Subtilisin

Endpoint summary

Description of key information

The repeated dose oral toxicity of subtilisin has been tested in a 90-day study, the repeated dose dermal toxicity was tested in a 28-day study, while the repeated dose inhalation toxicity was waived. 
- The repeated dose oral toxicity was a subchronic toxicity test similar to the principles of OECD guideline 408 (adopted 1981), and in compliance with GLP.  The conclusion was that the No Observed Adverse Effect Level (NOAEL) in rats was considered to be the intermediate dose level administered, equivalent to 400 mg of the subtilisin batch/kg bw/day or 360 mg Total Organic Solids (TOS)/kg bw/day.  
- The dermal study concluded that the dose applied daily, 10 mg/kg/day (only one dose level tested), was without any significant effects, only sporadic, minimal grade local skin reactions. It is further highly unlikely that enzymes should be absorbed through the skin due to the molecular weight and the physico-chemical properties of the protein molecule. 
- The inhalation study was waived because exposure is too low to exert any toxicity. Potential exposure by inhalation to an amount of enzyme, which is toxicologically relevant, is unrealistic due to the stringent work practices and the formulation of enzymes, enforced because of the risk of sensitization by inhalation. 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 February - 19 May, 1981

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Version / remarks:

1981

Deviations:

no

Principles of method if other than guideline:

Guideline OECD 408 was adopted for the first time in 1981, at the time where the present study was performed. The principles of the new guideline was however followed. The current version of OECD 408, revised in 1998, places additional emphasis on neurotoxic, immunological and reproductive organ effects as well as the need for more careful clinical observations of the animals compared to the 1981 version. These changes are not considered to be important for toxicological evaluation of enzymes produced by non-toxigenic, non-pathogenic strains for which the main safety issue of concern is respiratory allergy and in some cases primary irritation. This is supported by numerous 13-week oral toxicity studies performed on enzymes according to OECD 408 (1998), in which no effects on the additional parameters have been reported.
Therefore the present study is considered suitable for the evaluation of sub chronic toxicity of subtilisin.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, UK
- Weight at study initiation: 60-80 g
- Fasting period before study: None
- Housing: 3 animals per cage, separate sex
- Diet : ad libitum
- Water : ad libitum
- Acclimation period: 13 days

ENVIRONMENTAL CONDITIONS
- Temperature : 19-23°C
- Humidity : 50% ( range 26-80 %)
- Air changes (per hr): 14
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1981-02-16 To: 1981-05-19

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

Distilled water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
VEHICLE
- Concentration in vehicle: 16, 40 and 100 mg/mL, corresponding to 14, 36 and 89 mg TOS/mL
- Amount of vehicle (if gavage): constant volume 10 mL/kg b.w.
- Purity: distilled water

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
0, 16, 40 and 100 mg/mL, corresponding to 0, 14, 36 and 89 mg TOS/mL
Basis:
nominal in water

No. of animals per sex per dose:

15

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on experience from dose-range studies, the top dose was selected to provide some toxicological effects but still avoiding death as an endpoint

Positive control:

Not included

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: early morning and late afternoon each day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily and further more detailed examination of each animal once a week

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION:
- Food consumption for each cage, i.e. sum of three animals, was determined and mean daily diet consumption per group calculated as g feed/rat/week: Yes

WATER CONSUMPTION : Yes but only by visual assessment of water intake

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Week 6 and week 13
- Anaesthetic used for blood collection: Yes (ether anaesthesia)
- Animals fasted: No
- How many animals: 10 males and 10 females from negative control groups and high dose groups
- Parameters checked: Red blood cell count (RBC), White blood cell count (WBC), Packed cell volume (PCV), Haemoglobin conc (Hb), Differential leucocyte count, Platelet count.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Week 6 and week 13
- Animals fasted: No
- How many animals: 10 males and 10 females from negative control groups and high dose groups
- Parameters checked: Aspartate aminotransferase, Alanine aminotransferase, Alkaline phosphatase, lactate dehydrogenase, blood urea nitrogen, Glucose, Sodium (Na), Potassium (K), Protein (total), Chloride (Cl), Cholesterol.

URINALYSIS: Yes
- Time schedule for collection of urine: Week 6 and week 13
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Deprivation of feed and water during the 4-hour sampling period
- Parameters checked: Glucose, volume, protein, ketones, urobilinogen, colour, appearance, pH, specific gravity, microscopic examination of the spun deposit.

