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Developmental toxicity / teratogenicity

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developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented and reported study fully adequate for assessment. The study was conducted according to an internationally accepted technical guideline and in compliance with GLP in a recognized contract research organization.
Reason / purpose for cross-reference:
reference to same study

Data source

Reference Type:
study report

Materials and methods

Test guideline
according to guideline
other: OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test) of 1996
GLP compliance:
yes (incl. QA statement)
Limit test:

Test material


Test animals

Details on test animals or test system and environmental conditions:
- Sprague Dawley rats, strain: Crl:CD(SD) with appropriate range of bodyweight at study start.
- Source: Charles River (UK) Ltd.
- Age at treatment start: 70 days (approx.).
- Weight at treatment start: Males: minimum 333 g, maximum 384 g,
Females: minimum 227 g, maximum 285 g.
- Housing Inside a barriered rodent facility:
all animals pre-pairing + toxicity subgroups: In groups up to 5 by sex in solid floor polycarbonate cages.
during pairing (1 male+1 female/cage): In RB3 modified polypropylene cages with stainless steel grid-floor over absorbent paper-lined trays.
males after pairing: In groups of up to 5 in solid floor polycarbonate cages.
females during gestation and lactation: Females housed individually (+litter) in solid floor polycarbonate cages.
- Bedding material (in solid floor cages): Wood based bedding.
- Cage enrichment: Aspen chew block + plastic shelter (except during pairing or post gestation day 20).
- Diet (ad libitum): Standard rodent diet (SDS VRF1 Certified), pelleted, without chemotherapeutic or prophylactic agent.
- Fasting (diet withheld): Main phase males and Toxicity phase females overnight before blood sampling for clinical pathology.
- Water (ad libitum): Potable drinking water from the public supply.
- Acclimation period: 6 days before treatment start, under laboratory conditions.

Routine analysis of the batch of diet used and water, chew blocks and bedding material did not provide evidence of contamination that might have prejudiced the study.

- Duration of test, males & toxicity phase females: Five weeks
Duration of test, main phase females (i.e. reproductive subgroup): From 14 days prior to pairing to day 7 of lactation.
Duration of test, offspring: From birth to day 7 of lactation.


Air conditioned room kept at positve pressure without re-circulation of the filtered fresh air supplied to the room.
Controlled environment, environmental conditions were set at:
- Temperature (°C): 21 ± 2°C
- Relative Humidity (%): 40 to 70%
- Photoperiod (artificial lighting): 12 hrs day / 12 hrs night
Deviations from the target ranges for temperature and relative humidity were not evident.

Administration / exposure

Route of administration:
oral: gavage
propylene glycol
Details on exposure:
Treatment of parental animals by oral gavage administration. Test substance was not directly administered to F1 animals.

- Concentration in vehicle: 20, 60 and 200 mg/ml
- Amount (dose volume by gavage): 5 mL/kg bw/day.
Actual dose volumes were calculated at about weekly or shorter intervals accounting for the latest body weight.
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
- Quantitative analysis of test material formulations was performed by gravimetry because WS400505 was insoluble in any solvent suitable for chromatography
- Concentrations of the test material formulations were confirmed at each dose level in the first and last week of the study.
- Gravimetric analysis confirmed that the mean concentrations of WS400505 in prepared formulations were within +10%/-15% of the corresponding
nominal concentration, thus confirming accuracy of formulation.
- Due to insolubility of WS400505 stability in the vehicle could not be confirmed (but can be assumed based on the chemical composition). .
Details on mating procedure:
- Male/female ratio per cage: 1/1
- Length of cohabitation: At the most 14 days, until proof of pregnancy was confirmed. 
- Proof of successful mating: Formation of at least one copulation plug and a sperm positive vaginal smear.
The day this was found was referred to as day 0 of gestation.
(During cohabitation, females were checked every morning for pregnancy).

Duration of treatment / exposure:
- Treatment period, males & toxicity phase females: Daily, for five consecutive weeks, in males commencing 14 days prior to mating
- Treatment period, main phase females (i.e. reproductive subgroup): approx. 45 days (from 14 days prior to pairing to day 7 of lactation)
- Offspring were not dosed
Frequency of treatment:
Daily, 7 days/week (during parturition, dosing omitted as appropriate)
Duration of test:
- Duration of test, all F0 males & toxicity subgroup females: Five weeks
Duration of test, reproductive subgroup females (F0): From 14 days prior to mating to day 7 of lactation.
Duration of test, offspring: From birth to day 7 of lactation.
Doses / concentrations
Doses / Concentrations:
0 (vehicle control), 100, 300, 1000 mg/kg bw/day
actual ingested
No. of animals per sex per dose:
Main phase animals (i.e. reproductive subgroups): 10 males / 10 females
Control animals:
yes, concurrent vehicle
Details on study design:
This study was conducted to examine both repeated dose toxicity and  reproductive/developmental toxicity as an OECD screening combined study
(OECD 422 test guideline).  Therefore, animals initially entering the study were divided into toxicity subgroup animals (toxicity phase) and reproductive subgroup animals (main phase), whereby 5 of the 10 F0 males (used for pairing) per dose group formed the toxicity male subgroups.

