N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

There are no reproductive toxicity data on N-(3-dimethoxymethylsilyl)propyl)ethylenediamine (CAS No. 3069-29-2, EC No. 221-336-6) or its hydrolysis product, N-[3-(dihydroxymethylsilyl)propyl]ethylenediamine (CAS / EC Nos. not 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

There are no reproductive toxicity data on N-(3-dimethoxymethylsilyl)propyl)ethylenediamine or its hydrolysis product, N-[3-(dihydroxymethylsilyl)propyl]ethylenediamine. Reliable data for the related substance N-(3-(trimethoxysilyl)propyl)ethylenediamine are used as supporting information only to support the read-across justification for the genetic toxicity endpoint using this analogue substance.

N-(3-(Trimethoxysilyl)propyl)ethylenediamine has been evaluated in an oral combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP (Dow Corning Corporation, 2002, reliability score 1).

There were three unscheduled deaths during the conduct of the study. None of the unscheduled deaths were attributed to the test substance. Clinical findings attributed to test substance included clear perioral soiling in several high dose animals and either increased nasal sounds, laboured respiration, or soft vocalizations in approximately half of the high dose females and one high dose male. These signs were not seen in the control animals and infrequently seen in either of the two lower dose groups. Observations recorded at dosing indicated a dose-related resistance to dosing. Evaluating all 30 animals/dose (males, female toxicity and female reproductive groups) over the entire dosing period, the incidence of resistance was 3, 5, 27 and 62 for the controls, 25, 125 and 500 mg/kg bw/day dose groups, respectively. Similar incidence patterns were noted for salivation just prior to dosing, wetness around the mouth at dosing, and wetness around the mouth 5-30 minutes following dosing. There were no test substance-related effects on body weight or food consumption for any of the dose groups. No test substance-related changes on FOB and motor activity parameters were observed in the male and female toxicity animals evaluated. There were no test substance-related changes in haematology and serum chemistry parameters for these animals. No test substance-related effects were observed at the macroscopic examinations for any of the animals (males, females toxicity, female reproductive or the pups). There were no effects on mean organ weights or organ to body weight ratios attributable to the test substance for the selected organs evaluated (adrenal glands, brain, heart, kidneys, liver, spleen, thymus, uterus, ovaries, testes, epididymides, prostate, and seminal vesicles) in the male and toxicity female animals.

A thorough histopathological examination performed on all gross lesions, selected tissues and organs for control and high dose toxicity group animals demonstrated no microscopic findings directly attributable to test substance treatment. No test substance-related effects were observed in any of the reproductive parameters evaluated. Two high dose (500 mg/kg bw/day) and one low dose (25 mg/kg bw/day) reproductive group females that did not produce litters had positive evidence of copulation. Six of the eight surviving high dose reproductive group females produced litters that were similar in all respects to control litters.

No systemic was observed in this study and therefore the NOAEL for N-(3-(trimethoxysilyl)propyl)ethylenediamine was concluded to be greater than or equal to 500 mg/kg bw/day. The reproductive NOAEL would likewise be greater than or equal to 500 mg/kg bw/day, based on the absence of effects on reproductive parameters or organs.

Effects on developmental toxicity

Description of key information

In a study conducted according to OECD Test Guideline 414 and in compliance with GLP (BSL Bioservice Scientific Laboratories, 2023, reliability score 1), pregnant Wistar Han rats were administered N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine (CAS No. 3069-29-2, EC No. 221-336-6) at 0, 100, 600, and 750/1000 mg/kg bw/day via oral gavage (dried and deacidified corn oil vehicle) during days 5 through 19 of gestation. The maternal systemic NOAEL was 100 mg/kg bw/day, based on test item-related adverse findings (mortality, clinical signs, decreased body weight gain / food consumption, and gross pathology) at 600 and/or 750/1000 mg/kg bw/day. No effects were observed on mating or developmental parameters. The developmental NOAEL was identified as 750 mg/kg bw/day based on the absence of test item-related foetal effects up to 750/1000 mg/kg bw/day.

