Acetic acid, 2-cyano-2-[3-[(3-methoxypropyl)amino]-2-cyclohexen-1-ylidene]-, 2-ethoxyethyl ester, (2Z)-

Endpoint summary

Description of key information

The 90-days oral toxicity study (OECD 408, GLP) with the test item (CAS 1419401-88-9) a NOAEL of 300 mg/kg bw/day was determined in the rat. 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Additional information

Repeated dose toxicity, oral:

In the chosen key study according to OECD TG 408 and GLP, i.e. a repeated dose oral toxicity study (Charles River Laboratories (2013), 20027338), 2-ethoxyethyl (2Z)-2-cyano-2-[3-(3-methoxypropylamino)cyclohex-2-en-1-ylidene]acetate (C-1701 B_C_3) in Polyethylene glycol 300 (PEG 300) was administered by oral gavage to 10 Wistar rats/sex/group once a day at 0 (vehicle control), 100, 300 or 1000 mg/kg bw/day. During the treatment period, all animals were observed twice daily for mortality. Daily general clinical observations and weekly detailed observations were performed; with the exception of week 12 in which functional observation battery (FOB) and locomotor activity assessments were conducted. Body weights were recorded daily and food consumption was measured weekly during the treatment period. Vaginal lavage samples were collected daily for the last 28 days of the treatment period and on the day of scheduled necropsy for estrous cycle evaluations. Ophthalmological examinations were conducted on all animals once during the acclimatisation period and once prior to scheduled necropsy. Blood samples for clinical pathology examinations including assessment of hematology and clinical chemistry parameters were collected on the day of scheduled necropsy from all rats after an overnight fasting period. For the assessment of urinalysis parameters, urine samples were collected from female rats deprived of food overnight from the end of the last treatment day (day 90) to the morning of the day of necropsy (day 91). On the day of scheduled necropsy, all animals were examined macroscopically and the weights of selected organs were determined. Full histopathology was performed on the preserved organs/tissues of all premature decedents and of the animals of the control and high dose groups. Due to lesions observed in high dose group animals, the liver was also examined microscopically in low and mid dose group animals. All gross lesions of all animals were examined. Male reproductive assessments were conducted including sperm motility, sperm concentration, sperm morphology and spermatid counts.

Daily administration of C-1701 B_C_3 at 1000 mg/kg body weight/day resulted in clinical signs, consisting of urine-stained abdominal fur, increased incidence of dehydration and excess salivation. Body weight gains were slightly decreased in males. After study start, food consumption was slightly and transiently decreased in males and females. The bilirubin test in urine was positive for the female rats. Hematological and clinical chemistry examinations mainly revealed slightly decreased red blood cell parameters (hemoglobin and hematocrit in males, MCHC in females, MCH and MCV in both sexes) and increased reticulocyte counts and bilirubin concentrations in both sexes. Leukocyte and lymphocyte counts were slightly increased in the female rats. Liver weights were moderately increased in males and females, with minimal centrilobular hepatocellular hypertrophy as histopathological correlate. There were statistically significant changes in other organ weights, but there were no patterns, trends or associated microscopic findings to identify them as being toxicologically relevant. Slightly lower testicular spermatid count and spermatid density occurred in the male rats in the 1000 mg/kg body weight/day dose group; however, these differences were not considered to be adverse because there were no corresponding reductions in absolute testicular weights and no microscopic correlations in testicular histology.

At 300 mg/kg body weight/day, urine-stained abdominal fur and increased incidence of dehydration were still present in males and females. Minor differences occurred in single hematology parameters, but without consistency across genders. The bilirubin test in urine was positive for the female rats. These findings were not considered adverse. Liver weights were increased in both sexes, but without any histopathological correlates or any evidence of an impaired organ function by clinical chemistry parameters. Therefore, the organ weight changes at 300 mg/kg body weight/day were considered as compound-related, but were not considered adverse.

After administration of C-1701 B_C_3 at 100 mg/kg body weight/day, dehydration was observed in 3 females and the bilirubin test in the urine was positive in female rats. In the absence of any other effects, these differences from controls were not considered to be adverse. No compound related effects were observed in the male rats.

With regard to the present study, the No Observed Adverse Effect Level (NOAEL) was considered to be 300 mg/kg body weight/day.

In the associated 14 day dose range finding study (99C0284/11X221), male and female Crl:WI(Han) rats (20 per sex) were randomly assigned to 4 dose groups, 5 rats per sex per group. Preparations of the test substance, C-1701 B_C_3, in the control substance, polyethylene glycol 300 (PEG 300), were administered daily via oral gavage to the male and female rats on Days 1 through 14 of study (DSs 1 through 14). The first day of dose administration was designated as DS 1. The following parameters were evaluated: viability, clinical observations, body weights and body weight changes, food consumption, hematology, clinical chemistry, urinalysis, necropsy observations, organ weights, and histopathology.

No incidences of mortality and no toxicologically relevant test item related changes in hematology, clinical chemistry and urinalysis parameters in either the male or the female rats were observed. Except for the liver, no relevant test item-related changes in organ weights were noted on the day of scheduled necropsy. Macroscopical and histopathological examinations revealed no adverse test item related gross lesions or microscopic findings in both male and female rats.

Treatment of male rats with the test item resulted in adverse clinical signs (discoloured fur, mild to moderate dehydration, mild to moderate excess salivation, hunched posture, rales, decreased motor activity, swelling in the axillary region and ptosis), reductions in body weight gain and food consumption, and increases in liver weights at the high dose level of 1000 mg/kg bw/day. Females at the same dose level showed adverse clinical signs (discoloured fur, mild dehydration, urine-stained abdominal fur and chromorhinorrhea) and increased liver weights. Increases in liver weights were also seen in females treated at 300 mg/kg bw/day.

In the absence of concomitant macroscopical and histopathological findings, the increased liver weights noted in both sexes at 1000 mg/kg bw/day and in females also at 300 mg/kg bw/day were not considered to represent adverse effects.

Justification for classification or non-classification

The present data on repeated dose toxicity do not fulfill the criteria laid down in 67/548/EEC and regulation (EU) 1272/2008, and therefore, a non-classification is warranted.