NEUROBEHAVIOURAL EXAMINATION: No data
The animals were observed daily in accordance with state of the art in 1981

OTHER:

Sacrifice and pathology:

GROSS PATHOLOGY: Yes.
The majority of the 16 premature decedents were found dead with red staining around nose and mouth. Most decedents showed red patches and oedema of the lungs. Three animals had haemorrhagic tracts or holes in the left lung lobe on post mortem examinination, consistent with lung damage as a result of gavage dosing. Both control and treated rats showed hyperplasia of the submandibular lymph nodes. This could be due to a previous sialodacryoadenitis virus infection. None of the lesions were attributed to toxic effects of the test material.
HISTOPATHOLOGY: Yes. Mild and focal alveolitis was identified in both control and treated animals - the cause was not identified. One animal showed a focal chronic alveolitis. Foreign material was identified in the alveolar air spaces of this animal, suggesting that the cause was inhalation or misdosing of foreign test material.

Other examinations:

FAECAL ANALYSIS: Yes
- Time schedule for collection of faeces: Week 6 and week 13
- Metabolism cages used for collection: Yes
- Animals fasted: Deprivation of feed and water during the 4-hour sampling period
- Parameters presented in appendix 12, 13 and 14 were examined.

Weight of individual organs: yes
- Time schedule for collection of organs: At necropsy
- Results presented in table 12 and 13 .

Statistics:

Organ weight and body weight data were statically analysed by computerized analysis of variance incorporating t-test. The level of probability chosen as significant was p<0.05.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

There were 16 premature deaths. Within males: 8 animals in the top dose group, 1 in mid dose group. Within female: Two animals in the top and mid groups, and 3 animals in the low dose group.

Mortality:

mortality observed, treatment-related

Description (incidence):

There were 16 premature deaths. Within males: 8 animals in the top dose group, 1 in mid dose group. Within female: Two animals in the top and mid groups, and 3 animals in the low dose group.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights were significantly reduced at the highest dose level in males.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

There was a slight dose-related reduction in food consumption in males. Food consumption in females was lower than controls but without dose-relation.

Food efficiency:

not examined

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

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

There were no haematological changes considered to be related to treatment.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Urea nitrogen (BUN) and alanine aminotransferase (ALT) were significantly reduced at the highest dose level in males.

Urinalysis findings:

no effects observed

Description (incidence and severity):

There were no abnormalities considered to be related to treatment.

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

The changes that were identified were not considered to of toxicological significance.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

No lesions were seen at finalization of the study which could be attributed to toxic effects of the dosed test material. Many of the 16 premature deaths showed findings in the lungs from damage due to gavage dosing or unintended dosing of test material in

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The changes that were identified were not considered of toxicological significance.

Histopathological findings: neoplastic:

not specified

Details on results:

CLINICAL SIGNS AND MORTALITY: The major clinical observation in this study was increased difficulty of dosing animals receiving 1000 mg/kg bw/day ~ 891 mg TOS/kg bw/day. This difficulty, resulting from struggling during dosing, caused many of the 16 premature deaths due to aspiration. When using oral gavage dosing, the dose volume of 10 ml/kg body weight can easily lead to unintended exposure by inhalation because test substance is deposited in the pharyngeal cavity after reflux from the stomach. This is a likely event in struggling animals, but is as such an artifact caused by the way of dosing the animals.

BODY WEIGHT AND WEIGHT GAIN: : Body weights were significantly reduced at the highest dose level in males.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)

FOOD EFFICIENCY

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)

OPHTHALMOSCOPIC EXAMINATION

HAEMATOLOGY: There were no haematological changes considered to be related to treatment.

CLINICAL CHEMISTRY: Clinical Urea nitrogen (BUN) and alanine aminotransferase (ALT) were significantly reduced at the highest dose level in males.
The reduced clinical chemical parameters BUN and ALT could be indicators of lever damage but due to lack of histopathological changes in the lever of these animals, this change is considered of no toxicological significance.


