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Toxicological information

Acute Toxicity: oral

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Administrative data

Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
From August 29, 2017 to September 06, 2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-Regulatory Method. The test uses cultured human dermal fibroblasts in animal product-free culture, Neutral Red Uptake (NRU) method and a prediction model, based on the GHS classification system for acute toxicity

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: OECD Guideline 129: Guidance document on using cytotoxicity tests to estimate starting doses for acute oral systemic toxicity tests
Deviations:
not specified
Principles of method if other than guideline:
The Neutral Red Uptake (NRU) assay is used to determine cell viability as an indicator of acute toxicity. Neutral Red (a weak cationic dye), penetrates cellular membranes, entering cells via non-ionic diffusion and accumulates intracellularly in lysosomes. Viable cells take up and retain the Neutral Red (NR) dye, while damaged or dead cells do not, therefore, the Neutral Red Uptake (NRU) assay can be employed as a direct measure of cell viability, using membrane integrity as the measured endpoint. Incorporated NR is released from the cells using a solubilisation solution. The absorbance of the NR is quantified using a spectrophotometer.
GLP compliance:
yes (incl. certificate)
Test type:
other: Neutral Red Uptake (NRU) Cytotoxicity Test Using Human Dermal Fibroblasts in Xeno-Free Culture Conditions
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: Paste

Test animals

Species:
other: Cultured human dermal fibroblasts in animal product-free culture
Strain:
other: Not Applicable
Sex:
not specified
Details on test animals and environmental conditions:
Neonatal human dermal fibroblast cultures - “Xeno-Free” (HDFn-XF) were obtained commercially as cryopreserved primary cells (Lifeline Cell Technology, Carlsbad, USA). They were originally derived from donor tissue with informed consent for the tissue to be used for research purposes, in adherence with the Human Tissue Act (UK) 2004. Xeno-free culture medium and sub-culture reagents (Lifeline Cell Technology, Carlsbad, USA) were free of animal-derived components, providing a fully human cell culture system. Test system was extensively QC tested, by the manufacturer, for a range of parameters including viability upon thawing from cryopreservation, proliferation rate, morphology and sterility (absence of bacteria, fungal growth and mycoplasma). They were also demonstrated to be negative for HIV-1, HIV-2, HBV and HCV.

Administration / exposure

Route of administration:
other: Refer "Details on oral exposure"
Vehicle:
other: Serum-Free culture medium
Details on oral exposure:
1) Method of administration of test substance
A single application of 8 concentrations of the test substance (n=6) was applied in cell culture medium (dilution factor of 5 for the range finding experiment, 1.5 for the main experiments). The top concentration was previously determined by solubility testing.
Range finding experiment (µg/mL): 200000, 40000, 8000, 1600, 320, 64, 12.8, 2.56
Main experiments (µg/mL): 300, 200, 133.3, 88.9, 59.3, 39.5, 26.3, 17.6

2) Method of administration of reference substances:
a) Positive control: Sodium dodecyl sulphate (SDS) (Lot number: SLBL1461V, Expiry date: June 2020).
Concentration tested: 100, 83.3, 69.4, 57.9, 48.2, 40.2, 33.5, 27.9 μg/mL in cell culture medium (n = 6, dilution factor of 1.2)
b) Negative control: Fibrolife serum-free culture medium (Lot number: 05685, Expiry date: 30 Sep 17 for ME1, ME2, ME3, Sep 18 for RFE)
A single application of culture medium was applied as the negative control (n=12).

3) Exposure times of test substances and reference substances:
The cells were incubated with the test or reference substance for 24 ± 1h, at 37°C / 5% CO2, 95% RH (Relative Humidity) followed by NRU measurements
Doses:
Range finding experiment (RFE): 200000, 40000, 8000, 1600, 320, 64, 12.8, 2.56 µg/mL (dilution factor 5)
Main experiment (ME): 300, 200, 133.3, 88.9, 59.3, 39.5, 26.3, 17.6 µg/mL (dilution factor 1.5)
As per OECD guidance document 129, an initial range finding experiment (RFE) was performed with a range of concentrations based on the outcome of the solubility test (dilution factor of 5 was used) to determine a top concentration for three main experiments (ME) allowing the determination of a more accurate IC50.
No. of animals per sex per dose:
6 replicates for test substance and positive control
12 replicates for negative control
Control animals:
other: culture medium
Details on study design:
Overview

Preliminary testing: Determination of the top concentration by solubility testing

Range finding experiment (RFE): To determine a top concentration for the main experiment.