Dose selection was based on the results of a 7-day preliminary oral toxicity study in the rat in which dose levels of 100, 300 or 1000 mg/kg/day did not have any overt treatment-related effects on young adult animals (females nulliparous and non-pregnant). Accordingly the same dose levels were used in the present OECD 422 combined repeat dose toxicity and reproduction/developmental toxicity screening study.


Maternal examinations:
Clinical observations performed and frequency:
- Clinical signs : At least twice a day (before and after administration)
- Detailed physical examination
and arena observations: Before treatment start and at least once a treatment week.
- Body weight: Weekly for pre-pairing period; on gestation days 0, 6, 13, 20; on lactation days 1, 4 & 7.
- Food consumption: Weekly for pre-pairing period, during gestation for days 0-5, 6-12, 13-19, during lactation for days 1-3 & 4-6.
- Frequency of vaginal estrus: Daily by examination of vaginal smears taken from the beginning of the treatment period to the day of confirmed copulation.
(During the pairing period, females were checked every morning for pregnancy).

Additional parameters examined:
- No. of animals mating (evidence of successful copulation, i.e. sperm positive vaginal smear and at least one copulation plug)
- Pre-coital interval (pairing days until detection of mating)
- No. of animals achieving pregnancy
- No. of living pregnant females
- From Day 20 post copulation 3 times a day checks for evidence of parturition, any difficulties and numbers of live and dead offspring.
- Gross pathology
- Organ weights
adrenals, brain, heart, kidneys, liver,ovaries, pituitary, spleen, thymus, uterus with cervix & oviducts.
- Histopathology (gross lesions).

Ovaries and uterine content:
The ovaries and uterine content were macroscopically examined after termination on day 7 of lactation, i.e. day 7 post partum.
Numbers of uterine implantation sites were recorded and post implantation survival determined.
In addition, gestation length (time elapsing between detection of mating and commencement of parturition) was recorded.
Fetal examinations:
Litters were examined post partum as follows (day of birth = day 0):
- Number:  Daily until day 7 post partum.
- Sex: In total litter: 1st day; in live litter on days 1, 4 and 7
- Live births/mortality: Daily until day 7 post partum.
- Clinical signs: Daily until day 7 post partum
- Body weight of live pups: 1st, 4th, 7th day and weight change from days 1-4, 4-7 and 1-7.
- Necropsy:  7th day full macroscopic examination of all pups
(Missing or grossly autolysed or cannibalised pups could not be examined)
As detailed in Endpoint study record "7.5.1 Repeated dose toxicity: oral - Repeat dose tox combined_gavage_rat_HLS_GAH0235
- Percentage mating (No. of animals mating/No. of animals paired) x 100
- Conception rate (No. of animals achieving pregnancy/No. of animals mated) x 100
- Fertility index (No. of animals achieving pregnancy/ No. of animals paired) x 100
- Gestation index (No. of live litters born on day 0/No. of living pregnant females) x 100
- Post-implantation survival index  (Total no. of pups born/Total no. of uterine implantation sites) x 100
- Live birth index (No. of live pups on day 1 after littering/Total no. of pups born) x 100
- Sex ratio expressed as percentage males and calculated for total offspring on Day 1 and for live offspring on Days 1, 4 and 7
(No. of male pups in litter/No. of offspring in litter) x 100
- Viability index (No. of live pups on day 7 after littering /No. of live pups on day 1 after littering) x 100
Historical control data:
Not included in the study report.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
Effect level:
>= 1 000 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Key result
Dose descriptor:
Effect level:
>= 1 000 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects. Remark: see tables in attached background material

Effect levels (fetuses)

Key result
Dose descriptor:
Effect level:
> 1 000 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
changes in postnatal survival

Fetal abnormalities

not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Executive summary:

In this screening study, administration of WS400505 to rats at dose levels of 100, 300 and 1000 mg/kg/day was well tolerated with no effects to parental animals, to reproductive endpoints and to offspring. The NOAEL was derived at the highest dose, i.e. 1000 mg/kg/day.