3,3'-[(2,5-dichloro-p-phenylene)bis[imino(1-acetyl-2-oxoethylene)azo]]bis[4-chloro-N-(5-chloro-o-tolyl)benzamide]

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From Nov 2021 to Oct 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

29 July 2016

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

3,3'-[(2-chloro-5-methyl-p-phenylene)bis[imino(1-acetyl-2-oxoethylene)azo]]bis[4-chloro-N-[2-(4-chlorophenoxy)-5-(trifluoromethyl)phenyl]benzamide]

EC Number:

279-356-6

EC Name:

3,3'-[(2-chloro-5-methyl-p-phenylene)bis[imino(1-acetyl-2-oxoethylene)azo]]bis[4-chloro-N-[2-(4-chlorophenoxy)-5-(trifluoromethyl)phenyl]benzamide]

Cas Number:

79953-85-8

Molecular formula:

C55H37Cl5F6N8O8

IUPAC Name:

3,3'-{(2-chloro-5-methyl-1,4-phenylene)bis[imino(1,3-dioxobutane-2,1-diyl)diazene-2,1-diyl]}bis{4-chloro-N-[2-(4-chlorophenoxy)-5-(trifluoromethyl)phenyl]benzamide}

Test material form:

solid: nanoform, no surface treatment

Details on test material:

BET = 71.4 m2/g
Batch 0004079400
Purity 99.4%
Storage stability: The stability of the test substance under storage conditions was guaranteed until 27 Aug 2022 as indicated by the sponsor, and the sponsor holds this responsibility.

Specific details on test material used for the study:

TEST MATERIAL
Batch no. 0004079400
CAS no. 79953-85-8
Purity 99.4 wt%
Expiry/Retest date 27 August 2022
Appearance Yellow powder
Storage conditions Room temperature

Test animals

Species:

rat

Strain:

Wistar

Remarks:

Wistar Hannover rat

Details on species / strain selection:

The Wistar Hannover rat was the species and strain of choice because it is accepted by many regulatory authorities and there are ample experience and background data on this species and strain.
The oral route was selected as it is a possible route of exposure of the test item in man and has been specifically requested by the Regulatory Authorities.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Italia S.p.A., Calco (Lecco), Italy
- Females: nulliparous and non-pregnant
- Age at study initiation: 9 - 11 weeks old
- Weight at acquisition: 212-230 g for males and 182-193 g for females
- Housing arrival - mating: animals were housed up to 5 of one sex to a cage, in polysulfone solid bottomed cages measuring 59.5×38×20 cm, nesting material was provided inside suitable bedding bags and changed at least twice a week
- Housing during mating: animals were housed one male to one female in clear polysulfone cages measuring 42.5×26.6×18.5 cm with a stainless steel mesh lid and floor, each cage tray held absorbent material which was inspected and changed daily
- Housing after mating: the males were re-caged as they were before mating, females were transferred to individual solid bottomed cages for the gestation period, birth and lactation, nesting material was provided inside suitable bedding bags, additional suitable nesting material was provided as necessary, nesting material was changed at least twice a week
- Diet: ad libitum, laboratory rodent diet (4 RF 21,Mucedola S.r.l., Via G. Galilei, 4, 20019 SettimoMilanese (MI), Italy)
- Water: ad libitum, via water bottles
- Acclimation period: approx 2 weeks

DETAILS OF FOOD AND WATER QUALITY:
There was no information available to indicate that any non-nutrient substance likely to influence the effect of the test item was present in the drinking water or the diet.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 40-60
- Air changes (per hr): 15-20
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 21 Dec 2021 (allocation) To: 17 Feb 2022 (last day of necropsy)

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Remarks:

0.5% CMC in water, softened by reverse osmosis

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
- Concentration in vehicle: 10, 30 and 100 mg/mL
- Dose volume: 10 mL/kg body weight, dose volumes for males and females were adjusted once per week for each animal according to the last recorded body weight, dose volumes for females during the gestation and lactation periods were calculated according to the last recorded body weight
- Dosing preparation: preparations were made daily, preparations were kept under magnetic stirring for at least 16 hours at room temperature and up to completion of dosing

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analytical method was validated in a separate study in the range from 10 to 100 mg/mL. In the same study, a 28 hour stability at room temperature and a 8-day stability at 2- 8°C were verified in the range from 10 to 100 mg/mL. Samples of the formulations prepared during the current study (the first and the last week of treatment where possible) were analysed to check the concentration and homogeneity. Results of the analyses were within the acceptability limits for suspensions (85-115% for concentration and CV < 10% for homogeneity).

