1,6-Naphthyridine-3-carboxylic acid, 4-(4-cyano-2-methoxyphenyl)-5-ethoxy-1,4-dihydro-2,8-dimethyl-, 2-cyanoethyl ester

Endpoint summary

Description of key information

Skin irritation/corrosion

A study was performed for the assessment of the skin irritancy of the test item with reconstructed human epidermis (RhE). The experiment was carried out using the commercially available test method epiCS®. The study was conducted in accordance with OECD TG 439 and EU Test Method B.46. The mean value of cell viability was recorded to be 101 % (rounded). The test item was thus shown to be not irritating to reconstructed human skin in vitro.

Eye irritation

The test item (20 % (w/v) in physiologic saline) was tested in the BCOP test according to OECD TG 437. For determination of corneal damage opacity as well as tissue permeability was measured after a 4 hour exposure time. Based on these data, in comparison to the vehicle control, the In Vitro Irritancy Score (IVIS) value was calculated to be 11.7 which is below the IVIS cut-off threshold of 55 and thus identifying the test item as not inducing serious eye damage. The results of the positive (20 % imidazole solution) and vehicle (physiologic saline solution) controls confirmed the validity of the test.

An in vitro study for assessing ocular irritation properties of the solid test item was performed using the reconstructed human cornea-like epithelium (RhCE) cell model EpiOcularTM. The model used is standardized and commercially available. The EpiOcularTM Eye Irritation Test (EIT) was conducted in accordance with OECD 492. The solid test item was applied topically to the RhCE tissue surface in duplicate for 6 hours, followed by an 18 hour post-treatment incubation period. Cell viability was measured in a spectrophotometer by assessing the extent of MTT (methylthiazole tetrazolium) reduction. The optical density value obtained for the test item was used to calculate the percentage of viability relative to the negative control, which was set at 100 %. The results of the concurrent negative control (NC, deionized water) and positive control (PC, neat methyl acetate) demonstrated the viability (NC) and sensitivity (PC) of the tissue model.

The final mean percent tissue viability recorded for the test item is 140 % (rounded).

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: not applicable

Source strain:

other: not applicable

Justification for test system used:

commercially available test method

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: epiCS® (CellSystems, Troisdorf, Germany).


TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: RT (room temperature)
- Temperature of post-treatment incubation (if applicable): Incubator temperature: 37 ± 2° C (CO2 gas concentration: 5 %; Humidity: maximum)

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1mg/ml
- Incubation time: 3 hours
- Spectrophotometer: EL808, Bio-Tek
- Wavelength: 570 nm

NUMBER OF TESTING RUNS / EXPERIMENTS TO DERIVE FINAL PREDICTION: the optical density of the isopropanol-extracts of 3 insert was determined by duplicate per insert = 6 OD values.

PREDICTION MODEL / DECISION CRITERIA:

- The mean optical density (OD) values obtained with the test item were used to calculate the percentage of viability relative to the negative control, which is set at 100 %.
- according to UN GHS (Category 2 or Category 1) if the mean percent tissue viability after exposure and post treatment incubation is less than or equal (≤ ) to 50 %.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 30 mg (plus 30 µl 0.9% NaCl to moisten and ensure good contact with the epidermis surface)

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µl
- Concentration (if solution): 0.9% NaCl in water

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µl
- Concentration (if solution): 5% SDS in physiological saline

Duration of treatment / exposure:

20 minutes

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

three

Irritation / corrosion parameter:

% tissue viability

Value:

ca. 101

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- DEMONSTRATION OF TECHNICAL PROFICIENCY:

Reliability of the test was previously confirmed by interlaboratory validation

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: Yes
- Acceptance criteria met for positive control: Yes
- Acceptance criteria met for variability between replicate measurements: Yes

Table 1: Tabular Summary of the results

Sample No.	Test item	OD mean*	StdDev	% Viability
1-3	Negative Control NaCl 0.9 %	1.95	0.05	100.00
4-6	Positive control SDS 5 %	0.04	0.03	2.01
10 -12	Cyano-Naphthyridin	1.98	0.05	101.39

