3-(trimethoxysilyl)propiononitrile

Endpoint summary

Description of key information

In the key 90-day repeat dose toxicity study, conducted according to OECD TG 408 and in compliance with GLP, the NOAEL for 3-(trimethoxysilyl)propiononitrile was concluded to be 100 mg/kg bw/day based on tubulopathy observed at dose levels of 1000 and 300 mg/kg bw/day (Eurofins, 2019).

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:

05 June 2018 to 4 June 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:

1998

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature, store under dry argon blanket
- Stability under test conditions: Based on the results of stability testing (Eurofins Munich Study No. 171154), the test item formulations were prepared at least every 10 days. The prepared formulation was stored protected from light and at room temperature.
- Solubility and stability of the test substance in the solvent/vehicle: The test item was dissolved in corn oil. The vehicle was selected based on the test item’s characteristics.
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: not applicable

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test item was weighed into a tared plastic vial on a suitable precision balance and the vehicle was added to give the appropriate final concentration of the test item. The formulations were kept under magnetic stirring for approximately 10 minutes or 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.
- Preliminary purification step (if any): none
- Final dilution of a dissolved solid, stock liquid or gel: not applicable
- Final preparation of a solid: not applicable

FORM AS APPLIED IN THE TEST (if different from that of starting material)
The test material was administered dissolved in corn oil.

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Females (if applicable) nulliparous and non-pregnant: [yes]
- Age at study initiation: approx. 7-8 weeks old
- Weight at study initiation: males: 187 – 221 g; females: 144 – 177 g
- Fasting period before study: no
- Housing: The animals were kept in groups of 5 animals / sex / group / cage in IVC cages (type IV, polysulphone cages) on Altromin saw fibre bedding.
- Diet (e.g. ad libitum): Altromin 1324 maintenance diet for rats and mice, ad libitum
- Water (e.g. ad libitum): 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°C
- Humidity (%): 55 +/- 10%
- Air changes (per hr): 10 x / hour
- Photoperiod (hrs dark / hrs light): 12 hours light, 12 hours dark

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

- PREPARATION OF DOSING SOLUTIONS: The test item was weighed into a tared plastic vial on a suitable precision balance and the vehicle was added to give the appropriate final concentration of the test item. The formulations were kept under magnetic stirring for approximately 10 minutes or 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.

- VEHICLE
- Justification for use and choice of vehicle (if other than water): The vehicle was selected based on the test item’s characteristics.
- Concentration in vehicle: 25, 75 and 250 mg/mL
- Amount of vehicle (if gavage): application volume 4 mL/kg bw
- Lot/batch no. (if required): MKCC9871 / MKCF8882
- Purity: not specified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration analysis of the formulation samples was determined using a validated GC-FID method at three concentrations, 25 mg/mL, 75 mg/mL and 250 mg/mL in study weeks 1, 5, 9 and in the last week of the study.
The recoveries observed for the LD dose group were between 94.6% and 97.8 % of the nominal value, between 93.7 % and 97.8 % for the MD dose group and between 95.1 % and 98.0 % of the nominal value for HD dose group.
The mean recoveries observed in the LD, MD and HD groups were 96.3 %, 95.8 %, and 97.1 % of the nominal concentration, respectively.
The nominal concentrations were confirmed for all dose groups, as the measured concentrations were within the acceptance criterion of 10 %.

Duration of treatment / exposure:

90-day treatment and 28-day recovery period

Frequency of treatment:

daily

Dose / conc.:

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

Remarks:

low dose (LD)

Dose / conc.:

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

Remarks:

medium dose (MD)

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Remarks:

high dose (HD)

No. of animals per sex per dose:

Test group: 10 males and 10 females per group
Recovery groups: 5 males and 5 females per control and HD group
Total animals used in the study: 50 male and 50 female rats

Control animals:

yes, concurrent no treatment

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 demonstrating any dose-related response and a NOAEL. Dose selection was based on findings from a 7-day dose range-finding study and in consultation with the sponsor.
- Rationale for animal assignment: random
- Rationale for selecting satellite groups: random
- Post-exposure recovery period in satellite groups: 28-days
- Section schedule rationale: random

Positive control:

not included

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: once per day
- Cage side observations checked included: Once daily the general health condition of the animals was observed. 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: once before first administration, then once a week

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

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- Food consumption per cage was measured weekly during the treatment and recovery periods

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): 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 the treatment and recovery periods prior to or as part of the sacrifice of the animals
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: all animals
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the treatment and recovery periods prior to or as part of the sacrifice of the animals
- Animals fasted: Yes
- How many animals: all animals
- Parameters checked in table [No.1] were examined.