Duration of treatment / exposure:

Males were treated for 2 consecutive weeks prior to pairing and during pairing with females until the day before necropsy, for a total of 39 days.
Females were treated for 2 consecutive weeks prior to pairing, during pairing and throughout the gestation and lactation periods until day 13 post partum, for a period comprising from 51 to 55 days.

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Remarks:

Group 1
Control

Doses / concentrations 2

Dose / conc.:

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

Remarks:

Group 2
Low-level dose

Doses / concentrations 3

Dose / conc.:

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

Remarks:

Group 3
Medium-level dose

Doses / concentrations 4

Dose / conc.:

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

Remarks:

Group 4
High-level dose

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: dose levels of 100, 300 and 1000 mg/kg/day were selected based on information from subacute oral toxicity studies with structurally related pigments. 1000 mg/kg bw is the maximimum dose prescribed in the OECD testing guideline.
- Rationale for animal assignment: rats were allocated to the groups by computerised stratified randomisation to give approximately equal initial group mean body weights., individuals were uniquely identified within the study by sex, tattoo on the hind feet and ear notch and housed 5 of one sex per cage
- Fasting period before blood sampling for clinical biochemistry: yes

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Mortality: checked twice daily
- Clinical signs: once before commencement of treatment and at least once daily during the study

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: once before commencement of treatment and at least once a week thereafter
- Observation of changes in gait and posture, reactivity to handling, presence of clonic or tonic movements, stereotypies or bizarre behaviour and effects on the autonomic nervous system (e.g. lachrymation, piloerection, pupil size, unusual respiratory pattern), changes in fur, skin, eyes, mucous membranes, occurrences of secretions and excretions (see table No. 1 for observed parameters and evaluation scale)
- Animals were examined in an open arena for a minimum of three minutes

BODY WEIGHT: Yes
- Time schedule for examinations: males were weighed weekly from allocation to termination, females were weighed weekly from allocation to positive identification of mating and on days 0, 7, 14 and 20 post coitum, dams were also weighed on days 1, 4, 7, 13 post partum and just before to necropsy

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- the weight of food consumed by each cage of males and females were recorded weekly (whenever possible) during the pre-mating period starting from day 1 of dosing up to mating
- Individual food consumption for mated females were measured on gestation days 7, 14 and 20 post coitum starting from day 0 post coitum and on day 7 and 13 post partum starting from day 1 post partum

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of treatment period
- Anaesthetic used for blood collection: isoflurane
- Animals fasted: Yes (except for coagulation test in males)
- How many animals: 5 males and 5 females (with viable litters if possible), randomly selected
- Parameters checked in table No. 2 were examined
- Coagulation parameters investigated: prothrombin time and activated partial thromboplastin time

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of treatment period
- Animals fasted: Yes
- How many animals: 5 males and 5 females (with viable litters if possible), randomly selected
- Parameters checked in table No. 3 were examined

SERUM HORMONES: Yes
- Time of blood sample collection: at termination, timing of the blood collection for thyroid hormone determination was as close as possible between animals and at the same time of the day in case of sampling on different days
- Animals fasted: Yes
- How many animals: all parental animals, each litter (1 sample for males and 1 sample for females, when possible), blood samples from different pups was pooled to obtain the required volume
- Hormones analyzed: serum levels of total thyroxine (total T4) and thyroid stimulating hormone (TSH)

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule: once during study towards end of treatment, for males on day 39 and for females (with viable litters) on day 12 post partum
- Number of animals: 5 males and 5 females randomly selected from each dose group
- Studies conducted: grip strength and sensory reactivity to stimuli, motor activity assessment

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
- Necropsy: the clinical history of adult animals was studied and a detailed post mortem examination was conducted (including examination of the external surface and orifices), changes were noted, the requisite organs weighed and the required tissue samples preserved in fixative and processed for histopathological examination
- All females were examined also for the following: number of visible implantation sites (pregnant animals), number of corpora lutea (pregnant animals)
- Pups: all pups found dead in the cage were examined for external and internal abnormalities, all culled pups sacrificed at day 4 post partum were subjected to an external examination, all live pups sacrificed on day 14 post partum were examined for external abnormalities, gonads were inspected from all pups in order to confirm the sex previously determined by external examination

