent spontaneous abortion

Based on Smith

Gabriel-RobezCleft Palates and heart

defects in mice

Wilson’s Principles of Teratology

1. Susceptibility to Teratogenesis depends on the genotype of the conceptus and the manner in which this interacts with adverse environmental factors

2. Susceptibility to Teratogenesis varies with the developmental stage at the time of exposure to an adverse influence

3. Teratogenic agents act in specific ways (mechanisms) on developing cells and tissues to initiated sequences of abnormal developmental events (pathogenesis)

4. The access of adverse influences to developing tissues depends on the nature of the influence (agent)

5. The four manifestations of deviant development are death, malformation, growth retardation, and functional deficit

6. Manifestations of deviant development increase in frequency and degree as dosage increases, from the no-effect to the totally lethal level

Possible Inter-relationships of Developmental Toxicity Endpoints

Toxic Stimulus

Malformations

Functional Impairments

Growth Retardation

Death

Toxic Stimulus GrowthRetardation Death

Malformation

Functional Impairment

Percent Change Percent ChangeFetal Weight Embryolethality

5 10 5 10

Mice A/J 84 22 1176 324 C57BL/6 198 50 992 228 CDI 84 22 805 235

Rats CDb 52 16 858 248 OMc 44 12 723 216

Number of Litters (N)a to Detect Changesin Fetal Weights and Deaths in Mice and Rats

aNumber of litters/groupbCharles River, Wilmington, MAcOsborne-Mendel, Charles River, Wilmington, MA

From Nelson and Holson, 1978

Animal:Human Concordance Studiesfor Prenatal Toxicity

Nisbet & Karch, 1983 Many chemicalsRelied on authors’ conclusionsEmphasis on fertilityNo measures of internal dose

Attributes

Interdisciplinary team Criteria for acceptance of data/conclusionsConcept of multiple developmental toxicology endpoints No measures of internal dose

Authors

Holson et al., 1981 (Tox Forum)Kimmel et al., 1984 (NCTR Report)

Attributes

Interspecies inhalatory doses adjustedRelied on authors’ conclusions23 occupational chemicals and mixtures No measures of internal dose

Provided detailed informationOnly 4 drugsEmphasis on morphologyFocus on NOAELsNo measures of internal dose

Many chemicals and agentsVariably relied on authors’ conclusionsNo measures of internal dose nor criteria for inclusion or exclusion of studies

Authors

Hemminki & Vineis, 1985

Newman et al., 1993

Schardein, 1995 & 2000*

Animal:Human Concordance Studiesfor Prenatal Toxicity

*Misnomer to refer to thousands of experimental developmental toxicants

Awareness of Developmental Toxicity of Selected Agents

Agent Year First Reported Species*

Alcohol(ism)

Aminopterin

Cigarette Smoking

Diethylstilbestrol

Heroin/Morphine

Ionizing Radiation

Methylmercury

Polychlorinated Biphenyls

Steroidal Hormones

Thalidomide

1957

1950

1941

1940

1969

1950

1953

1969

1943

1961

(gp), ch, hu, mo, rat

(mo & rat), ch, hu

(rab), hu, rat

(rat), hu, mi, mo

(rat), ha, hu, rab

(mo), ha, hu, rat, rab

(rat), ca, hu, mo

(hu), rat

(monk), ha, hu, mo, rat, rab

(hu), mo, monk, rab

*ca - cat, ch - chicken, ha - hamster, gp - guinea pig, hu - human, mi - mink, mo - mouse, monk - monkey, rat - rat, rab - rabbit

Effect-Levels for Teratogensin Humans and Test Species

Aminopterin Death/Malformations

Death/Malformations

Agent ResponseHuman

Rat

Species Dose0.1 mg/kg/da

0.1 mg/kg

Diethylstilbestrol Genital Tract Abnormalities/Death

Genital Tract Abnormalities/Death

Human

Mouse

0.8-1.0 mg/kg

1 mg/kg

Ionizing Radiation Malformations

Malformations

Human

Rat/Mouse

20 rads/da

10-20 rads/da

Cigarette Smoking Growth Retardation

Growth Retardation

Human

Rats

>20 cigarettes/da

>20 cigarettes/da

Thalidomide Malformations

Malformations

Malformations

Human

Monkey

Rabbit

0.8-1.7 mg/kg

5.0-45 mg/kg

150 mg/kg

What is Meant by Maternal Toxicity?

