Avermectin A1a, 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 04 Jul to 05 Aug 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Standard Procedures of the Centre de Recherche, Amboise

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

(1'R,2S,4'S,5S,6R,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-6-cyclohexyl-21',24'-dihydroxy-12'-{[(2R,4S,5S,6S)-5-{[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy}-4-methoxy-6-methyloxan-2-yl]oxy}-5,11',13',22'-tetramethyl-5,6-dihydro-3',7',19'-trioxaspiro[pyran-2,6'-tetracyclo[15.6.1.1⁴,⁸.0²⁰,²⁴]pentacosane]-10',14',16',22'-tetraen-2'-one

EC Number:

601-490-4

Cas Number:

117704-25-3

Molecular formula:

C50H74O14

IUPAC Name:

(1'R,2S,4'S,5S,6R,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-6-cyclohexyl-21',24'-dihydroxy-12'-{[(2R,4S,5S,6S)-5-{[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy}-4-methoxy-6-methyloxan-2-yl]oxy}-5,11',13',22'-tetramethyl-5,6-dihydro-3',7',19'-trioxaspiro[pyran-2,6'-tetracyclo[15.6.1.1⁴,⁸.0²⁰,²⁴]pentacosane]-10',14',16',22'-tetraen-2'-one

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

Batch No.: 15497-120-1
Purity: 92.1%

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Interfauna, U.K.
- Age at study initiation:
- Weight at study initiation: 3.61±0.17 (mean, kg±SD)
- Fasting period before study:
- Housing: separately in metal cages (size 50x56x38 cm), on wire grid floors, in a room separate from animals of other studies.
- Diet (e.g. ad libitum): Animals were given daily 150 grams of a pelleted commercial laboratory animal food (diet 112C, from Usine d'Alimentation Rationnelie, Villemolsson-sur-Orge, France)
- Water (e.g. ad libitum): Animals had free access to tap water.
- Acclimation period:

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18±3
- Humidity (%): 60±20
- Air changes (per hr): 14 times per hour
- Photoperiod (hrs dark / hrs light): From 7:00H to 19:00H.

IN-LIFE DATES: From 4 to 8 Jul To 1 to 5 Aug 1988

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: Sesame oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: 0.75, 1.5, 3 mg/mL
- Amount of vehicle (if gavage): 1 mL/kg bw/day
- Lot/batch no. (if required):
- Purity:

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples were collected from the top, middle and bottom of the suspensions used to treat the animals, before gavage. They were extracted and diluted by the mobile phase used for HPLC, and analysed in triplicate.

Details on mating procedure:

Human chorionic gonadotrophin hormone (25 I.U., i.v.) was used one hour before aritificial insemination to induce ovulation respectively. The females were artifically inseminated with heterospermic samples of semen collected from male rabbits of the same strain and obtained from the same breeder. The day of insemination was called day 0 post insemination (p.i.). Induction of pseudo-gestation and insemination were staggered over a 5-day period at a rate of 16 females a day.

Duration of treatment / exposure:

12 days (Day 7 to day 18 p.i.)

Frequency of treatment:

Once daily in the morning

Duration of test:

From day 0 to day 28 post-insemination (p.i.)

Doses / concentrations

Remarks:

Doses / Concentrations:
0.75, 1.5 and 3 mg/kg
Basis:
actual ingested

No. of animals per sex per dose:

20 females per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were chosen according to the results of the maternal toxicity study in rabbits (protocal 88077) performed at 1.5, 3 and 6 mg/kg and in which a body weight decrease was observed in dams and fetuses at 6 mg/kg, when compared to controls.

Examinations

Maternal examinations:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily during the treatment period and once daily at week-ends and before and after the treatment period.

BODY WEIGHT: Yes
- Time schedule for examinations: Main study: on days 1, 3, 7, 9, 12, 15, 19, 21, 24 and 28 p.i.

FOOD CONSUMPTION: Twice daily during the treatment period and once daily at week-ends and before and after the treatment period.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on day 28 p.i. in the morning
- Organs examined: Ovaries and uterine

OTHER:

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: No data
- Number of late resorptions: No data
- Other:

Fetal examinations:

All fetuses were carefully examined for external and buccal malformations and weighed. Then the fetuses were numbered and killed by an intraperitoneal injection of sodium pentobarbitone (Dolethal). The skeletons of alternate fetuses from each litter were examined for the degree of ossification and for the presence of anomalies and the ribs were counted and their degree of ossification were evaluated by the presence or absence of supernumerary ribs.
The remaining fetuses were fixed in Bouin-Allen fluid before being serially hand-sectioned by the slicing technique of Wilson (1965). The slices were examined for visceral abnormalities or anatomical variations.

Statistics:

A covariance analysis was carried out on days 12, 19, 24 and 28 p.i. body weight of those pregnant females which produced at least one viable fetus, taking the day 7 p.i. body weight as covariates. Student's t-tests were used to compare the mean value of each treated group (adjusted for covariance) with that of the control group (adjusted for covariance); the estimates of residual variance were used in the Student's t-test. The day 7 p.i. body weights were also analysed using anlysis of variance and comparing the treated group means with those of the controls by Student's t-test; the estimates of residual variance were used in the Student's t-test.
Analysis of variance (F test) was also used to analyse the number of corpora lutea, the number of implantation sites and the number of live fetuses.
A chi-square test was used to analyse the embryomottality rate.
Statistical analysis of fetal weights was carried out by the method described by Healy (1972), taking into account both the between and the within litter variability. The mean litter weights are calculated using individual fetal data. The adjusted means were weighted, taking into account the litter size and within litter variability (litters showing high variability have less impact on adjusted treatment means). Each of the treated groups was compared with controls using the approximate t-test on standard errors of adjusted means.

Indices:

None stated

Historical control data:

Yes

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
There were no deaths and no drug-related clinical signs. The matertnal body weights at 0.75 and 1.5 mg/kg were not statistically different from that of controls. At 3 mg/kg the maternal body weight was impaired during and after the treatment period (p<0.05 on day 7 p.i.; p<0.01 on day 12 p.i.; p<0.001 on days 19, 24 and 28 p.i.). There were no changes in the food consumption of the low dose group while at the mid and top dose levels, 4/18 and 14/19 females respectively showed a reduced food consumption on several occasions. The reproductive parameters were similar between control and treated groups.

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

1.5 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
There were no differences between control and treated groups with regard to the mean fetal weights. At external examination of fetuses, no anomalies were observed in control, low and mid dose groups. In the top dose group, 3 fetuses in the same litter (F811) had a cleft palate; in addition, one of these fetuses presented encephalocoelia. In another litter (F820), one fetus had phocomelia, syndactylia and coelosomia. There were no severe skeletal anomalies among the fetuses examined. The number of fetuses with delayed ossification of pubic bones was slightly increased at 1.5 and 3 mg/kg, compared to controls. Visceral examination revealed three cases of ventricular septal defect (one in each treated group) and one case of diaphragmatic hemia at the top dose in the fetus with coelosomia, phocomelia and syndactylia.

Effect levels (fetuses)

Dose descriptor:

NOEL

Effect level:

0.75 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: embryotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The test substance, when orally administered at 0.75 or 1.5 mg/kg to pregnant female rabbits during organogenesis was not considered to be toxic to dams or fetus, although some delay in ossification of fetal public bones occured at the latter dose. The dose level of 3 mg/kg induced maternal toxicity.
The dose of 0.75 mg/kg can be considered as the no-observable-effect-level (NOEL).