[(9-oxo-9H-thioxanthen-2-yl)oxy]acetic acid

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

22 Oct 2018 to 23 Oct 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Version / remarks:

adopted October 09, 2017

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

[(9-oxo-9H-thioxanthen-2-yl)oxy]acetic acid

EC Number:

282-803-8

EC Name:

[(9-oxo-9H-thioxanthen-2-yl)oxy]acetic acid

Cas Number:

84434-05-9

Molecular formula:

C15H10O4S

IUPAC Name:

2-[(9-oxo-9H-thioxanthen-2-yl)oxy]acetic acid

Test material form:

solid

Specific details on test material used for the study:

Appearance: Yellow powder
Purity/Composition: 98.25%, assumed 100% for testing
Test item storage: At room temperature protected from light desiccated

Test animals / tissue source

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

Specification:
Corneas from bovine eyes were obtained from a local abattoir. The eyes were removed after slaughter, completely immersed in physiological saline in a suitably sized container and transported on the same day to the testing facility.

Assessment on Arrival:
On arrival at the test facility the eyes were carefully examined for defects including increased opacity, scratches and neovascularisation. Only corneas free from such defects were used.

Excision and Preparation of Corneas:
The isolated corneas were stored in a petri dish with cMEM (Earle’s Minimum Essential Medium (Life Technologies, Bleiswijk, The Netherlands) containing 1% (v/v) L-glutamine (Life Technologies) and 1% (v/v) Foetal Bovine Serum (Life Technologies)). The isolated corneas were mounted in a corneal holder (one cornea per holder) of BASF (Ludwigshafen, Germany) with the endothelial side against the O-ring of the posterior half of the holder. The anterior half of the holder was positioned on top of the cornea and tightened with screws. The compartments of the corneal holder were filled with cMEM of 32 ± 1°C. The corneas were incubated for the minimum of 1 hour at 32 ± 1°C.

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

- The negative control substance was physiological saline, 750 µL, supplied by Eurovet Animal Health, Bladel, The Netherlands .
- The positive control substance was 20% (w/v) Imidazole, 750 µL, supplied by Merck KGaA, Darmstadt, Germany.
- The test article was administered without a vehicle (319.8 to 342.0 mg).

Duration of treatment / exposure:

240 ± 10 minutes at 32 ± 1°C

Duration of post- treatment incubation (in vitro):

Corneas were incubated in a horizontal position for 90 ± 5 minutes at 32 ± 1°C

Number of animals or in vitro replicates:

3

Details on study design:

Cornea Selection and Opacity Reading
After the incubation period, the medium was removed from both compartments and replaced with fresh cMEM. Opacity determinations were performed on each of the corneas using an opacitometer (BASF-OP3.0, BASF, Ludwigshafen, Germany).
 
The opacity of each cornea was read against a cMEM filled chamber, and the initial opacity reading thus determined was recorded. Corneas that had an initial opacity reading higher than 7 were not used. Three corneas were selected at random for each treatment group.

Test Item Preparation:
Since no workable suspension of CMTX 2-carboxymethyloxy-thioxanthone in physiological saline could be obtained, the test item was used as delivered by the sponsor and added pure on top of the corneas. To protect the test item from light glassware was wrapped in tin-foil.

Treatment of Corneas and Opacity Measurements:
The medium from the anterior compartment was removed and 750 µl of the negative control and 20% (w/v) Imidazole solution (positive control) were introduced onto the epithelium of the cornea. CMTX 2-carboxymethyloxy-thioxanthone was weighed in a bottle and applied directly on the corneas in such a way that the cornea was completely covered (319.8 to 342.0 mg).The holder was slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the solutions over the entire cornea. Corneas were incubated in a horizontal position for 240 ± 10 minutes at 32 ± 1°C. After the incubation the solutions and the test compound were removed and the epithelium was washed at least three times with MEM with phenol red (Earle’s Minimum Essential Medium Life Technologies). Possible pH effects of the test item on the corneas were recorded. Each cornea was inspected visually for dissimilar opacity patterns. The medium in the posterior compartment was removed and both compartments were refilled with fresh cMEM and the opacity determinations were performed.

