2,2,4,4-tetramethyl-7-oxa-3,20-diazadispiro[5.1.11.2]-henicosan-21-one

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

A study on reproductive toxicity does not need to be conducted because a pre-natal developmental toxicity study is available. A reproductive toxicity is not mandatory since no effects on the reproductive organs were observed in the course of several repeated dose studies.

Link to relevant study records

Reference

Endpoint:

extended one-generation reproductive toxicity - basic test design (Cohorts 1A, and 1B without extension)

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because a pre-natal developmental toxicity study is available

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

n.a.

Effects on developmental toxicity

Description of key information

The developmental properties of the test item were studied in a developmental toxicity study in rats. Four groups of females were dosed with 0, 10, 25 and 62.5 mg/kg bw/d from day 6 to day 19 post coitum. All females were sacrificed on day 20 post coitum and the fetuses were removed by Caesarean section.
All dams survived. Cold to touch, hunched posture, emaciation and an increase in piloerection and hairloss were noted in the high dose females receiving 62.5 mg/kg/day. In addition, in this group marked maternal toxicity was present as demonstrated by the moderate reduction in food consumption, body weight, body weight gain, uterus weight and absolute weight gain. As a consequence of the marked maternal toxicity, foetal toxicity was present as lower foetal weight (82 out of 364 foetuses were small) and delay in the ossification. The delay in the ossification was observed in most parts of the skeleton, such as skull, sternebrae, thoracic, cervical and sacral vertebrae, hind and forepaws and pelvic girdle. Malformations were observed only in the high dose group, which showed marked maternal toxicity. These malformations could be an expression of the lower foetal weight observed rather than a direct effect of the test item on foetuses.
Moderate maternal toxicity was noted in mid-dose females receiving 25 mg/kg/day as demonstrated by reduction on body weight and body weight gain. In addition a reduction in food consumption was observed. Terminal body weight, uterus weight and absolute weight gain were statistically significantly reduced compared to controls.
Low dose females receiving the dosage of 10 mg/kg/day showed a slight reduction in food consumption.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Sept - Oct 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Specific details on test material used for the study:

Batch No.: DEFD097971
Puritiy: > 99.9%
Expiry date: 26.07.2012

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Italy s.r.l., San Pietro al Natisone, Italy
- Age at study initiation: 9 weeks
- Weight at study initiation: 200-225 g
- Housing: no more than 5 per cage (clear polycarbonte with stainless steel mesh and floor)
- Diet (e.g. ad libitum): laboratory rodent diet (4 RF 21, Mucedola S.r.l., Settimo Milanese, Italy), ad libitum
- Water (e.g. ad libitum): drinking water, ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+/-2°C
- Humidity (%): 55+/-15%
- Air changes (per hr): 15 - 25
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES:
From: 25.09. To:23.10.2008

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): Solubility
- Concentration in vehicle: 1.00, 2.50 and 6.25 mg/mL
- Amount of vehicle (if gavage): 10 mL/kg

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Prior to commencement of treatment, analysis was performed to confirm that the proposed formulation procedure was acceptable. Stability data at room temperature up to 24 hours were available from RTC Studies.
Samples of the formulations prepared during the first and the last week of treatment were analysed to check the homogeneity and concentration of the test item.
The results were within the limits of acceptance.

Details on mating procedure:

Females were paired one to one in the home cage of the male and left overnight. The day of mating, as judged by the presence of sperm on the vaginal smear or by the presence of a copulation plug, was considered as Day 0 of gestation (or Day 0 post coitum).

Duration of treatment / exposure:

gestation days 6 to 19

Frequency of treatment:

once daily

Duration of test:

21 days

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

No. of animals per sex per dose:

24 mated females

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
Based on previously performed dose range finding study

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice dauly

BODY WEIGHT: Yes
- Time schedule for examinations: on days 0, 6, 9, 12, 15 and 20 post partum

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, on days 6, 9, 12, 15, and 20 post partum

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: uterus, ovaries
The clinical history of the animal was studied and a detailed post motem examination was conducted including examination of the external surface and orifices

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: gross evaluation of placentae

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]

Statistics:

For continuous variables the significance of the differences amongst group means was assessed by Dunnett's test or a modified t test, depending on the homogeneity of data.
Statistical analysis of non-continuous variables was carried out by means of the Kruskal-Wallis test and intergroup differences between the control and treated groups assessed by a non-parametric version of the Williams test.