Main experiment (ME) x 3:
Day 1: Seeding cells (1 x 96-well plates for RFE; 3 x 96-well plate for ME).
Day 2: 24 h after seeding, apply test and reference substances for 24 ± 1h
Day 3: Evaluate the Neutral Red Uptake
Statistics:
Data Analysis for this study were performed following XCellR8 SOP L0064: “Neutral Red Uptake (NRU) Cytotoxicity Test Using Human Dermal Fibroblasts in Xeno-Free Culture Conditions”, using XCellR8 Form F0058: Acute Toxicity Analysis Spreadsheet v01, for processing. This is a Microsoft Excel workbook (created during the project funded by Innovate UK (project number 131726) and validated in-house in August 2017, containing formulae to process the raw data as per SOP L0064. The final data output is a percentage viability value for cells exposed to the test substance relative to the negative control and the IC50 value.

Results and discussion

Preliminary study:
As per OECD guidance document 129, an initial range finding experiment (RFE) was performed with a range of concentrations based on the outcome of the solubility test (dilution factor of 5 was used) to determine a top concentration for three main experiments (ME) allowing the determination of a more accurate IC50 (i.e. the concentration at which a decrease in cell viability of 50% was observed). Based on solubility data, top concentration used in the RFE was 200 mg/mL (200,000 µg/mL).
Effect levelsopen allclose all
Key result
Dose descriptor:
other: IC50
Remarks:
the time taken to reduce cell viability to 50% of the negative control
Effect level:
ca. 25.3 - ca. 40.5 other: µg/mL
Based on:
test mat.
Remarks on result:
other: Equivalent predicted LD50: 300-2000 mg/kg bw
Remarks:
Potential EU CLP classification: Category 4
Key result
Dose descriptor:
other: IC50
Remarks:
the time taken to reduce cell viability to 50% of the negative control
Effect level:
ca. 12.903 - ca. 20.655 other: µg/mL
Based on:
act. ingr.
Remarks on result:
other: Equivalent predicted LD50: 300-2000 mg/kg bw
Remarks:
Potential EU CLP classification: Category 4
Other findings:
The IC50 value obtained in all experiments were between 10-1000 µg/mL, therefore, the test substance was classified as GHS Category 4 “Harmful if swallowed”, suggesting a low acute toxicity potential.

Any other information on results incl. tables

Results

Solubility Results

 

The solubility was first determined following OECD guidance document 129 to determine the top concentration for the RFE:

Tier 1: 200mg/mL in cell culture medium - SOLUBLE

Therefore the top concentration used in the range finding experiment (RFE) described here after was 200 mg/mL (200,000 µg/mL).

 

Range Finding Experiment

An initial Range Finding Experiment (RFE) was performed where a top concentration of 200,000 µg/mL (200 mg/mL) of the test substance was used, as described above. The dilution factor was 5. A positive control plate was run in parallel, to validate the assay with a top concentration of 100 µg/mL and a dilution factor of 1.2.

 

 

Positive Control-RFE

 

PC-RFE

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

100.0

83.3

69.4

57.9

48.2

40.2

33.5

27.9

0.0

% of Negative Control

102.5%

-0.9%

-0.6%

10.4%

51.6%

60.4%

81.5%

97.9%

108.3%

97.5%

SD

6.9%

0.9%

0.9%

3.5%

7.2%

10.1%

5.0%

4.8%

5.1%

2.1%

% CV

6.73%

-100.78%

-145.76%

33.83%

14.01%

16.65%

6.12%

4.94%

4.75%

2.15%

Table 1: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8.

