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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
L-TEE was found to be a skin sensitiser using OECD 407, hence L-TEE is classified as Skin Sens. 1 and R43 in accordance to GHS/CLP and DSD-DPD, respectively. Due to the structural similarity and the similarity in physico-chemical properties determining skin sensitisation and no hydrolysis is taking place, L-TME is considered to be a skin sensitizer based on read-across to data on L-TEE. Therefore, the same classification applies for L-TME. Further information on read across to L-TEE using the analogue approach can be found in the data matrix table attached as background material and in section 13.
Justification for type of information:
Data on target substance is not available. Thus, read-across has been applied using data from the source substance L-Threonine Ethyl Ester (L-TEE). See further read-across justification in attached background material and in section 13.
Cross-reference
Reason / purpose for cross-reference:
read-across source
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
May 12, 2000 - June 23, 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Minor deviations from protocol: acclimatisation period was slightly longer than envisaged in the protocol, and it was not considered likely to compromise the study integrity. The references in the protocol to study days from Day 7 onward are one day later than actually occurred in the study.
Qualifier:
according to guideline
Guideline:
EU Method B.6 (Skin Sensitisation)
Deviations:
yes
Remarks:
acclimatisation period, and references to study days.
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
yes
Remarks:
acclimatisation period, and references to study days.
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
yes
Remarks:
acclimatisation period, and references to study days.
Principles of method if other than guideline:
NA
GLP compliance:
yes (incl. QA statement)
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
Study was performed before implementation of the LLNA test guideline.
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: 142-576-6

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: < 10 °C when not in use

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Final dilution of a dissolved solid, stock liquid or gel: 1% m/v in purified water up to the maximum practical concentration of
25% m/v in purified water
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: D Hall Ltd, Burton
- Age at study initiation: 4 to 6 weeks
- Weight at study initiation: 341 to 392g
- Housing: suspended polypropylene cages with open tops, solid floors and stainless steel mesh front panels, 5 animals/cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25°C
- Humidity (%): 40 to 70% RH
- Air changes (per hr): 14 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours illumination by fluorescent strip-lights

IN-LIFE DATES: From 3 April 2000 to 23 June 2000
Route:
intradermal
Vehicle:
water
Concentration / amount:
4% m/v Threonineethylester
Day(s)/duration:
2
Route:
epicutaneous, occlusive
Vehicle:
water
Concentration / amount:
65% m/m Threonineethylester
Day(s)/duration:
10
Route:
epicutaneous, occlusive
Vehicle:
water
Concentration / amount:
10 and 20%
Day(s)/duration:
1 day
No. of animals per dose:
Number of animals in test group: 10
Number of animals in negative control group: 5
Details on study design:
RANGE FINDING TESTS:
The first screening test (intradermal injection phase of induction):
- vehicle and six formulations.
- range of concentrations from 1% m/v in purified water up to the maximum practical concentration of 25%m/v in purifed water, 0.1mL per site
-Site: scapular zone of the denuded dorsum

The second screening test (topical application phase of induction):
- four formulations
- range of concentrations: from 20 to 65% m/m in purified water, approx 1mL
- preparation: intradermal injection of FCA into the suprascular dorsom 11 days prior to application of the test formualtion
- application: occluded, four 25x25mm lint pads
-Site: suprascapular dorsum

The third screening test (topical application at challenge):
- four formulations
- range of concentaiotns: from 1 to 20% m/m in purified water, approx 1mL
- preparation: intradermal injection of FCA into the suprascular dorsom 18 days prior to application of the test formualtion
- application: occluded, four 25x25mm lint pads

MAIN STUDY
A1. INDUCTION EXPOSURE-intradermal
- No. of exposures: 3 paired injections
- Exposure period: NA
- Test groups: FCA, L-TEE 4%m/v in purified water, L-TEE 4%m/v in FCA
- Control group: FCA, purifed water, 50% v/v purified water in FCA
- Site: Dorsal : Anterior, Middle, Posterior
- Frequency of applications: once
- Duration: NA
- Concentrations: 0.1 mL per site

A2. INDUCTION EXPOSURE-topical
- No. of exposures: 1
- Exposure period: 48 hours
- Test groups: 65% m/m L-TEE in purifed water
- Control group: purifed water alone
- Site: Dorsal
- Frequency of applications: once
- Duration: 48 hours
- Concentrations: 2 mL