No universally accepted definition Varies among laboratories and regulatory agencies

Broad range of severity in endpoints Maternal deaths (~10%) Minimal changes in weight gain (as low as 5%)

Endpoints used to define should vary depending on species Rat vs. rabbit

Why is Maternal Toxicity Important?

Pregnant female provides physical environment, nutrients, and metabolic waste disposal

Perturbation of the maternal physiological state can impact the well-being of her embryos

Relationship between Maternal Toxicity and Fetal Outcome in Humans

Embryo/fetal toxicity in presence of overt maternal toxicity Aminopterin Methylmercury Polychlorinated biphenyls

Embyro/fetal toxicity in presence of maternal stress (physiological changes) Steroidal hormones Ethanol Cigarette smoking

Embryo/fetal toxicity without significant maternal effects Thalidomide Accutane Diethylstilbestrol Ionizing radiation

Comparative Early Placentation

Amniotic Cavity

Extra-Embryonic Coelom

Decidua

Yolk Sac

Uterine Lumen

Uterine Artery

Decidua

Ectoplacenta

Allantois

Visceral Yolk Sac

Vascular Lacuna

Human Conceptus (Pre-Chorioallantoic Placental Stage) Day 10 Rat Conceptus

The inverted yolk sac surrounds rodent embryo but not human

Comparative Definitive Placentation

Amniotic Cavity

Extra-Embryonic Coelom

DeciduaYolk Sac

Uterine Artery

Decidua

Re-EstablishedUterine Lumen

Amniotic Cavity

Visceral Yolk Sac

VascularLacuna

Human Conceptus at the Time of Chorioallantoic Placental Establishment Day 12 Rat Conceptus

ChorioallantoicPlacenta

ChorioallantoicPlacenta

YSP may be site of effect in rodents not existent in human conceptus

Establishment of theUteroplacental Circulation

Yolk Sac (YS) contained within chorion and not directly exposed to chemicals in maternal tissues and blood

YS

Human Teratogens

Why do we know so little? Early wastage of severely affected embryos Human exposure information is not well documented Human exposures may be extremely low Readily recognizable and consistent lesions are rare Other types of reproductive problems may be related,

but not thoroughly investigated Population monitoring is limited Testing of environmental chemicals and

pharmaceuticals identified potential agents Pregnant women frequently choose to avoid

exposure to many substances

Human Epidemiology Studies vs. Experimental Animal Assessments

Less rigorously monitoredGreater phenotypic heterogeneityLess amenable to dose-response

evaluationsRamifications of endpoints better

ascertainedRetrospective studies plagued with recall

bias

Terminology

Developmental deviation

Structural changeMalformationAnomalyCongenital defect

Anatomical alteration

TerataStructural aberrationDeformationVariation

(minor vs. normal)

Observational Determinants of Anatomical/Functional Deviations

Degree of deviation from averageIncidence (prevalence)*Impact on salubrityCosmetic significance

*In humans convention of <4%; no medical or surgical significance has been used

*In experimental studies, no convention used – statistical

FDA Definition

Rare Event – “an endpoint that occurs in less than 1 percent of the control animals in a study and in historical control animals”

Reviewer Guidance(Draft)

Integration of Study Results to AssessConcerns About Human Reproductive

And Developmental Toxicities

CDER, 10/2001Pharmacology/Toxicity

Comparison of Overall Spontaneous Malformation Rates in Different Species

Multiple Surveys3-94.0Human

* Actual number in laboratory population ~44,000

1675.3-5.75.5Dog

47080-103.2Rabbit

52070-31.2Mouse

96430-1.60.33Rat*

NRange (%)Mean %Species

Rare Events (Low-Incidence Findings): Typical Reaction to, and Subsequent Scenario

Disbelief, rely on statistical insignificanceComparison to concurrent controlComparison to historical control (HC)Comparison to other HC databasesAsk experience/opinions of othersConstruct explanation to negateAgency rejectsRe-do study or label appropriately

