3,7-dimethylnona-1,6-dien-3-ol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10/11/2005 - 07/07/2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study was conducted according to a FDA guideline and under GLP conditions. Due to the read-across purpose it was given a Klimisch 2 rating, in accordance with the ECHA Practical guide #6 on the reporting of read-across in IUCLID. Ethyllinalool and linalool are structural homologues which differ only by a methyl-group. Their physical-chemical properties are comparable and available experimental data on same toxicological endpoints, showed identical toxicological properties. Therefore, it is assumed that all toxicological properties are as well comparable and thus read-across is justified.

Justification for type of information:

Linalool was neither developmental toxic nor teratogenic in a respective state of the art, guideline and GLP compliant developmental toxicity study in rats up to the limit dose of 1000 mg/kg bw/d (Politano et al 2009) even at maternal toxic doses. In screening assays for reprotoxicity, neither coriander oil (main constituent linalool 73%) nor structurally related dehydrolinalool had adverse effects on female and/or female and male fertility as well as development of the offspring at dose levels that were not maternal toxic. Based on the data it is concluded that further testing of linalool is not required for animal welfare reasons.
The RIFM Expert Panel concluded in their assessment on cyclic and non-cyclic terpene alcohols including linalool that “reproductive and developmental toxicity data are limited but give no indication of a relevant adverse effect on reproductive function or the development organism”. (Belsito et al 2008)

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: ICH Guideline on detection of toxicity to reproduction for medicinal products (FDA, 1994)

Deviations:

no

Principles of method if other than guideline:

No remarks

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Linalool

EC Number:

201-134-4

EC Name:

Linalool

Cas Number:

78-70-6

Molecular formula:

C10H18O

IUPAC Name:

3,7-dimethylocta-1,6-dien-3-ol

Details on test material:

- Name of test material (as cited in study report): Linalool
- Physical state: Liquid (clear colorless)
- Storage condition of test material: At room temperature, protected from light

Test animals

Species:

rat

Strain:

other: Crl:CD (SD)

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc.
- Age at arrival: approx. 62 days
- Weight at study initiation: 207-253 g
- Housing: Individually, except during cohabitation with male
- Diet (e.g. ad libitum): Ad libitum, rodent diet
- Water (e.g. ad libitum): Ad libitum, local water
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-26
- Humidity (%): 30-70
- Air changes (per hr): >10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES:
From: 14 November 2005
To: 9 December 2005

Administration / exposure

Route of administration:

oral: gavage

Type of inhalation exposure (if applicable):

other: Not applicable

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Suspensions of the test article were prepared weekly at the testing facility. Prepared formulations were stored at room temperature, protected from light.

VEHICLE
- Concentration in vehicle: 25, 50 or 100 mg/mL (different dosing groups)
- Amount of vehicle (if gavage): 10 mL/kg
- Lot/batch no.: 015K0115

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration, homogeneity and stability of test samples prepared during study were within acceptable range of +/- 15% error, +/- 5% RSD and +/- 10% error, respectively.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: max. 5 days
- Proof of pregnancy: vaginal plug or sperm in vaginal smear referred to as day 0 of pregnancy

Duration of treatment / exposure:

11 days (GD 7-17)

Frequency of treatment:

Once daily

Duration of test:

26 days (including 21 days of gestation)

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
Dosages were selected on the basis of a dosage-range study (TIF00008) with the same test article.

1000 mg/kg/day (limit dose) has been selected as the high dose for this definitive study. This dosage, 1000 mg/kg/day, was not expected to affect body weights and/or feed consumption, or result in adverse clinical observations. Based on these data, dosages of 0 (Vehicle), 250, 500 and 1000 mg/kg/day of Linalool were recommended for the developmental toxicity study in rats. The 250 mg/kg/day dosage was expected to be a no-observable-adverse-effect-level (NOAEL) for both maternal and embryo-fetal toxicity, and the 1000 mg/kg/day dosage was expected to produce minimal maternal toxicity and little or no developmental toxicity.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily during study (weekly during acclimatisation period)
- Cage side observations: Viability

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily (before and approx. 3 hours after dosage administration) during dosing period and once daily during postdosage period

BODY WEIGHT: Yes
- Time schedule for examinations: Daily

FOOD CONSUMPTION: Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, on DGs 0, 7, 10, 12, 15, 18 and 21

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #21
- Organs examined by gross necropsy: thoracic, abdominal and pelvic viscera, uterus and ovary.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Number of live and death fetuses. Placenta was examined for size, color and shape.

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter

Statistics:

Clinical observations and other proportional data were analyzed using the Variance Test for Homogeneity of the Binomial Distribution.
Continuous data (e.g., body weights, body weight changes, feed consumption values and litter averages for percent male fetuses, percent resorbed conceptuses, fetal body weights and fetal anomaly data) were analyzed using Bartlett¿s Test of Homogeneity of Variances and the Analysis of Variance, when appropriate [i.e., Bartlett's Test was not significant (p>0.001)]. If the Analysis of Variance was significant (p=0.05), Dunnett's Test was used to identify the statistical significance of the individual groups. If the Analysis of Variance was not appropriate [i.e., Bartlett's Test was significant (p=0.001)], the Kruskal-Wallis Test was used, when less than or equal to 75% ties were present. In cases where the Kruskal-Wallis Test was statistically significant (p=0.05), Dunn's Method of Multiple Comparisons was used to identify the statistical significance of the individual groups. If there were greater than 75% ties, Fisher's Exact Test was used to analyze the data. Count data were evaluated using the procedures described above for the Kruskal-Wallis Test.

