(R)-5-isopropyl-2-methylcyclohexa-1,3-diene

Endpoint summary

Description of key information

Based on thes results of the OECD 422 study, the NOAEL of the test substance for systemic toxicity was considered to be 200 mg/kg/day for males and 75 mg/kg bw/day for females.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-07-17 to 2017-12-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

29th July, 2016

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on species / strain selection:

Sprague-Dawley rats are commonly used in both the general systemic toxicity and reproductive and developmental toxicity studies with a large historical control data base. In addition, the rat is a required species in the regulatory guidelines.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Females nulliparous and non-pregnant: yes
- Age at study initiation: males: 10 weeks, females: 10 weeks
- Weight at study initiation: females at start of administration: 232.9–284.8 g, males at start of administration 352.5–406.0 g
- Housing: Stainless wire mesh cage, 260W×350D×210H (mm), Polycarbonate cage, 260W×420D×180H (mm)
Two animals (during the quarantine-acclimation period); One animal (during the dosing period)
One male and one female (during the mating period)
One female and neonates (during the lactation period)
- Diet: ad libitum, Pelleted rodent chow (Teklad Certified Irradiated Global 18% Protein Rodent Diet 2918C)
- Water: ad libitum
- Acclimation period: 7 days

DETAILS OF FOOD AND WATER QUALITY:
The certificate of feed analysis was provided by the manufacturer, Envigo RMS, Inc. The results of feed analysis met the allowable standard of this facility.
Samples of drinking water are analyzed for specified microorganisms once a month and all environmental contaminants once a year by the Research Institute of Health & Environment, Chungbuk (184, Osong saengmyeong 1 (il)-ro, Osong-eup, Heungdeok-gu, Cheongju-si, Chungcheongbuk-do, Republic of Korea) according to the Regulation of Quality Criteria for Potable Water and Test (Ministry of Environment Ordinance No. 684, Revision Dec. 30, 2016). The results of water analysis met the allowable standard of this facility.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.3 -23.9
- Humidity (%): 45.6-58.4
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
The required amount of the test substance was weighed using an electronic balance (CP423S, ENTRIS423i-1S, Sartorius, Germany) and placed in a container. The test substance was mixed with a small amount of vehicle to dissolve using a magnetic stirrer, and then the vehicle was gradually added to yield the desired concentrations. The dosing formulation was stored in a refrigerator (4.0–5.6°C). These dosing formulations were used within 7 days.

VEHICLE
- Justification for use and choice of vehicle: Through the preliminary solubility test to determine the solubility and dispersion characteristics of the test substance, corn oil was selected as the vehicle because the test substance was dissolved in it.
- Lot/batch no.: MKBZ9899V, MKCC0462

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

As a result of homogeneity and stability analyses conducted in the Biotoxtech Study No.: B16852, the 0.5 and 500 mg/mL dosing solutions were confirmed to be homogenous and stable for 4 hours at room temperature and for 7 days under refrigeration.
Analyses of the dosing formulations were conducted using a Gas Chromatography (GC-2010 series, Shimadzu Corp., Japan). Analyses of the dosing formulations were conducted based on the method used in Biotoxtech Study No.B16852 and samples were taken three times from the middle layer of each dosing formulation prior to dosing and analyzed for verification of dose concentration. The results of dose concentration analyses were determined to be in the range of 106.40–110.83%. These results were within the acceptable limits (±15% of nominal values).

Duration of treatment / exposure:

Males of the main group were dosed once daily for a total of 49 days (for 2 weeks prior to mating, during 2 weeks of mating and 21 days of post-mating). Also, males and females of the recovery group were dosed once daily for 49 days. Females of the main group were dosed once daily for 2 weeks prior to mating until Postpartum Day 13. Also, females showing no evidence of parturition signs were dosed until Gestation Day 25.

Frequency of treatment:

once daily

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

No. of animals per sex per dose:

12

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: In a previously conducted 2-week repeated oral dose range finding study (Biotoxtech Study No.: B16853), all five males and all five females were found moribund or dead at 1,000 mg/day/day. Decreases in body weight and/or food consumption were shown in males at 100 mg/kg/day and in both sexes at 300 mg/kg/day. Increases of the absolute and relative liver weights (up to ca. 50%) were noted in both sexes at 300 mg/kg/day. An enlargement of the liver was observed in one male at 300 mg/kg/day. Therefore, the high dose level was selected at 200 mg/kg/day. Then, the mid and low dose levels were selected at 75 and 25 mg/kg/day, respectively.