ORGAN WEIGHTS:
- Parental animals: from all animals completing the scheduled test period, the organs indicated in table No. 4 were dissected free of fat and weighed, the ratios of organ weight to body weight was calculated for each animal
- Pups at day 14 post partum: thyroid was weighed from one male and one female pup selected for blood collection and preserved in 10% neutral buffered formalin, the thyroid weight was determined after fixation

HISTOPATHOLOGY: Yes
- Samples of all tissues (parental animals) required for histopathological examination are listed in table No. 4
- Samples of the tissue were fixed and preserved in 10% neutral buffered formalin (except testes and epididymides which were fixed in Modified Davidson’s fluid and preserved in 70% ethyl alcohol)
- After dehydration and embedding in paraffin wax, sections of the tissues were cut at 5 micrometer thickness and stained with haematoxylin and eosin, in addition, the testes and epididymides were cut at 2-3 micrometer thickness and stained with Periodic Acid Schiff (PAS), the morphological evaluation of the seminiferous epithelium (staging of spermatogenic cycle) was performed

The examination was restricted as detailed below:
(i) Sexual organs (cervix, clitoral gland, ovaries, uterus and vagina) and thyroid glands from all parental females
(ii) Sexual organs (coagulation gland, epididymides, preputial gland, prostate gland, seminal vesicles and testes) and thyroid glands from all parental males
(iii) Tissues specified in section 4.5.7 from 5 males and 5 females randomly selected (animals evaluated for clinical pathology) in the control and high dose group killed at term
(iv) Morphological evaluation of the seminiferous epithelium (staging of the spermatogenic cycle) from all males in control and high dose groups
(v) All abnormalities in all groups

Other examinations:

PARTURITION AND GESTATION LENGTH:
- Parturition check from day 20 - 25 post coitum, three rimes a day during working day or twice daily during weekends and Public Holidays
- Females which did not give birth after 25 days of post coitum period were sacrificed shortly after
- Gestation length calculated as the time between the day of successful mating (day 0 post coitum) and the day of birth
- Day of birth was defined as day 0 post partum

PUPS IDENTIFICATION, WEIGHT AND OBSERVATIONS:
- As soon as possible after parturition was considered complete (day 0 post partum), all pups (live and dead) were counted, sexed and live pups were identified
- Live pups were individually weighed on days 1, 4, 7 and 13 post partum
- Pups dying during the lactation period were weighed before the despatch to necropsy
- Observation was performed once daily for all litters from day 0 post partum until termination
- After culling, all pups were sacrificed with the dams on Day 14 post partum

ANOGENITAL DISTANCE (AGD):
- For each pup measured on day 1 post partum
- AGD was normalized to the cube root of body weight collected on day 1 post partum

NIPPLE COUNT CHECK:
- presence of nipples/areolae in male pups was checked on day 13 post partum

REPRODUCTIVE INDICES:
- Males: copulation index, fertility index
- Females: copulatory index, fertility index, pre-natal loss, post-natal loss at day 0, 4 and 13 post partum
- Pre coital interval
- Sex ratio of litter

Statistics:

Standard deviations were calculated as appropriate.
For continuous variables the significance of the differences amongst group means was assessed by Dunnett’s test or a modified t-test, depending on the homogeneity of data. The non-parametric Kruskal-Wallis analysis of variance was used for the other parameters. Intergroup differences between the control and treated groups were assessed by the nonparametric version of the Williams test. The mean values, standard deviations and statistical analysis were calculated from actual values in the computer without rounding off.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

mortality observed, non-treatment-related

Description (incidence):

One control female was sacrificed for humane reason on Day 22 of gestation phase due to difficulties in parturition.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weight and body weight gain for male and female animals were comparable between treated and control groups through the study. The statistically significant decrease in body weight gain recorded in high dose males and mid-dose females were considered incidental.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption was unaffected by treatment in both genders during the study.