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 Oct 2021 (study initiation) - 17 Jan 2023

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

adopted 25 June 2018

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

Crl: WI(Han)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: 16-17 weeks (males at start pairing), 11-12 weeks (females, at arrival)
- Weight at study initiation: 375 - 472 g (males), 197 - 247 g (females), before initiation of pairing
- Fasting period before study: No
- Housing: Type III H, polysulphone cages, housed individually except during mating
- Diet: Altromin 1324 maintenance diet for rats and mice, ad libitum
- Water: Tap water, sulphur acidified to a pH of approximately 2.8, ad libitum
- Acclimation period: At least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 55 +/- 10
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 5 Nov 2020 To: 18 Feb 2021

Route of administration:

oral: gavage

Vehicle:

corn oil

Remarks:

dried and de-acidified

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test item was dissolved in dried and de-acidified corn oil. Corn oil was filtered through a mixture of activated silica gel 60 and aluminium oxide (1:1, volume/volume), which had been filled into a glass chromatography column to three quarters of its height. For filtering, a vacuum of 75 mbar was applied. The dried and de-acidified vehicle was overlaid with argon and stored until usage.

The test item was weighed into a tared glass vial on a suitable precision balance and the vehicle was added to give the appropriate final concentration of the test item. The formulation was vortexed and/or stirred until visual homogeneity was achieved. After homogenization, the formulation was overlaid with argon to prevent instability caused by repeated contact of the test item formulation with air.

Based on the results of stability testing (separate study), the test item formulations were prepared fresh on each day of administration, and used within 2 hours. The prepared formulation was stored protected from light and at room temperature.

The test item formulation and vehicle were administered as a single daily dose to the animals by oral gavage. The application volume for all groups was 4 ml/kg bw. For each animal, the individual dosing volume was calculated on the basis of the body weight most recently measured.

A specified procedure was required for cleaning of the gavage apparatus (needle, flexible cannula or tube) after drawing up the test item and before administering the item by gavage as follows: Following completion of filling of the syringe attached to the gavage apparatus with the required amount of test item, the outside of the gavage tube was wiped clean of all test item residue. The gavage tube was then lightly tapped onto a clean towel to remove the remaining droplet from the tip of the tubing. Additionally, the canula was dipped into 5% aqueous glucose solution immediately prior to application to further reduce the risk of irritation during administration.

VEHICLE
- Justification for use and choice of vehicle: Suggested by sponsor based on the test item’s characteristics
- Concentration in vehicle: 0, 25, 150, 187.50, 250 mg/ml
- Amount of vehicle: 4 ml/kg, total dosing volume

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

In a separate study, test item formulations (15, 25, 250 mg/ml) were homgenous and stable for 2 hr at room temperature and for 2 days at -15 to -35C.

Details on mating procedure:

Mating was performed using a ratio of 1:2 (male to female). Females were paired for cohabitation in batches in order to control the number of animals for terminal sacrifice on a particular day. On the subsequent mornings, the vaginal smear of the females was checked to confirm evidence of mating. The day on which sperm is observed in the vaginal smear was considered as gestation day (GD) 0. After getting 92 sperm-positive females, the remaining females and males were discarded without any observation. However, in the case of the high dose (HD) group, an additional 3 females were mated due to mortality at 1000 mg/kg bw/day and assigned to the new 750 mg/kg bw/day HD group in order to obtain at least 20 pregnant females per group.

Duration of treatment / exposure:

GDs 5-19

Frequency of treatment:

Once daily

Duration of test:

GDs 0-20

Dose / conc.:

0 mg/kg bw/day (nominal)

Dose / conc.:

100 mg/kg bw/day (nominal)

Dose / conc.:

600 mg/kg bw/day (nominal)

Dose / conc.:

750 mg/kg bw/day (nominal)

Remarks:

Due to severe clinical signs and subsequent morbidity, the HD level was reduced from 1000 mg/kg bw/day to 750 mg/kg bw/day on 2 Dec 2020. The respective gestation days of the HD animals on this date are provided in Table 1 under other information on method and materials.

Dose / conc.:

1 000 mg/kg bw/day (nominal)

Remarks:

HD level from study initiation through 1 Dec 2020

No. of animals per sex per dose:

At least 20 pregnant females per group

Control animals:

yes

Details on study design:

- Dose selection rationale: The highest dose level was chosen with the aim of inducing toxic effects, but not death or severe suffering. Thereafter, a descending sequence of dose levels was selected with a view to demonstrate any dose-related response and a NOAEL. Due to severe clinical signs and subsequent morbidity, the HD level was reduced from 1000 mg/kg bw/day to 750 mg/kg bw/day on 2 Dec 2020. The respective gestation days of the HD animals on this date are provided in Table 1 under other information on method and materials.
- Rationale for animal assignment: Random
- Fasting period before blood sampling for (rat) dam thyroid hormones: Not specified
- Time of day for (rat) dam blood sampling: At termination, time of day not specified

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
Twice daily, all animals were observed for morbidity and mortality except on weekends and public holidays when observations were made once daily.