Positive control:

none

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least once daily
- Cage side observations checked: All animals were observed for general condition and clinical signs at least once daily throughout the study. All animals were observed for moribundity and mortality twice daily. Females were also observed for signs of abortion and premature birth.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals were observed prior to dosing and once weekly for the dosing and recovery periods.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights of males of the main groups and animals of both sexes of the recovery groups were recorded just prior to dosing on Day 1 (the first day of dosing), once a week throughout the dosing and recovery periods, the day prior to necropsy and on the day of necropsy (body weights after fasting). Body weights of females of the main groups were recorded just prior to dosing on Day 1 (the first day of dosing), once a week throughout the dosing period, on Gestation Days 0, 7, 14 and 20, on Postpartum Days 0, 4 and 13, the day prior to necropsy and on the day of necropsy.

FOOD CONSUMPTION AND COMPOUND INTAKE
Food consumption of males of the main groups and animals of both sexes of the recovery groups was recorded just prior to dosing on Day 0 (one day before the first dosing), once a week during the dosing and recovery periods (except during mating) and the day prior to necropsy. Food consumption of females of the main group was recorded just prior to dosing on Day 0 (one day before the first dosing), once a week throughout the dosing period (except during mating), on Gestation Days 0, 6, 13 and 19, on Postpartum Days 0, 3 and 12 and the day prior to necropsy. Residual feed was recorded on the next day. Individual food consumption was calculated by subtracting the amount of residual feed from the given quantity.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at necropsy.
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes (appr. 18 h)
- How many animals: all animals
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at necropsy.
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes (appr. 18 h)
- How many animals: all animals
- Parameters checked in table 2 were examined.

URINALYSIS: Yes
Six males per group were randomly selected from the main group animals in addition to all male recovery animals for urinalysis a few days before necropsy. Fresh (3-hour) urine and 24-hour urine samples were collected from selected animals and analyzed. Animals were fasted during the fresh urine collection, but were allowed free access to drinking water. Parameters listed in table 3 were examined.

OTHER: Sensory function and motor activity:
Six males and six females per group were randomly selected from the main groups in addition to all recovery animals and evaluated for the following examinations a few days before necropsy. The tests on the dams of the main group were carried out on lactation days 6–11. Parameters examined were: Pinna reflex, auditory reflex, corneal reflex, pupillary reflex, grip strength, motor activity.

Thyroid hormone analysis
Blood samples were taken based on the following schedule:
- from at least two pups (preferably one male and one female) per litter on PND 4 and on PND 13, each (When the number of pups allowed, from pups available above the culling target of 8 pups/litter from at least two pups per litter on both PNDs 4 and 13 otherwise. When only one pup was available above the culling target, only one pup was used for the determination of PND 4. When the litter size was below the culling target, blood collection was not carried out on PND 4. On PND 13, blood samples of all male and female pups were taken and pooled according to sex for analysis.)
- from all adult males and dams at termination
Animals were fasted for more than 18 hours before necropsy (except pups) and anesthetized with isoflurane. Blood samples were collected from the heart (PND 4) or abdominal aorta in a vacutainer. Blood samples of male and female pups were pooled by litter. Blood samples were centrifuged at 3,000 rpm for 10 minutes to obtain serum. Serum samples from the pups on PND 13 and all adult males were analyzed.
Thyroid hormones (T4 and TSH) were preferably measured in “total”.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table 4)

HISTOPATHOLOGY: Yes (see table 5 )

Statistics:

The statistical analysis of this study was conducted using the SAS program (SAS® 9.3, SAS Institute Inc., U.S.A.).

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Salivation was observed in males and females at 200 mg/kg bw/day in the main and recovery groups, however, it was considered to have little toxicological significance since it was caused by physicochemical characteristics.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

In the main group, a significant decrease in body weights was noted in pregnant females at 200 mg/kg/day compared to controls from gestation day (GD) 7 to postpartum day (PPD) 13 (body weights on PPD 13; -10.6% vs. controls). In the recovery group, a decreasing tendency of body weights was noted in females at 200 mg/kg/day (body weights on Day 49; -8.6% vs. controls) although there was no statistical difference. This decrease or decreasing tendency of body weights was considered to be a test substance-related adverse effect.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

In the main group, a significant decrease in food consumption was noted in females at 200 mg/kg/day on GD 7 (-16.4% vs. controls) and PPD 13 (-15.8% vs controls). It was considered to be a test substance-related adverse effect since it was related to the decrease of body weight gain.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