Freehand Section

Whole-Body Microdissection

½ Skeletal ½ Visceral 100%

Guideline minimum = 25%, 175 + 175 vs. 1400

4 Groups

(of 25 Dams)X

350 Fetuses =1400 Fetuses

½ & ½ Control and High Group (per guideline)

Size Comparison at Near Term

CR Length 75 mmCR Length 35 mm

3.6 grams 47 grams

CR Length 19 mm

1.3 grams

RabbitRatMouse

Taylor, 1986

Case Study: Dystocia, Extended Parturition and/or Pregnancy

2-generation with second mating phase of F1, vapor inhalation, used industrially, OTC pharmaceutically

0/121/181/2100F1-2nd

1/170000F1-1st

3/262/24000F0

700500300700PPM

HC then: 2/333 = 0.60%HC now: 4/1100 = 0.36%

Case Study: Malformation Example Topical Antibiotic for Oral Mucosa

MaxMinMean% PL

TotalMalformation

0.3%PL0.0% PL0.02%2/9643Retroesophageal Aortic Arch

Historical Control Data

4321Malformation

1 (0.3%PL)1 (0.3%PL)00Retroesophageal Aortic Arch

Rat Study Data

Selected Reproductive Endpoints Exhibiting Strong Signals from Rare Events/Low Incidence

6.5g strong signal

1 is equivocal 2 is more significant signal

91%

decrease of 1

Mean = 7.0g 0.23 range 6.5-7.4g n = 1100 litters

Newborn Pup Weights

Mean = 0.94% (10/1061)

Total Litter Loss

Mean = 96.2% Min/Max 91-95%

Mortality PND 4

13.9 1.02Mean Viable Litter Size

Examples from WIL Research Historical Control in Crl:CD(SD)IGS BR

Endpoint

Rare Events: Control vs. Treated Groups

3

1

3:1 Probability that spontaneous event will occur in treated group

Paradigm to Evaluate Rare Findings

Comparison to concurrent control Evaluate dose-responsiveness including TK, AUC/Cmax Compare to HC range and mean, consider other statistical tests,

including Monte-Carlo Analysis Evaluate signals of developmental toxicity among dose groups Compare to second species Compare to findings in the combined pre-/postnatal study Perform confirmatory study:

Increasing N Increasing number of concurrent controls Increasing dose (based on TK: AUC/Cmax) Consider unbalanced study design Delimited exposure regime Evaluate pharmacologic action relative to ontogeny of receptors, etc. and

reconcile with modified dosing regime Label and follow-up in birth defects registry

Interpretative Difficulties of Developmental Variations in Experimental Studies

Variability in occurrence of findings

Fate/reversibility studies infrequent

Biologic significance -- extrapolation

High background incidence

Factors Determining Teratogenicity

Chemical and pharmacological propertiesMagnitude and duration of dosageMaternal modulation of dosageAccess to the conceptusDevelopmental stage at time of dosageDisposition within the conceptusSusceptibility of species and individual

There is no single best model. Combinations of these factors determine value of the model.

Regulatory Entities and Concerns

FDA EPA

FDAMA (Pediatrics)

Advocacy Groups

Pharmaceutical Product

Registration

ICH

Food Additives

AnimalHealth

Products

FQPA

TSCATest

Rules

SWDA

Environmental Exposures

FIFRAProduct

Registrations

TradeAssociations

Knowledge of whether condition, agent, procedure, chemical/drug exerts adverse effects on reproduction or development?

What is relative risk to human beings?

Sufficient degree of comfort to enable sound decision-making Guideline studies Additional evaluations Burden of proof is on industry

Reproductive ToxicologyWhat Do the Regulators Want?

Synopsis of Regulatory Assessment Process

Guideline Study

Hazard Identification Data

Animal-Human ConcordanceDevelopmental - High

Reproductive - Less Certain

Regulatory Analysis & Decision

Toxicologist/Regulatory

Regulator

Com

mun

icat

ion

Reproductive Toxicology Is Complicated

Conceptually Dynamic Anatomy & Physiology Interdependence of endpoints Statistics

Litter basedImportance of Historical Controls

• mean

• range

Neurobehavior (potential for latency) Infinite (?) modes of Action

ACE Inhibitors

Dystocia

Logistically Size/design of studies # and diversity of endpoints Decreasing training programs Ease of scoring endpoints

direct effectslatent effects

Cabergoline

DES

Reproductive Toxicology Is Complicated

Selected Differences in Developmental vs. Oncogenic Endpoint Ascertainment

Smaller group sizes (25 vs. minimum 100/group) Macroscopic – histopathology very rare Physical constraints/difficulty Less standardized nomenclature No certification, controls over training, etc.