 

The calculated IC50was 58.3 µg/mL was within the range of the historical data obtained during the project funded by Innovate UK (project number 131726) in which the assay was set up (range 26.5-70.9 µg/mL).

 

Test substance-RFE

 

TA2-RFE

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

200000

40000

8000

1600

320

64

12.8

2.6

0.0

% of Negative Control

13.5%

-1.2%

5.2%

9.9%

-0.1%

19.1%

0.2%

156.8%

173.3%

186.5%

SD

28.7%

1.1%

6.7%

11.2%

8.0%

15.5%

2.6%

5.8%

9.9%

6.9%

% CV

212.42%

-95.93%

130.51%

113.13%

-7054.08%

81.09%

1150.65%

3.71%

5.69%

3.71%

Table 2: Cell viability measurements 24 h ± 1 h after application of the test substance. NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. *SD value above 15%, a maximum of 2 outliers were removed for the final calculation. It should be noted that the percentage of viability value of the negative control one (NC1) was below 50%, possibly due to volatility of the test substance. Therefore, the NC1 value was excluded from calculation. Final results are presented in Table 3.

 

TA2-RFE

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

200000

40000

8000

1600

320

64

12.8

2.6

0.0

% of Negative Control

-0.6%

2.8%

5.3%

-0.1%

10.3%

0.1%

84.1%

92.9%

100.0%

SD

0.6%

3.6%

6.0%

4.3%

8.3%

1.4%

3.1%

5.3%

3.7%

% CV

-95.93%

130.51%

113.13%

-7054.08%

81.09%

1150.65%

3.71%

5.69%

3.71%

Table 3: Cell viability measurements 24 h ± 1 h after application of the test substance. NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. Final results are presented here.

 

The calculated IC50 was 33.6 µg/mL.

 

Main Experiments

Three Main Experiments were performed, with a top test substance concentration of 300 µg/mL and a dilution factor of 1.5. A positive control plate was run in parallel, to validate the assay with a top concentration of 100 µg/mL and a dilution factor of 1.2.

 

Positive Control-ME1

 

PC-ME1

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

100.0

83.3

69.4

57.9

48.2

40.2

33.5

27.9

0.0

% of Negative Control

86.5%

5.4%

1.9%

9.0%

25.6%

23.9%

54.8%

83.8%

113.2%

113.5%

SD

22.2%

7.3%

8.3%

4.8%

6.9%

4.8%

13.0%

12.7%

16.0%

25.0%

% CV

25.63%

134.65%

429.11%

53.26%

27.09%

20.02%

23.81%

15.13%

14.11%

22.01%

Table 4: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8: * For SD value above 15%, a maximum of 2 outliers were removed for the final calculation. Final results are presented in Table 5.

 

PC-ME1

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

100.0

83.3

69.4

57.9

48.2

40.2

33.5

27.9

0.0

% of Negative Control

99.7%

5.5%

2.0%

9.2%

26.0%

24.3%

55.6%

85.0%

121.2%

100.3%

SD

16.4%

7.4%

8.4%

4.9%

7.0%

4.9%

13.2%

12.9%

5.6%

12.7%

% CV

16.41%

134.65%

429.11%

53.26%

27.09%

20.02%

23.81%

15.13%

4.60%

12.62%

Table 5: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. A maximum of 2 outliers were removed from calculation was removed for IC50calculation. Final results are presented here. Note that SD value for the NC1 was still above 15%. However, this is not considered to impact the IC50 calculation because calculated value was within historical range.

 

The calculated IC50was 45.4 µg/mL was within the range of the historical data obtained during theproject funded by Innovate UK (project number 131726) in which the assay was set up (range 26.5-70.9 µg/mL).

 

Test substance-ME1

 

TA2-ME1

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

300.0

200.0

133.3

88.9

59.3

39.5

26.3

17.6

0.0

% of Negative Control

102.2%

13.9%

13.1%

14.3%

24.2%

42.2%

50.4%

61.1%

73.6%

97.8%

SD

5.3%

3.5%

11.0%

7.9%

5.0%

8.4%

11.5%

10.9%

9.7%

12.1%

% CV

5.16%

25.07%

83.67%

55.09%

20.47%

19.95%

22.75%

17.78%

13.16%

12.42%

Table 6: Cell viability measurements 24 h ± 1 h after application of the test substance. NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8.