Indices:

Pre-implantation loss was calculated as a percentage from the formula:
(no. of corpora lutea-no. of implantations)/no. of corpora lutea x 100

Post-implantation loss was calculated as a percentage from the formula:
(no. of implantations-no. of live young)/no. of implantations x 100

Total implantation loss was calculated as a percentage from the formula:
(no. of corpora lutea-no. of live young)/no. of corpora lutea x 100

Sex ratios of the foetuses were calculated as the percentage of males per litter.
All derived values (e.g. means, percentages, ratios) first were calculated within the litter and the group values derived as a mean of individual litter values. Foetal structural deviations
were expressed as the percentage of affected foetuses relative to all foetuses examined per group, as well as in terms of the mean litter percentage of affected litters.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Signs of toxicity such as cold to touch, hunched posture, emaciation and piloerection were noted in the high dose females receiving 62.5 mg/kg/day towards the end of the treatment period.
Hairloss was also reported in the other treated groups, but due to the low incidence of this sign, it was considered to be incidental.

Dermal irritation (if dermal study):

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

A statistically significant decrease in body weight was noted in the high dose females from gestation Day 9 to gestation Day 20 and in the mid- dose females on gestation Day 20, when compared to controls.
A lower body weight gain was observed in mid- and high dose females compared to controls starting from gestation Day 9. The differences were statistically significant from gestation Day 12 to gestation Day 20 for mid-dose females and from gestation Day 9 to gestation Day 20 for high dose females.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

A statistically significant decrease in food consumption was noted in all treated females compared to controls from gestation Day 9.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Gravid uterus weight of the high dose females was statistically significantly lower than controls by approximately 20%.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Small size of the thymus was reported in 5 females allocated to the high dose group. This change could be considered related to the general conditions of the high dose group animals. Also hairloss, which was detected on several regions of the body in 9/24 high dose animals and rated from mild to marked, was considered to be treatment-related.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Description (incidence and severity):

Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

body weight and weight gain

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

Foetal weight and consequently litter weight of the high dose females were statistically significantly lower than controls by ca. 20%.
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): effects observed, treatment-related
Field "Description (incidence and severity)" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.DescriptionIncidenceAndSeverityFetalPupBodyWeightChanges): Foetal weight and consequently litter weight of the high dose females were statistically significantly lower than controls by ca. 20%.

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

effects observed, treatment-related

Description (incidence and severity):

Foetal weight and consequently litter weight of the high dose females were statistically significantly lower than controls by ca. 20%.

Changes in postnatal survival:

not examined

External malformations:

effects observed, non-treatment-related

Description (incidence and severity):

One low dose foetus and 3 mid-dose foetuses from three different litters showed lower foetal weight (less than 2.7g) and were classified as small. Due to the low incidence of this finding, it was considered to be incidental. A total of 82 small foetuses out of 364 foetuses from 14 different litters were noted in the high dose group. The lower foetal weight of some litters was highly pronounced (i.e. the weight of foetus no. 5 from litter 74240163 was 1.18g, which was 69% less than the mean foetal weight of the control group foetuses).
One control foetus (exencephalia (protrusion of the brain from the skull)), and two high dose foetuses, , showed external malformations (acaudia/anus imperforate and anus imperforate/tail rudimentary) . Both high dose foetuses showed lower foetal weight (2.35g and 1.75g) .

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

Skeletal examination was comparable between the control and the low and mid-dose group. Skeletal malformations were described in one high dose foetus the same foetus showed malformations at the external examination. The foetus showed all sacral arches absent, thoracic centra 8th to 13th absent, all lumbar arches absent, ribs (left and right) 8th to 13th absent.
An increased incidence in incomplete or no ossification of the skeleton was noted in high dose foetuses, compared to control foetuses. The delay in the ossification was present in most parts of the skeleton such as skull, sternebrae, thoracic, cervical and sacral vertebrae, hind and forepaws and pelvic girdle.
No ossification of the pubis, bilateral, classified as a major anomaly (malformation), was described in 10 foetuses, 9 from one litter. All foetuses showed marked lower foetal weight.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Exencephalia observed at external examination in control foetus was confirmed during visceral examination. In addition, the same foetus showed malformations such as cleft palate and macroglossia (enlarged tongue). Anomalies such as testis and displaced lens were also observed.
Acaudia and anus imperforate observed at external examination in high dose foetus were confirmed during visceral examination. During the examination this foetus also showed unilateral kidney, ureter aplasia and persistent truncus arteriosus of the great vessels. In addition, anomalies such as heart septal defect and presence of an abnormal mass in the abdominal cavity were also described.
Unilateral testis, not descended, was observed in one foetus of the low dose group and in two mid-dose foetuses. These findings were considered to be incidental and not dose-related.