More impact because earlier in development due to women in clinical trials

Involves coapt organisms (dam & fetuses) Always potential for maternal influence, but goes both ways

Dynamic morphology & function ACE example

Animals evaluated in the midst of changing morphology No two points in development are the same

Exposure hourly and daily key to outcome An important aspect of human studies

Comparison of Study Scale/Size

Major Processes in Mammalian Reproduction

SpermatogenesisOogenesis/ovulationCyclicity (estrous/menstrual)Libido/receptivityConception ImplantationPrenatal developmentParturitionPostnatal development and maturation

Comparative Endocrinology of Menstrual and Estrous Cycles and Early Pregnancy

2816 1612 128 84 4Days from LH Peak

16 20 2412840 12 8 4 0

Human LHFSHE2

P4

Ovulation Ovulation

2 4 6 8 10

Rat

OvulationOvulationand Coitus

PRL

Metestrus Diestrus DiestrusProestrus ProestrusEstrus Metestrus 12

hCG

rCG

A B C D E F

Premating to Conception

Conception to Implantation

Implantation to Closure of Hard Palate

Hard-Palate Closure to End of Pregnancy

Birth to Weaning Weaning to Sexual Maturity

Parturition Litter Size Landmarks of Sexual DevelopmentGestation Length Pup Viability Neurobehavioral Assessment F1 Mating and Fertility Pup Weight Acoustic Startle Response

Organ Weights Motor Activity Learning & Memory

ParturitionGestation Length Pup Viability Litter SizeLandmarks of Sexual Development Pup WeightNeurobehavioral Assessment Organ Weights Acoustic Startle Response F1 Mating and Fertility Motor Activity Hormonal Analyses Learning & Memory Ovarian QuantificationHistopathology Premature Senescence

Postimplantation LossViable FetusesMalformations & VariationsFetal Weight

Postimplantation LossViable FetusesMalformationsVariationsFetal Weight

Estrous Cyclicity Mating Corpora Lutea Fertility Implantation SitesPre-Implantation Loss Spermatogenesis

Estrous CyclicityMatingFertilityCorpora LuteaImplantation SitesPre-Implantation LossSpermatogenesis

Denotes Dosing Period

Standard DART Study Designs

Single- and Multigenerational

Satellite Phase

OECD 415, OECD 416, OPPTS 870.3800, FDA Redbook I, NTP RACB

F1

F2 ????????????????

????????????????

Pre- and Postnatal Development

F1

ICH 4.1.2F0

????????????????

Prenatal DevelopmentICH 4.1.3 OECD 414

OPPTS 870.3600 870.3700

Fertility StudyICH 4.1.12W4W

CMAX

AUC

CMAX

AUC

10W

Endpoints Not Assessed by Current Testing Guidelines

Maternal endocrine profiles Levels of agent in milk, fetus Reproductive events through puberty Reproductive life span Ovarian toxicity (for drugs) Male-mediated effects Postnatal physiology and function apart from

neurobehavior Transplacental carcinogenesis Placental pathology Drug or chemical interaction

Relevancy & Risk Analysis

BiologicDynamics &Dimensions

Integrity of Data Base

Regulators’ Questions

1) was an established, validated model used? 2) was a NOAEL (NOEL) demonstrated? 3) does increasing dose increase severity/incidence?

4) when was the when effect exerted? 5) is the effect reversible? 6) are there indications of sensitization (generational effects or

imprinting)? 7) is the effect gender specific?

8) appropriate TK (AUC/CMAX) comparison between experimental study and estimated human PK or exposure scenarios?

9) are there significant differences in the pattern, timing or magnitude of exposure between guideline studies and human scenarios?

10) is there concordance of effects among species?11) is the mode of action known or deducible?12) is the mechanism of action known?