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

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Once before the first exposure and once in the last week of exposure as well as in the last week of the recovery period
- Dose groups that were examined: all animals
- Battery of functions tested: functional observational battery of tests

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table No 2)

HISTOPATHOLOGY: Yes (see table No 2). Histopathological examination was performed to animals of the control and HD groups sacrificed at the end of the treatment period and any animal found dead or euthanised before the planned day of sacrifice. For testis, a detailed qualitative examination was made, taking into account the tubular stages of the spermatogenic cycle. Kidneys and urinary bladder were also examined in all animals of the LD and MD groups. Furthermore, ureters were examined in all animals of all main and recovery groups. These examinations were also extended to animals subjected to necropsy at the end of the recovery period. Any gross lesion macroscopically identified was examined microscopically in all animals. Discoloration possibly due to the test item was evaluated in the organs of all dose groups.

Other examinations:

Examination of fertility parameters: Daily over a period of 8 days, the estrous cycle of all female animals was examined in the last week of treatment. In the recovery animals the estrous cycle was also examined during the last week of the recovery period.
At necropsy (one day after the last administration) and at the end of the recovery period, the left epididymis and left testis were separated and used for evaluation of sperm parameters. Epididymal sperm motility and testicular sperm count were evaluated in all male animals.

Statistics:

A statistical assessment of the results of the body weight, food consumption, parameters of haematology, blood coagulation and clinical biochemistry and absolute and relative organ weights will be performed for each gender by comparing values of dosed 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. Furthermore, statistical comparisons of data acquired during the recovery period may be performed with a Student’s t-Test or Mann-Whitney U-Test when appropriate. These statistics were performed with Ascentos 1.3.4 software or GraphPad Prism V.6.01 software (p<0.05 is considered as statistically significant).

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

One male rat of the MD group (no. 22) was euthanised in a moribund condition for animal welfare reasons on day 57. This rat was observed with moving the bedding materials, apathy, lethargic, reduced spontaneous activity, tremors, prone position and abnormal breathing on day 57.
Slight to moderate salivation was noted in male animals of the LD group (5/10), of the MD group (7/10) and of the HD group (15/15) and in female animals of the MD group (3/10) and the HD group (10/15) on several days of treatment. Furthermore, moving the bedding was regularly observed in all males and females of the treatment groups. The clinical signs salivation and moving the bedding were observed immediately after the dose administration and therefore were considered to be a sign of a local reaction to the test item rather than a systemic adverse effect.
During the weekly detailed clinical observation, no significant changes or differences between the groups were found except for a statistically significant higher score of moving in the cage and a statistical significant lower score of sleeping in the cage for male animals of the LD group in week 2, a statistically significant lower score of moving in the cage and a higher score of sleeping for male animals of the LD, MD and HD groups in week 6 and a statistically significant higher score of moving in cage and a lower score of sleeping in male animals of the HD group in week 15.
In females, a statistically significant higher score of moving in the cage in the MD and HD groups and of animals sleeping in the LD group and a lower score for ataxic/hypotonic gait in the LD, MD and HD groups in week 4, a statistically significant lower score of moving in cages and a higher score of sleeping in the LD and MD groups in week 5 and in the MD and HD group in week 7 and statistically significant higher score of sleeping and a lower mean score of moving in the cages in the MD and HD groups in week 9 were observed.
The statistically significant effects on detailed clinical examination parameters were not considered to be treatment-related as they were seen occasionally in single weeks without dose dependency.

