3,7-dimethyloctan-3-yl acetate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 dec 2017 - 03 dec 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Objective of study:

toxicokinetics

Test guideline

Qualifier:

according to guideline

Guideline:

other:

Version / remarks:

ICH S3a. Toxicokinetics: The Assessment of Systemic Exposure in Toxicity Studies,
October 1994.

Deviations:

not applicable

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

3,7-dimethyloctan-3-yl acetate

EC Number:

244-033-0

EC Name:

3,7-dimethyloctan-3-yl acetate

Cas Number:

20780-48-7

Molecular formula:

C12H24O2

IUPAC Name:

3,7-dimethyloctan-3-yl acetate

Test material form:

liquid

Remarks:

Clear liquid

Details on test material:

Test item storage: At room temperature protected from light, container flushed with nitrogen, desiccated
Test item handling: Use amber glassware or wrap container in aluminum-foil

Specific details on test material used for the study:

No correction factor required

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

The Wistar Han rat was chosen as the animal model for this study as it is an accepted rodent species for toxicity testing by regulatory agencies. Charles River Den Bosch has general and reproduction/ developmental historical data in this species from the same strain and source. This animal model has been proven to be susceptible to the effects of reproductive toxicants.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
Charles River Deutschland, Sulzfeld, Germany
- Age at study initiation:
10 weeks (males and 13 weeks (females)
- Weight at study initiation:
266 - 309 g (males), 202 - 238 g (females)
- Fasting period before study:
no (F0-males were fasted overnight with a maximum of 24 hours before blood sampling, but water was available. F0-females were not fasted overnight.)
- Housing:
On arrival and following the pre-test (females only) and pre-mating period, animals were group housed (up to 5 animals of the same sex and same dosing group together) in polycarbonate cages. During the mating phase, males and females were cohabitated on a 1:1 basis in Macrolon plastic cages. During the post-mating phase, males were housed in their home cage with a maximum of 5 males/cage. Females were individually housed in Macrolon plastic cages. During the lactation phase, females were housed in Macrolon plastic cages (MIII type, height 18 cm). Pups were housed with the dam, except during locomotor activity monitoring of the dams, when the pups were kept warm in their home cage using bottles filled with warm water. In order to avoid hypothermia of pups, pups were not left without their dam or a bottle filled with warm water for longer than 30-40 minutes. During locomotor activity monitoring, animals were housed individually in a Hi-temp polycarbonate cage without cage enrichment, bedding material, food and water.
- Diet: Pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany), ad libitum (except during motor activity measurements)
- Water: tap water, ad libitum
(except during motor activity measurements)
- Acclimation period:
6 days

DETAILS OF FOOD AND WATER QUALITY:
The feed was analyzed by the supplier for nutritional components and environmental contaminants. Periodic analysis of the water is performed.

ENVIRONMENTAL CONDITIONS
- Temperature (°C):
21-22
- Humidity (%):
38-59
- Air changes (per hr):
10 or more
- Photoperiod (hrs dark / hrs light):
12/12

IN-LIFE DATES: From 05 Dec 2017 to 30 Jan 2018

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

- PREPARATION OF DOSING SOLUTIONS:
Test item dosing formulations (w/w) were homogenized to visually acceptable levels at appropriate concentrations to meet dose level requirements. The dosing formulations were
prepared daily as a solution and dosed within 4 hours after adding the test item to the vehicle protected from light. The test item was directly mixed with the vehicle to prevent any loss; therefore vehicle was weighed prior to the test item. Test item dosing formulations were kept at room temperature protected from light until dosing. If practically possible, the dosing formulations and vehicle were continuously stirred until and during dosing. Adjustment was made for specific gravity of the vehicle and test item. No correction was made for the purity/composition of the test item.

- VEHICLE
- Justification for use and choice of vehicle (if other than water):
Vehicle testing was performed at the Test Facility to select the suitable vehicle and to establish a suitable formulation procedure.
- Concentration in vehicle:
0, 10, 30 and 100 mg/mL
- Amount of vehicle (if gavage):
5 mL/kg

Duration and frequency of treatment / exposure:

Daily via oral gavage

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

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

No. of animals per sex per dose / concentration:

10

Control animals:

yes, concurrent vehicle

Positive control reference chemical:

no

Details on study design:

- On Day 10 of treatment, blood samples (~0.4 mL using K2-EDTA tubes) were collected from TK animals in all dose groups at predose and at 0.25, 0.5, 1, 2, 4, 8 and 24 hours postdose by sampling from the jugular vein.

Details on dosing and sampling:

- On Day 10 of treatment, blood samples (~0.4 mL using K2-EDTA tubes) were collected from TK animals in all dose groups at predose and at 0.25, 0.5, 1, 2, 4, 8 and 24 hours postdose by sampling from the jugular vein.
- Samples were collected at 0 (before dosing) and at 15 min, 30 min, 1, 2, 4, 8 and 24 hours (after dosing).
- Parameters that were calculated included tlast, tmax, Cmax, AUClast, dose effect, sex effect and exposure to metabolite versus parent. The t1/2 value could only be calculated in females at the high dose. For low- and mid-dose females and all groups of males t1/2 values could not be calculated since no log linear regression was possible.

Statistics:

Descriptive statistics (means and standard deviation) for concentration data, using appropriate grouping and sorting variables, were generated using Phoenix. Concentration and TK parameter values were tabulated and concentration vs time graphs were generated. Dose effect, sex differences and parent versus metabolite evaluations of Cmax and/or AUC values were evaluated where appropriate. To conclude on dose-proportional exposure, group means should be roughly within a 2-fold of the dose increment. To conclude on comparable exposure, respective groups mean should be roughly within a factor of 2.