Extent to Which Guideline Studies Answer Key Regulatory Questions

Fert. P/P DT DT 2-G DNT DT 1-G 2-G Screen DNT4.1.1 4.1.2 4.1.3 3700 3800 6300 414 415 416 421 426

1Validated

Model

2NOAEL

Determined

3Rare Event

w/Dose

4Insult Timing

Elucidated

5 Reversibility

6Imprinting

Phenomenon

7 Gender Basis

8 TK Profiled

9Exposure Mimicked

? ? ? ? ? ? ? ?

10Interspecies

Concordance

11Mode of Action

12Mechanism of

Action

What do regulators want to

know?

OECDEPAICH

(1) Was an Established, Validated Model Used?

Conducted well by trained personnel using sound methodology

Stable experienced staff?

These are not a given and problems occur frequently

For developmental studies rat and rabbit most common

For reproduction, rat alone most common, some use of repro organ data from dog, rabbit and monkey

(2) Was a NOAEL (NOEL) Demonstrated?

Rare events/findings, even if not s.s. may signal treatment-related effect

C D1 D2 D3

0 1 2 1

0 0 0 2

0 2 0 1

Absence of dose response does not fully negate observations

Careful comparison to H.C. mean & range; probably a real signal

Increase dose level and repeat to confirm or refute

Most regulators will rely heavily on concurrent (contemporaneous) control value for comparison

Unbalanced study design may be useful

Total litter loss: In today’s facilities with good care and technical attention 1 or 2 probably constitutes treatment effect

(2) Continued - Was a NOAEL (NOEL) Demonstrated?

Dystocia - similar to above; 1 questionable but 2 or more very likely a real signal. Again not amenable to statistical analysis!

Reduced litter size and early neonatal deaths (< pnd 4) is very sensitive endpoint. May be very low as a mean percentage but deaths exceeding 8/group should be heeded and closely evaluated - may depend on litter size

Live litter size sensitive measure down to mean of 0.5 - 0.75 offspring/litter with n of ~ 30

(2) Continued - Was a NOAEL (NOEL) Demonstrated?

(3) Does Increasing Dose IncreaseSeverity/Incidence?

Increases in no. of litters affected

Increases in no. of fetuses/progeny affected/litter

These represent signals of enhanced concern

(4) When Was the When Effect Exerted?

Single or multiple exposures required; need to identify timing of insult

Very important for further study of developmental effects; shorten study effort, etc.

In reproductive studies can greatly benefit evaluative process by identifying mode of action

Pre-ovulatory LH surge in rats, validity to human reproduction and differention between central or peripheral sites of action

(5) Is the Effect Reversible?

Was full recovery demonstrated

Reduced fetal weight in D.T.; clarify increased postnatal loss in repro-phase

High dose, MTD, clarifications

However, remember that disrupted schedule of development may have consequences later in life especially for neurobehavioral measures

(6) Are There Indications of Sensitization(Generational Effects or Imprinting)?

In 2-generation studies remember: a decreased response in later generations may be result of loss of sensitive F0/F1 individuals (selection)

An increased response in F1 or F2 may represent sensitization unless bioaccumulation is demonstrated

(7) Is the Effect Gender Specific?

Designates population at risk

Often can be deduced from organ histopathology or other measures

With agents not producing overt toxic signs discerning gender basis not always straightforward

Gives guidance to possible mode of action

In 2-generation studies, may need to do additional mating to untreated males or females

(8) Appropriate TK (AUC/CMAX) ComparisonBetween Experimental Study and EstimatedHuman PK or Exposure Scenarios (i.e., MHRD)

Key for: Standardizing “internal dose” or exposure

Comparing interspecies concordance for determining differences in biologic sensitivity

Establishing bioavailability

Discerning dose-dependent PK or changes in metabolism over course of exposure

(9) Are There Significant Differences in the Pattern, Timing or Magnitude of Exposure Between Guideline Studies and Human Scenarios?

Is product use such that human exposure may be very brief (hrs.) or intermittent. PBPK model useful here for reproduction

For developmental studies, no point in developmental time is the same, so abbreviated exposures (i.e., 1 hr/day) not acceptable?

Children’s dietary intake different in make-up, and changes with age.

Children’s GFRs much greater than adult & decrease with maturity

(10) Is There Concordance of Effects Among Species?