Mortality:

mortality observed, treatment-related

Description (incidence):

During the treatment period, one male rat of the MD group (no. 22) was euthanised in a moribund condition for animal welfare reasons on day 57. This rat was observed with moving the bedding materials, apathy, lethargic, reduced spontaneous activity, tremors, prone position and abnormal breathing on day 57. Macroscopic observation showed kidneys with pelvic dilatation and abnormal color (white) and enlarged mandibular lymph node, abnormal color (red). The morbidity of the animal was considered to be most likely related to a moderate cardiac dilatation recorded in this animal histologically.
One female rat of the control group (no. 59) was found dead on day 89 in an autolytic condition. No clinical signs were observed throughout the treatment period. The cause of the death could not be established from the organs and tissues examined histologically. However, its premature death was considered to be incidental and not test item-related.
All other animals survived their scheduled study period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

At the end of the treatment period a tendency towards lower body weights (6 % below controls) in male animals of the HD group was observed. There were no test item-related effects on body weight gain during the study.
Body weight gain was moderately and statistically significantly lower in males of the MD group in week 1 and in week 9, when compared to controls. In the males of the HD group body weight gain was moderately and statistically significantly lower in week 12. In females, moderately and statistically significantly higher body weight gain was seen in the LD and HD groups in week 9 and in the MD group markedly and statistically significantly lower weight gain was seen in week 12. The differences were transient and considered to be of no toxicological or biological relevance, when compared to the overall body weight development during the treatment period.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

There was no test item-related effect on food consumption in any of the dose groups.
In males of the HD group there was a statistically significant reduction in food consumption in weeks 1 and 2. However, during the overall treatment period, the mean daily food consumption was comparable between all male and female dose groups and controls.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

None of the animals showed any abnormalities during the ophthalmoscope examinations at the end of treatment period.

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

A slight and statistically significant increase in MCHC and a decrease in MCV in males of the HD group were found at the end of the treatment period and a slight statistically significant increase in PLT in males of the HD group was found at the end of the recovery period. In females statistically significant higher HGB was observed in the MD group. All of the above mentioned effects are considered to be isolated, incidental findings. The values were found to be within the historical control data range.
A slight and statistically significant increase in WBC in males of the MD and HD groups (65 and 100 % above controls, respectively) and in females of the HD group (84 % above controls) were observed at the end of the treatment period. This could be related to chronic inflammation seen in kidneys in this group.
The very slight and statistically significant increase in PT (11.65 % above control) in females of the HD group at the end of the treatment period and a very slight and statistically significant increase in PT in males of the HD group at the end of the recovery period (9 % below controls) were not considered to be of toxicological relevance as all values were within the historical control data range.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

An increase in urea level in the HD group at the end of the treatment period (males 21 % above controls; statistically significant and females 19 % above controls; statistically non-significant) is assumed to be related to kidney findings. This is also most likely to be the reason for a statistically significant higher potassium level in male animals of the HD group (16 % above controls).
Slight but statistically significant decreases in serum ASAT and creatinine levels were observed in MD and HD females at the end of treatment. As a decrease of these parameters is not associated with a pathological condition and as all individual values were found to be within the normal range of historical control data this is not considered to be of toxicological relevance.
A moderate and statistically significant increase in AP levels in male animals of the HD group seen at the end of the recovery period, is possibly also related to kidney findings. The test item had no other effects on clinical biochemistry parameters.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

Occasional high values in individual animals of the HD group, (i.e. erythrocytes, leukocytes or hazy appearance of the urine observed at the end of the treatment period) are possibly related to nephropathy. There were no test item-related effects on urine parameters measured at the end of the recovery period in the HD group

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

No test item-related effects were observed in any parameter of the functional observation battery at the end of the treatment period when compared to observations before treatment.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