DETAILED CLINICAL OBSERVATIONS: Yes
General clinical observations were made at least once a day, preferably at the same time each day.

BODY WEIGHT: Yes
All animals were weighed once before initiation of pairing to ensure that the body weights were within 20% variation. Sperm-positive females were weighed on GDs 0, 5, 8, 11, 14, 17 and 20, with body weights presented for these intervals: GDs 0-5, 5-8, 8-11, 11-14, 14-17 and 17-20. Males were not weighed in this study except once before initiation of pairing.

FOOD CONSUMPTION: Yes
Food consumption of sperm-positive females was determined for GDs 0-5, 5-8, 8-11, 11-14, 14-17 and 17-20. Food consumption was not measured for males during the entire study or for either sex during the mating period.

WATER CONSUMPTION: No

SACRIFICE:
On GD 20, sperm-positive (presumed pregnant) females were sacrificed using anaesthesia (ketamine/xylazin) and subjected to caesarean section.

Immediately after the termination or as soon as possible after death, the uteri were removed, the pregnancy status of the dams was confirmed, and the uterine content of pregnant females examined.

ORGAN WEIGHT: Yes
Each gravid uterus with cervix was weighed. However, the gravid uterus obtained from dead animals was not weighed.

The weight of thyroid/parathyroid glands was measured after 24 hours fixation in 4% neutral-buffered formaldehyde. Relative weights of thyroid/parathyroid glands were calculated in relation to the body weight (measured at necropsy) and were presented as percentage.

GROSS PATHOLOGY: Yes
At the time of termination or death during the study, each dam (presumed pregnant female) was examined macroscopically for any structural abnormalities or pathological changes which may have influenced the pregnancy. Any macroscopic findings were preserved in 4% neutral-buffered formaldehyde.

HISTOPATHOLOGY: Yes
A histopathological evaluation was carried out on the thyroid/parathyroid glands from all dams sacrificed at the end of treatment.

Ovaries and uterine content:

The uterine content of pregnant females was examined after termination including:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Position and number of foetuses in each uterine horn: Yes
- Number of live and dead foetuses: Yes

Blood sampling:

At termination, dam thyroid hormone levels (T3, T4, TSH) in abdominal aorta serum were assessed at the end of treatment using ELISA.

Fetal examinations:

SACRIFICE:
On GD20 via dam sacrifice with anaesthesia (ketamine/xylazin)

BODY WEIGHT: Yes
All foetuses were weighed on GD 20.

EXTERNAL: Yes
Each foetus was examined for external anomalies and sexed using the measured AGD. External sex was compared to internal sex. Relative AGD was calculated as AGD / Cube root of foetus weight. Incomplete testicular descent / cryptorchidism was noted in male foetuses.

VISCERAL: Yes
One half of each litter (20 litters per dose) was examined for soft tissue anomalies by a microdissection technique. Particular attention was paid to the reproductive tract which was examined for signs of altered development.

HEAD: Yes
The same half of each litter as for visceral (20 litters per dose) was subjected to craniofacial examination (eyes, brain, nasal passage and tongue) by razor blade serial sectioning technique.

SKELETAL: Yes
The remaining half of foetuses from each litter (20 litters per dose) was processed by Alizarin red staining and were examined for skeletal alterations.

Statistics:

All results were reported in tabular form (summarised in mean or summary tables and/or listed in individual data tables). A statistical assessment of the results of the body weight and food consumption was performed by comparing test item-treated groups with control using a one-way ANOVA and a post-hoc Dunnett Test. Results of absolute and relative organ weights, thyroid hormones and foetal evaluation parameters like external, visceral, craniofacial and skeletal parameters were statistically analysed by comparing values of treated animals with control animals using either a parametric one-way ANOVA and a post-hoc Dunnett Test or a non-parametric Kruskal-Wallis Test and a post-hoc Dunn’s Test, based on the results of homogeneity and normality tests. The statistics were performed with GraphPad Prism V.6.01 software or Ascentos 1.3.4 software (p<0.05 was considered as statistically significant).