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: Day 21
- Exposure period: 24 hours
- Test groups: no
- Control group: 20% m/m L-TEE in purifed water, 10% m/m L-TEE in purifed water
- Site: left flank, right flank
- Concentrations: 1 mL
- Evaluation (hr after challenge): 24 and 48 hours after removal of the dressings
Challenge controls:
None
Positive control substance(s):
no
Positive control results:
NA
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
10 %
No. with + reactions:
7
Total no. in group:
10
Clinical observations:
1, 1, 1S, 1HQ, 1SQ, 1, 2S
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 10 %. No with. + reactions: 7.0. Total no. in groups: 10.0. Clinical observations: 1, 1, 1S, 1HQ, 1SQ, 1, 2S.
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
20 %
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
2HS, 2, HES#, 2, 1, 2HQ, 2SQ, 2SQ, 1, 2SH. #: Erythema score not possible to assess due to hardened, scabbed test site
Remarks on result:
other: see Remark
Remarks:
Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 20 %. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: 2HS, 2, HES#, 2, 1, 2HQ, 2SQ, 2SQ, 1, 2SH. #: Erythema score not possible to assess due to hardened, scabbed test site.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
10 %
No. with + reactions:
9
Total no. in group:
10
Clinical observations:
1HQ, 0QS, 0Q, 0Q, 1QS, 2QS, 0Q, 1Q, 2QS
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 10 %. No with. + reactions: 9.0. Total no. in groups: 10.0. Clinical observations: 1HQ, 0QS, 0Q, 0Q, 1QS, 2QS, 0Q, 1Q, 2QS.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
20 %
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
1QS, 1HQ, HES#, 1QS, 1Q, 1HQS, 2QS, 1QS, 1Q, 2QS. #: Erythema score not possible to assess due to hardened, scabbed test site.
Remarks on result:
other: see Remark
Remarks:
Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 20 %. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: 1QS, 1HQ, HES#, 1QS, 1Q, 1HQS, 2QS, 1QS, 1Q, 2QS. #: Erythema score not possible to assess due to hardened, scabbed test site. .
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
10 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 10 %. No with. + reactions: 0.0. Total no. in groups: 5.0.
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
20 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 20 %. No with. + reactions: 0.0. Total no. in groups: 5.0.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
10 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 10 %. No with. + reactions: 0.0. Total no. in groups: 5.0.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
20 %
No. with + reactions:
1
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 20 %. No with. + reactions: 1.0. Total no. in groups: 5.0. Clinical observations: 0D.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
4% (intradermal), 60% (topocal) - 60 and 30% for challenge phase
No. with + reactions:
8
Total no. in group:
10
Clinical observations:
No information
Remarks on result:
positive indication of skin sensitisation

None

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
The skin sensitisation potential of L-TEE was evaluated using the challenge procedure. The study was performed following Magnusson and Kligman procedures. The results indicated that all ten animals gave a positive response indicative of delayed contact hypersensitivity.

Based on the results of this study, the level of positive responses to challenge with L-TEE was sufficient for the risk phrase R43 “May cause sensitisation by skin contact” to be required under the terms of the General Classification and Labelling Requirements for Dangerous Substances and Preparations, as stated in Annex V to Commission Directive 96/54/EC.
Executive summary:

This study was conducted to assess the potential of L-TEE to elicit skin sensitisation (delayed contact hypersensitivity) in the guinea pig following Magnusson and Kligman procedures. Ten test and five control animals were used in this study. Based on the results of the preliminary studies, the following dose levels were chosen:

- Intradermal injection: 4% m/v L-TEE in purified water and/or adjuvant

- Topical induction: 65% m/m L-TEE in purified water

- Challenge application: 10 and 20% m/m L-TEE in purified water

L-TEE elicited a positive response, indicative of skin sensitisation (delayed contact hypersensitivity) in all ten test animals following the challenge application.

Based on the results of this study, the level of positive responses to challenge with L-TEE was sufficient for the risk phrase R43 “May cause sensitisation by skin contact”.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000
Report date:
2000

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
EU Method B.6 (Skin Sensitisation)
Deviations:
yes
Remarks:
acclimatisation period, and references to study days.
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
yes
Remarks:
acclimatisation period, and references to study days.
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
yes
Remarks:
acclimatisation period, and references to study days.
Principles of method if other than guideline:
NA
GLP compliance:
yes (incl. QA statement)
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
Study was performed before implementation of the LLNA test guideline.

