Nα-acetyl-DL-tryptophan

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Effects on developmental toxicity

Description of key information

Oral, rats: NOAEL = 2500 mg/kg bw/day

Link to relevant study records

Reference

Reference 1

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

no guideline followed

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

- Short description of test conditions: The developmental toxicity study of N-acetyl-L-tryptophan was conducted in Wistar rats. N-acetyl-L-tryptophan was administered orally at doses of 2.5 and 5.0 g/kg bw/day from GD 7 to 17. All dams were autopsied for the assessment of fetal development parameters on GD 20.

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: KITAYAMA LABES CO.,LTD., Ina-city, Japan
- Age at study initiation: 11 weeks
- Diet: MF except for gestation and lactation period and NMF for gestation and lactation period, purchased by Oriental Yeast Co., Ltd, Japan, were given ad libitum
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2
- Humidity (%): 55 ± 5

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
VEHICLE
- Justification for use and choice of vehicle (if other than water): due to the low water solubility, CMC was used as vehicle
- Concentration in vehicle: 1%

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1

Duration of treatment / exposure:

females: 11 days; (from Day 7 to 17 of gestation (GD))

Frequency of treatment:

daily

Duration of test:

GD 7 - 20

Dose / conc.:

2 500 mg/kg bw/day (actual dose received)

Remarks:

oral

Dose / conc.:

5 000 mg/kg bw/day (actual dose received)

Remarks:

oral

No. of animals per sex per dose:

21, 22 and 20 dams (control, 2500, 5000 mg/kg bw/day)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Since the LD50 value was 15000 mg/kg bw/day for oral administration, 5000 mg/kg bw/day was applied as the highest dose.

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: every second day

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: every second day

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on Day 20 of gestation
- Organs examined: brain, pituitary, thymus, heart, lungs, liver, kidneys, spleen, adrenals, ovaries

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on Day 20 of gestation
- Anaesthetic used for blood collection: Yes, chloroform
- How many animals: 21 in control, 22 in 2500, and 20 in 5000 mg/kg bw/day
- Parameters checked: red blood cell count (RBC), white blood cell count (WBC), hemoglobin, hematocrit, platelet

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on Day 20 of gestation
- How many animals: 21 in control, 22 in 2500, and 20 in 5000 mg/kg bw/day
- Parameters checked: total protein, A/G, urea N, glucose, GOT (glutamate oxaloacetate transaminase), and GPT (glutamate pyruvate transaminase)

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: No
- Number of implantations: Yes
- Number of early resorptions: No
- Number of late resorptions: No

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: No
- Skeletal examinations: Yes: all per litter
- Head examinations: No

Statistics:

Wilcoxon test for % of fetal death, the number of abnormal fetus, the number of live offsprings, % of malformation, % of anomaly, effects on development of offspring, and the number of variation and ossification except for ossified calnei and ossified tail.
Chi-squared test for copulation index, fertility index, delivery index, rearing index, sex ratio of fetus and offspring.
t test for the rest items.

Indices:

copulation index, fertility index, delivery index, rearing index, sex ratio

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

One dam of the 5000 mg/kg bw/day dose group died caused by pneumonia. This is considered to be an incidental occurrence.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The body weight gain during gestation was significantly decreased (35%) in the 5000 mg/kg bw/day group compared with the control group. The body weight gain in the 2500 mg/kg bw/day group was reduced by 9% compared with the control group; this change was not significant.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

Food consumption was significantly decreased in the 2500 and 5000 mg/kg bw/day dose groups compared with the control group (9 and 15%, respectively).

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

effects observed, non-treatment-related

Description (incidence and severity):

Water consumption was significantly increased in the 5000 mg/kg bw/day group. This is considered to be an incidental occurrence as no effects were seen on the kidneys.

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

The leucocyte level was significantly increased in the 5000 mg/kg bw/day group. As no relevant hematological or histopathological effects were observed, this is not considered to be a treatment-related effect.

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

The absolute weight of thymus was significantly decreased in the 5000 mg/kg bw/day group. As no relevant effects were observed on the relative organ weight or during gross pathology examination, this is not considered to be a treatment-related effect.

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Number of abortions:

not examined

Pre- and post-implantation loss:

not examined

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

effects observed, treatment-related

Description (incidence and severity):

Fetal death was significantly increased in the 5000 mg/kg bw/day group. This is considered to be related to maternal toxicity observed at this dose level.

