[No public or meaningful name is available]

Endpoint summary

Description of key information

Acute oral toxicity:

The amino acids in the spider silk protein are found in foods, and the daily exposure from food use would result in a much larger systemic dose than that resulting from use of spider silk proteins. Therefore, additional testing (in experimental animals) would provide no additional toxicological knowledge about the safe use of the substance.

Acute dermal toxicity:

Dermal absorption can be excluded. Dermal toxicity is therefore unlikely to occur.

Acute toxicity inhalation:

For MW ≥ 40 kDa there is a low likelihood that an inhaled protein would cross into the systemic circulation to potentially cause pharmacological effects.

 

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

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

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

GLP compliance:

not specified

Remarks:

Literature data, GLP not stated

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male

Route of administration:

oral: gavage

Vehicle:

not specified

Doses:

silkworm powder from 3 races at dose of 1,000, 1,500 and 2,000 mg/kg b.w.

No. of animals per sex per dose:

10 groups, 6 rats per group

Control animals:

yes

Key result

Sex:

male

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

none

Interpretation of results:

GHS criteria not met

Conclusions:

The LD50 was reported as > 2000 mg/kg bw.

Executive summary:

The LD50 was reported as > 2000 mg/kg bw.

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 420 (Acute Oral Toxicity - Fixed Dose Method)

Deviations:

not specified

GLP compliance:

not specified

Remarks:

not reported, publication

Test type:

fixed dose procedure

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Route of administration:

oral: gavage

Vehicle:

not specified

Doses:

16 g/kg

No. of animals per sex per dose:

10

Control animals:

not specified

Key result

Sex:

male

Dose descriptor:

LD50

Effect level:

> 16 000 mg/kg bw

Based on:

test mat.

Mortality:

none

Clinical signs:

lethargy (hypoactivity)

Interpretation of results:

GHS criteria not met

Conclusions:

Citation from CIR-Report: "Ten male Sprague-Dawley rats were dosed orally (16 g/kg) with silk.42 The form of silk administered, test concentration, vehicle, and dosing method were not stated. Dosing was followed by a 14-day observation period. None of the animals died, and, except for slight lethargy, there were no signs of toxicity during the observation period. The oral LD50 was > 16 g/kg, and silk was considered nontoxic in this study."

Reference 3

Endpoint:

acute toxicity: oral

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

Acute oral toxicity:

Proteins are large complex macromolecules, consisting of amino acid structural units linked together by peptide bonds. A total of 20 different amino acids exist in proteins and hundreds to thousands of these amino acids are attached to each other in long chains to form a protein.

The amino acids in the spider silk protein are found in foods, and the daily exposure from food use would result in a much larger systemic dose than that resulting from use of spider silk proteins.

Therefore, additional testing (in experimental animals) would provide no additional toxicological knowledge about the safe use of the substance.

Furthermore, acute oral toxicity studies with silk protein from the silk worm, Bombyx mori in rats and mice showed no signs of toxicity during the observation period. The LD50 values ranged from > 2 to > 16 g/kg body weight. The silk substances were found to be practically non-toxic.

In conclusion, from the available data combined with the knowledge of the fate of proteins in the gastrointestinal system, it can be concluded that absorption of proteins in toxicological significant amounts through the gastrointestinal tract is unlikely. Proteins, in general, are a natural and necessary part of human and animal diets, and are subjected to rapid degradation by digestive enzymes in the gastrointestinal tract into individual amino acids and small peptides that can be absorbed by the body to support nutritional needs. Large proteins are not known to be absorbed by the intestinal epithelium.

Therefore, testing for acute oral toxicity is not considered to provide additional (see attached justification).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

> 2 000 - <= 16 000 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

The MW of recombinant eADF4(C48-CS25C) protein is 142.8 kDa and therefore the likelihood that the substance is capable of crossing biological membranes like the alveoli epithelial cell layer, interstium and the capillary endothelial cell layer very low.
Therefore. there is a low likelihood that an inhaled protein would cross into the systemic circulation to potentially cause pharmacological effects.

In addition,inhalation exposure during manufacturing is unlikely to occur (see attached justification).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Physical form:

inhalation: dust

Acute toxicity: via dermal route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the physicochemical and toxicological properties suggest no potential for a significant rate of absorption through the skin

Justification for type of information:

The recombinant spider silk protein eADF4(C48-CS25C) has a molecular weight of 142.8 kDa and therefore dermal absorption can be excluded. Dermal toxicity is unlikely to (see attached justification).

Reference 2

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2011

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

not specified

GLP compliance:

not specified

Test type:

other: patch test with silk protein film

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Type of coverage:

occlusive

Vehicle:

physiological saline

Duration of exposure:

24 hours

Doses:

patch test with films of silk proteins

No. of animals per sex per dose:

6

Control animals:

yes, concurrent vehicle

Mortality:

no

Interpretation of results:

GHS criteria not met

Conclusions:

Silk proteins did not cause acute dermal toxicity in rats.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Justification for classification or non-classification

Based on the absent acute oral toxicity , the low likelihood of absorption through the skin due to the physico-chemical properties of the protein and the low exposure by inhalation , the substance is not to be classified.