Test material

Constituent 1
Chemical structure
Reference substance name:
Methyl L-threoninate
EC Number:
222-158-1
EC Name:
Methyl L-threoninate
Cas Number:
3373-59-9
Molecular formula:
C5H11NO3
IUPAC Name:
Methyl (2S,3R)-2-amino-3-hydroxy-butanoate
Test material form:
solid: particulate/powder
Details on test material:
- Name of test material (as cited in study report): L-threonine methyl ester
- Physical state: white crystalline powder
- Analytical purity: 99.8%

In vivo test system

Test animals

Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: D Hall Ltd, Burton
- Age at study initiation: 4 to 6 weeks
- Weight at study initiation: 341 to 392g
- Housing: suspended polypropylene cages with open tops, solid floors and stainless steel mesh front panels
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25°C
- Humidity (%): 40 to 70% RH
- Air changes (per hr): 14 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours illumination by fluorescent strip-lights

IN-LIFE DATES: From 3 April 2000 to 23 June 2000

Study design: in vivo (non-LLNA)

Inductionopen allclose all
Route:
intradermal and epicutaneous
Vehicle:
water
Remarks:
purified water
Concentration / amount:
Concentration of test material and vehicle used at induction: Intradermal injection: 4% (m/v) Threoninethylester in purified water. Topical induction: 65% (m/m) Threoninethylester in purified water. Concentration of test material and vehicle used for each challenge: 10% and 20% (m/m) Threoninethylester in purified water.
Challengeopen allclose all
Route:
epicutaneous, occlusive
Vehicle:
water
Remarks:
purified water
Concentration / amount:
Concentration of test material and vehicle used at induction: Intradermal injection: 4% (m/v) Threoninethylester in purified water. Topical induction: 65% (m/m) Threoninethylester in purified water. Concentration of test material and vehicle used for each challenge: 10% and 20% (m/m) Threoninethylester in purified water.
No. of animals per dose:
Number of animals in test group: 10
Number of animals in negative control group: 5
Details on study design:
RANGE FINDING TESTS:
The first screening test (intradermal injection phase of induction):
- vehicle and six formulations.
- range of concentrations from 1% m/v in purified water up to the maximum practical concentration of 25%m/v in purifed water, 0.1mL per site
-Site: scapular zone of the denuded dorsum

The second screening test (topical application phase of induction):
- four formulations
- range of concentrations: from 20 to 65% m/m in purified water, approx 1mL
- preparation: intradermal injection of FCA into the suprascular dorsom 11 days prior to application of the test formualtion
- application: occluded, four 25x25mm lint pads

The third screening test (topical applucation at challenge):
- four formulations
- range of concentaiotns: from 1 to 20% m/m in purified water, approx 1mL
- preparation: intradermal injection of FCA into the suprascular dorsom 18 days prior to application of the test formualtion
- application: occluded, four 25x25mm lint pads

MAIN STUDY
A1. INDUCTION EXPOSURE-intradermal
- No. of exposures: 3 paired injections
- Exposure period: NA
- Test groups: FCA, Threonineethylester 4%m/v in purified water, Threonineethylester 4%m/v in FCA
- Control group: FCA, purifed water, 50% v/v purified water in FCA
- Site: Dorsal : Anterior, Middle, Posterior
- Frequency of applications: once
- Duration: NA
- Concentrations: 0.1 mL per site

A2. INDUCTION EXPOSURE-topical
- No. of exposures: 1
- Exposure period: 48 hours
- Test groups: 65% m/m Threonineethylester in purifed water
- Control group: purifed water alone
- Site: Dorsal
- Frequency of applications: once
- Duration: 48 hours
- Concentrations: 2 mL

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: Day 21
- Exposure period: 24 hours
- Test groups: no
- Control group: 20% m/m Threonineethylester in purifed water, 10% m/m Threonineethylester in purifed water
- Site: left flank, right flank
- Concentrations: 1 mL
- Evaluation (hr after challenge): 24 and 48 hours after removal of the dressings
Challenge controls:
None
Positive control substance(s):
no