Changes in pregnancy duration:

not examined

Description (incidence and severity):

Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not examined

Changes in number of pregnant:

no effects observed

Other effects:

no effects observed

Key result

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

2 500 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

Remarks on result:

other: reduced body weight gain observed at 5000 mg/kg bw/day

Key result

Dose descriptor:

NOAEL

Remarks:

fertility

Effect level:

5 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: no treatment-related adverse effects observed up and including to the highest dose level

Key result

Abnormalities:

no effects observed

Fetal body weight changes:

effects observed, treatment-related

Description (incidence and severity):

The fetal weight of female offspring was significantly decreased in the 5000 mg/kg bw/day group. This is considered to be a secondary effect caused by the reduced weight gain observed in the dams.


Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): not examined

Reduction in number of live offspring:

not examined

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

not examined

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

The incidence of bipartite, asymmetrical sternebrae was significantly increased in the treatment groups, compared with the control group. Poorly ossified sternebrae was also significantly increased in the 5000 mg/kg bw/day group, compared with the control group. The variation (in bipartite, asymmetrical sternebrae) was minimal and the delay in ossification was very slight; the high value observed in the control group indicates that the structure was developing rapidly at the time of the Cesarean section. This means that some animals had already completed the fusion of the sternebral ossification centres, while others had not, and that a relatively small difference in the time point of examination will result in different values. Therefore, the changes are not considered to be treatment-related effects, but an incidental finding.
The ossification of the caudal vertebrae was significantly increased in the treated groups, compared with the control group (see Table 3 under 'Any other information on results incl tables'. The difference was minimal (< 15%) and has no developmental relevance and is therefore considered to be incidental.

Visceral malformations:

no effects observed

Other effects:

no effects observed

Details on embryotoxic / teratogenic effects:

After oral administration of 5000 mg/kg bw/day, an increase in mortality and a decrease in body weight gain were noted in fetuses. These effects are considered to be secondary effects casued by the maternal toxicity observed at his dose level (decreased body weight gain and food consumption).

Key result

Dose descriptor:

NOAEL

Effect level:

2 500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reduction in number of live offspring

fetal/pup body weight changes

Remarks on result:

other: effect noted only at level of maternal systemic toxicity and at a dose considerably higher than the limit dose recommended in the OECD guideline 414

Key result

Dose descriptor:

LOAEL

Effect level:

5 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reduction in number of live offspring

fetal/pup body weight changes

Remarks on result:

other: effect noted only at level of maternal systemic toxicity and at a dose considerably higher than the limit dose recommended in the OECD guideline 414

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

no

Table 1. Effect of N-acetyl-L-Tryptophan on pregnant females treated orally on days 7 to 17 of gestation

	Control	N-acetyl-L-tryptophan (g/kg)
		2.5	5.0
No. of pregnant females	21	22	20
Maternal death	0	0	1
Body weight gain during gestation (g ± S.D.)	124 ± 24	114 ± 14	79 ± 36**
Food consumption during gestation (g/100g ± S.D.)	145 ± 11	133 ± 9**	124 ± 12**
Organ weight Thymus  (g ± S.D.)	0.26 ± 0.07	0.20 ± 0.07	0.18 ± 0.08**
Hematological findings Erythrocytes (10000/mm3 ± S.D.)	96 ± 23	103 ± 29	115 ± 32*

*:        significantly different from control at P≤0.05

**:      significantly different from control at P≤0.01

 

Table 2. Effect of N-acetyl-L-Tryptophan on fetus from pregnant females treated orally on days 7 to 17 of gestation

	Control	N-acetyl-L-tryptophan (g/kg)
		2.5	5.0
No. of pregnant females	21	22	19
% Fetal death (Mean ± S.D.)	5.3 ± 14.2	3.9 ± 6.8	19.5 ± 30.9**
Fetal weight Female (g ± S.D.)	3.81 ± 0.23	3.71 ± 0.31	3.53 ± 0.45*

*:        significantly different from control at P≤0.05

**:      significantly different from control at P≤0.01

 

 

Table 3. Effect of N-acetyl-L-Tryptophan on visceral and skeletal development of fetus from pregnant females treated orally on days 7 to 17 of gestation

