N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine

Endpoint summary

Description of key information

In the key 90-day oral repeated dose toxicity study with the registered substance, N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine, conducted according to OECD Test Guideline 408 and in compliance with GLP, the concluded NOAEL for systemic toxicity for male and female rats was ≥ 50 mg/kg bw/day based on no observed adverse effects at the highest dose tested ( BSL Bioservice Munich, 2020).

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23rd May 2019 to 16th December 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Version / remarks:

Adopted 25th of June 2018

Deviations:

yes

Remarks:

Clinical observations and functional observation parameters were not recorded for some of the animals during week 2 and 13 respectively; weight of uterus with cervix was not determined for one animal.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Crl: WI(Han); derived from a controlled full-barrier maintained breeding system.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Females, nulliparous and non-pregnant: yes
- Age at study initiation: approximately 7-8 weeks old
- Weight at study initiation:
males: 174 – 202 g (mean: 190.96 g, ± 20 % = 152.77 – 229.15 g)
females: 132 – 156 g (mean: 143.64 g, ± 20 % = 114.92 – 172.37 g)
- Fasting period before study: No
- Housing: IVC cages (type IV, polysulphone cages) on Altromin saw fibre bedding
- 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

DETAILS OF FOOD AND WATER QUALITY: Certificates of food, water and bedding are filed for two years at BSL Munich and afterwards archived at Eurofins Munich

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

IN-LIFE DATES: From: 11th of June 2019 To: 11th of September 2019

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test item was dissolved in dried and de-acidified corn oil and thereafter, was overlaid with argon and stored until usage.

VEHICLE
- Justification for use and choice of vehicle: The vehicle was selected in consultation with the sponsor based on the test item’s characteristics.
- Concentration in vehicle: 0, 1.25, 3.75, 12.5 mg/mL
- Amount of vehicle: 0, 1.25, 3.75, 12.5 mg/mL
- Lot/batch no.: MKCH1635
- Purity: not specified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Before beginning of the treatment period, formulation samples were prepared and analysed in order to obtain knowledge about stability and homogeneity of the test item in the selected vehicle.
Prestart homogeneity investigation was included on the samples collected from various levels (top, middle and bottom) of high dose and low dose groups.
As the test item was shown to be homogenous according to Eurofins Study No. 188762 (after 30 min without stirring), samples were not collected during the study for the investigation of homogeneity and only samples (duplicate) were taken for substance concentration in study week 1, 5, 9 and in the last week of treatment (16 samples in total).

Duration of treatment / exposure:

90-day exposure with 28-day recovery period.

Frequency of treatment:

7 days a week for 90 days

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

Control

Dose / conc.:

5 mg/kg bw/day (nominal)

Remarks:

Low dose (LD)

Dose / conc.:

15 mg/kg bw/day (nominal)

Remarks:

Middle dose (MD)

Dose / conc.:

50 mg/kg bw/day (nominal)

Remarks:

High dose (HD)

No. of animals per sex per dose:

10 animals/sex for each dose group and 5 additional animals/sex for the high dose and control recovery group animals.

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The doses were based on the results of a previous dose range finding study and the known corrosive properties of the test item. The highest dose level was chosen with the aim of inducing toxic effects, but not death or severe suffering. To avoid suffering due to the known corrosive properties of the test item, no higher dose than 50 mg/kg bw/day were administered. Thereafter, a descending sequence of dose levels is selected with a view to demonstrate any dose-related response and a NOAEL.
- Rationale for animal assignment: Random
- Fasting period before blood sampling for clinical biochemistry: yes (overnight)
- Rationale for selecting satellite groups: 5 animals/sex from the control and high dose group were selected as satellite groups.
- Post-exposure recovery period in satellite groups: 28 days
- Section schedule rationale (if not random): randomised

Positive control:

No

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: The health condition of the animals was recorded at least once a day, preferably at the same time each day. 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
- Time schedule: Detailed clinical observations considering spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalisation, diarrhoea, changes in skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size were made outside the home cage in a standard arena once before the first administration and at least once a week thereafter. Inadvertently, detailed clinical observations were not recorded in week 2 for animals 41-50, 56-60, 66-70, 76-80, 85-90 and 91-100.