Opacity Measurement
The opacity of a cornea was measured by the diminution of light passing through the cornea. The light was measured as illuminance (I = luminous flux per area, unit: lux) by a light meter.
The opacity value (measured with the device OP-KIT) was calculated according to:
Opacity=(I_0/I-0.9894)/0.0251
With I0 the empirically determined illuminance through a cornea holder but with windows and medium, and I the measured illuminance through a holder with cornea.
The change in opacity for each individual cornea (including the negative control) was calculated by subtracting the initial opacity reading from the final post-treatment reading. The corrected opacity for each treated cornea with the test item or positive control was calculated by subtracting the average change in opacity of the negative control corneas from the change in opacity of each test item or positive control treated cornea.
The mean opacity value of each treatment group was calculated by averaging the corrected opacity values of the treated corneas for each treatment group.
Application of Sodium Fluorescein
Following the final opacity measurement, permeability of the cornea to Na-fluorescein (Sigma-Aldrich, Germany) was evaluated.
The medium of both compartments (anterior compartment first) was removed. The posterior compartment was refilled with fresh cMEM. The anterior compartment was filled with 1 mL of 5 mg Na-fluorescein/mL cMEM solution (Sigma-Aldrich Chemie GmbH, Germany).
The holders were slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the sodium-fluorescein solution over the entire cornea. Corneas were incubated in a horizontal position for 90  5 minutes at 32  1C.
Permeability Determinations
After the incubation period, the medium in the posterior compartment of each holder was removed and placed into a sampling tube labelled according to holder number. 360 l of the medium from each sampling tube was transferred to a 96-well plate. The optical density at 490 nm (OD490) of each sampling tube was measured in triplicate using a microplate reader (TECAN Infinite® M200 Pro Plate Reader). Any OD490 that was 1.500 or higher was diluted to bring the OD490 into the acceptable range (linearity up to OD490 of 1.500 was verified before the start of the experiment). OD490 values of less than 1.500 were used in the permeability calculation.
The mean OD490 for each treatment was calculated using cMEM corrected OD490 values. If a dilution has been performed, the OD490 of each reading of the positive control and the test item was corrected for the mean negative control OD490 before the dilution factor was applied to the reading.

Results and discussion

In vitro

Results

Results 1

Irritation parameter:

cornea opacity score

Remarks:

Mean value

Value:

4.9

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

Mean opacity = -0.4

Positive controls validity:

valid

Remarks:

Mean opacity = 172

Results 2

Irritation parameter:

other: Corneal permeability

Remarks:

Mean value

Value:

0.446

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

Mean permeability = 0.019

Positive controls validity:

valid

Remarks:

Mean permeability = 1.728

Results 3

Irritation parameter:

in vitro irritation score

Remarks:

Mean

Value:

12

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

Mean In vitro Irritation score = -0.1

Positive controls validity:

valid

Remarks:

Mean In vitro Irritation score = 198

Other effects / acceptance of results:

CMTX 2-carboxymethyloxy-thioxanthone was tested as it is.

Table 1 of Appendix 1 summarizes the opacity, permeability and in vitro irritancy scores of CMTX 2-carboxymethyloxy-thioxanthone and the controls. The opacity, permeability and in vitro scores of the individual corneas are shown in Appendix 2, Table 2 - 5.

The individual in vitro irritancy scores for the negative controls ranged from -0.6 to 0.6. The corneas treated with the negative control item were clear after the 240 minutes of treatment. The individual positive control in vitro irritancy scores ranged from 195 to 202 (Appendix 2, Table 5). The corneas treated with the positive control were turbid after the 240 minutes of treatment.

The corneas treated with CMTX 2-carboxymethyloxy-thioxanthone showed opacity values ranging from 2.8 to 6.5 and permeability values ranging from 0.256 to 0.795. The corneas were turbid after the 240 minutes of treatment with the test item. No pH effect of the test item was observed on the rinsing medium. Hence, the in vitro irritancy scores ranged from 7.1 to 18 after 240 minutes of treatment with CMTX 2-carboxymethyloxy-thioxanthone.

Any other information on results incl. tables

The negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas.  The mean in vitro irritancy score of the positive control (20% (w/v) Imidazole) was 198 and within two standard deviations of the current historical positive control mean (Appendix 3, Table 6).  It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

CMTX 2-carboxymethyloxy-thioxanthone induced ocular irritation through both endpoints, resulting in a mean in vitro irritancy score of 12 after 240 minutes of treatment.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

In conclusion, since CMTX 2-carboxymethyloxy-thioxanthone induced an IVIS > 3 ≤ 55, no prediction on the classification can be made.

Executive summary:

The objective of this study was to evaluate the eye hazard potential of CMTX 2-carboxymethyloxy-thioxanthone as measured by its ability to induce opacity and increase permeability in an isolated bovine cornea using the Bovine Corneal Opacity and Permeability test (BCOP test).

This report describes the potency of chemicals to induce serious eye damage using isolated bovine corneas.  The eye damage of the test item was tested through topical application for approximately 240 minutes.

The study procedures described in this report were based on the most recent OECD guideline.

The test item was a yellow powder.  Since no workable suspension in physiological saline could be obtained, the test item was used as delivered and added pure on top of the corneas.

The negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas.  The mean in vitro irritancy score of the positive control (20% (w/v) Imidazole) was 198 and within two standard deviations of the current historical positive control mean.  It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

The test item induced ocular irritation through both endpoints, resulting in a mean in vitro irritancy score of 12 after 4 hours of treatment.

In conclusion, since the test item induced an IVIS > 3 ≤ 55, no prediction on the classification can be made.