3-methoxybutan-1-ol

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11-12-2020 to 16-03-2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The objective of this study was to obtain information on the pharmacokinetics of 3-methoxybutyl acetate and 3-methoxybutan-1-ol following single intravenous administration to male Sprague Dawley rats, and to directly test the hypothesized metabolism of 3-methoxybutan-1-ol to butane-1,3-diol and to support the read across assessment (see n Section 13).

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Version / remarks:

July 22, 2010

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

3-methoxybutan-1-ol

EC Number:

219-741-8

EC Name:

3-methoxybutan-1-ol

Cas Number:

2517-43-3

Molecular formula:

C5H12O2

IUPAC Name:

3-methoxybutan-1-ol

Details on test material:

- Name of test material (as cited in study report): butolether rein
- Physical state: clear liquid
- Analytical purity: 99.5%
- Impurities (identity and concentrations): <0.1% n-butanol, <0.1% methoxybutyraldehyd, <0.1% butoxyl, 0.5% unknown ingredients
- pH value in water: 7
- Batch No.: production date 1 August 1991
- Melting point: <-85°C
- Boiling point: 156-160°C
- Storage condition of test material: dark at room temperature
- Expiration date of the lot/batch: 1995
- Stability in test solvent: proven for 4 hours

Specific details on test material used for the study:

3-methoxybutyl acetate:
Batch No: 120001291757
Expiry date: 10 03 2021 (retest date)
Physical Description: clear colourless liquid
Purity: 99.8%
Test Facility Test Item: 210574/D

3-methoxybutan-1-ol
Batch No: 120001291759
Expiry Date: 10 09 2021
Physical Description: clear colourless liquid
Purity: 99.8%
Test Facility test item No: 211769/A

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Administration / exposure

Route of administration:

intravenous

Vehicle:

DMSO

Remarks:

The correct amount of test item was added to a suitable container, and was first dissolved in DMSO (v/v), followed by addition PEG200 (v/v) and then WFI (v/v) under stirring. The final formulation was a clear solution.

Details on exposure:

Method: The first day of dosing was designated as Day 1. The dose formulations were not stirred during dosing. Animals were placed in a 40°C stove (in Makrolon type II cages, or equivalent) in preparation for dose administration according to CRL SOP. The animals were temporarily restrained for dose administration and were not sedated. The doses were given using a disposable syringe and butterfly needle in as quick as possible. The actual dosing time was 5-9 seconds.

Duration and frequency of treatment / exposure:

Dose route: intravenous (slow bolus) injection to the tail vein
Frequency: Once
Duration: single dose

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

10 mg/kg bw/day

Remarks:

3-methoxybutyl acetate

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day

Remarks:

3-methoxybutyl acetate

Doses / concentrations 3

Dose / conc.:

50 mg/kg bw/day

Remarks:

3-methoxybutan-1-ol

No. of animals per sex per dose / concentration:

8 males per dose

Details on dosing and sampling:

The intravenous route of exposure was selected as it is most suitable to provide a bolus dose that allows an accurate characterization of the pharmacokinetics of the test items and metabolism of 3-methoxybutan-1-ol to butane-1,3-diol.
Butoxyl (3-methoxybutyl acetate) has proven to be non-toxic in acute and repeat-dose toxicity tests. For example, in an acute inhalation toxicity test with rats, the animals were exposed to saturated air concentrations of approximately 10000 mg/m3 for five hours with no deaths. In another study, rats were injected subcutaneously with a 10% solution of Butoxyl in vegetable oil at a dose level of 1000 mg/kg and no clinical symptoms or deaths were reported. In a guideline developmental toxicity study with rats, there were no maternal or developmental effects in rats gavaged with 1000 mg/kg. In a four week inhalation study with rats, no effects were observed at near saturated air concentrations of 10000 mg/kg (similar to the acute study).
Considering the route of exposure is intravenous and anticipated human exposures are maximally expected to be in the low mg/kg range, doses in the low mg/kg range are justified. As such, 10 and 50 mg/kg were chosen as dose levels for use in the metabolism study. Having a low and a high concentration should allow the Sponsor and regulatory agencies to determine if there is a concentration dependent metabolic rate and/or if there is metabolic saturation at the top dose used in the study.

Statistics:

Pharmacokinetic parameters were estimated using Phoenix pharmacokinetic software. A non-compartmental approach consisted with the intravenous route of administration was used for the dosed test items, and non-compartmental approach consistent with the extravascular route for metabolites were used for parameter estimation. All parameters were generated from 3-methoxybutyl acetate (parent compound in Groups 1 and 2) and 3-methoxybutan-1-ol (parent compound in Group 3 and metabolite in Groups 1 and 2) and butane-1,3-diol (metabolite in Groups 1, 2 and 3) composite concentrations in plasma.
Parameters that were calculated included tlast, tmax, Cmax, C0, AUC, λz, t½, Vz, Vss, MRT, Cl, dose effect, and metabolite/parent ratios when possible.

