6-deoxy-L-mannose

Endpoint summary

Description of key information

13-Week feeding study; rat; NOAEL > 1% (highest dose tested; equivalent to 516 and 665 mg/kg in males and females, respectively); Reliability = 2

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) Guideline M3(R2) (ICH, 2009). 2.2.1.

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: US FDA Redbook Guideline for Subchronic Toxicity Studies with Rodents (US FDA, 2003)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Specific details on test material used for the study:

- Purity: 98.8%
-Impurities: Not reported

Species:

rat

Strain:

other: Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: PND 21
- Weight at study initiation: not reported
- Housing: F1 pups post-weaning, were individually housed in suspended, stainless steel, wire-mesh type cages,
- Diet: Meal Lab Diet Certified Rodent Diet #5002 (ad libitum)
- Water: tap water (ad libitum)



ENVIRONMENTAL CONDITIONS
- Temperature: 20–26 °C
- Humidity: 30–70%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

TEST SUBSTANCE PREPARATION
- Preparation frequency: weekly
- Preparation details: administered in the diet
- Adjusted for purity: no

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

Not reported

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

Daily

Dose / conc.:

0.25 other: %

Remarks:

nominal in diet

Dose / conc.:

0.5 other: %

Remarks:

nominal in diet

Dose / conc.:

1 other: %

Remarks:

nominal in diet

No. of animals per sex per dose:

Control and high dose groups (F1) consisted of 30 animals/sex, for which 10 animals/sex were used in a one-month recovery group. Low and middle dose groups consisted of 20 animals/sex.

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: : The concentration levels were selected based on a previous preliminary study in which no compound-related effects were observed in P females or their offspring following maternal dosing at the same concentrations for 14 days starting from PND 7. The highest dietary concentration of 1% was selected as the top dose to allow for a sufficient margin of safety when compared to potential human infant exposures. The test item was administered in the diet at dose levels of 0.25%, 0.5%, and 1.0% to groups of 26 male (during mating) and female (28 days prior to mating through weaning of the F1 generation) rats.
- Rationale for animal assignment (if not random): : At weaning on PND 21, selected F1 pups were weighed and observed individually, and one male or one female from each litter in each group was randomly selected to continue onto the 13-week phase.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily for mortality and moribundity

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Clinical cage side examinations were performed daily and detailed clinical examiniations were performed weekly.

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION: Yes
- Time schedule for examinations: Weekly

FOOD EFFICIENCY: Yes

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Prior to administration of test substance and at the end of the study

HAEMATOLOGY: Yes
- Time schedule for collection of blood: end of the 13-week administration period
- Anaesthetic used for blood collection: carbon dioxide
- Animals fasted: Yes
- How many animals: 5 animals/sex/group
- Blood samples were analysed for routine haematology, coagulation, and clinical chemistry parameters. Standard haematology parameters were measured using an automated instrument or were calculated from measured values. Blood cells also were examined for morphology. Coagulation parameters were analysed with a Stago Compact.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: end of the 13-week administration period
- Anaesthetic used for blood collection: carbon dioxide
- Animals fasted: Yes
- How many animals: 5 animals/sex/group
- Standard clinical chemistry parameters were analysed with an Olympus Au2700/Au640.

URINALYSIS: Yes
- Time schedule for collection of urine: end of the 13-week administration period
- Metabolism cages used for collection of urine: yes
- Animals fasted: not reported
- Urinalysis was performed to examineappearance, colour, volume, specific gravity, and pH, and the presence of protein, glucose, bilirubin, ketone bodies, occult blood. Urine sediments also were microscopically examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Study week 12

OTHER: Yes
- 1 Generation Reproduction Study

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
- All necropsied animals (sacrificed on Day 92 of the 13-week study) were examined carefully for external abnormalities including palpable masses, and were subjected to a full and detailed macroscopic examination of organs and tissues and the results recorded. Body weights and organ weights were recorded for F1 animals of the 13-week study and recovery groups. Paired organs were weighed together. Organ weight ratios were calculated relative to body and brain weights. Organs and tissues from all animals were fixed in 10% neutral buffered formalin. Formalin was infused into the lungs via the trachea and into the urinary bladder. The eye (with optic nerve), testes, and epididymides were fixed in a modified Davidson’s fixative. Target organs, gross lesions, and tissue masses with regional lymph nodes also were collected and fixed in formalin. Fixed tissue samples were paraffin-embedded, sectioned, and stained with haematoxylin–eosin.


HISTOPATHOLOGY: Yes
- Routine histopathological examination of all organs/tissues was performed for F1 animals in the control and high-dose groups (10 animals/sex/group). Histopathological examination of target organs, gross lesions, and tissue masses (with regional lymph nodes) also was performed for all animals.

Statistics:

Statistical analyses were conducted comparing each treated group to the control group for each sex and each endpoint. The results of all pair-wise comparisons were reported at the 0.05 and 0.01 significance levels.