BODY WEIGHT: Yes
- Time schedule for examinations: once before the assignment to the experimental groups, on the first day of administration and weekly during the treatment and recovery periods.

FOOD CONSUMPTION: Yes
- Food consumption was measured weekly during the treatment and recovery periods.

FOOD EFFICIENCY: No

WATER CONSUMPTION AND COMPOUND INTAKE: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: before the first administration and in the last week of the treatment period as well as at the end of the recovery period in the recovery animals.
- Dose groups that were examined: all animals.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of treatment and recovery period as part of the sacrifice of the animals.
- Anaesthetic used for blood collection: Yes, ketamine/xylazine
- Animals fasted: Yes, overnight
- How many animals: all surviving animals
- Parameters checked in table were examined: yes, see table 1

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Yes, ketamine/xylazine
- Animals fasted: Yes, overnight
- How many animals: all surviving animals
- Parameters checked in table were examined: yes, see table 1

URINALYSIS: Yes
- Time schedule for collection of urine: prior to or as part of the sacrifice.
- Metabolism cages used for collection of urine: No
- Animals fasted: Not specified
- Parameters checked in table were examined.: yes, see table 1

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Once before the first exposure and once in the last week of exposure (week 13) as well as in the last week of the recovery period (week 17) multiple detailed behavioural observations were made outside the home cage using a functional observational battery of tests
- Dose groups that were examined: all animals
- Battery of functions tested: Sensory reactivity to different modalities, grip strength and motor activity assessments and other behavioural observations as well as rearing supported and not supported, urination, defecation, startle / auditory response, equilibrium reflex, positional passivity, visual placing, fore and hind limb grip strength, tail pinch response, toe pinch reflex, extensor thrust/limb tone, hind limb reflex, righting reflex on the ground, air righting reflex, pupil response, body temperature and ophthalmoscopy using an ophthalmoscope (anterior chamber of the eye and fundus of eye).

IMMUNOLOGY: No

OTHER:
Examination of fertility parameters occurred daily over a period of 14 days where the oestrous cycle of all female animals was monitored in the last two weeks of treatment. During the last week of the recovery period, the oestrous satellite group was monitored.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 2)

HISTOPATHOLOGY: Yes (see table 2)

Statistics:

A parametric one-way ANOVA, a post-hoc Dunnett Test, a non-parametric Kruskal-Wallis Test and a post-hoc Dunn’s Test were used based on the results of homogeneity and normality tests. Statistical comparison of data acquired during the recovery period were performed with a Student’s t-Test or Mann-Whitney U-Test when appropriate.

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Increased salivation and moving the bedding were considered as treatment related local reactions to the test item. Following exposure to 15 mg/kg bw/day, two females were observed to have hairless areas on the head on study days 14 to 18 and 14 to 43, respectively. These are considered as incidental findings. Some parameters of weekly detailed clinical observations showed statistical significant differences in test item treated animals compared to controls: piloerection in week 7, animal sleeps/animal moving in cage in week 6, 10, 11 and 12, grooming in week 3 and 7, response to handling in week 6 and 8. Values were still within the normal variation range and differences were not considered as toxicologically relevant.
Over the whole study and recovery period no toxicologically relevant clinical findings were observed in the control or any of the dose groups.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Two female animals from the HD group were found dead on study days 22 and 90 respectively. The reason for the death of one animal depended on misapplication whereas it was impossible to determine the cause of the death in the other animal since this animal was cannibalised. However, since no signs of an impaired health were noted prior to death, e.g. clinical symptoms or lower body weight, it was considered the death was not caused by systemic toxicity of the test item. Besides, no further mortalities occurred during the treatment or recovery phase of the study.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Overall the mean body weight increased during the treatment and recovery period of the study in control as well as in all dose groups.
No treatment related or statistically significant effects could be observed.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