 

The calculated IC50was 40.5 µg/mL.

 

Positive Control-ME2

 

PC-ME2

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

100.0

83.3

69.4

57.9

48.2

40.2

33.5

27.9

0.0

% of Negative Control

84.2%

1.5%

3.5%

2.3%

14.9%

23.3%

44.6%

72.4%

115.8%

115.8%

SD

29.5%

3.0%

5.8%

1.4%

6.9%

6.9%

4.6%

7.0%

5.8%

15.9%

% CV

34.99%

204.55%

163.63%

62.45%

46.50%

29.74%

10.26%

9.74%

5.02%

13.77%

Table 7: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. * For SD value above 15%, a maximum of 2 outliers were removed for the final calculation. Final results are presented in Table 8.

 

PC-ME2

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

100.0

83.3

69.4

57.9

48.2

40.2

33.5

27.9

0.0

% of Negative Control

89.8%

1.4%

3.2%

2.1%

13.6%

21.4%

40.8%

66.2%

105.9%

110.2%

SD

23.7%

2.8%

5.3%

1.3%

6.3%

6.4%

4.2%

6.4%

5.3%

11.3%

% CV

26.42%

204.55%

163.63%

62.45%

46.50%

29.74%

10.26%

9.74%

5.02%

10.25%

Table 8: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. A maximum of 2 outliers were removed from calculation was removed for IC50calculation. Final results are presented here. Note that SD value for the NC1 was still above 15%. However, this doesn’t impact on the IC50calculation.

 

The calculated IC50was 37.8 µg/mL was within the range of the historical data obtained during the project funded by Innovate UK (project number 131726) in which the assay was set up (range 26.5-70.9 µg/mL).

 

Test substance-ME2

 

TA2-ME2

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

300.0

200.0

133.3

88.9

59.3

39.5

26.3

17.6

0.0

% of Negative Control

96.8%

7.8%

3.9%

6.0%

17.2%

29.3%

36.1%

48.0%

65.1%

103.2%

SD

9.2%

9.1%

8.9%

2.4%

4.4%

5.4%

8.9%

10.4%

6.8%

9.6%

% CV

9.46%

117.33%

230.55%

39.94%

25.71%

18.35%

24.63%

21.74%

10.38%

9.34%

Table 9: Cell viability measurements 24 h ± 1 h after application of the test substance. NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8.

 

The calculated IC50was 25.3 µg/mL.

 

Positive Control-ME3

 

PC-ME3

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

100.0

83.3

69.4

57.9

48.2

40.2

33.5

27.9

0.0

% of Negative Control

102.0%

-3.5%

-3.5%

12.6%

18.8%

35.8%

58.2%

85.9%

117.2%

98.0%

SD

9.2%

9.5%

12.8%

11.9%

6.7%

8.6%

5.6%

6.5%

5.0%

5.2%

% CV

9.01%

-273.90%

-369.22%

94.87%

35.65%

23.95%

9.64%

7.53%

4.26%

5.28%

Table 10: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8.

 

The calculated IC50was 43.1 µg/mL was within the range of the historical data obtained during the project funded by Innovate UK (project number 131726) in which the assay was set up (range 26.5-70.9 µg/mL).

 

Test substance-ME3

 

TA2-ME3

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

300.0

200.0

133.3

88.9

59.3

39.5

26.3

17.6

0.0

% of Negative Control

105.3%

16.0%

11.4%

16.0%

12.1%

17.2%

47.3%

59.8%

68.7%

94.7%

SD

7.8%

10.0%

7.9%

5.6%

4.5%

8.3%

14.5%

18.0%

13.7%

4.7%

% CV

7.44%

62.58%

69.74%

34.77%

37.38%

48.23%

30.72%

30.11%

19.88%

4.94%

Table 11: Cell viability measurements 24 h ± 1 h after application of the test substance. NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. For SD value above 15%, a maximum of 2 outliers were removed for the final calculation. Final results are presented in Table 12.

