6-deoxy-L-mannose

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Feeding Study, equivalent to OECD 415; rats. NOAEL >1%. No effects were observed in reproductive parameters examined at the highest concentration tested. Reliability = 2.

Link to relevant study records

Reference

Endpoint:

one-generation reproductive toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 415 [One-Generation Reproduction Toxicity Study (before 9 October 2017)]

Deviations:

no

GLP compliance:

yes

Limit test:

yes

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: (P) 6 wks
- Weight at study initiation: (P) Males: 202–239 g; Females: 166–204 g
- Fasting period before study: no
- Housing: Animals, including F1 pups post-weaning, were individually housed in suspended, stainless steel, wire-mesh type cages, except during mating, near parturition, and during lactation. Rats were housed two per cage (one per sex) during the mating period.
- Diet: Meal Lab Diet Certified Rodent Diet #5002 (ad libitum)
- Water: tap water (ad libitum)
- Acclimation period: 1 week

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 exposure:

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

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: 7 days
- Proof of pregnancy: not reported
- After successful mating each pregnant female was caged (how): Females were individually housed in plastic cages containing wood chip bedding on approximately gestational day (GD) 20 and were allowed to deliver their litters naturally.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

In the reproduction study, dosing of P females started 28 days prior to mating and continued throughout mating, gestation, lactation, and weaning of the F1 generation. The P males were exposed only during mating.

Frequency of treatment:

Daily in feed

Details on study schedule:

- Age at mating of the mated animals in the study: 7 weeks

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:

26 male and female rats

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.
- 13 Week Feeding Study and Recovery Group: 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. The control and high-dose group consisted of 30 animals of each sex per group, while the low- and mid-dose groups consisted of 20 animals of each sex per group. After 13 weeks of administration, 10 animals of each sex of the control and high-dose groups were selected to continue on to the one-month recovery period.

Parental animals: Observations and examinations:

In-life examinations on P females consisted of the following examinations and measurements: morbidity and mortality observations, detailed clinical examinations, body weights, body weight change, food consumption, food efficiency, compound consumption, reproductive performance, and parturition and litter observations. Examinations in P males were conducted for health purposes only (limited to morbidity and mortality observations, detailed clinical examinations, and body weight).

Litter observations:

STANDARDISATION OF LITTERS
- On post-natal day (PND) 0, eight pups (four males and four females) per litter were randomly selected for inclusion in the study. On PND 4, litters were weighed and culled to include only the selected pups.

PARAMETERS EXAMINED
- Pups were individually weighed and a gross examination was conducted on PND 0, 4, 7, 14, and 21. In-life examinations on F1 animals consisted of the following examinations and measurements: morbidity and mortality observations, cageside clinical observations, detailed clinical examinations, ophthalmoscopic examinations, body weights, body weight change, food consumption, food efficiency, and compound consumption. Neurobehavioral evaluations [functional observational battery (FOB) tests and locomotor activity tests] and routine clinical pathology (haematology, coagulation, clinical chemistry, and urinalysis) were performed in F1 animals.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: P males were euthanized after completion of the mating period without further examination.
- Maternal animals: All P females were euthanized and subjected to necropsy on PND 22.

GROSS NECROPSY
- All necropsied P females 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.

HISTOPATHOLOGY / ORGAN WEIGHTS
- Organs and tissues from P females, 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. Uteri from P females that appeared nongravid were opened and placed in 10% ammonium sulfide solution for detection of implantation sites. Any foci detected were considered early resorptions, and the data included in the mean calculations. Fixed tissue samples were paraffin-embedded, sectioned, and stained with hematoxylin- eosin.

Postmortem examinations (offspring):

SACRIFICE
- All F1 offspring not selected for the 13-week study phase were euthanized and subjected to
necropsy on PND 22. These animals were subjected to postmortem examinations (macroscopic and/or microscopic examination).