Following exposure to 50 mg/kg bw/day, statistical significantly lower food consumption occurred in males between study days 43 and 50; between study days 71 and 78 as well as between study days 78 and 85. Additionally, higher food consumption between study day 112 and 118 in the recovery group of females were observed. However, those incidents are not considered as toxicologically relevant.
Overall no treatment-related effects on food consumption were observed during the treatment or recovery period of the study in control as well as in all dose groups.

Food efficiency:

not specified

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Following exposure of 50 mg/kg bw/day, statistically significant lower MCV levels in males was observed compared to controls. Additionally, following exposure to 5 and 50 mg/kg bw/day, reduced reticulocyte rate occurred when compared to controls. These alterations are not considered as toxicologically relevant as values were within the normal variation range. Therefore, no toxicologically relevant, treatment-related effects on blood coagulation or haematology were observed in the control or any of the dose groups during the entire study and recovery period.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

Following exposure to 5 mg/kg bw/day, statistically significantly lower potassium concentrations were recorded in males compared to control at the end of the treatment period. Additionally, at the end of the recovery period, statistically significantly reduced TBA levels compared to controls were determined in males exposed to 50 mg/kg bw/day. Moreover, females exposed to 50 mg/kg bw/day exhibited marginally increased LDL levels compared to the control group. These differences are not considered as toxicologically relevant since they were marginal, lacked dose-dependency and were within the range of historical control data.
No toxicologically relevant, treatment-related effects on thyroid hormones were observed in the control or any of the dose groups during the entire study and recovery period.

Urinalysis findings:

effects observed, non-treatment-related

Description (incidence and severity):

Following exposure to 50 mg/kg bw/day, a male animal exhibited noticeably high levels of bilirubin, erythrocytes, urobilinogen, protein, nitrite, glucose, leucocytes and the urine was hazy and had a reddish colour. These findings coincided with histopathological observations with hyaline droplets and the dilatation of the renal pelvic and tubules. No other animals had any treatment-related abnormalities. Therefore, the effects seen in this one animal were not considered to be toxicologically relevant.

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Overall, no toxicologically relevant effects determined via functional observation battery were observed in the control or any of the dose groups at the end of the treatment or recovery period. Increased salivation is deemed to be a local reaction to the test item.
In detail, in study week 13 (last treatment week), HD males showed statistically significantly increased salivation and MD males statistically significantly reduced response to handling compared to controls. MD females exhibited statistically significantly decreased response to handling as well as an increased startle response versus controls. Equilibrium reflex scores were statistically significantly higher in LD females than in controls.
Functional Observation Battery during pre-treatment revealed that statistically significantly more HD males were moving around in their cage / less animals were sleeping compared to controls. Differences during pre-treatment alone are not considered as toxicologically relevant.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

At the end of the treatment period, splenic weights and mean spleen to body ratio were slightly, however, statistically significantly increased in males exposed to 15 mg/kg bw/day compared to controls. Females exposed to 5 mg/kg bw/day exhibited a statistically significant increase in the splenic weights compared to the control group. Additionally, following 15 mg/kg bw/day, males exhibited a marginally, however, statistically significant increased weights in the adrenal glands compared to controls.
At the end of the recovery period, males exposed to 50 mg/kg bw/day, showed a statistically significant higher mean brain weights although marginally higher compared to controls. Besides, the mean spleen to brain weight ratio was reduced in males exposed to 50 mg/kg bw/day and the mean thymus to body weight ratio was reduced in females exposed to 50 mg/kg bw/day compared to control group. All the mentioned effects were marginal and did not show a dose dependent relationship and consequently, not considered as toxicologically relevant.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