A dose dependent increase in kidney weight (absolute or relative) was seen in male and female animals with statistically significant differences of the HD group. Kidney weight of males was 28 % (absolute weight) or 36 % (relative to body weight) or 29 % (relative to brain weight) above control weights; kidney weight of females was 27 % (absolute weight) or 28 % (relative weights) above control weights. This effect was dose dependent with a similar tendency also observed in the LD and MD groups. These findings were highly correlated with histopathological changes.
At the end of the treatment period there was a statistically significant decrease in thymus weight in male animals of the HD group (absolute 30 % below controls; relative to body weight 25 % below controls; relative to brain weight 29 % below controls). This was not associated with any histopathological abnormalities. A tendency towards higher thymus weight was observed in female animals of this group (approx. 14 % above controls). In the absence of histopathological findings, these thymus changes are not assumed to be toxicologically relevant.
Spleen weight was dose-dependently higher in all dose groups when compared to controls. In female animals of the HD group relative weights reached statistical significance (relative to body weight: 20 % above controls; relative to brain weight: 19 % above controls).
In females of the HD group, there was a statistically significant increase in relative heart weight. This is considered to be of no toxicological relevance as there were no test item-related finding observed histologically.
At the end of the recovery period a tendency towards lower thymus weight, higher spleen weight and increased kidney weight was seen in male animals. Moreover, liver weight was slightly lower in HD group male animals. In female animals a tendency towards higher spleen, thymus and uterus weight and a statistically significant higher thyroid gland weight (absolute and relative weights between 36 and 40 % above controls) were observed.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Following pathology at the end of the treatment period, pale or white kidneys were observed in 4/10 males and 1/10 females from MD group. This effects was also observed in 8/10 males and 7/10 females from HD group. Moreover, spotted kidneys were seen in 4/10 MD males and 1/10 MD females, as well as in 9/10 HD males and 6/10 HD females. Unilateral or bilateral dilatation was observed in the kidneys of two MD males and three HD males, and one HD female. Dilatation in ureter was observed in one MD male animal. Thickened bladder wall and bladder stone was observed in one HD group female.
Following pathology at the end of the recovery period, abnormal kidney surface was seen in 4/5 HD males and 3/5 HD females. Unilateral or bilateral kidney dilatations was seen in 1/5 HD males.
All of the above listed gross lesions were considered to be treatment-related. All other gross lesions recorded were considered to be within the range of normal background alterations, which may be seen in rats of this strain and age.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In the kidneys, higher degrees of tubulopathy were recorded in treated animals from the medium and high dose groups. The tubulopathy was characterized by tubular dilatation (nephrohydrosis), tubular degeneration, tubular basophilia and inflammation (mainly chronic or chronic active), and sometimes it was associated with pelvic dilatation (hydronephrosis). Slight degrees of unilateral tubulopathy were also recorded in one low dose group male. Another low dose group male showed slight unilateral pelvic dilatation. After the recovery period, the tubulopathy and pelvic dilatation regressed only minimally.
Minimal to slight luminal dilatation and urothelial hyperplasia were recorded in high dose animals. In one male and in one female from the high dose group, luminal concrements were observed in up to moderate dilated, hyperplastic and/or inflamed ureters. There was also minimal or slight luminal dilatation in the ureters of few medium dose animals. After the recovery period, the luminal dilatation showed partial regression. All other findings were fully reversible.
Minimal to slight degrees of urothelial hyperplasia were recorded in the urinary bladder of high dose animals. One high dose female, which presented macroscopically bladder stones, showed also slight inflammation along with urothelial hyperplasia. The urothelial hyperplasia showed partial regression in recovery animals, whereas the inflammation regressed completely.
There were no microscopic findings in the male and female reproductive organs that could be attributed to the treatment with the test item.
All findings recorded were within the range of normal background lesions which may be recorded in animals of this strain and age and in this study type.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Description (incidence and severity):

There were no treatment-related effects on the mean testis weight, mean sperm motility and mean testis sperm count in both treatment and recovery periods. All the findings were found to be comparable with that of control and were within the normal range in this strain. In addition, treatment with the test item did not show effects on the completeness of stages or cell populations histologically. There was no indication for maturation arrest, reabsorption of sperm or of any other type of degenerative effects. All findings recorded were within the range of normal background alterations.
There was no effect on the estrous cyclicity, i.e. cycle length or sequence of cycle stages.