	Control	N-acetyl-L-tryptophan (g/kg)
		2.5	5.0
No. of litters	21	22	17
Skeletal observation No. of fetus examined	171	186	131
Variation Bipartite, asymmetrical sternebrae	17.9 (33)	28.0 (51)*	35.7 (47)**
Poorly ossified sternebrae	15.9 (29)	23.0 (43)	43.6 (58)*
Ossification Caudal vertebrae	4.2 ± 0.3	3.8 ± 0.3**	3.6 ± 0.8*

*:        significantly different from control at P≤0.05

**:      significantly different from control at P≤0.01

Conclusions:

The effects in the offspring were noted only at level of maternal systemic toxicity, therefore the test substance is considered to have no effect on effect on intrauterine development, thus the highest dose level of 5000 mg/kg bw/day was considered as a NOAEL for fertility, and 2500 mg/kg bw/day was considered as a NOAEL for developmental effects.

Reference 2

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

no guideline followed

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

- Short description of test conditions: The teratogenic effects of N-acetyl-L-tryptophan were investigated in JCL-ICR mouse.
The test substance was orally administered to pregnant mice at doses of 2500 and 5000 mg/kg bw/day from Day 6 to Day 15 of gestation. All dams (F0) were autopsied to assess fetal parameters on Day 18 of gestation.

GLP compliance:

no

Limit test:

no

Species:

mouse

Strain:

ICR

Remarks:

JCR-ICR

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: CLEA Japan, Meguro, Japan
- Age at study initiation:ad libitum
- Diet: MF except for gestation and lactation period and NMF for gestation and lactation period, purchased by Oriental Yeast Co., Ltd, Japan, were given ad libitum
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2
- Humidity (%): 55 ± 5

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water): Due to the low water solubility, CMC was used as vehicle for oral application.
- Concentration in vehicle: 1%

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1

Duration of treatment / exposure:

females: 10 days; (from Day 6 to 15 of gestation (GD))

Frequency of treatment:

once daily

Duration of test:

GD 6 - 18

Dose / conc.:

5 000 mg/kg bw/day (nominal)

Dose / conc.:

2 500 mg/kg bw/day (nominal)

No. of animals per sex per dose:

20, 23, and 20 animals in control, 2500 and 5000 mg/kg bw/day, respectively

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Doses were selected based on range-finding tests.
Based on a LD50 of 12500 mg/kg bw/day, a dose of 5000 mg/kg bw was selected as the highest applied dose.

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: every other day

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: every other day

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- sacrifice on GD 18
- Organs examined: brain, pituitary, thymus, heart, lungs, liver, kidneys, spleen, adrenals, ovaries

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: No
- Number of implantations: Yes
- Number of early resorptions: No
- Number of late resorptions: No

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: No
- Skeletal examinations: Yes: all per litter
- Head examinations: No

Statistics:

Wilcoxon test: fetal mortality, number of fetus with external abnormalities, number of fetus with skeletal abnormalities except for ossification, number of fetus with visceral abnormallities, number of offspring with malformation and variation, number of live offspring, and postnatal differentiation.
Chi-squared test: sexratio, copulation ratio, pregnancy rate, delivering rate, and mortality.
t test: other items.

Indices:

sex ratio of fetuses

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

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:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Number of abortions:

not examined

Pre- and post-implantation loss:

no effects observed

Total litter losses by resorption:

not examined

Early or late resorptions:

not examined

Dead fetuses:

no effects observed

Changes in pregnancy duration:

not examined

Description (incidence and severity):

Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not examined

Changes in number of pregnant:

not examined

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

>= 5 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: no treatment-related adverse effects observed up and including to the highest dose level

Key result

Dose descriptor:

NOAEL

Remarks:

fertility

Effect level:

>= 5 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: no treatment-related adverse effects observed up and including to the highest dose level

Key result

Abnormalities:

no effects observed

Fetal body weight changes:

not examined

Description (incidence and severity):

Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): not examined

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

not examined

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

not examined

Other effects:

not examined

Key result

Dose descriptor:

NOAEL

Effect level:

>= 5 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no treatment-related adverse effects observed up and including to the highest dose level

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

no

Conclusions:

Due to the absence of any treatment-related effects on reproductive and developmental toxicity, a dose level ≥ 5000 mg/kg bw/day was considered as a NOAEL for fertility and developmental effects