Indices:

Not specified

Historical control data:

Historical control data for the strain of rat used (Wistar Han) mentioned for the prenatal data, foetal weights, visceral findings, and craniofacial findings.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Test item-related adverse clinical signs were observed in all animals at 600 mg/kg bw/day (MD) and 750/1000 mg/kg bw/day (HD), with the severity of signs occurring in a dose-dependent manner. No test item-related clincal signs were seen at 100 mg/kg bw/day (LD).

Predominant clinical signs in the MD and HD groups (with control and LD also shown) included:
- increased salivation (slight, moderate/severe; control-1/23, LD-1/23, MD-10/23, HD-20/26)
- moving the bedding (control-0/23, LD-1/23, MD-21/23, HD-25/26)
- abnormal breathing (control-0/23, LD-0/23, MD-6/23, HD-11/26)
- piloerection (control-0/23, LD-1/23, MD-3/23, HD-7/26)
- spontaneous reduced activity (slight/moderate/severe; control-0/23, LD-0/23, MD-2/23, HD-2/26).

A few incidences of both eyelids closed, dehydration, nasal discharge and coughing/sneezing were also observed in the MD and HD groups.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

Test item-related mortality was observed in 600 mg/kg bw/day (MD) and 1000 mg/kg bw/day (initial HD). No mortality was observed at 100 mg/kg bw/day (LD), at 750 mg/kg bw/day (HD as of 2 Dec 2020), or in the control group.

Prior to reducing the HD level, one MD animal (no. 47) and four HD animals (nos. 70, 75, 76 and 77) were moribund sacrificed. After reducing the HD from 1000 to 750 mg/kg bw/day, no mortality was observed during the study and all other animals survived until the end of the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

A test item-related adverse effect on body weight gain was observed at 750/1000 mg/kg bw/day (HD) when compared with the control group. No test item-related effect on this endpoint was seen at 100 mg/kg bw/day (LD) or 600 mg/kg bw/day (MD). For mean body weight, no test item-related effect was identified at any dose.

For body weight gain over GDs 5-20, there was a slight (not significant) decrease in mean body weight gain observed in the HD group (9.52% below control) when compared to the control group. This effect was considered test item-related and adverse.

For two GD subintervals, the mean body weight gain was found to be decreased: on GDs 5-8 in all treated groups (LD-28.24%, MD-11.01% and HD-35.92% below control), and on GDs 11-14 in the MD (9.53% below control) and HD (29.47% below control) groups without statistical significance. The MD and HD decreases in mean body weight gain during these intervals improved at later gestation days, and were considered not related to the test item.

Mean body weight increased with the progress of the study in all the treated groups and the control group, and no test item-related effect was identified for this endpoint.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

A test item-related adverse effect on food consumption was observed at 750/1000 mg/kg bw/day (HD). No test item-related effect on this endpoint was seen at 100 mg/kg bw/day (LD) or 600 mg/kg bw/day (MD).

For GDs 5-20, mean food consumption observed in the LD, MD and HD groups were comparable to the control group. However, a slight (statistically significant) decrease in food consumption was observed in the HD group (7.77% below control) when compared to the control group. This effect was considered test item-related and adverse.

For a few GD subintervals, there was a slight decrease in food consumption observed in the HD group (8.99% on GDs 5-8, 6.61% on GDs 11-14, and 11.06% on GDs 14-17), but this effect was considered not related to the test item.

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

Description (incidence and severity):

The results for thyroid hormones in serum are presented under endocrine findings.

Endocrine findings:

effects observed, non-treatment-related

Description (incidence and severity):

No test item-related effects on thyroid hormone levels in serum were observed up to 750/1000 mg/kg bw/day (HD).

With one exception, the mean T3, T4 and TSH hormone levels in aortic serum were comparable between the treatment groups and the control group. At 600 mg/kg/kg bw/day (MD), there was a statistically significant increase in mean TSH. In the absence of dose dependency, this finding was not considered to be test item-related.

See also organ weight and histopathology findings.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No statistically significant differences were observed for uterine weight (gravid with cervix) up to 750/1000 mg/kg bw/day (HD) when compared to the control group, and all values were within the historical control range for this strain of rat.

No statistically significant differences were observed for absolute and relative (to body weight) thyroid/parathyroid weights up to the HD when compared to the control group.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Test item-related adverse macroscopic lesions were observed at 600 mg/kg bw/day (MD) and 750/1000 mg/kg bw/day (HD), but not at 100 mg/kg bw/day (LD).