In the HD female found dead, the thoracic cavity was filled with red fluid correlating histopathologically to oesophageal haemorrhages, arguing for misapplication and therefore, the cause of the death of this animal.
HD male no. 50 exhibited a pale, firm mass on the external side of the sternum. In LD female no. 63 the cortex of the kidneys was amorphous and yellow. Moreover, the right kidney was attached to the liver and a dark red firm mass was found in the abdominal cavity. In LD female no. 65 the diaphragm had an irregular surface and a fluid filled cyst was found on it. For LD female no. 68 a mass with a diaphragmatic surface was detected on the liver. On the thymus of HD female no. 88 few fluid filled masses were found
According to histopathological analyses, the above mentioned findings are considered as incidental and not test item related.
Uteri of control female no. 60, MD female no. 71 and HD female no. 100 were dilated, which is related to the oestrus cycle and not considered as test item related.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

In one animal that died, red fluid was observed in the thoracic cavity during necropsy, histopathologically correlating with multifocal haemorrhages in the connective tissue adjacent to the oesophagus. This indicates that the cause of morbidity was most likely related to an accidental oesophageal mechanical injury and therefore, not of toxicological relevance. Hyaline droplets and the dilatation of the renal pelvic and tubules were noted in one high dose male animal which were correlated with noticeably high levels of bilirubin, erythrocytes, urobilinogen, protein, nitrite (positive), glucose, leucocytes and the urine was hazy and had a reddish colour during urinalysis. Since this finding was seen in only one animal, it was not considered to be treatment-related.
Cortical vacuolization of the adrenal glands was observed in some animals of the control and high dose groups. This finding is a common spontaneous lesion that can be encountered in rats and may occurs secondary to stressful conditions. Therefore, it was considered not related to systemic toxicity of the test item.

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Description (incidence and severity):

Overall no treatment-related effects on estrous cycle were observed during the treatment or recovery period of the study in control as well as in all dose groups.

Dose descriptor:

NOEL

Effect level:

>= 50 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed.

Critical effects observed:

no

Conclusions:

In a 90-day oral repeated dose toxicity study with the test substance N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine, conducted according to OECD Test Guideline 408 and in compliance with GLP, the concluded systemic NOAEL for male and female rats was ≥ 50 mg/kg bw/day based on no observed adverse effects at the highest dose tested.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

50 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In a 14-day dose range finding study, rats were exposed to the test substance N-(dimethylvinylsilyl)-1,1dimethyl-1-vinylsilylamine at doses of 0, 50, 125/75 and 250 mg/kg bw/day.

On study day 1, 3/3 males and 3/3 females at the dose of 250 mg/kg bw/day (group 2) were euthanised in a moribund condition for welfare reasons. Severe clinical signs including apathy, prone position, and piloerection (slight) were observed immediately after dosing. There were no macroscopic findings at necropsy. At 50 mg/kg bw/day (group 3) both males and females showed moving the bedding at post-dose observation on different treatment days. This is considered to be a local reaction to the test item administration and not a sign of systemic toxicity.

At 125 mg/kg bw/day (group 4), both males and females showed clinical signs immediately after dosing on day 1 including prone position, reduced spontaneous activity (moderate to severe) and piloerection (slight); all animals recovered at around 4-6 hours post-dose. On the beginning of treatment day 2, these group 4 animals were dosed daily with a reduced dose level of 75 mg/kg bw/day for the remaining 13 days of treatment. During this period, all animals were found to be normal (days 2-14).

Body weight gain throughout the study period was noted in males of the control and group 3 (50 mg/kg bw/day). Group 4 males (125/75 mg/kg bw/day) showed less individual body weight gain when compared to the control (day 1-14). Group 3 and 4 females (50 mg/kg bw/day and 125/75 mg/kg bw/day, respectively) showed comparable body weight gain when compared to the control. There was no treatment-related adverse finding in body weight development.