URINALYSIS

NEUROBEHAVIOUR

ORGAN WEIGHTS: The top dose males showed reduced absolute liver and spleen weights with no concurrent change in relative weights, unaltered absolute but increased relative brain weight, increased absolute and relative adrenal weights - could be the result of the difficulty in dosing (see reference 1 and 2 below). The males receiving 400 and 1000 mg/kg bw/day also showed increased relative lung weights, but this could be due to reduction in body weight.
References:
1. Scharer, K. (1977). The effect of the chronic underfeeding on organ weights of rats. Toxicology, 7: 45-46.
2. Oishi, S., Oishi H. and Hiraga, K. (1979). The effect of food restriction for 4 weeks on common toxicity parameters in male rats. Toxicol. Appl. Pharmacol., 47: 15-22.
The absolute and relative thyroid weights were found to be significantly increased in all treated males, but this finding is not judged to be of great significance for the following reasons:
1) The thyroid gland is small in rats with a color similar to the surrounding tissue and very difficult to dissect precisely for weighing. This is also indicated by the coefficient of variability (CV = 100 x SD/mean weight) which can be calculated from the thyroid weight data in table 12. The CV is above 20% in all groups and in the female control group, it is even 55%, showing a very high variability in these data.
2) The histopathology did not reveal any changes.
3) Historical data showed that the seen increase in weight was possibly due to unusual low thyroid weight data in the control animals for both males and females.
4) The present study was finalized Sept. 1981, and reports covering 13 week oral toxicity studies in rats from the same CRO in the following year, 1982 and onwards, does no longer include the thyroid weight as a parameter. This decision of excluding the organ weight of the thyroids is most likely taken because these data do not provide any added value. Further, the OECD test guideline 408, 'Subchronic Oral Toxicity - Rodent: 90-Day Study', which was adopted 12 May 1981, has supported this decision as weighing of the thyroid gland was not required in this guideline.


GROSS PATHOLOGY: The effects in the lungs (irregular brown areas) are considered artifacts originating from dosing by gavage especially in case of the higher dose level.

HISTOPATHOLOGY: NON-NEOPLASTIC : The effects in the lungs (brown pigments) are considered originating from dosing by gavage especially in case of the higher dose level.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)

HISTORICAL CONTROL DATA (if applicable)

OTHER FINDINGS

Key result

Dose descriptor:

NOAEL

Effect level:

> 360 - < 891 mg/kg bw/day (nominal)

Based on:

other: TOS

Sex:

male/female

Basis for effect level:

other: body weight: Slight reduction; food consumption: Slight reduction

Critical effects observed:

not specified

For details, please see the attached report (scanned pdf file as it is written before electronic files were used).

Conclusions:

The No Observed Adverse Effect Level (NOAEL) in rats is 400 mg of the subtilisin batch/kg bw/day equivalent to 360 mg Total Organic Solids (TOS)/kg bw/day.

Executive summary:

Guideline OECD 408 was adopted for the first time in 1981, at the time where the present study was performed. The principles of this OECD guideline were, however, followed and the study performed in compliance with GLP. The current version of OECD 408, revised in 1998, places additional emphasis on neurotoxic, immunological and reproductive organ effects as well as the need for more careful clinical observations of the animals compared to the 1981 version. These changes are not considered to be important for toxicological evaluation of enzymes produced by non-toxigenic, non-pathogenic strains for which the main safety issue of concern is respiratory allergy and in some cases primary irritation. This is supported by several 13-week oral toxicity studies performed on enzymes according to OECD 408 (1998), in which no effects on the additional parameters have been reported. The present study is therefore considered suitable for the evaluation of sub chronic toxicity of subtilisin.

 

In conclusion, oral administration (by gavage) of subtilisin to rats at the highest dose level, 1000 mg subtilisin batch/kg bw/day, equivalent to 809 mg Total Organic Solids (TOS)/kg bw/dayfor thirteen weeks, resulted in significantly reduced body weights in males and remarkable struggling against the gavage. Apart from these effects, dosing did not produce any toxicologically significant changes. Consequently, the No Observed Adverse Effect Level (NOAEL) in rats was considered to be the intermediate dose level administered, equivalent to 400 mg of the subtilisin batch/kg bw/day or 360 mg Total Organic Solids (TOS)/kg bw/day.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

360 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

High quality. The key study is GLP compliant and Klimisch 1.

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Data waiving:

exposure considerations

Justification for data waiving:

other:

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Data waiving:

exposure considerations

Justification for data waiving:

other:

Critical effects observed:

not specified

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Critical effects observed:

not specified

Reference 2

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

The subacute percutaneous toxicity of Subtilisin was assessed. The systemic and local effects of daily repeated applications of 10 mg/kg/day of the test material Subtilisin, prepared as a 0.5% w/v solution in water and 0.5% w/v in sodium tripolyphosphate buffer, respectively. The application was performed daily for 28 consecutive days without occlusion to the abraded and intact skin of the albino rabbit, an area equal to 10% of the total body surface clipped free of hair. Four female and four male rabbits were used per group, i.e. 32 rabbits in total including two negative control groups.