For the MD and HD groups, test item-related adverse macroscopic lesions were observed in moribund sacrificed animals. Animal no. 47 (MD group) had a gas-filled stomach, duodenum, jejunum, ileum and caecum. Animal no. 70 (HD group) had a gas filled stomach, duodenum, jejunum, ileum and caecum. Animal no. 75 (HD group) had many red foci in the glandular mucosa of the stomach and the stomach, and the jejunum, caecum and colon were gas filled. Female no. 76 (HD group) had a gas filled stomach, an enlarged thymus and enlarged hindlimb and female no. 77 (HD group) had a small thymus. The macroscopic findings observed in the gastrointestinal tract were most likely due to the irritating properties of the test item and, hence, considered to be test item-related and adverse.

No test item-related macroscopic lesions were observed in the LD group. Animal no. 34 of the LD group had a hard, brown mass in the liver facing the thoracic cavity near the diaphragmatic surface, which was considered incidental.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

No test item-related effects on post-fixed thyroid/parathyroid histopathology were observed up to 750/1000 mg/kg bw/day (HD) when compared to the control group.

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Number of abortions:

no effects observed

Description (incidence and severity):

None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice up to 750/1000 mg/kg bw/day (HD).

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

No statistical significance was observed for pre- or post-implantation up to 750/1000 mg/kg bw/day (HD) when compared to the control group, and all values were within the historical control range for this strain of rat.

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Description (incidence and severity):

No statistical significance was observed for early or late resorptions up to 750/1000 mg/kg bw/day (HD) when compared to the control group, and all values were within the historical control range for this strain of rat.

Dead fetuses:

no effects observed

Description (incidence and severity):

No dead foetuses were noted up to 750/1000 mg/kg bw/day (HD).

Changes in pregnancy duration:

not examined

Description (incidence and severity):

Changes in pregnancy duration were not observed (no signs of abortion or premature delivery) prior to the scheduled sacrifice up to 750/1000 mg/kg bw/day (HD).

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

Successful mating resulted in 21/23 pregnancies at 100 mg/kg bw/day (LD), 22/22 at 600 mg/kg bw/day (MD) and 20/22 at 750/1000 mg/kg bw/day (HD) compared to 20/23 pregnancies in the control group.

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Effect level:

100 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

clinical signs

food consumption and compound intake

gross pathology

mortality

Remarks on result:

other: Based on maternal systemic effects at 600 and 750/1000 mg/kg bw/day

Key result

Abnormalities:

no effects observed

Description (incidence and severity):

other: No maternal abnormalities related to developmental toxicity observed up to 750/1000 mg/kg bw/day

Fetal body weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

No test item-related effects on foetal body weight were observed up to 750/1000 mg/kg bw/day (HD).

On an individual basis (sum of weight of all foetuses in the group divided by the total number of foetuses in respective group), the mean male and female foetal weights observed in the LD (100 mg/kg bw/day), MD (600 mg/kg bw/day) and HD groups were comparable to the control group. However, a statistically significant decrease was observed in the MD group in both male (4.90% below control) and female (4.52% below control) foetal weights on a per foetal basis when compared to the control group. This finding was considered incidental since there was no dose dependency and the values were within the historical control range for this strain of rat.

Reduction in number of live offspring:

no effects observed

Description (incidence and severity):

No statistical significance was observed for the number of live foetuses up to 750/1000 mg/kg bw/day (HD) when compared to the control group, and all values were within the historical control range for this strain of rat.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

No statistical significance was observed for sex ratio up to 750/1000 mg/kg bw/day (HD) when compared to the control group, and all values were within the historical control range for this strain of rat.

Changes in litter size and weights:

no effects observed

Description (incidence and severity):

On a per litter basis (group mean of individual litter mean), no statistically significant effects on mean foetal weight, male and female foetal weight were observed up to 750/1000 mg/kg bw/day (HD) when compared to the control group.

Anogenital distance of all rodent fetuses:

effects observed, non-treatment-related

Description (incidence and severity):

ANOGENITAL DISTANCE:
No test item-related effects on AGD were observed up to 750/1000 mg/kg bw/day (HD).