In animals of both sexes in the main and recovery group, there were no test substancerelated effects on auditory reflex, pinna reflex, pupillary reflex and corneal reflex tests compared to the control group.
In animals of both sexes in the main and recovery groups, there was no test substancerelated effect on grip strength when compared to the control group. In the main group, there was a statistically significant decrease in ambulatory counts and/or vertical count in both sexes at 200 mg/kg/day and in females at 25 mg/kg/day. However, the statistical significance had little toxicological meaning because it was a temporary change or it showed no dose-dependency. In the recovery group, there was a statistically significant decrease in ambulatory count in females at 200 mg/kg/day. However, it was considered not to be a test substancerelated adverse effect since the values were similar levels to the control group of the main group.

Immunological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were no test substance-related adverse effects in total thyroxine (total T4) and thyroid-stimulating hormone (TSH) levels in adult males of the main and recovery groups and F1 male pups and female pups on PND 13 at 25, 75 and 200 mg/kg/day. Other statistical significances were considered not to be test substance-related changes because of small differences and the values were within the range of historical reference data.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

In the main group, the absolute and/or relative organ weights of the liver were significantly increased in both sexes at 75 and/or 200 mg/kg/day.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Macroscopic examination at necropsy did not reveal treatment-related changes. At the end of the recovery period, macroscopic examination at necropsy did not reveal test substance-related changes. In addition, among three dams whose pups were all dead, only one dam showed dilatation with gas in the stomach, enlargement of the adrenal glands, and small thymus and spleen. The others showed no gross findings. Also, two non-delivered females were revealed as non-pregnant females but no findings were noted. The other macroscopic findings were considered to be incidental and not related to the test substance.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related changes were observed in the liver.
Centrilobular hepatocellular hypertrophy was observed at minimal to slight severity in males at 75 mg/kg bw/day and in males and females at 200 mg/kg bw/day in the main groups. At the end of the recovery period, this finding was not observed in all males and females at 200 mg/kg bw/day in the recovery group. Centrilobular hepatocellular hypertrophy was completely recovered in all animals at 200 mg/kg bw/day after recovery period. It was considered to have little toxicological significance since hepatocellular hypertrophy in the centrilobular zone is generally considered to be an adaptive response in nature in the absence of associated inflammation or necrosis, and it was completely recovered in all animals after the recovery period in this study.

Histopathological findings: neoplastic:

no effects observed

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

male

Basis for effect level:

other: no adverse effects observed

Key result

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Sex:

female

Basis for effect level:

other: reduced food consumption and body weight

Key result

Critical effects observed:

no

Conclusions:

The NOAEL of the test item for systemic toxicity was considered to be 200 mg/kg bw/day for males and 75 mg/kg bw/day for females.

Executive summary:

The purpose of the combined repeated dose oral gavage toxicity study with the reproduction/developmental toxicity screening was to determine the No Observed Adverse Effect Level (NOAEL) of the test item for both the general systemic and reproduction/developmental toxicity when administered orally to male and female rats at dose levels of 0 (control), 25, 75 and 200 mg/kg bw/day. Males of the main group were dosed once daily for a total of 49 days (prior to mating for 2 weeks, during 2 weeks of mating and 21 days of post-mating), and females of the main group were dosed once daily for 2 weeks prior to mating, throughout gestation and for 13 days after delivery. Also, males and females of the recovery group were dosed for 49 days. All animals of the main and recovery groups survived the duration of the study. Salivation was observed in males and females at 200 mg/kg bw/day in the main and recovery groups, however, it was considered to have little toxicological significance since it was caused by physicochemical characteristics. Dystocia and delayed delivery were observed in one female at 25 mg/kg bw/day. It was considered to be incidental since there was no dose-dependent relationship. In the detailed clinical signs, salivation was observed in some females at 200 mg/kg bw/day in the main and recovery groups. A decrease in body weight gains was noted at 200 mg/kg bw/day in females in the main and recovery groups. A decrease in food consumption was noted in females at 200 mg/kg bw/day in the main group. No test substance-related adverse effects were noted in the results of sensory function, motor activity, urinalysis, hematology, clinical chemistry and thyroid hormone analysis in adult animals of both sexes in the test substance-dosed groups. In the main group, increases in the absolute and/or relative organ weights of the liver were noted in both sexes at 75 and/or 200 mg/kg bw/day. Hepatocellular hypertrophy was observed in males at 75 mg/kg bw/day and in both sexes at 200 mg/kg bw/day. It was considered to have little toxicological significance since hepatocellular hypertrophy in the centrilobular zone is generally considered to be an adaptive response in nature.