Indices:

No remarks

Historical control data:

Not relevant

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
- All rats survived until scheduled sacrifice
- All clinical observations were considered unrelated to linalool
- Body weight gains were reduced by 11% (not significant) in the 1000 mg/kg/day group during the dosage period as compared to controls
- Absolute and relative feed consumption were significantly reduced in the 1000 mg/kg/day group during dosage. Postdosage the absolute and relative feed consumption were significantly increased as compared to controls. No effects were seen in the other treatment groups

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

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

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
- Litter averages appeared normal, as well as all placentae.
- No gross external, soft tissue or skeletal fetal alterations appeared to be caused by linalool in the dosage groups up to 1000 mg/kg/day. No dosage-dependent effects or significant differences were observed. This was confirmed by historical control data.

Effect levels (fetuses)

Key result

Basis for effect level:

other: no adverse teratogenic effects. No adverse effects observed

Remarks on result:

not determinable due to absence of adverse toxic effects

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Read across:

Linalool, dehydrolinalool (CAS 29717-20-8) and ethyllinalool are structurally related substances having similar chemical structures. Difference between linalool and dehydrolinalool is the triple bond at position 1 in dehydrolinalool compared to a double bond at the same position in linalool. Both substances have similar physical-chemical properties. Ethyllinalool is a structural homologue of linalool which differs by a methyl-group only. The physical-chemical properties of ethyllinalool are comparable to the two other substances and available experimental data on the same toxicological endpoints, showed identical toxicological properties. Therefore, it is assumed that all toxicological properties are as well comparable and thus read-across is justified.

Linalool was tested with regard to developmental toxicity / teratogenicity in two studies: screening test (applied in coriander oil at 72.9%) and full guideline compliant developmental toxicity study (pure substance) in rats. Both studies showed no evidence of adverse effects on fetuses and pups at doses which were not maternal toxic. Dehydrolinalool was also tested negative for this endpoint in a screening assay. Comparable results are predicted for ethyllinalool based on the read-across approach.

Applicant's summary and conclusion

Conclusions:

Under the conditions of this study, the No Observed Adverse Effect Level (NOAEL) for maternal toxicity of linalool was established to be 500 mg/kg/day because of effects on weight gain and feed consumption (reversible after treatment period). For developmental toxicity a NOAEL of 1000 mg/kg/day was found. Based on the results of this study, linalool does not need to be classified for maternal and developmental toxicity according to the criteria outlined in Annex I of 1272/2008/EC.

Executive summary:

One hundred pregnant Crl:CD(SD) rats were randomly assigned to four dosage groups (Groups I through IV), 25 rats per group. The test article, Linalool, or the vehicle, Corn Oil, was administered orally (via gavage) once daily on days 7 through 17 of gestation (GDs 7 through 17) at dosages of 0 (Vehicle), 250, 500 and 1000 mg/kg/day to rats in Groups I through IV, respectively. All rats were examined for clinical observations of effects of the test article, abortions, premature deliveries and deaths. Body weights and feed consumption were recorded. All rats were sacrificed and gross necropsy of the thoracic, abdominal and pelvic viscera was performed. Fetuses were weighed and examined for sex, gross external, soft tissue and skeletal alterations.

All prepared formulations were acceptable for use on this study. All rats survived until scheduled sacrifice. There were no clinical observations or gross lesions that were considered related to Linalool. During the dosage period, body weight gains were reduced by 11% in the 1000 mg/kg/day dosage group. The reductions were not statistically significant and probably reflected the reductions in feed consumption that occurred in this dosage group. During the postdosage period, body weight gains in the 1000 mg/kg/day were increased over the vehicle control group value.

Absolute and relative feed consumption values were reduced or significantly reduced (by 7%) in the 1000 mg/kg/day dosage group for the entire dosage period in comparison to the vehicle control group values. During the postdosage period, absolute and relative feed consumption values were signficantly higher than vehicle control values. This observation corresponded to the increase in body weight gains in the 1000 mg/kg/day dosage group during this same period.

Pregnancy occurred in 20 to 23 rats per dosage group. No Caesarean-sectioning or litter parameters were affected by dosages of linalool as high as 1000 mg/kg/day. No other gross external, soft tissue or skeletal fetal alterations (malformations or variations) were caused by dosages of linalool as high as 1000 mg/kg/day. All ossification site averages were comparable and did not significantly differ from the vehicle control group values.

On the basis of these data, the maternal No Observable Advers Effect Level (NOAEL) of linalool is 500 mg/kg/day. The 1000 mg/kg/day dosage of linalool caused non-significant reductions in body weight gain and also reduced absolute and relative feed consumption values during the dosage period. However, following the completion of the dosage period, these effects of linalool were reversed (i.e., increases in body weight gains and feed consumption).

The developmental No Observed Adverse Effect Level (NOAEL) is 1000 mg/kg/day. There were no adverse effects on embryo-fetal development as evaluated in this study, and based on these data, linalool does not need to be classified for maternal and developmental toxicity according to the criteria outlined in Annex I of 1272/2008/EC.