Key result

Dose descriptor:

NOAEL

Effect level:

ca. 100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

histopathology: non-neoplastic

Critical effects observed:

yes

Lowest effective dose / conc.:

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

System:

urinary

Organ:

kidney

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Table 1: Incidence of Main Macroscopic Findings

Findings	Group 1 Control 0 mg/kg bw	Group 1 Control 0 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group4 High Dose 1000 mg/kg bw	Group4 High Dose 1000 mg/kg bw
Main Animals	10 M	10 F	10 M	10 F	10 M	10 F	10 M	10 F
Kidneys Abnormal color – pale/white	0	0	0	0	4	1	8	7
Kidneys Abnormal color – spotted	0	0	0	0	4	1	9	6
Kidneys Dilatation/pelvis dilatation - unilateral/bilateral	0	0	0	0	2	0	3	1
Ureters Dilatation	0	0	0	0	1	0	0	0
Urinary Bladder Thickened wall/bladder stone	0	0	0	0	0	0	0	1
Recovery Animals	5 M	5 F	n/a	n/a	n/a	n/a	5 M	5 F
Kidneys Abnormal surface	0	0	n/a	n/a	n/a	n/a	4	3
Kidneys Dilatation/pelvis dilatation - unilateral/bilateral	0	0	n/a	n/a	n/a	n/a	1	0

Table 2. Incidence and Mean Severity of Main Findings in Kidneys

Incidence/Mean Severity	Group 1 Control 0 mg/kg bw	Group 1 Control 0 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group4 High Dose 1000 mg/kg bw	Group4 High Dose 1000 mg/kg bw
Main Animals	10 M	10 F	10 M	10 F	10 M	10 F	10 M	10 F
Tubulopathy	0	0	1/2.0	0	7/2.4	2/2.5	10/3.6	8/2.5
Pelvic dilatation	0	0	1/2.0	0	1/3.0	0	2/3.0	1/1.0
Recovery Animals	5 M	5 F	n/a	n/a	n/a	n/a	5 M	5 F
Tubulopathy	0	0	n/a	n/a	n/a	n/a	5/2.8	4/2.3
Pelvic dilatation	0	0	n/a	n/a	n/a	n/a	1/3.0	0

Table 3. Incidence and Mean Severity of Main Findings in Ureters

Incidence/Mean Severity	Group 1 Control 0 mg/kg bw	Group 1 Control 0 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group4 High Dose 1000 mg/kg bw	Group4 High Dose 1000 mg/kg bw
Main Animals	10 M	10 F	10 M	10 F	10 M	10 F	10 M	10 F
Luminal concrements (incidence only)	0	0	0	0	0	0	1	1
Luminal dilatation	0	0	0	0	1/2.0	1/1.0	7/1.6	6/1.3
Urothelial hyperplasia	0	0	0	0	0	0	2/1.5	3/1.3
Inflammation	0	0	0	0	0	0	1/2.0	0
Recovery Animals	5 M	5 F	n/a	n/a	n/a	n/a	5 M	5 F
Luminal concrements (incidence only)	0	0	n/a	n/a	n/a	n/a	0	0
Luminal dilatation	0	0	n/a	n/a	n/a	n/a	2/1.5	1/1.0
Urothelial hyperplasia	0	0	n/a	n/a	n/a	n/a	0	0
Inflammation	0	1/1.0	n/a	n/a	n/a	n/a	0	0

Table 4. Incidence and Mean Severity of Main Findings in Urinary Bladder

Incidence/Mean Severity	Group 1 Control 0 mg/kg bw	Group 1 Control 0 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group2 Low Dose 100 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group3 Medium Dose 300 mg/kg bw	Group4 High Dose 1000 mg/kg bw	Group4 High Dose 1000 mg/kg bw
Main Animals	10 M	10 F	10 M	10 F	10 M	10 F	10 M	10 F
Urothelial hyperplasia	0	0	0	0	0	0	7/1.6	5/1.2
Inflammation	0	0	0	0	0	0	0	2/1.0
Recovery Animals	5 M	5 F	n/a	n/a	n/a	n/a	5 M	5 F
Urothelial hyperplasia	0	0	n/a	n/a	n/a	n/a	2/1.5	2/1.0
Inflammation	0	0	n/a	n/a	n/a	n/a	0	0