Group pair-wise comparisons were performed to analyse the following endpoints: body weight, body weight changes, food consumption, haematology (except leukocyte counts), blood coagulation, clinical chemistry, absolute and relative organ weights, continuous functional observational battery parameters (body weight, body temperature, urination, defecation, rearing, thermal response, forelimb and hindlimb grip strength, and hindlimb splay), and locomotor activity. For total and differential leukocyte counts, a log transformation was first performed, and the transformed data then analysed by group pair-wise comparison. Levene’s test was applied to analyse the homogeneity of group variances for these endpoints. If the results of Levene’s test was not significant (p > 0.01) (i.e., homogeneity of variance), a pooled estimate of the variance (mean square error) was computed from a one-way analysis of variance and utilized by a Dunnett’s comparison of each test group with the control group. If the results of Levene’s test was significant (p < 0.01), comparisons with the control group were performed using Welch’s t-test with a Bonferroni correction.

All endpoints were analysed using two-tailed tests. The data for food efficiency, urine volume, urine specific gravity, and urinary pH was first subjected to a rank transformation, and the transformed data then analysed by Dunnett’s test (two-tailed).

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Description (incidence and severity):

After 13-weeks of administration, the only statistically significant finding in the haematology and coagulation data was a slightly increased absolute reticulocyte count in high-dose females compared to control females (163.59 vs. 128.40E10e3/mm3). Given the small magnitude of change and the fact that all values were within historical control ranges for this parameter, this lone finding was not ascribed any toxicological significance. At the end of the 4-week recovery period, a very slight, yet statistically significant, decrease in the mean corpuscular haemoglobin (MCH) was observed in high-dose males relative to control males (16.98 vs. 17.50 pg). In high-dose females, slight, yet statistically significant, differences at the end of the recovery period consisted of increased haematocrit (49.26% vs. 46.16%), mean corpuscular volume (MCV) (57.18 vs. 55.16 fL), and MCH (18.36 vs. 17.80 pg) and decreased neutrophil count (0.744 vs. 1.224 10e3/µL) relative to control females. While a few statistically significant differences were noted in the haematology results in the treated groups, no dose-dependent responses were identified, and the changes were considered to be incidental variations.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

A single statistically significant change was noted in the analysis of the clinical chemistry data, and consisted of a very slight increase in chloride in females of the high-dose group compared to control females (101.7 vs. 99.9 mEq/L); values, however, were within historical control ranges. At the end of the 4-week recovery period, in the high-dose males, statistically significant differences consisted of decreased potassium (7.52 vs. 9.70 mg/dL) and phosphorus (7.52 vs. 9.70 mg/dL) and slightly increased globulin (3.54 vs. 3.26 g/dL) relative to the controls. In high-dose females, following the 4-week of recovery period, creatinine was slightly increased relative to the controls (0.46 vs. 0.40 mg/dL). While a few statistically significant differences were noted in the clinical chemistry results in the treated groups, no dose-dependent responses were identified, and the changes were considered to be incidental variations.

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

The only statistically significant finding was decreased relative-to-body pituitary gland weight in the mid-dose (0.5%) females compared to control females (0.0064% vs. 0.0073%). The magnitude of decrease was very minimal and showed no dose-dependency. No statistically significant changes were observed in males. At the end of the recovery period, a few statistically significant differences were observed in high-dose animals compared to controls. The relative to brain weight, but not absolute or relative to body weight, of the pituitary gland was slightly decreased in high-dose males compared to the controls (0.0081% vs. 0.0091%). Also, a slight decrease in absolute (1.805 vs. 2.250 g) and relative to brain weights (0.8064% vs. 1.0117%) of the seminal vesicles was observed in recovery group males. The absolute weight (3.912 vs. 4.122 g) of the testes was slightly reduced; however, no statistically significant differences in the relative weights of the testes were noted. In high-dose recovery group females, the absolute (0.079 vs. 0.064 g), relative-to-body (0.0271% vs. 0.0214%), and relative-to-brain (0.0389% vs. 0.0312%) weights of the adrenal glands were slightly increased relative to control females.

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

One high-dose female was found to present with a mass in the subcutis of the left inguinal area. Upon histopathological examination, this mass correlated with a mammary adenocarcinoma; however, similar findings were not observed in other animals and no evidence of preneoplastic and/or proliferative changes were observed in the mammary glands of other high-dose females.

Other effects:

no effects observed

Description (incidence and severity):

1 Generation Reproduction Study. A statistically significant reduction in pup body weight in females on PND 21 in the low-dose group was considered of no toxicological significance given the absence of any dose–response relationship, occurrence in a single sex, and small magnitude of effect. At the high-dose level, pup weights were nearly identical to the controls. The NOAEL for the reproduction study is equal to 1% in diet, the highest dose tested.