The absolute and relative AGD in treatment groups remained unaffected when compared to the control group, except for a statistically significant increase in relative AGD of male foetuses at the MD (600 mg/kg bw/day). However, this finding occurred without any dose dependency and was not considered to be test item-related.

TESTICULAR DESCENT:
No effects observed. Testicular descent (abdominal) was complete in all male foetuses up to 750/1000 mg/kg bw/day (HD).

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Description (incidence and severity):

There were no external abnormalities observed in any of the foetuses up to 750/1000 mg/kg bw/day (HD) or in the control group.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

No test item-related skeletal findings were observed up to 750/1000 mg/kg bw/day (HD) when compared to the control group and historical control data.

At GD 20, incomplete ossification was seen in several bones of litters in all treated groups and the control group. Mostly, bones of the skull, sternum, paws, limbs, and vertebra were affected by variations in the status of expected ossification, described in terms of incomplete ossification, irregular ossification, unossified or increased ossification throughout all experimental groups. However, no dose dependency and no trend towards a treatment-related ossification effects of bones were observed. Statistical analysis revealed only a significantly lower foetal incidence of skull frontal, incomplete ossifications in the 100 mg/kg bw/day (LD), 600 mg/kg bw/day (MD) and HD groups (0%) when compared to the control group (2.14%). This finding was considered incidental in nature and not a test item-related effect. Overall, observed ossification-related findings were observed at lower or higher incidences, without dose-dependency, and almost entirely without statistical significance and thus considered not related to the test item.

Other skeletal findings in the treated groups also were considered not test-item related, occurring at slightly higher or lower litter incidences than the control group and without any statistical significance or dose dependency.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

There were no visceral findings related to treatment observed up to 750/1000 mg/kg bw/day (HD) when compared to the control group and historical control data.

No statistical significance was observed in any of the treated groups when compared to the control group. Higher litter incidences for umbilical artery, malpositioned were observed at 100 mg/kg bw/day (LD; 76.2% compared to 63.2% in the control group). Higher litter incidences of abdomen internal haemorrhage were observed (66.7%, 68.2% and 78.9% in the LD, MD (600 mg/kg bw/day) and HD groups, respectively, compared to 63.2% in the control group).

Visceral findings observed in the treated groups were at frequencies generally comparable to or in some cases slightly higher or lower in frequency compared to the controls. As the observed findings were either minor variations and/or lacking dose dependency and consistency, no toxicological significance can be attributed and the findings were considered to be spontaneous in nature. All litter incidences from treated groups were well within the historical control data range and statistically insignificant when compared to the control group.

Other effects:

effects observed, non-treatment-related

Description (incidence and severity):

CRANIOFACIAL:
There were no test item-related craniofacial findings observed up to 750/1000 mg/kg bw/day (HD).

Craniofacial examination revealed midbrain, haematoma, subdural in the 600 mg/kg bw/day (MD) and HD groups (13.6% and 10.5%, respectively) at lower incidences when compared to the control group (21.1%). These findings were considered spontaneous in nature and not related to the treatment with the test item. Statistical analysis of the data revealed no statistical significance for any of these findings. In addition, all values were within the historical control range for this strain.

Key result

Dose descriptor:

NOAEL

Effect level:

750 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: Based on the absence of test item-related foetal effects up to 750/1000 mg/kg bw/day.

Key result

Abnormalities:

no effects observed

Description (incidence and severity):

other: No test item-related foetal abnormalities observed up to 750/1000 mg/kg bw/day.

Key result

Developmental effects observed:

no

Mean and summary tables are attached in full, please see below additional information for location of specific tables:

Hormone measurements in tabular format (average results/ dose group is sufficient): Page 8

Caesarean section data in tabular format:

• Anogenital distance - Page 9
• Prenatal and litter data - Starts on Page 12
• Fetal weight - Page 15
• External fetal findings - Page 17
• Fetal Visceral findings - Page 18
• Fetal Craniofacial findings - Page 22
• Fetal skeletal findings - Page 23
• Maternal weight/fetal weight - Page 37
• Body and organ weights - Page 38

Conclusions:

In a study conducted according to OECD Test Guideline 414 and in compliance with GLP (reliability score 1), pregnant Wistar Han rats were administered N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine at 0, 100, 600, and 750/1000 mg/kg bw/day via oral gavage (dried and deacidified corn oil vehicle) during days 5 through 19 of gestation. The maternal systemic NOAEL was 100 mg/kg bw/day, based on findings considered to be test item-related and adverse (mortality, clinical signs, decreased body weight gain / food consumption, and gross pathology) at 600 and/or 750/1000 mg/kg bw/day. No effects were observed on mating or developmental parameters. The developmental NOAEL was identified as 750 mg/kg bw/day based on the absence of test item-related foetal effects up to 750/1000 mg/kg bw/day.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

750 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Key reliability score 1 study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine was evaluated in a study conducted according to OECD Test Guideline 414 and in compliance with GLP (BSL Bioservice Scientific Laboratories, 2023, reliability score 1). Pregnant Wistar Han rats were administered the test item at 0, 100 (LD), 600 (MD), and 750/1000 (HD) mg/kg bw/day via oral gavage (dried and deacidified corn oil vehicle) during days 5 through 19 of gestation. During the study, the HD was reduced from 1000 to 750 mg/kg bw/day due to severe clinical signs and subsequent morbidity. Observations and examinations were conducted per OECD Test Guideline 414. Maternal systemic parameters included mortality, clinical observations, body weight, food consumption, gross pathology, and thyroid/parathyroid endpoints (serum T3, T4, and TSH levels, organ weight, and histopathology). Uterine examination consisted of pregnancy status and, for pregnant females, gravid uterine weight, numbers of corpora lutea, pre- and post-implantations, early and late resorptions, and live and dead foetuses. In addition, foetal / litter weight, sex and sex ratios, anogenital distance (AGD) and, in male foetuses, testicular descent were determined. Detailed foetal examinations included external, visceral, craniofacial, and skeletal.

For the maternal animals, no effects on the thyroid endpoints (serum T3, T4, and TSH levels, organ weight, and histopathology), mating, or the prenatal (uterine) parameters were observed up to the HD. As discussed below, several systemic effects (maternal mortality, clinical signs, decreased body weight gain / food consumption, and gross pathology) were considered test item-related and adverse.

Prior to reducing the HD, one MD animal and four HD animals were moribund sacrificed. After reducing the HD from 1000 to 750 mg/kg bw/day, no mortality was observed during the study and all other animals survived until the end of the study.

Test item-related adverse clinical signs were observed in all animals at the MD and HD, with the severity of signs occurring in a dose-dependent manner. The predominant clinical signs these groups included: increased salivation (slight, moderate/severe; MD-10/23, HD-20/26), moving the bedding (MD-21/23, HD-25/26), abnormal breathing (MD-6/23, HD-11/26), piloerection (MD-3/23, HD-7/26), and spontaneous reduced activity (slight/moderate/severe; MD-2/23, HD-2/26). No test item-related clinical signs were observed at the LD.

A test item-related adverse slight decrease in mean body weight gain on GDs 5-20 (9.52% below control) and food consumption on GDs 5-20 (7.77% below control) were observed at the HD, but without statistical significance for body weight gain. No test item-related effect on mean body weight gain and food consumption was observed at the LD or MD when compared to the control group. No test item-related effect was identified for mean body weight at any dose.

Test item-related adverse macroscopic lesions were observed in moribund sacrificed animals of the MD group (one animal) and HD group (four animals). These findings were primarily related to the gastrointestinal tract (gas-filled stomach, duodenum, jejunum, ileum and/or caecum in the MD animal and three of the HD animals; red foci in the stomach and stomach glandular mucosa in one HD animal). In addition, one HD animal had an enlarged thymus and enlarged hindlimb, while another HD animal had a small thymus. The macroscopic findings seen in the gastrointestinal tract were most likely due to the irritating properties of the test item and, hence, considered test item-related and adverse. No test item-related macroscopic lesions were observed in the LD group.

For the foetuses, no test item-related effects were observed for the foetal parameters (foetal / litter weight, sex ratios, AGD, testicular descent) up to the HD. Test item-related effects also were not identified based on the detailed foetal external, skeletal, visceral, and craniofacial examinations. The latter are briefly discussed below.

There were no external findings observed in any of the foetuses of test item-treated groups or the control group.

For the visceral exam, a range of findings were observed in the treated groups and the control group. Visceral findings observed in the treated groups were at frequencies generally comparable to or in some cases slightly higher or lower in frequency compared to the control group. Higher litter incidences were observed for umbilical artery, malpositioned (76.2% in LD compared to 63.2% in the control group) and abdomen internal haemorrhage (66.7%, 68.2% and 78.9% in the LD, MD and HD groups, respectively, compared to 63.2% in the control group). As the observed findings were either minor variations and/or lacked dose dependency, they were considered spontaneous in nature and unrelated to test item treatment. All litter incidences from the treated groups were statistically insignificant when compared to the control group, and well within the historical control range.