 

TA2-ME3

NC1

C1

C2

C3

C4

C5

C6

C7

C8

NC2

Concentration (µg/mL)

0.0

300.0

200.0

133.3

88.9

59.3

39.5

26.3

17.6

0.0

% of Negative Control

105.3%

16.0%

11.4%

16.0%

12.1%

17.2%

47.3%

49.6%

68.7%

94.7%

SD

7.8%

10.0%

7.9%

5.6%

4.5%

8.3%

14.5%

10.6%

13.7%

4.7%

% CV

7.44%

62.58%

69.74%

34.77%

37.38%

48.23%

30.72%

21.44%

19.88%

4.94%

Table 12: Cell viability measurements 24 h ± 1 h after application of positive control (SDS). NC1 and 2: negative control (untreated cells), C1 to C8: Concentration 1 to 8. A maximum of 2 outliers were removed from calculation was removed for IC50calculation. Final results are presented here.

 

The calculated IC50was 26.1 µg/mL.

Assay acceptance criteria

 

Results were checked against the following acceptance criteria:

 

1) Each run includes a Positive Control (SDS) plate with a defined series of concentrations to determine the IC50. In order for the run to be valid, the IC5 0for SDS must be within the mean ± 1.5 SD of the historical set of runs with this substance (48.7 µg/mL ± (1.5x14.8)) - For the RFE, and the 3 ME, the IC50 values obtained with the PC were in the range of the historical data obtained during the project funded by Innovate UK (project number 131726) in which the assay was set up.

 

2) SD (Standard Deviation) of the 6 values for each condition should be ≤15% (when viability percentage is above 30%) - In some cases, a maximum of 2 outliers was removed to achieve SD ≤15%.

Applicant's summary and conclusion

Interpretation of results:
study cannot be used for classification
Conclusions:
Under the study conditions, the test substance predicted LD50 was considered to be 300 to 2000 mg/kg bw (Based on in vitro experimental IC50: 12.90 to 20.66 µg/mL).
Executive summary:

An in vitro study was conducted to determine the acute toxicity potential of test substance, 'Cocodimonium hydroxypropyl hydrolysed silk (active: 51%)', using cytotoxicity based on Neutral Red Uptake Method, according to OECD Guideline 129, in compliance with GLP. The study was assessed in vitro using XCellR8’s internally validated Human Cell-Based Screen (Non-Regulatory Method). The test uses cultured human dermal fibroblasts in animal product free culture, Neutral Red Uptake (NRU) method and a prediction model, based on the GHS classification system for acute toxicity. After a 24 h ± 1 h exposure of 8 concentrations (300, 200, 133.3, 88.9, 59.3, 39.5, 26.3, 17.6 µg/mL) of test substance in cell culture medium of Human Dermal Fibroblasts neonatal (HDFn), cytotoxicity was evaluated. Using a prediction model, determined previously, the IC50 value was converted to a corresponding GHS classification for oral acute toxicity. The percentage of viability for each concentration was calculated and normalised to viability results of the negative control (untreated cells) arbitrarily set to 100%. The IC50 (i.e. the concentration at which a decrease in cell viability of 50% was observed) was calculated as being 33.6 µg/mL (17.14 µg a.i./mL) in the Range Finding Experiment (RFE); 40.5 µg/mL (20.66 µg a.i./mL) in the main experiment 1 (ME1); 25.3 µg/mL (12.90 µg a.i./mL) in ME2 and 26.1 µg/mL (13.31 µg a.i./mL) in ME3. Based on the study results (IC50: 12.90 to 20.66 µg/mL), the study author concluded, the test substance could fall in potential EU CLP category 4 (LD50: 300 to 2000 mg/kg bw) (XCellR8, 2017). However, it is known that the in vitro NRU cytotoxicity assay has a high false positive rate and, therefore, positive results cannot be readily used in a meaningful way in characterising the acutely toxic substances.