Table 5. Kidney weight changes

Kidney weights Deviationvs.controls [%]	LD 100 mg/kg bw/day	LD 100 mg/kg bw/day		MD 300 mg/kg bw/day	MD 300 mg/kg bw/day	HD 1000 mg/kg bw/day	HD 1000 mg/kg bw/day
End of Treatment Period	10 M	10 F		10 M	10 F	10 M		10 F
Absolute	6	3		10	10	28**		27***
Relative to body weight	11	4		15	13*	36***		28***
Relative to brain weight	6	3		11	9	29***		28***
End of Recovery Period	n/a	n/a	n/a		n/a	5 M		5 F
Absolute	n/a	n/a	n/a		n/a	8		1
Relative to body weight	n/a	n/a	n/a		n/a	13		3
Relative to brain weight	n/a	n/a	n/a		n/a	11		3

* = p < 0.05; ** = p < 0.01; *** = p < 0.001

Conclusions:

In the 90-day repeat dose toxicity study, conducted according to OECD TG 408 and in compliance with GLP, the NOAEL for 3-(trimethoxysilyl)propiononitrile was concluded to be 100 mg/kg bw/day based on tubulopathy observed at doses of 1000 and 300 mg/kg bw/day.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

subchronic

Species:

rat

System:

urinary

Organ:

kidney

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 the key 90-day repeat dose toxicity study, conducted according to OECD TG 408 and in compliance with GLP, the NOAEL for 3-(trimethoxysilyl)propiononitrile was concluded to be 100 mg/kg bw/day based on tubulopathy observed at dose levels of 1000 and 300 mg/kg bw/day (Eurofins, 2019).

In the study, doses of 100 (low dose, LD), 300 (mid dose, MD) or 1000 (high dose, HD) mg/kg bw/day were administered via oral gavage daily to 10 male and 10 female Wistar rats per group for 90 days. A negative control group was also included. Additional 5 male and 5 female rats were included in the control group and in the high dose group which were observed for 28 days after termination of the treatment (recovery group). During the period of administration, the rats were observed daily for signs of systemic toxicity and mortality. Animals that died were examined microscopically. Body weights and food consumption were measured weekly. Rats were also subjected to detailed clinical examinations weekly and functional observation battery (FOB) and ophthalmoscope examination at the end of treatment and recovery periods. At the end of the treatment period, all surviving rats were sacrificed and subjected to necropsy. Organ weights were measured and all rats were observed for macroscopic lesions. The wet weight of a subset of tissues was taken and a set of organs/tissues was preserved. The estrous cycle, epididymal sperm motility and testicular sperm count was evaluated at the end of the treatment and recovery periods. Haematological, coagulation, urine analysis and clinical biochemistry parameters were examined from all animals. A full histopathological evaluation of the tissues was performed on HD and control animals. These examinations were extended to animals of all other dosage groups for kidneys, ureters and urinary bladder. Only organs and tissues of the other dosage groups showing changes in the HD group were examined. These examinations were also extended to animals subjected to necropsy at the end of the recovery period. Any gross lesion identified macroscopically was also examined microscopically in all animals.

One male rat from MD group was moribund after showing clinical signs such as moving the bedding materials, apathy, lethargy, reduced spontaneous activity, tremors, prone position and abnormal breathing on day 57 and was sacrificed for animal welfare reasons. Macroscopic observation showed kidneys with pelvic dilatation, abnormal color (white) and an enlarged mandibular lymph node, abnormal color (red). The morbidity of the MD male was considered to be related to a moderate cardiac dilatation at histopathology examination. One female rat from the control group was found dead on Day 89 and autolyzed. This animal showed no clinical symptoms throughout the treatment period. The cause of the death could not be established from the organs and tissues examined histologically. Its premature death was considered to be incidental and not test item-related. All remaining animals survived the treatment period.