In the craniofacial exam, midbrain, haematoma, subdural was observed in the MD and HD groups (13.6% and 10.5%, respectively) and control group (21.1%). However, this finding was considered spontaneous in nature and not related test item treatment. Statistical analysis revealed no statistical significance for any of the findings in the treated groups, and all values were within the historical control range.

Skeletal examination revealed a range of findings in all groups including the control group. Observed ossification-related findings in the treated groups were observed at lower or higher incidences when compared to the control group. At gestation day 20, incomplete ossification was seen in several bones of litters in all treated groups and the control group. Mostly, bones of the skull, sternum, paws, limbs and vertebra were affected by variations in ossification, described as incomplete ossification, irregular ossification, unossified or increased ossification, throughout all experimental groups. However, no dose dependency and no trend towards a treatment-related ossification effect were observed. With one exception, statistical analysis revealed no statistical significance for any of the ossification findings. A slight but statistically significant lower foetal incidence of skull frontal, incomplete ossification was seen in the LD, MD and HD groups (0%) when compared to the control group (2.14%) but this finding was considered incidental in nature and not a test item-related effect. There were slightly higher or lower litter incidences of other skeletal findings in the treated groups, but they did not show any dose dependency or statistical significance and were not considered related to test item treatment. 

In summary, the maternal systemic NOAEL for N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine in the Wistar Han rat was identified as 100 mg/kg bw/day, based on systemic findings considered to be test item-related and adverse (mortality, clinical signs, decreased body weight gain / food consumption, and gross pathology) at 600 and/or 750/1000 mg/kg bw/day. No effects were observed on mating or developmental parameters. The developmental NOAEL was identified as 750 mg/kg bw/day based on the absence of test item-related foetal effects up to 750/1000 mg/kg bw/day.

In a developmental toxicity range finding study conducted in compliance with GLP (BSL Bioservice Scientific Laboratories, 2020, reliability score 2), Wistar Han rats were administered N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine at 0, 100, 600, and 1000 mg/kg bw/day via oral gavage (dried and de-acidified corn oil vehicle) on gestation days 5-19. Maternal endpoints assessed included: mortality, clinical observation, body weight, food consumption, gross pathology, and reproductive parameters (pregnancy status and uterine content). Foetal evaluations included: body weight, sex, and detailed external exam. No signs of systemic toxicity up to 1000 mg/kg bw/day (HD) were found in the females. There may have been a slight local effect of the test item at the HD leading to increased appearance of clinical signs like increased salivation and moving the bedding. However, these reactions of the animals could also be attributed to general discomfort directly after test item administration. No signs of foetal toxicity were seen based on the prenatal data or external examination findings up to the HD. Thus, the maternal / developmental NOAELs are considered to be 1000 mg/kg bw/day. The findings were used for the initial dose selection (0, 100, 600, and 1000 mg/kg bw/day) for the main developmental toxicity study.

A supporting developmental toxicity test for the analogue substance N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS No. 1760-24-3, EC No. 217-164-6) is included only to support the read-across justification for the genetic toxicity endpoint currently using this analogue substance.

In the prenatal developmental toxicity study conducted with the analogue substance N-(3-(trimethoxysilyl)propyl)ethylenediamineand according to OECD Test Guideline 414 and in compliance with GLP (Charles River, 2016, reliability score 1), the substance was administered orally by gavage to bred Crl:CD(SD) rats. No evidence of maternal or developmental toxicity was noted at 100, 500, or 750 mg/kg bw/day. Test substance-related effects were limited to increased incidences of rales, clear material around the mouth, and/or salivation prior to dosing at 500 and 750 mg/kg bw/day. However, in the absence of any other signs of maternal toxicity at these dosage levels, the clinical observations were not considered to be adverse. Based on these results, a dosage level of 750 mg/kg bw/day, the highest dose tested, was considered the NOAEL for maternal toxicity and embryo/foetal development.

Justification for classification or non-classification

Based on the reliable data available, N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine is not classified for effects on reproduction and development according to Regulation (EC) No. 1272/2008.