Based on these result, the NOAEL of the test item for systemic toxicity was considered to be 200 mg/kg bw/day for males and 75 mg/kg bw/day for females.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

75 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

GLP and guideline compliant study

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

Supporting study

This dose-range finder study was conducted to evaluate the potential toxicity of the test substance, when administered once daily to 10-week-old male and 12-week-old female Sprague-Dawley rats by oral gavage for two weeks and to determine the dose levels for combined repeated dose toxicity study with the reproduction/developmental toxicity screening test. A total of 4 groups were designated as follows:

Three groups of the test substance were designated as Groups 2, 3 and 4 (low, mid and high dose groups, respectively) at dose levels of 100, 300 and 1,000 mg/kg/day, respectively, in addition to a control group (Group 1, corn oil). Each group consisted of 5 males and 5 females. Parameters were evaluated including clinical signs, body weights, food consumption, hematology, clinical chemistry, gross postmortem examinations and organ weights of selected tissues. At 1,000 mg/kg/day, all five males and all five females were found dead or moribund. These animals showed bad condition in clinical signs, body weight loss and a decrease in food consumption. Also, changes in several parameters of hematology and clinical chemistry were noted in the moribund animals. Increases of the absolute and relative liver weights were noted in the animals. An enlargement of the adrenal gland, small thymus/spleen, discoloration of the thymus and/or liver, and hydrothorax in the thoracic cavity were commonly observed in most animals. Focus/spot of the glandular stomach, discoloration of the lung/pancreas or area/enlargement/spot of the lung were observed in a few animals. In surviving animals, a decrease in body weight was observed in males at 100 and 300 mg/kg/day and females at 300 mg/kg/day. A decrease in food consumption was observed in males at 100 mg/kg/day and females at 300 mg/kg/day. Increases in the absolute and relative liver weights were noted in both sexes at 300 mg/kg/day. An enlargement of the liver was observed in one male at 300 mg/kg/day.

Based on the results of this study, the dose levels for combined repeated dose toxicity study with reproduction/developmental toxicity screening test should be selected at 200 mg/kg/day for the high dose level, at 75 mg/kg/day for the mid dose level, and at 25 mg/kg/day for the low dose level.

 

 

Key study

The purpose of the combined repeated dose oral gavage toxicity study with the reproduction/developmental toxicity screening was to determine the No Observed Adverse Effect Level (NOAEL) of the test item for both the general systemic and reproduction/developmental toxicity when administered orally to male and female rats at dose levels of 0 (control), 25, 75 and 200 mg/kg bw/day. Males of the main group were dosed once daily for a total of 49 days (prior to mating for 2 weeks, during 2 weeks of mating and 21 days of post-mating), and females of the main group were dosed once daily for 2 weeks prior to mating, throughout gestation and for 13 days after delivery. Also, males and females of the recovery group were dosed for 49 days. All animals of the main and recovery groups survived the duration of the study. Salivation was observed in males and females at 200 mg/kg bw/day in the main and recovery groups, however, it was considered to have little toxicological significance since it was caused by physicochemical characteristics. Dystocia and delayed delivery were observed in one female at 25 mg/kg bw/day. It was considered to be incidental since there was no dose-dependent relationship. In the detailed clinical signs, salivation was observed in some females at 200 mg/kg bw/day in the main and recovery groups. A decrease in body weight gains was noted at 200 mg/kg bw/day in females in the main and recovery groups. A decrease in food consumption was noted in females at 200 mg/kg bw/day in the main group. No test substance-related adverse effects were noted in the results of sensory function, motor activity, urinalysis, hematology, clinical chemistry and thyroid hormone analysis in adult animals of both sexes in the test substance-dosed groups. In the main group, increases in the absolute and/or relative organ weights of the liver were noted in both sexes at 75 and/or 200 mg/kg bw/day. Hepatocellular hypertrophy was observed in males at 75 mg/kg bw/day and in both sexes at 200 mg/kg bw/day. It was considered to have little toxicological significance since hepatocellular hypertrophy in the centrilobular zone is generally considered to be an adaptive response in nature.

Based on these result, the NOAEL of the test item for systemic toxicity was considered to be 200 mg/kg bw/day for males and 75 mg/kg bw/day for females.

 

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008
The available experimental test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. Based on available data on repeated dose toxicity, the test item is not classified according to Regulation (EC) No 1272/2008 (CLP), as amended for the tenth time in Regulation (EU) No 2017/776.