Results and discussion

Main ADME results

Type:

absorption

Results:

The blood of all treated rats contained test item, indicating that the test item was absorbed from the gastrointestinal tract.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The toxicokinetic evaluation showed the following:
• The blood of all treated rats contained test item, indicating that the test item was absorbed from the gastrointestinal tract. The metabolite could be quantified only in rats of the 500 mg/kg group (between 1-8 h post-dose in females and at 4 h post-dose in males).
• Blood concentrations of the test item increased slowly. The peak blood concentration, Cmax, was reached at 2-4 h. Tlast ranged from 4 to 24 h post-dose and increased with increasing dose levels.
• Peak concentrations of the test item increased dose-dependent, being more than doseproportional in females from 50 to 150 mg/kg and from 50 to 500 mg/kg.
• The systemic exposure, expressed as AUClast of the test item, increased with increasing dose in a slightly more than dose-proportional manner over the dose range tested in most cases.
• Systemic exposure to the test item showed no sex differences at 50 and 150 mg/kg. At 500 mg/kg, systemic exposure in terms of AUClast tended to be higher in females than in males.
• Systemic exposure to the metabolite, in terms of Cmax and AUClast, was about 100 times lower than that to the unchanged test item at 500 mg/kg.

Details on distribution in tissues:

not available

Transfer into organs

Observation:

not determined

Toxicokinetic parameters

Toxicokinetic parameters 1

Toxicokinetic parameters:

half-life 1st:

Remarks:

No log-linear regression was possible, as a consequence the half-life could not be calculated.

Toxicokinetic parameters 2

Toxicokinetic parameters:

AUC: see table

Toxicokinetic parameters 3

Toxicokinetic parameters:

Cmax: see table

Remarks:

AUClast, increased with increasing dose in a slightly more than dose-proportional manner, except in males from 150 to 500 mg/kg where a dose proportional increase was noted.

Toxicokinetic parameters 4

Toxicokinetic parameters:

Tmax: see table

Metabolite characterisation studies

Metabolites identified:

yes

Remarks:

Tetrahydrolinalool

Details on metabolites:

Blood was analysed for the concentrations of the test item and a defined metabolite Tetrahydrolinalool.
The peak blood concentration, Cmax, of the metabolite Tetrahydrolinalool was 4 hours after dosing of 500 mg/kg Tetrahydrolinalyl Acetate in females. In females, at 500 mg/kg Tetrahydrolinalyl Acetate, the exposure of the metabolite Tetrahydrolinalool, in terms of Cmax and AUClast, was approximately a factor 100 times lower compared to Tetrahydrolinalyl Acetate.

Applicant's summary and conclusion

Conclusions:

The blood of all treated rats contained test item, indicating that the test item was absorbed from the gastrointestinal tract. The metabolite Tetrahydrolinalool could be quantified only in rats of the 500 mg/kg group (between 1-8 h post-dose in females and at 4 h post-dose in males). Blood concentrations of the test item increased slowly. The peak blood concentration, Cmax, was reached at 2-4 h. Tlast ranged from 4 to 24 h post-dose and increased with increasing dose levels. Peak concentrations of the test item increased dose-dependent, being more than dose-proportional in females from 50 to 150 mg/kg and from 50 to 500 mg/kg. The systemic exposure, expressed as AUClast of the test item, increased with increasing dose in a slightly more than dose-proportional manner over the dose range tested in most cases. Systemic exposure to the test item showed no sex differences at 50 and 150 mg/kg. At 500 mg/kg, systemic exposure in terms of AUClast tended to be higher in females than in males. Systemic exposure to the metabolite, in terms of Cmax and AUClast, was about 100 times lower than that to the unchanged test item at 500 mg/kg.

Executive summary:

This report describes the toxicokinetics (TK) of Tetrahydrolinalyl Acetate in male and female Wistar Han rats following daily oral gavage administration at dose levels of 50, 150 and 500 mg/kg for a minimum of 28 days.

On Day 10 of treatment, blood samples (~0.4 mL using K2-EDTA tubes) were collected from the jugular vein at various timepoints after dosing. Animals were restrained during blood collection. Samples were analyzed for the concentration of test item and the specified metabolite Tetrahydrolinalool using a validated GC-MS method. Toxicokinetic parameters were estimated using Phoenix pharmacokinetic software. A noncompartmental approach consistent with the oral route of administration was used for parameter estimation. All parameters were generated from Tetrahydrolinalyl Acetate (THLAc) and Tetrahydrolinalool (THL) using composite concentrations in plasma. Parameters that were calculated included tlast, tmax, Cmax, AUClast, dose effect, sex effect and exposure to metabolite versus parent. No log-linear regression was possible, as a consequence the half-life could not be calculated.

The toxicokinetic evaluation showed that:

-       The blood of all treated rats contained test item, indicating that the test item was absorbed from the gastrointestinal tract.

-       The metabolite Tetrahydrolinalool could be quantified only in rats of the 500 mg/kg group (between 1-8 h post-dose in females and at 4 h post-dose in males).

-       Blood concentrations of the test item increased slowly.

-       The peak blood concentration, Cmax, was reached at 2-4 h.

-       Tlast ranged from 4 to 24 h post-dose and increased with increasing dose levels.

-       Peak concentrations of the test item increased dose-dependent, being more than dose-proportional in females from 50 to 150 mg/kg and from 50 to 500 mg/kg.

-       The systemic exposure, expressed as AUClast of the test item, increased with increasing dose in a slightly more than dose-proportional manner over the dose range tested in most cases.

-       Systemic exposure to the test item showed no sex differences at 50 and 150 mg/kg. At 500 mg/kg, systemic exposure in terms of AUClast tended to be higher in females than in males.

-       Systemic exposure to the metabolite, in terms of Cmax and AUClast, was about 100 times lower than that to the unchanged test item at 500 mg/kg