GLP compliance:

no

Remarks:

The study was performed before GLP was implemented but was performed according to state of the art at that time.

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Source: Morton Commercial Rabbits, Parsonage Farm, Stanstedt, UK
- Fasting period before study: None
- Housing: individually in stainless steel cages
- Weight at study initiation: between 2.2 - 2.7 kg
- Age at study initiation: Young adults, 3 - 3.5 months
- Diet (e.g. ad libitum): Standard diet ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: minimum 14 days
- Temperature (°C): 14-18C
- Humidity : 50% ( range 40-60 %)
- Air changes (per hr): 17
- Photoperiod (hrs dark / hrs light): 10 hrs/14 hrs

Type of coverage:

open

Vehicle:

other: water, respectively sodium tripolyphosphate buffer

Details on exposure:

TEST SITE
- Area of exposure: 10% of body surface
- Time intervals for shavings or clipplings: The animals were shaven as needed - no specific interval given in report.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes
- Time after start of exposure: Four hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 mg/kg
- Concentration (if solution): 0.5% w/v
- Constant volume or concentration used: yes
- For solids, paste formed: no

VEHICLE
- Amount(s) applied (volume or weight with unit): 2 mL/kg
- Concentration (if solution): 0.1 % sodium tripolyphosphate buffer


USE OF RESTRAINERS FOR PREVENTING INGESTION: no - however, collars were worn by the animals four hours post-application.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

Four hours per day

Frequency of treatment:

Each day for 28 days.

Remarks:

Doses / Concentrations:
10 mg/kg, i.e. 2.0 mL/kg of a 0.5% w/v solution in water and sodium tripolyphosphate buffer, respectively.
Basis:
nominal per unit body weight

No. of animals per sex per dose:

4

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on experience from short term dose-range studies, the dose was selected to provide some toxicological effects but still avoiding extreme irritation as an endpoint

Positive control:

No positive control

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

DERMAL IRRITATION (if dermal study): Yes
- Time schedule for examinations: Days 1, 2, 3, 7, 14, 21, 28

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No data


OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Before commencement and after 4 weeks of treatment
- Anaesthetic used for blood collection: No
- Animals fasted: No
- How many animals: 32
- Parameters checked in table No 4 & 5 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Before commencement and after 4 weeks of treatment
- Animals fasted: No
- How many animals: 32
- Parameters checked in table No 6 & 7 were examined.

URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes ( Appendix 9 in report)
HISTOPATHOLOGY: Yes (Appendix 9 in report)

Other examinations:

Twelve main organs were weighed

Statistics:

Organ weights were evaluated by analysis of variance.

Clinical signs:

no effects observed

Dermal irritation:

no effects observed

Description (incidence and severity):

skin reactions were confined to sporadic, minimal grade

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:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Any effects were confined to slight acanthosis, and a variable, slight infiltration of the underlying dermis by leucocytes

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: No clinical effects and no mortality

BODY WEIGHT AND WEIGHT GAIN: Within normal limits during the study.

FOOD CONSUMPTION: Within normal ranges during the study.

HAEMATOLOGY: Within normal ranges, unaffected by treatment.

CLINICAL CHEMISTRY Within normal ranges, unaffected by treatment.

NEUROBEHAVIOUR: Behaviour normal throughout the study

ORGAN WEIGHTS: No differences between groups.

GROSS PATHOLOGY: No treatment related gross lesions present

HISTOPATHOLOGY: NON-NEOPLASTIC There were no treatment related effects other than minor local skin effects. These were slight acanthosis, occasional patchy parakeratosis and variable slight infiltration of underlying dermis by leucocytes.

Key result

Dose descriptor:

conc. level:

Effect level:

> 10 mg/kg bw/day (nominal)

Based on:

dissolved

Remarks:

0.5% w/v solution in water or buffer

Sex:

male/female

Basis for effect level:

other: detailed skin reactions, clinical signs; mortality; body weight; food consumption; haematology; clinical chemistry; gross pathology; organ weights; histopathology;

Critical effects observed:

not specified

Conclusions:

The only effects of 28-day repeated treatment of intact and abraded skin with Subtilisin, buffered and unbuffered, were microscopically detected minor changes at the site of application.