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

2 500 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

The available information comprises adequate and reliable studies from a reference substance with similar structure and intrinsic properties. Read-across is justified based on stereoisomerism. Source and target substance differ only in the three-dimensional orientations of their atoms in space (please refer to the analogue justification). The selected studies are thus sufficient to fulfil the standard information requirements set out in Annex VIII-IX, 8.7, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

Justification for RA

There are no available data assessing the developmental toxicity potential of N-acetyl-DL-tryptophan (CAS 87-32-1). The assessment of developmental toxicity was therefore based on studies conducted with a source substance (N-acetyl-L-tryptophan (CAS 1218-34-4) as part of a read across approach, which is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. in order to fulfil the standard data requirements defined in Regulation (EC) No 1907/2006, Annex VIII, 8.7. Structural similarities and comparable toxicokinetic properties of the source and target substance are the basis of read-across. A detailed justification for the analogue read-across approach is provided in the technical dossier (see IUCLID Section 13).

 

Developmental toxicity/teratogenicity: Oral

CAS 1218-34-4

In a non-guideline study of the systemic and developmental/teratogenic effects of N-acetyl-L-tryptophan, the test substance was orally administered to pregnant Wistar rats at the doses of 2500 and 5000 mg/kg bw/day from day 7 to 17 of gestation (Kadota et al., 1980). There were 21, 22 and 20 females in the control, 2500 and 5000 mg/kg b/day groups, respectively. All dams were sacrificed on gestation day (GD) 20. In the dams, the mortality, clinical signs, body weight and food consumption were recorded. At sacrifice, haematological and clinical chemistry parameters were examined, and a gross pathology examination was performed. In addition, the ovaries and uterine content were examined to record the gravid uterus weight and number of implantations. The fetal examinations included number of live foetuses, fetal body weight and external and skeletal examinations. In the dams, the body weight gain during gestation was significantly decreased (35%) in the 5000 mg/kg bw/day group compared with the control group. The food consumption was significantly decreased in the 2500 and 5000 mg/kg bw/day dose groups (by 9 and 15%, respectively) compared with the control group. In the offspring, an increase in mortality and a decrease in body weight gain at 5000 mg/kg bw/day were observed. These effects are considered to be secondary effects caused by the maternal toxicity observed at this dose level. The administration of N-acetyl-L-tryptophan did not cause changes in the fertility parameters at any dose level. No other effects were observed on the parameters assessed for developmental toxicity or teratogenicity. Based on the results of this study, the NOAEL systemic in the dams was considered to be 2500 mg/kg bw/day and NOAEL fertility was considered to be ≥ 5000 mg/kg bw/day. The NOAEL for developmental toxicity in the offspring was considered to be 2500 mg/kg bw/day.

The developmental/teratogenic effects of N-acetyl-L-tryptophan were assessed in a non-guideline study performed in JCL-ICR mice (Ueshima et al., 1980a). The test substance was orally administered to pregnant mice at doses of 2500 and 5000 mg/kg bw/day from Day 6 to Day 15 of gestation. There were 20, 23 and 20 females in the control, 2500 and 5000 mg/kg bw/day groups, respectively. All dams (F0) were sacrificed on Day 18 of gestation. The following maternal parameters for systemic toxicity were evaluated: mortality, clinical signs, body weight, food consumption and gross pathology. In addition, the ovaries and uterine content were examined to record the gravid uterus weight and number of implantations. The fetal examinations included number of live foetuses, fetal body weight and external and skeletal examinations. No maternal systemic toxicity was observed in the treatment groups when compared with the control group. The administration of N-acetyl-L-tryptophan did not cause changes in the fertility parameters at any dose level. No effects were observed on the parameters assessed for developmental toxicity or teratogenicity. Based on the results of this study, the NOAEL systemic in the dams was considered to be ≥ 5000 mg/kg bw/day and NOAEL fertility was considered to be ≥ 5000 mg/kg bw/day. The NOAEL for developmental toxicity in the offspring was considered to be ≥ 5000 mg/kg bw/day.