Clinical signs like slight to moderate salivation and moving the bedding materials were observed immediately after the dose administration in the dose groups and are therefore considered to be a sign of a local reaction to the test item rather than a systemic adverse effect and without toxicological relevance. Further signs like alopecia, piloerection, crust; scratch/cut, nasal discharge and lacrimation were observed transiently in all the groups including control and were therefore considered to be incidental findings. There were no treatment-related clinical signs during the recovery period.

There were no test item-related clinical signs observed in detailed clinical examination, functional observation battery and ophthalmoscopy examination in any of the animals of the dose groups when compared to controls during both treatment and recovery periods.

In males of the HD group a tendency towards lower body weights was seen at the end of the treatment period. The test item did not affect body weight and body weight gain during both treatment and recovery periods in LD and MD males or in any females.

There was no test item-related effect on food consumption in any of the dose groups when compared to control in both treatment and recovery periods.

At the end of the treatment period higher WBC count was observed in males of the MD and HD groups and in females of the HD group. Serum urea was increased in both genders of the HD group. In male animals of the HD group higher serum potassium level was found at the end of the treatment period and moderately increased AP at the end of the recovery period. Finally, high urinary levels of erythrocytes, leukocytes or hazy urine in single animals of the HD group might be linked to histopathological findings of nephropathy in the renal system.

There was no test item-related effect on haematological, coagulation, clinical biochemistry or urinalysis parameters in any of the dose groups at the end of treatment and recovery periods.

There were no test item-related effects on mean testes weight, mean sperm motility and mean testis sperm count at the end of treatment and recovery periods.There was no effect on the estrous cyclicity.

Test item-related macroscopic findings like abnormal color kidneys (spotted, pale/white), dilatation of pelvis (unilateral/bilateral), ureters dilatation, thickened urinary bladder/bladder stone and abnormal surface of kidneys were observed mostly in MD and HD groups at the end of the treatment period. All of these findings were also observed in the HD group at the end of recovery. A test item-related increase in kidney weight (absolute and relative) was observed in male and female animals of the MD and HD groups when compared to the control group. These changes were highly correlated with histopathological changes observed. Other statistically significant changes observed in thymus weight, spleen weight and heart weight were considered to be of no toxicological relevance, as they were incidental in nature and without histological findings. At histopathological evaluation in the kidneys, higher degrees of tubulopathy were observed in treated rats of the MD and HD groups. The tubulopathy was characterized by nephrohydrosis (tubular dilatation), tubular degeneration, tubular basophilia and inflammation (mainly chronic or chronic active), sometimes in association with hydronephrosis (pelvic dilatation). Slight degrees of unilateral tubulopathy were also recorded in one LD group male. Another LD group male showed slight unilateral pelvic dilatation. After the recovery period, the tubulopathy and pelvic dilatation regressed only minimally.

Minimal to slight luminal dilatation and urothelial hyperplasia were recorded in high dose animals. In one male and in one female from the HD group, luminal concrements were observed in up to moderate dilated, hyperplastic and/or inflamed ureters. There was also minimal or slight luminal dilatation in the ureters of a few MD animals. After the recovery period, the luminal dilatation showed partial regression. All other findings were fully reversible.

There were no microscopic findings in the male and female reproductive organs that could be attributed to the treatment with the test item. All other findings recorded were within the range of normal background lesions which may be recorded in animals of this strain and age.

At dose formulation analysis, the nominal concentrations were confirmed for all dose groups, as the measured concentrations were within the acceptance criterion of 10% in study weeks 1, 5, 9 and in the last week of the study.

The OECD 422 study on the structural analogue, 3-(triethoxysilyl)propiononitrile (CAS 919-31-3), is included in support of read-across for the genetic toxicity endpoint.

Justification for classification or non-classification

Based on the available data, 3-(trimethoxysilyl)propiononitrile is not classified for specific target organ toxicity following repeated exposure according to Regulation (EC) No 1272/2008.