GROSS NECROPSY
- All necropsied F1 animals 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.

HISTOPATHOLOGY / ORGAN WEIGTHS
- Organs and tissues from F1 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. 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 F1 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

Reproductive indices:

Reproductive performance and parturition

Offspring viability indices:

Litter observations

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

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

A few macroscopic findings were noted in the glandular stomach in the low- and high-dose groups; not compound related.

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

HISTOPATHOLOGY (PARENTAL ANIMALS)
- A few macroscopic findings were noted in the glandular stomach in the low- and high-dose groups, but were mild in nature and showed no definitive compound-related toxic effects.

Key result

Dose descriptor:

NOAEL

Effect level:

>= 1 other: percent in diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Description (incidence and severity):

A statistically significant decrease in mean body weight in females at 0.25% on PND 21 was obserrved, but was considered not toxicologically meaningful.

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

BODY WEIGHT (OFFSPRING)
- A statistically significant decrease in mean body weight was noted in females at 0.25% dose level on PND 21. Based on the lack of statistically significant changes in body weight at the higher dose groups (0.5% and 1.0%), this change was considered spurious in nature and not toxicologically meaningful. No statistically significant differences were observed between female groups.

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

>= 1 other: percent in diet

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: highest dose tested

Key result

Reproductive effects observed:

no

Conclusions:

NOAEL greater than or equal to 1% in diet.
The test item was without maternal toxicity or compound-related adverse effects on female reproduction and general growth and development of offspring at a maternal dietary level up to 1%, equivalent to a dose of 1655 mg/kg body weight (bw)/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. Female rats and pups not selected for the 13-week post-weaning dietary study were sacrificed on PND 22. Reproductive parameters were evaluated. Feed consumption, body-weight gain, selected organ-weights, gross pathology and appropriate histopathology were also evaluated.

No biologically significant differences in body weight gain, food consumption, and food efficiency were noted. Also, no effects of the test item administration were observed at necropsy. A few macroscopic findings were noted in the glandular stomach in the low- and high-dose groups, but were mild in nature and showed no definitive compound-related toxic effects. No statistically or biologically significant effects on reproductive and fertility parameters or on parturition and litter parameters were observed between any of the test item and control groups. During the pre-weaning period, there were no observable differences with respect to the clinical signs exhibited by pups of the test item groups relative to the controls. All clinical signs were sporadic and incidental in nature with no relationship to test item administration. A statistically significant decrease in mean body weight was noted in females at 0.25% dose level on PND 21. Based on the lack of statistically significant changes in body weight at the higher dose groups (0.5% and 1.0%), this change was considered spurious in nature and not toxicologically meaningful. No statistically significant differences were observed between female groups.

The test item was without maternal toxicity or compound-related adverse effects on female reproduction and general growth and development of offspring at a maternal dietary level up to 1%, equivalent to a dose of 1655 mg/kg body weight (bw)/day. The NOAEL is greater than or equal to 1% of the test substance in the diet.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 655 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Comparable to guideline with acceptable restrictions.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

No reproductive toxicity screening study with the test substance is available. An OECD 415 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. Female rats and pups not selected for the 13-week post-weaning dietary study were sacrificed on PND 22. Reproductive parameters were evaluated. Feed consumption, body-weight gain, selected organ-weights, gross pathology and appropriate histopathology were also evaluated. The test item was without maternal toxicity or compound-related adverse effects on reproduction and general growth and development of offspring at a maternal dietary level up to 1%, equivalent to a dose of 1655 mg/kg body weight (bw)/day. The NOAEL is greater than or equal to 1% (1655 mg/kg) of the test substance in the diet.

Effects on developmental toxicity

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Justification for classification or non-classification

No test substance-related adverse effects on reproductive outcomes were observed in a rat feeding study with the read-across chemical, L-fucose. No developmental data are available for the test substance. Therefore, the substance cannot be classified at this time for reproductive toxicity according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.