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

he statistically significant differences between contrTol and treated animals (neutrophils in males and platelets in females) were recorded only in animals dosed at 300 mg/kg/day, therefore they were considered to be incidental.

Clinical biochemistry findings:

no effects observed

Endocrine findings:

no effects observed

Description (incidence and severity):

The determination of T4 and TSH was performed on:
- Samples from all parental males from all groups
- Samples from pups on Day 14 post partum.
No treatment-related changes were recorded. Thyroid stimulating hormone was statistically significantly lower than controls in parental males (31%). This is due to 2 control animals, which showed values above the range of historical data, therefore the differences observed has no biological/toxicological significance.

The oestrous cyclicity of the treated females monitored during the pre-mating period, for a total of 14 days, was not affected by treatment. The mean number of oestrous cycles observed in treated animals and control group was comparable.
No differences were recorded in pre-coital interval and copulation plugs between treated and control groups. Copulatory index and fertility index did not show any treatment-related differences.

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

Observation of treated animals at removal from the cage and in an open arena did not reveal significant changes when compared to controls.
No alterations in motor activity, grip strength, landing footsplay and sensory reactivity to stimuli were observed in any treatment group at the examination performed at the end of treatment.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no treatment-related macroscopic observations at the end of the treatment period. Any macroscopic observations were within the range of occasionally observed and expected spontaneous changes in rats of the same age and therefore considered unrelated to treatment.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

There were no treatment-related microscopic observations at the end of the treatment period. There were no test item-related microscopic observations in the testis (stage were evaluation on PAS-stained slides). Any microscopic observations had a comparable incidence in control and treated groups and/or are characteristically seen in untreated rats of the same age and were considered incidental and unrelated to treatment.

Histopathological findings: neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Effect levels

Dose descriptor:

NOAEL

Remarks:

systemic toxicity

Effect level:

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

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Target system / organ toxicity

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

The oral administration of the test substance by gavage to male and female Wistar rats revealed no signs of systemic toxicity up to the highest tested dose level. Therefore, a NOAEL for general systemic toxicity was set to 1000 mg/kg bw/day.

Executive summary:

Under the conditions of the OECD TG 422 and in compliance with GLP, a combined repeated dose toxicity study with the reproductive/developmental screening test was conducted in male and female Wistar rats. The test substance was administered daily as a solution to groups of 10 male and 10 female Wistar rats (P0 animals) by gavage at dose levels of 0 mg/kg bw/d (control; test group 1), 100 mg/kg bw/d (test group 2), 300 mg/kg bw/d (test group 3) and 1000 mg/kg bw/d (test group 4). 0.5% carboxymethylcellulose served as vehicle, control animals were dosed daily with the vehicle only. All doses were administered at a constant volume of 10 mL/kg body weight. For males, the duration of treatment covered a 2-week premating period and pairing with females until the day before necropsy (a total of 39 days). Females were treated for 2 consecutive weeks prior to pairing, during pairing and throughout the gestation and lactation periods until day 13 post partum, for a period comprised from 51 to 55 days.

No test-item related mortality occurred throughout the study and no treatment-related clinical signs were noted during the study. No signs of neurotoxicity (weekly observations at removal from the cage and in an open arena, alterations in motor activity, grip strength and sensory reactivity to stimuli) were observed during the study in parental males and females. No differences in body weight and food consumption were observed in treated animals, compared to the control group. No treatment-related changes were observed in haematological (including coagulation and blood clotting time) or clinical chemistry parameters. Thyroid hormone evaluation in parental animals and pups sacrificed on day 14 post partum did not show treatment-related changes. No treatment-related changes were observed in terminal body weight or absolute and relative organ weights of treated animals of both sexes, when compared to the controls. No treatment-related changes were observed at post mortem macroscopic observations and microscopic evaluation. No treatment-related changes were observed in reproductive and developmental parameters.

Copulatory and fertility indices did not show any treatment related differences among treated and control groups. Parturition, lactation, implantation, litter data and sex ratio did not show changes. No differences in the anogenital distance (normalised value) and no nipple were seen between control and treated groups both for male and female pups. Necropsy findings and thyroid weight in pups did not reveal any treatment-related effect.

Therefore, the no observed adverse effect level (NOAEL) for general systemic toxicity was determined to be 1000 mg/kg bw/day for male and female Wistar rats.