 

Developmental toxicity/teratogenicity: intraperitoneal

CAS 1218-34-4

In the study performed by Ueshima et al. (1980a), the potential systemic and developmental effects of N-acetyl-L-tryptophan were also assessed via the intraperitoneal route. The test substance was administered intraperitoneally (i.p.) to the mice at doses of 100, 300 and 900 mg/kg bw/day from Day 6 to Day 15 of gestation (Ueshima et al., 1980a). In group 1, there were 20, 22, 23, and 22 animals in the control, 100, 300 and 900 mg/kg bw/day group, respectively, which were sacrificed on GD 18. In group 2, there were 13, 11, 12 and 12 animals in control, 100, 300 and 900 mg/kg bw/day, respectively, which were sacrificed on Day 21 postpartum. Maternal examinations (F0) included clinical signs, body weight, gross pathology, haematology and clinical chemistry. In addition, the influence on ovaries and uterine content, gravid uterus weight and number of implantations were investigated. Group 1 was sacrificed for fetal examination including external and skeletal examinations on Day 18 of gestation. Group 2 was allowed to deliver naturally for the observation of their offspring (F1) postnatally. The examination of the F1 offspring included detailed clinical signs, body weight, gross pathology, haematology, clinical chemistry and functional observations (Irwins`s test and Preyer`s reflex, activity wheel test, open-field test and Water T-Maze test). 1 male and 1 female F1 -offspring (12 -13 weeks old) from each litter were used for mating (maximum 14 days, no rats from the same litter were paired). The fertility parameters copulation rate, pregnancy rate, body weights (on GD 0, 6, 14 and 18), food consumption during pregnancy and organ weights were assessed. Effects on F2-fetuses (number of implantations, fetal death, number of fetuses with external abnormalities, number of live fetuses, sex ratio, skeletal examination, visceral examination) and on F2-offspring (number of live offspring, sex ratio, birth weight, dead offspring postnatal days, body weight gain, skeletal examination on postnatal day 4, differentiation (pinna detachment, incisor eruption, eye opening, vaginal opening and testis descending) from F1-females were determined. In the F0- and F1-dams, no treatment-related and toxicologically relevant effects were observed. Based on these results, the NOAEL systemic was considered to be ≥ 900 mg/kg bw/d in dams. As no adverse effects on fertility parameters were observed up to and including the highest dose level, the NOAEL fertility was considered to be ≥ 900 mg/kg bw/day in dams. No treatment-related adverse effects on developmental toxicity were observed up and including to the highest dose level. Based on the results in the offspring, the NOAEL for developmental toxicity/teratogenicity was derived to be ≥ 900 mg/kg bw/d for the F1-and F2-offspring.

 

In the study performed by Kadota et al. (1980), the potential systemic and developmental effects of N-acetyl-L-tryptophan via the intraperitoneal route were evaluated in Wistar rats (Kadota et al., 1980). N-acetyl-L-tryptophan was intraperitoneally (i.p.) administered to pregnant dams (F0) at doses of 150, 300 and 600 mg/kg bw/day from GD 7 to 17. Two thirds of the dams were sacrificed on day 20 of gestation, while the remaining dams were allowed to litter and sacrificed on postpartum day 21-28. There were a total of 33, 33, 33, and 34 animals in control, 150, 300 and 600 mg/kg bw/day, respectively. On day 21 and 40 postpartum, 7 offspring (F1) per dam (F0) were sacrificed for these observations. The remaining F1-offspring were mated and their offspring (F2) assessed. The maternal parameters that were assessed included mortality, clinical signs, effects on body weight and food consumption, haematology and clinical chemistry parameters, and gross necropsy. In addition, the ovaries and uterine content were examined to record the gravid uterus weight and number of implantations in the dams sacrificed on GD 20. The fetal examinations included external and skeletal examinations for F1 and F2 offspring. The F1-offspring of the dams that littered was subjected to functional observations (Irwin`s Test, Preyer`s Reflex Test, Open-Field Test and the Water T-Maze Test) 35-42 days postpartum.

In the F0- and F1-dams, no treatment-related and toxicologically relevant systemic effects and no adverse effects on fertility parameters were observed up to and including the highest dose level. The examination of fetal parameters revealed no indication for effects on developmental toxicity and teratogenicity. No treatment-related effects for any functional parameters were observed in the F1-offspring. Based on these results, the NOAEL systemic was considered to be ≥ 600 mg/kg bw/d and NOAEL fertility was considered to be ≥ 600 mg/kg bw/day in F0 and F1 dams. The NOAEL for developmental toxicity was considered to be ≥ 600 mg/kg bw/day in the F1- and F2-offspring.