Executive summary:

A percutaneous 28-day repeated application study in rabbits was conducted by Life Science Research (now Huntingdon Life Sciences Ltd.) to assess the potential of the test substance, Subtilisin (batch FPF 312/20), to cause dermal toxicity. Only one dose was applied daily, 10 mg/kg/day, diluted in either water or buffer, to the closely-clipped dorsa of New Zealand White rabbits, equal to 10% of the body surface. Vehicle controls were included. Each group consisted of 4 males and 4 females. The study was conducted before GLP was implemented but the principles was the same and state of the art was followed. The study concluded that the test substance, Subtilisin, was without any significant effects and thus may be considered virtually harmless.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

10 mg/kg bw/day

Study duration:

subacute

Species:

rabbit

Quality of whole database:

Klimisch 2 study - only one dose level tested.

Repeated dose toxicity: dermal - local effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Critical effects observed:

not specified

Reference 2

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

The subacute percutaneous toxicity of Subtilisin was assessed. The systemic and local effects of daily repeated applications of 10 mg/kg/day of the test material Subtilisin, prepared as a 0.5% w/v solution in water and 0.5% w/v in sodium tripolyphosphate buffer, respectively. The application was performed daily for 28 consecutive days without occlusion to the abraded and intact skin of the albino rabbit, an area equal to 10% of the total body surface clipped free of hair. Four female and four male rabbits were used per group, i.e. 32 rabbits in total including two negative control groups.

GLP compliance:

no

Remarks:

The study was performed before GLP was implemented but was performed according to state of the art at that time.

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Source: Morton Commercial Rabbits, Parsonage Farm, Stanstedt, UK
- Fasting period before study: None
- Housing: individually in stainless steel cages
- Weight at study initiation: between 2.2 - 2.7 kg
- Age at study initiation: Young adults, 3 - 3.5 months
- Diet (e.g. ad libitum): Standard diet ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: minimum 14 days
- Temperature (°C): 14-18C
- Humidity : 50% ( range 40-60 %)
- Air changes (per hr): 17
- Photoperiod (hrs dark / hrs light): 10 hrs/14 hrs

Type of coverage:

open

Vehicle:

other: water, respectively sodium tripolyphosphate buffer

Details on exposure:

TEST SITE
- Area of exposure: 10% of body surface
- Time intervals for shavings or clipplings: The animals were shaven as needed - no specific interval given in report.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes
- Time after start of exposure: Four hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 mg/kg
- Concentration (if solution): 0.5% w/v
- Constant volume or concentration used: yes
- For solids, paste formed: no

VEHICLE
- Amount(s) applied (volume or weight with unit): 2 mL/kg
- Concentration (if solution): 0.1 % sodium tripolyphosphate buffer


USE OF RESTRAINERS FOR PREVENTING INGESTION: no - however, collars were worn by the animals four hours post-application.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

Four hours per day

Frequency of treatment:

Each day for 28 days.

Remarks:

Doses / Concentrations:
10 mg/kg, i.e. 2.0 mL/kg of a 0.5% w/v solution in water and sodium tripolyphosphate buffer, respectively.
Basis:
nominal per unit body weight

No. of animals per sex per dose:

4

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on experience from short term dose-range studies, the dose was selected to provide some toxicological effects but still avoiding extreme irritation as an endpoint

Positive control:

No positive control

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

DERMAL IRRITATION (if dermal study): Yes
- Time schedule for examinations: Days 1, 2, 3, 7, 14, 21, 28

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No data


OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Before commencement and after 4 weeks of treatment
- Anaesthetic used for blood collection: No
- Animals fasted: No
- How many animals: 32
- Parameters checked in table No 4 & 5 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Before commencement and after 4 weeks of treatment
- Animals fasted: No
- How many animals: 32
- Parameters checked in table No 6 & 7 were examined.

URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes ( Appendix 9 in report)
HISTOPATHOLOGY: Yes (Appendix 9 in report)

Other examinations:

Twelve main organs were weighed

Statistics:

Organ weights were evaluated by analysis of variance.

Clinical signs:

no effects observed

Dermal irritation:

no effects observed

Description (incidence and severity):

skin reactions were confined to sporadic, minimal grade

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:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Any effects were confined to slight acanthosis, and a variable, slight infiltration of the underlying dermis by leucocytes

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: No clinical effects and no mortality

BODY WEIGHT AND WEIGHT GAIN: Within normal limits during the study.