Results and discussion

Preliminary studies:

Since: 1) 3-methoxybutyl acetate eliminated so rapidly that no animals or time points yielded quantifiable results in blood, tissues, or excreta ; 2) there was only one animal in which elimination of 3-methoxybutan-1-ol was quantifiable at three time points; and 3) 3-methoxybutan-1-ol elimination was so rapid that a large percentage of dose was eliminated before the earliest time point in this study (5 min), a follow study was deemed necessary to better characterize the half-life of 3-methoxybutyl acetate and 3-methoxybutanol. The ongoing new study is using higher dose levels of 10 mg/kg and 50 mg/kg 3-methoxybutyl acetate and earlier time points, starting at 30 sec after dosing. In the follow-up study, metabolite 1 (3-methoxybutan-1-ol) is also being dosed, to increase the possibility of detecting metabolite 2: (1,3-butane diol).

Any other information on results incl. tables

Summary of 3-methoxybutan-1-ol Pharmacokinetic Parameters in Male Sprague Dawley Rat Blood Following Single Intravenous Administration of 3-methoxy-butyl acetate or 3-methoxybutan-1-ol

Group		1	2	3
Test Item		3-methoxy-butyl acetate	3-methoxy-butyl acetate	3-methoxybutan-1-ol
Analyte		3-methoxybutan-1-ol	3-methoxybutan-1-ol	3-methoxybutan-1-ol
Dose Level (mg/kg)		10	50	50
tlast	h	0.167	0.25	0.25
tmax	h	0.00833	0.00833	n/a
C0	µg/mL	n/a	n/a	94.1
C0/Dose	kg∙µg/mL/mg	n/a	n/a	1.88
Cmax	µg/mL	26.6	66.4	n/a
Cmax/Dose	kg∙µg/mL/mg	2.66	1.33	n/a
AUClast	h∙µg/mL	1.32	6.31	10.4
AUClast/Dose	h∙kg∙µg/mL/mg	0.132	0.126	0.208
AUC∞	h∙µg/mL	1.68^1	7.82	13.2^1
AUC∞/Dose	h∙kg∙µg/mL/mg	0.168^1	0.156	0.264^1
% extrapolated	%	21^1	19	21^1
λz	1/h	9.47^1	7.03	5.91^1
t1/2	h	0.0732^1	0.0987	0.117^1
no. points		4^1	5	4^1
r^2		0.9655^1	0.9537	0.9731^1
Cl	mL/h/kg	n/a	n/a	3790^1
Vz	mL/kg	n/a	n/a	642^1
Vss	mL/kg	n/a	n/a	584^1
MRT∞	h	n/a	n/a	0.154^1

n/a: not applicable;¹: %extrapolated >20%, all related parameters are approximations.

Applicant's summary and conclusion

Conclusions:

Sprague Dawley rats were treated with 3-methoxybutyl acetate or 3-methoxybutan-1-ol by single intravenous (slow bolus) injection at dose levels of 10 or 50 mg/kg.
Test formulations prepared were considered homogeneous at the concentrations tested and analysis of the accuracy was in agreement with the target concentrations.
No clinical signs were noted during the observation period. The male animals weighted between 313 and 364 g on the day of dosing.
All 3 methoxybutyl acetate-treated animals were exposed to 3 methoxybutyl acetate and its metabolite 3 methoxybutan-1-ol. All 3 methoxybutan-1-ol-treated animals were exposed to 3 methoxybutan 1-ol. No quantifiable exposure to the metabolite butane 1,3 diol was observed.

3-methoxybutyl acetate
After intravenous administration of 10 and 50 mg/kg 3-methoxybutyl acetate the average concentration at t = 0 hours, in terms of C0, was 158 and 495 µg/mL, respectively.
Apparent average terminal half-lives were 0.00802 and 0.0105 hours (i.e. 0.48 and 0.63 minutes, respectively) after dosing at 10 and 50 mg/kg 3-methoxybutyl acetate, respectively. The compound was highly cleared and moderately to highly distributed at 10 and 50 mg/kg.
The exposure, in terms of C0 and AUClast, increased with increasing dose in a slightly less than dose proportional manner for C0 and in a close to dose proportional manner for AUClast.