If so, there is enhanced concern, in its absence no diminished concern

Greater the number of species stronger the signal

TK should be used to compare internal exposures

Ensure that design/statistical power is comparable between different studies (species) prior to declaring nonconcordance

(11) Is the Mode of Action Known or Deducible?

Key for the discipline’s “learning curve” and refinement of risk assessment process

Because in-utero studies involved coapt organisms role of maternal toxicity may be crucial especially at exaggerated doses

Discerning mode of action very useful in understanding effects occurring during lactation

(12) Is the Mechanism of Action Known?

Very difficult and not fully illuminated for known developmental toxicants

Few reproductive toxicants well studied

Key for the discipline’s learning curve and refinement of risk assessment process

Comparison of Prenataland Postnatal Toxicity Profiles

Toxicity

Log of Dose

MaternalMaternal

DevelopmentalDevelopmental

Prenatal – valid and insightful – Embryonic exposure – Mode of action

Postnatal – valid only – when xenobiotic level is measured in both mother and

offspring

Relationship Between Developmentand Phenotypic Diversity

Phenotypic Expression

and Diversity

Time in Development (Age)

EmbryonicPeriod

EmbryonicPeriod

FetalPeriodFetal

PeriodPostnatal

PeriodPostnatal

Period

Extent of Differentiation

BirthBirth

Effects on Prenatal and Postnatal Development Including Maternal Function

ICH 4.1.2 (Segment III)

Denotes Treatment Period

GD 6 PND 20

Gestation Lactation

Weaning Growth Mating GestationPN day 21 9 wks 2 wks 3 wks

F1

F2

Female (Rat)

(Macroscopic Pathology)

PN day 17 PN day 80

Behavioral/Anatomic Measures

Motor ActivityAuditory StartleWater MazeDevelopmental Landmark

Vaginal PatencyPreputial Separation

Denotes Possible Transfer Via Milk

Comparison of Prenatal and Postnatal Modes of Exposure

Drug Transfer to Offspring

Drug Levels in Offspring

Maternal Blood vs.Offspring Levels

Exposure Route toOffspring

Commentary

Prenatal

Nearly all transferred

Cmax and AUC measured

Maternal often a surrogate

Modulated IV exposure, via placenta

Timing of exposure is critical

Postnatal

Apparent selectivity (“barrier”)

Not routinely measured

Maternal levels probably NOT a good predictor

Oral, via immature GI tract

Extent of transfer to milk and neonatal bioavailability is key to differentiating indirect (maternal) effectsfrom neonatal sensitivity

Prenatal Treatment Postnatal

Embryo/Fetus Placenta Mother Mammae Neonate

Organogenesis (classically defined) is unaffected

Effects are severe

Risk is low

Caused by ACEinh that cross placenta

ACEinhFetal

Hypotension

RenalCompromise

(Anuria)Oligohydramnios

Calvarial Hypoplasia

Neonatal Anuria

IUGR

Death

Case Study: Functional Alteration Example ACE Inhibition-Induced Fetopathy (Human)

Case Study: Functional Alteration Example

ACE Inhibition in Developing Rats

RAS (renin-angiotensin system) begins GD17

No ‘apparent’ effect in initial reproductive studies Nonstatistically significant increase in postnatal mortality (~8%)

Subsequent postnatal studies with direct administration to pups Growth retardation

Renal alterations (anatomic and functional)

Mortality increased to more than 30%

Selective Juvenile Toxicity of Quinilones

Drug

Ofloxacin (and other quinilones)

Modified from Stahlmann et al., 1997.

Species &Treatment

Multiple species,postnatal exposure.20 mg/kg (dog, 3 mo.)600 mg/kg (rat, 5 wk)

Effects

Chondrotoxic effects. Cartilage erosion in weight-bearing joints.

Gait alterations in juvenile dogs only.

Remarks

Human relevance unknown; drugs contraindicated in juvenile patients.

Mechanism: Probable deficiency of bioavailable Mg2+ in cartilage (quinilones chelate divalent cations).

No effect in routine segment III studies.

Reasons for Apparent Failed Predictions

Appropriate studies not conducted Incidence of effect too low for experimental

detectionUnknown/unstudied type(s) of effectHypersensitive individuals in human population Interaction of multiple agentsUnfounded/nonexistent claims or effectsHuman exposure is overestimated by

experimental design