 

Developmental toxicity/teratogenicity: intravenous

The systemic and developmental/teratogenic effects of N-acetyl-L-tryptophan were assessed in a non-guideline study performed in rabbits (Ueshima et al., 1980b). The test substance was intravenously administered to pregnant rabbits from gestation day 6 - 18 at doses of 125, 250, 500 and 1000 mg/kg bw/day. There were 13, 12, 12, 12 and 11 dams in the control, 125, 250, 500 and 1000 mg/kg bw/day group, respectively. Dams were sacrificed on gestation day 29. The mortality and clinical signs, and body weight was recorded in the dams. Haematological and clinical chemistry parameters were assessed, and gross pathology examination was performed at sacrifice. In addition, the ovaries and uterine content were examined to record the gravid uterus weight and number of implantations. Fetal examinations included number of live foetuses, fetal body weight and external and skeletal examinations. Significantly decreased levels of RBC (red blood cell count), haemoglobin and haematocrit were observed in the 1000 mg/kg bw/day dams in comparison to the control group. No other treatment-related adverse effects were observed in the dams. The number of implantations was significantly increased in the high-dose group; this was considered to be an incidental effect. In the offspring, the number of offspring with unossified proximal epiphyses of the humerus was significantly decreased in the 250 mg/kg bw/day group and the number of offspring with unossified distal epiphyses of femur was significantly increased in the 1000 mg/kg bw/day. However, these findings were considered to be incidental occurrences due to the lack of dose-response and no correlation was shown over the test groups. Based on the results of the conducted study, the NOAEL systemic was considered to be 500 mg/kg bw/day and the NOAEL fertility was considered to be ≥ 1000 mg/kg bw/day in dams. The NOAEL for developmental toxicity was considered to be 1000 mg/kg bw/day in the offspring.

Overall conclusion

Following the oral administration of the source substance (N-acetyl-L-tryptophan) to pregnant rats the fetal weight was decreased in the 5000 mg/kg bw/day group resulting in a NOAEL for developmental toxicity of 2500 mg/kg bw/day. The effect on body weight gain was considered to be a secondary effect caused by the reduced body weight gain observed in the dams. No treatment-related developmental effects were observed in mice following the oral administration of N-acetyl-L-tryptophan. No treatment-related effects on fertility were observed in the mouse or in the rat.

Administration of the source substance to rats and mice via the intraperitoneal route and to rabbits via the intravenous route did not result in treatment-related effects on any reproductive parameters (fertility, development, teratogenicity) at dose levels ≥ 600 mg/kg bw/day.

The doses administered via the oral exposure route in the rat and the mouse are substantially higher than the limit dose of 1000 mg/kg bw/day recommended in the current relevant OECD guidelines. Moreover, data on toxicity to reproduction following repeated exposure after intraperitoneal and intravenous administration did not indicate any treatment-related adverse effects of the source substance. Exposure via these routes can be regarded as a worst case situation, as the substance is directly and entirely systemically available.

Overall, the available data consistently indicates a lack of reproductive toxicity, including developmental toxicity and teratogenicity in several species via several routes of exposure. Therefore the available data are considered to be sufficient to meet the data requirements and to be suitable to read across to the target substance N-acetyl-DL-tryptophan. The NOAEL for developmental toxicity is derived to be 2500 mg/kg bw/day in the rat

Justification for classification or non-classification

According to Article 13 of Regulation (EC) No. 1907/2006 "General Requirements for Generation of Information on Intrinsic Properties of substances", information on intrinsic properties of substances may be generated by means other than tests e.g. from information from structurally related substances (grouping or read-across), provided that conditions set out in Annex XI are met. Annex XI, "General rules for adaptation of this standard testing regime set out in Annexes VII to X” states that “substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. This avoids the need to test every substance for every endpoint". Since the analogue concept is applied to N-acetyl-DL-tryptophan, data will be generated from information on reference source substance(s) to avoid unnecessary animal testing. Additionally, once the analogue read-across concept is applied, substances will be classified and labelled on this basis.

 

Therefore the available source and target substance data on developmental toxicity do not meet the classification criteria according to Regulation (EC) 1272/2008, and are therefore conclusive but not sufficient for classification.