3-methoxybutan-1-ol
It should be noted that several calculated parameters should be interpreted with caution, since an extrapolation to infinity >20% was observed due to detectable levels of the analytes being present at the last time point evaluated (i.e., 15 minutes after dosing).
After intravenous administration of 50 mg/kg 3-methoxybutan-1-ol the average concentration at t = 0 hours, in terms of C0, was 94.1 µg/mL. At 50 mg/kg, apparent average terminal half-life was 0.117 hours (i.e. 7.02 minutes) after dosing of 3-methoxybutan-1-ol. The compound was highly cleared and highly distributed at 50 mg/kg.
After 10 and 50 mg/kg intravenous dosing of 3-methoxybutyl acetate, blood concentrations of 3-methoxybutan-1-ol increased very fast.
Terminal half-life of the metabolite 3-methoxybutan-1-ol after intravenous administration of 50 mg/kg 3-methoxybutyl acetate was 0.0987 hours (i.e. 5.92 minutes) which was similar to the elimination after intravenous administration at 50 mg/kg of the compound 3-methoxybutan-1-ol.
The exposure of the metabolite 3-methoxybutan-1-ol, in terms of AUClast, after single intravenous dosing of 3-methoxybutyl acetate was 155/181% of the exposure of 3-methoxybutyl acetate at 10/50 mg/kg, respectively.
The exposure to the metabolite 3-methoxybutan-1-ol, in terms of Cmax and AUClast, after single intravenous dosing of 3-methoxybutyl acetate increased with increasing dose in a slightly less than dose proportional manner for Cmax and in a close to dose proportional manner for AUClast.
In general, the exposure to the metabolite 3-methoxybutan-1-ol after dosing of 3-methoxybutyl acetate was slightly lower than the exposure to 3-methoxybutan-1-ol as dosed Test Item.

butane-1,3-diol
For the metabolite butane-1,3-diol, all samples were below the LLOQ, however, after dosing of 3-methoxybutyl acetate at 50 mg/kg in Group 2 for samples taken between 0.05 and 0.25 hours (3 and 15 minutes) detectable but not quantifiable peaks were observed, see bioanalytical phase report. Since all samples were not quantifiable, no PK evaluation could be performed for the metabolite butane-1,3-diol.
By undertaking a more targeted toxicokinetic approach for confirming the demethylation reaction in the (follow-up) toxicokinetic study with both 3-methoxybutyl acetate and 3-methoxybutan-1-ol (Charles River Laboratories, 2021), Celanese now provides empirical support for the read across from 1,3-butanediol to 3-methoxybutyl acetate and 3-methoxybutan-1-ol for reproductive toxicology endpoints.
In Groups 1 and 2, the Target Substance 3-methoxybutyl acetate was rapidly metabolized, primarily to 3-methoxybutan-1-ol. In Group 2, the metabolite butane-1,3-diol (Source Substance 2) was observed at concentrations above the limit of detection (LOD) but below the limit of quantification, between 3 and 15 minutes (last sampling time) after dosing.
Toxicokinetic parameters were not calculated for butane-1,3-diol, as the detections between 3 and 15 minutes after dosing were below the LOQ, even if above the LOD. However, the rate of demethylation is rapid, as the demethylated product 1,3-butanediol was detectable within three minutes after i.v. dosing.

Executive summary:

The objective of this study was to obtain information on the pharmacokinetics of 3-methoxybutyl acetate and 3-methoxybutan-1-ol following single intravenous administration to male Sprague Dawley rats, and to directly test the hypothesized metabolism of 3-methoxybutan-1-ol to butane-1,3-diol.
The study design was as follows:

Experimental Design^a

Group No.	Test Item Id.	Dose Level (mg/kg)	Dose Volume^b (mL/kg)	Dose Concentration (mg/mL)	Number of Animals
					Males
1	3-methoxybutyl acetate / 210574/D	10	1	10	8
2	3-methoxybutyl acetate / 210574/D	50	1	50	8
3	3-methoxybutan-1-ol / 211769/A	50	1	50	8

Id.= identification.^aBlood samples for analysis collected at 0.5, 1, 3, 5, 10 and 15 minutes. ^b Based on the most recent body weight measurement