Mean food consumption was comparable up to 125/75 mg/kg bw/day (group 4) when compared to the control in females from treatment day 1 to 14. Mean food consumption was moderately lower during days 8-14 in group 3 males (50 mg/kg bw/day) and group 4 males (125/75 mg/kg bw/day) when compared to the control. However, the reduction in food consumption did not affect the body weight gain.

Treatment with the test item had no dose-dependent effect on haematology and clinical biochemistry parameters in any of the test item-treated groups. Differences between test item-treated males and females and their respective controls showed no dose dependency or consistency and thus were not considered toxicologically relevant.

There were statistically significant increases or decreases in organ weights and ratios observed in group 3 (50 mg/kg bw/day) and group 4 (125/75 mg/kg bw/day). However, the mean organ weights showed no dose-dependent differences between males and females treated with the test item and their respective control groups. There were no treatment-related gross pathological lesions at scheduled necropsy in any of the dose levels tested.

The doses for the main 90-day repeated dose study were established at 5, 15 and 50 mg/kg bw/day with the highest dose of 50 mg/kg bw/day to avoid suffering due to the observed clinical signs in the range finding study and the expectation that the severity of the local effects would be greater with 90 exposures compared with only 14 exposures in the range finding study (BSL Bioservice, 2019a). Considering that N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine hydrolyses extremely rapidly to form ammonia and dimethylvinylsilanol, it is likely that the observed effects of the test substance are attributable to the formation of ammonia.

In the key 90-day oral repeated dose toxicity study with the registered substance, N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine, conducted according to OECD Test Guideline 408 and in compliance with GLP, the concluded NOAEL for systemic toxicity for male and female rats was ≥ 50 mg/kg bw/day based on no observed adverse effects at the highest dose tested (BSL Bioservice Munich, 2020).

Following daily oral (gavage) administration of 0, 5, 15 or 50 mg/kg bw/day test substance in corn oil for 90 days to male and female rats, no test item-related mortalities occurred during the treatment or recovery period of the study. HD females no. 87 and 96 were found dead on study days 22 and 90, respectively. The cause of mortality in female no. 87 was misapplication. For animal no. 96 the cause of mortality could not be determined, as this animal was cannibalized.

Over the whole study and recovery period no toxicologically relevant findings concerning clinical symptoms, detailed clinical observations or the functional observation battery were observed in the control or any of the dose groups. Increased salivation and moving the bedding observed in the dose groups are deemed to be local reactions to the test item.

 

No treatment related or toxicologically relevant effects on body weight, food consumption, blood coagulation, estrous cycle, thyroid hormones, parameters of haematology and clinical biochemistry were observed during the treatment and recovery period of the study in any of the dose groups.

Urine of HD male no. 31 exhibited noticeably high levels of bilirubin, erythrocytes, urobilinogen, protein, nitrite (positive), glucose, leucocytes and the urine was hazy and had a reddish colour. These findings coincided histopathologically with hyaline droplets and the dilatation of the renal pelvic and tubules. Apart from that finding, there were no further treatment-related abnormalities in any of the other animals.

Macroscopic findings observed during necropsy are considered as incidental and not test item related.

Differences in organ weights were marginal and did not show dose dependency and were therefore not considered as toxicologically relevant.

Histopathologically, no test item related alterations were found in tissues/organs of animals of the high dose group.

Justification for classification or non-classification

Based on the available data, N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine does not require classification for specific target organ toxicity following repeated exposure according to Regulation (EC) No 1272/2008. Even though clinical effects were seen in the animals treated with 125 or 250 mg/kg bw/day in the dose range-finding study, there were no treatment-related gross pathological lesions observed at necropsy in any of the dose levels tested (50, 75/125, 250 mg/kg bw/day); there were statistically significant increases or decreases in organ weights and ratios observed in group 3 (50 mg/kg bw/day) and group 4 (125/75 mg/kg bw/day), but the mean organ weights showed no dose-dependent differences between males and females treated with the test item and their respective control groups. Therefore, there is no evidence that the observed effects were indicative of target organ toxicity.