Results and discussion

Positive control results:
NA

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
10 %
No. with + reactions:
7
Total no. in group:
10
Clinical observations:
1, 1, 1S, 1HQ, 1SQ, 1, 2S
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 10 %. No with. + reactions: 7.0. Total no. in groups: 10.0. Clinical observations: 1, 1, 1S, 1HQ, 1SQ, 1, 2S.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
20 %
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
2HS, 2, HES#, 2, 1, 2HQ, 2SQ, 2SQ, 1, 2SH. #: Erythema score not possible to assess due to hardened, scabbed test site
Remarks on result:
other: see Remark
Remarks:
Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 20 %. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: 2HS, 2, HES#, 2, 1, 2HQ, 2SQ, 2SQ, 1, 2SH. #: Erythema score not possible to assess due to hardened, scabbed test site.
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
10 %
No. with + reactions:
9
Total no. in group:
10
Clinical observations:
1HQ, 0QS, 0Q, 0Q, 1QS, 2QS, 0Q, 1Q, 2QS
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 10 %. No with. + reactions: 9.0. Total no. in groups: 10.0. Clinical observations: 1HQ, 0QS, 0Q, 0Q, 1QS, 2QS, 0Q, 1Q, 2QS.
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
20 %
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
1QS, 1HQ, HES#, 1QS, 1Q, 1HQS, 2QS, 1QS, 1Q, 2QS. #: Erythema score not possible to assess due to hardened, scabbed test site.
Remarks on result:
other: see Remark
Remarks:
Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 20 %. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: 1QS, 1HQ, HES#, 1QS, 1Q, 1HQS, 2QS, 1QS, 1Q, 2QS. #: Erythema score not possible to assess due to hardened, scabbed test site. .
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
10 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 10 %. No with. + reactions: 0.0. Total no. in groups: 5.0.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
20 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 20 %. No with. + reactions: 0.0. Total no. in groups: 5.0.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
10 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no observations
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 10 %. No with. + reactions: 0.0. Total no. in groups: 5.0.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
20 %
No. with + reactions:
1
Total no. in group:
5
Clinical observations:
No information
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 20 %. No with. + reactions: 1.0. Total no. in groups: 5.0. Clinical observations: 0D.
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
4% (intradermal), 60& (topical) - 60 and 30% for challenge phase
No. with + reactions:
8
Total no. in group:
10
Clinical observations:
No information
Remarks on result:
positive indication of skin sensitisation

Any other information on results incl. tables

The toxicokinetic properties of L-TEE and L-TME are evaluated to be different. Read across to L-TEE is possible for endpoints in which hydrolysis of the ester bond does not take place, e.g. skin irritation and sensitisation. For endpoints in which hydrolysis takes place, thereby liberating the alcohols, i.e. methanol in the case of L-TME and ethanol in the case of L-TEE, the toxicities of the hydrolysis products must be taken into account. In general, no interaction of toxicological relevance between L-threonine and the alcohol parts is expected.

L-TME holds the same structure as L-TEE except that L-TME contains a methyl alkyl-side group to the ester bond and L-TEE an ethyl alkyl-side group. Both substances are characterized by a high water solubility, a low log Pow and low vapour pressure.

The slight difference in molecular size and chemical structure is not considered to result in any significant differences with respect to the reactivity and sensitizing potential of the substances.

Based on read across to data on L-TEE, L-TME is considered to be a skin sensitizer.

Further information on the analogue approach can be found in the data matrix attached as background material (see section below).

Applicant's summary and conclusion

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
L-TEE was found to be a skin sensitiser using OECD 407, hence L-TEE is classified as Skin Sens. 1 and R43 in accordance to GHS/CLP and DSD-DPD, respectively. Due to the structural similarity and the similarity in physico-chemical properties determining skin sensitisation, L-TME is considered to be a skin sensitizer based on read-across to data on L-TEE. Therefore, the same classification applies for L-TME.
Executive summary:

The skin sensitisation potential of L-TEE was evaluated using the challenge procedure (OECD 407). The study was performed following Magnusson and Kligman procedures. The results indicated that all ten animals gave a positive response indicative of delayed contact hypersensitivity. Based on these results, L-TEE is classified as Skin Sens. 1 and R43 in accordance to GHS/CLP and DSD-DPD, respectively.

L-TME holds the same structure as L-TEE except that L-TME contains a methyl alkyl-side group to the ester bond and L-TEE an ethyl alkyl-side group. Both substances are characterized by a high water solubility, a low log Pow and low vapour pressure. The slight difference in molecular size and chemical structure is not considered to result in any significant differences with respect to the reactivity and sensitizing potential of the substances.

Due to the structural similarity and the similarity in physico-chemical properties determining skin sensitisation and no hydrolysis is taking place, L-TME is considered to be a skin sensitizer based on the availabel test results on L-TEE using the analogue approach. Hence, L-TME is classified as Skin Sens. 1 and R43 in accordance to GHS/CLP and DSD-DPD, respectively.