Chemical analyses of formulations were conducted to assess accuracy and homogeneity. Test formulations prepared were considered homogeneous at the concentrations tested and analysis of the accuracy was in agreement with the target concentrations. The following parameters and end points were evaluated in this study: mortality/moribundity, clinical signs, body weights and pharmacokinetic parameters.
No mortality or clinical signs were noted during the observation period. The male animals weighted between 313 and 364 g on the day of dosing.
All 3-methoxybutyl acetate-treated animals (Groups 1 and 2) were exposed to
3-methoxybutyl acetate and its metabolite 3-methoxybutan-1-ol. All 3-methoxybutan-1-ol-treated animals (Group 3) were exposed to 3-methoxybutan-1-ol. No quantifiable exposure to the metabolite butane-1,3-diol was observed.
All 3-methoxybutyl acetate-treated animals (Groups 1 and 2) were exposed to
3-methoxybutyl acetate and its metabolite 3-methoxybutan-1-ol. All 3-methoxybutan-1-ol-treated animals (Group 3) were exposed to 3-methoxybutan-1-ol. Detectable, but not quantifiable exposure to the metabolite butane-1,3-diol was observed between 3 and 15 minutes (last sampling time) in Group 2.

3-methoxybutyl acetate

After intravenous administration of 10 and 50 mg/kg 3-methoxybutyl acetate the average concentration at t = 0 hours, in terms of C0, was 158 and 495 µg/mL, respectively.
The average terminal half-lives were 0.00802 and 0.0105 hours (i.e. 0.48 and 0.63 minutes, respectively) after dosing at 10 and 50 mg/kg 3-methoxybutyl acetate, respectively. The compound was highly cleared and moderately to highly distributed at 10 and 50 mg/kg.
The exposure, in terms of C0 and AUClast, increased with increasing dose in a slightly less than dose-proportional manner for C0 and in a close to dose-proportional manner for AUClast.

3-methoxybutan-1-ol

It should be noted that several calculated parameters should be interpreted with caution, since an extrapolation to infinity >20% was observed.
After intravenous administration of 50 mg/kg 3-methoxybutan-1-ol the average concentration at t = 0 hours, in terms of C0, was 94.1 µg/mL. At 50 mg/kg, average terminal half-life was 0.117 hours (i.e. 7.02 minutes) after dosing of 3-methoxybutan-1-ol. The compound was highly cleared and highly distributed at 50 mg/kg.
After 10 and 50 mg/kg intravenous dosing of 3-methoxybutyl-acetate, blood concentrations of 3-methoxybutan-1-ol increased very fast.
The terminal half-life of the metabolite 3-methoxybutan-1-ol after intravenous administration of 50 mg/kg 3-methoxybutyl acetate was 0.0987 hours (i.e. 5.92 minutes) which was similar to the elimination after intravenous administration at 50 mg/kg of the compound
3-methoxybutan-1-ol.
The exposure of the metabolite 3-methoxybutan-1-ol, in terms of AUClast, after single intravenous dosing of 3-methoxybutyl acetate was 155/181% of the exposure of 3-methoxybutyl acetate at 10/50 mg/kg, respectively.The exposure to the metabolite 3-methoxybutan-1-ol, in terms of Cmax and AUClast, after single intravenous dosing of 3-methoxybutyl acetate increased with increasing dose in a slightly less than dose-proportional manner for Cmax and in a close to dose-proportional manner for AUClast.
In general, the exposure to the metabolite 3-methoxybutan-1-ol after dosing of
3-methoxybutyl acetate was slightly lower than the exposure to 3-methoxybutan-1-ol as dosed Test Item.

butane-1,3-diol

For the metabolite butane-1,3-diol, all samples were below the LLOQ, however, after dosing of 3-methoxybutyl acetate at 50 mg/kg in Group 2 for samples taken between 0.05 and 0.25 hours (3 and 15 minutes) detectable but not quantifiable peaks were observed, see Bioanalysis Phase Report. Since all samples were not quantifiable, no PK evaluation could be performed for the metabolite butane-1,3-diol.

By undertaking a more targeted toxicokinetic approach for confirming the demethylation reaction in the (follow-up) toxicokinetic study with both 3-methoxybutyl acetate and 3-methoxybutan-1-ol (Charles River Laboratories, 2021), Celanese now provides empirical support for the read across from 1,3-butanediol to 3-methoxybutyl acetate and 3-methoxybutan-1-ol for reproductive toxicology endpoints.

In Groups 1 and 2, the Target Substance 3-methoxybutyl acetate was rapidly metabolized, primarily to 3-methoxybutan-1-ol. In Group 2, the metabolite butane-1,3-diol (Source Substance 2) was observed at concentrations above the limit of detection (LOD) but below the limit of quantification, between 3 and 15 minutes (last sampling time) after dosing.

Toxicokinetic parameters were not calculated for butane-1,3-diol, as the detections between 3 and 15 minutes after dosing were below the LOQ, even if above the LOD. However, the rate of demethylation is rapid, as the demethylated product 1,3-butanediol was detectable within three minutes after i.v. dosing.