Key result

Dose descriptor:

NOAEL

Effect level:

1 other: % in diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects at highest dose tested

Key result

Critical effects observed:

no

Conclusions:

Male NOAEL = 1% in diet (516 mg/kg/day)
Female NOAEL = 1% in diet (665 mg/kg/day)

Executive summary:

The test item was administered in the diet at dose levels of 0.25%, 0.5%, and 1.0% to groups of 26 male (during mating) and female (28 days prior to mating through weaning of the F1 generation) rats. At weaning on PND 21, selected F1 pups were weighed and observed individually, and one male or one female from each litter in each group was randomly selected to continue onto the 13-week phase. In the 13-week feeding study, control and high dose groups (F1) consisted of 30 animals/sex, for which 10 animals/sex were used in a one-month recovery group. Low and middle dose groups consisted of 20 animals/sex. Dose levels were 0.25%, 0.5%, and 1.0% in the diet of the F1 animals. Reproductive parameters were evaluated. Feed consumption, body-weight gain, selected organ-weights, gross pathology and appropriate histopathology were also evaluated.

In the 13-week study performed in the F1 generation, body weight, body weight gain, feed consumption, clinical pathology, urinalysis, and FOB measurements/analyses showed no effects of the test item administration up to the highest concentration tested of 1.0% in the diet. While a few statistically significant differences were noted in the haematology and clinical chemistry results in the test item administered groups, no dose-dependent responses were identified, and the changes were considered to be incidental variations. Coagulation parameters were unaffected. Likewise, there were no effects on organ weights or on the results of the macroscopic or histopathological examinations.

Based on the results of the 13-week study, the test item was considered to be without compound-related adverse effects at dietary levels of up to 1.0%, the highest level administered. As a result, the corresponding no-observed-adverse-effect level (NOAEL) for oral toxicity was determined to be 516 mg/ kg bw/day in male rats and 665 mg/kg bw/day in female rats.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

665 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Read-across guideline 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

No repeated dose oral toxicity study with the test substance is available. An OECD 408 Guideline study in rats with L-fucose was used as a read across to fulfill the data gap for the test substance. The underlying hypothesis supporting read-across from L-Fucose to L-Rhamnose includes the following: (1) L-Fucose and L-Rhamnose are fully hydrolysed monosaccharide stereo isomers with the exception of one methyl group differing at one of four stereocenters. (2) L-Fucose and L-Rhamnose have similar physicochemical properties. (3) L-Fucose and L-Rhamnose share identical OECD QSAR Toolbox v3.4 alert profiles. (4) L-Fucose and L-Rhamnose share identical chemical descriptor profiles, based on descriptors calculated with ADMET Predictor7.2and OASIS TIMES v2.27.19. These same chemical descriptors are the constituent components of QSAR models in ADMET Predictor and OASIS Times. Therefore, the predictions for L-Fucose and L-Rhamnose for all endpoints assessed by ADMET Predictor and OASIS TIMES will be identical. Additional documentation, provided within the IUCLID Assessment Reports section, supports the read-across approach.

The test item was administered in the diet at dose levels of 0.25%, 0.5%, and 1.0% to groups of 26 male (during mating) and female (28 days prior to mating through weaning of the F1 generation) rats. At weaning on PND 21, selected F1 pups were weighed and observed individually, and one male or one female from each litter in each group was randomly selected to continue onto the 13-week phase. In the 13-week feeding study, control and high dose groups (F1) consisted of 30 animals/sex, for which 10 animals/sex were used in a one-month recovery group. Low and middle dose groups consisted of 20 animals/sex. Dose levels were 0.25%, 0.5%, and 1.0% in the diet of the F1 animals. Reproductive parameters were evaluated. Feed consumption, body-weight gain, selected organ-weights, gross pathology and appropriate histopathology were also evaluated. In the 13-week study performed in the F1 generation, body weight, body weight gain, feed consumption, clinical pathology, urinalysis, and FOB measurements/analyses showed no effects of the test item administration up to the highest concentration tested of 1.0% in the diet. While a few statistically significant differences were noted in the haematology and clinical chemistry results in the test item administered groups, no dose-dependent responses were identified, and the changes were considered to be incidental variations. Coagulation parameters were unaffected. Likewise, there were no effects on organ weights or on the results of the macroscopic or histopathological examinations. Based on the results of the 13-week study, the test item was considered to be without compound-related adverse effects at dietary levels of up to 1.0%, the highest level administered. As a result, the corresponding no-observed-adverse-effect level (NOAEL) for oral toxicity was determined to be 516 mg/ kg bw/day in male rats and 665 mg/kg bw/day in female rats.

Justification for classification or non-classification

Based on no adverse test substance-related effects at 1% (highest dose tested) in a 13-week rat feeding study with the read-across chemical, L-fucose, the test substance does not need to be classified for repeat dose toxicity according to EU Classification and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.