FOOD CONSUMPTION: Within normal ranges during the study.

HAEMATOLOGY: Within normal ranges, unaffected by treatment.

CLINICAL CHEMISTRY Within normal ranges, unaffected by treatment.

NEUROBEHAVIOUR: Behaviour normal throughout the study

ORGAN WEIGHTS: No differences between groups.

GROSS PATHOLOGY: No treatment related gross lesions present

HISTOPATHOLOGY: NON-NEOPLASTIC There were no treatment related effects other than minor local skin effects. These were slight acanthosis, occasional patchy parakeratosis and variable slight infiltration of underlying dermis by leucocytes.

Key result

Dose descriptor:

conc. level:

Effect level:

> 10 mg/kg bw/day (nominal)

Based on:

dissolved

Remarks:

0.5% w/v solution in water or buffer

Sex:

male/female

Basis for effect level:

other: detailed skin reactions, clinical signs; mortality; body weight; food consumption; haematology; clinical chemistry; gross pathology; organ weights; histopathology;

Critical effects observed:

not specified

Conclusions:

The only effects of 28-day repeated treatment of intact and abraded skin with Subtilisin, buffered and unbuffered, were microscopically detected minor changes at the site of application.

Executive summary:

A percutaneous 28-day repeated application study in rabbits was conducted by Life Science Research (now Huntingdon Life Sciences Ltd.) to assess the potential of the test substance, Subtilisin (batch FPF 312/20), to cause dermal toxicity. Only one dose was applied daily, 10 mg/kg/day, diluted in either water or buffer, to the closely-clipped dorsa of New Zealand White rabbits, equal to 10% of the body surface. Vehicle controls were included. Each group consisted of 4 males and 4 females. The study was conducted before GLP was implemented but the principles was the same and state of the art was followed. The study concluded that the test substance, Subtilisin, was without any significant effects and thus may be considered virtually harmless.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

167 µg/cm²

Study duration:

subacute

Species:

rabbit

Quality of whole database:

Klimisch 2 study - only one dose level tested.

Additional information

The repeated dose oral toxicity of subtilisin has been tested in a 90-day study, the repeated dose dermal toxicity was tested in a 28-day study, while the repeated dose inhalation toxicity was waived.

- The repeated dose oral toxicity was a subchronic toxicity test similar to the principles of OECD guideline 408 (adopted 1981), and in compliance with GLP. The conclusion was that the No Observed Adverse Effect Level (NOAEL) in rats was considered to be the intermediate dose level administered, equivalent to 400 mg of the subtilisin batch/kg bw/day or 360 mg Total Organic Solids (TOS)/kg bw/day. 

- The dermal study concluded that the dose applied daily, 10 mg/kg/day (only one dose tested), was without any significant effects, only sporadic, minimal grade local skin reactions. It is further highly unlikely that enzymes should be absorbed through the skin due to the molecular weight and the physico-chemical properties of the protein molecule.

- The inhalation study was waived because exposure is too low to exert any toxicity. Potential exposure by inhalation to an amount of enzyme, which is toxicologically relevant, is unrealistic due to the stringent work practices and the formulation of enzymes, enforced because of the risk of sensitization by inhalation.

Therefore, based on weight of evidence, subtilisin does not exert any repeated dose inhalation toxicity to workers or consumers

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The present key study was selected based on quality, duration, GLP status and lowest NOAEL.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
This endpoint study was waived as potential exposure by inhalation to an amount of enzyme, which is toxicologically relevant, is unrealistic due to the stringent work practices and the formulation of enzymes, enforced because of the risk of sensitization by inhalation.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
This endpoint study was waived as potential exposure by inhalation to an amount of enzyme, which is toxicologically relevant, is unrealistic due to the stringent work practices and the formulation of enzymes, enforced because of the risk of sensitization by inhalation.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
The dermal study supports the information from the physico-chemical properties of the enzyme molecule (high MW, logPow value <0), that enzymes are not absorbed through the skin.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
The only repeated dose study available.

Justification for classification or non-classification

No classification as NOAEL is above guidance level of 100 mg/kg bw/day. The installed controls to insure no risk of respiratory sensitization generally ensure no repeated dose inhalation or dermal toxicity to workers or consumers