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male/female

Basis for effect level:

fetal/pup body weight changes

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

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

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

For clarification on the substance`s mode of action please refer to attached document "Assessment of toxicological mode of action_Hostavin N 20"

Conclusions:

On the basis of the results of this prenatal developmental study the dosage of 25 mg/kg/day could be considered the NOAEL (No Observed Adverse Effect Level) for dams and offsprings.

Executive summary:

The effects of the test item during pregnancy and embryo-foetal development were investigated in the rat after oral administration from Day 6 to Day 19 of gestation. Three groups of females with positive identification of mating received the test item at dosages of 10, 25 and 62.5 mg/kg/day. One group received the control item (sesame oil) during the same treatment period and acted as a control.

Cold to touch, hunched posture, emaciation and an increase in piloerection and hairloss were noted in the high dose females receiving 62.5 mg/kg/day. In addition, in this group marked maternal toxicity was present as demonstrated by the moderate reduction in food consumption, body weight, body weight gain, uterus weight and absolute weight gain. As a consequence of the marked maternal toxicity, foetal toxicity was present as lower foetal weight (82 out of 364 foetuses were small) and delay in the ossification. The delay in the ossification was observed in most parts of the skeleton, such as skull, sternebrae, thoracic, cervical and sacral vertebrae, hind and forepaws and pelvic girdle. Malformations were observed only in the high dose group, which showed marked maternal toxicity. These malformations could be an expression of the lower foetal weight observed rather than a direct effect of the test item on foetuses.

Moderate maternal toxicity was noted in mid-dose females receiving 25 mg/kg/day as demonstrated by reduction on body weight and body weight gain. In addition a reduction in food consumption was observed. Terminal body weight, uterus weight and absolute weight gain were statistically significantly reduced compared to controls.

Low dose females receiving the dosage of 10mg/kg/day showed a slight reduction in food consumption.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

25 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

reliable without restriction

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Toxicity to reproduction: other studies

Description of key information

no data

Mode of Action Analysis / Human Relevance Framework

Likely mode of action based on the read-across approach:

Hostavin N20 belongs to the so called “hindered amine light stabilizer (HALS)” compounds. The most characteristic structural feature of HALS compounds is the 2,2,6,6- tetramethylpiperidine moiety which spontaneously undergoes piperidine nitroxide formation. It should be noted that the piperidine nitroxide moiety is also the active site of heterocyclic nitroxide drugs, which may explain that some of the effects found in toxicity studies with Hostavin N20 are comparable to the pharmacological actions of these nitroxide drugs. A readacross approach therefore may be considered when discussing the mode of action of Hostavin N20 in absence of any other relevant data such as kinectis/metabolism studies.

4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide, primarily used for antihypertensive (blood pressure lowering) effect. The underlying mechanism is related to the superoxide dismutase mimic action on the sympathetic nervous system, further related to vasodilatative effect. Among the various effects attibuted to tempol, body weight decreasing effects as well as sex-specific and/or hormone statues dependent antihypertensive effects are known and extensively investigated.

The likelihood emerges that Hostavin N20 exhibited a comparable superoxide dismutase mimic activity, resulting in the impairment of cardiovascular system after repeated exposure. The observed higher susceptibility of females after exposure to Hostavin N20 would be then comparable to the observed gender different response as well as hormone statues dependent responses to tempol application in animal studies. Even more enhanced susceptibility of pregnant animals could be attributed to the changed physiological conditions of pregnancy such as increased hypervolemia, increased cardiac output, and a decreased total peripheral resistance. The evident clinical findings of Hostavin N20 were emaciation, which seems to be comparable to the body weight decreasing effect of tempol. The decreased value of LDH then can be interpreted as a result of superoxide dismutase mimicking activity of Hostavin N20.

Justification for classification or non-classification

There is no evidence to suggest that a classification for reproductive or developmental toxicity is appropriate.

With reference to the valid developmental toxicity study according OECD 414 and the lack of reproductive/developmental effects, it is concluded that Hostavin N 20 is not subject to classification and labelling according to Regulation 1272/2008/EC regarding reproductive and developmental toxicity.