* 6 values

Interpretation of results:

other: negative

Executive summary:

A study was performed for the assessment of the skin irritancy of the test item with reconstructed human epidermis (RhE). The experiment was carried out using the commercially available test method epiCS®. The study was conducted in accordance with OECD TG 439 and EU Test Method B.46. The mean value of cell viability was recorded to be 101 % (rounded). The test item was thus shown to be not irritating to reconstructed human skin in vitro.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

October 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Solubility and stability of the test substance in the solvent/vehicle: Analytical determination of stability and homogeneity of the test item in the vehicle was not performed specifically for this study.
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: The usage of physiologic saline solution for formulation of the test item is plausible based on the current knowledge of the sponsor. No objections were seen particularly in regard to stability.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test item was suspended with a glass rod shortly prior to application in isotonic saline solution.
- Final preparation of a solid: 20% (w/v)

FORM AS APPLIED IN THE TEST (if different from that of starting material): The preparation was visually described as suspension.

Details on test animals or tissues and environmental conditions:

Bovine eyes of slaughtered cattle were extracted and transferred in containers with Hank’s salt solution (HSS) with 1% penicillin/streptomycin solution. For transportation the containers were ice cooled.
Eyes with defects were sorted out and disposed of, eyes without any defects were transferred into fresh HSS supplemented with 1% penicillin/streptomycin solution and 1 % fetal bovine serum (FBS) and stored overnight at 2-8 °C. On the next day (day of testing) the containers with the eyes were placed in an incubator at 32 ° C (± 1 ° C) for about 2 hours before preparation of the corneas.

Vehicle:

physiological saline

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 750 μL per cornea and chamber
- Concentration (if formulation): 20 % (w/v)

VEHICLE
- Amount(s) applied (volume or weight with unit): 750 μL per cornea and chamber
- Concentration (if solution): 0.9% NaCl (w/v)

Duration of treatment / exposure:

4 hours

Duration of post- treatment incubation (in vitro):

no further incubation required

Number of animals or in vitro replicates:

3 corneas

Details on study design:

Immediately before application, the medium was aspirated from the anterior chamber. 750 μL of the test material formulations were applied to the corneas, each through the holes of the anterior chamber. The holes of both chambers were sealed with adhesive tape and the holders were kept with the front side up, so that the formulations covered the cornea sufficiently (closed chamber method). The holders were transferred into the incubator at 32 °C (± 1 °C) for the exposure time of 4 hours. After the exposure, the formulations were aspirated from the anterior chamber and the corneas were rinsed at least 3 times with phenol red containing MEM to show effectiveness of test substance removal. During the final rinse cycle the corneas were rinsed again with pure MEM medium in order to remove residues of the dye. The anterior chamber was then filled again with MEM medium to avoid drying out of the cornea. Before measuring opacity, fresh MEM medium was filled in the chambers.



TREATMENT METHOD: closed chamber

POST-INCUBATION PERIOD: no

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity: The opacity of a cornea was measured by the diminution of light passing through the cornea. The measurements of opacity were carried out using an opacitometer BASF OP3.0 (with integrated light meter testo 545 and Comfort 3.4 SP6 software from Testo AG, Lenzkirch). Before each measurement the opacitometer was adjusted to about 1000 LUX and a filter calibration measurement was carried out by using 3 different filters.
- Corneal permeability:The medium in anterior chamber of each holder was replaced by 1ml of fluorescein sodium solution (concentration 5 mg/mL). Afterwards the holders were incubated at 32 °C (± 1 °C) for about 90 minutes. After the incubation period, the medium of the posterior chamber was aspirated by a syringe and filled into a 10 mL tube. Three wells of a 96 well plate were filled with 300 μL of each tube (triplicate determination). In addition, a standard series of 5 mg/mL sodium fluoresceinsolution was prepared and also filled into the 96-well plate, in triplicates.
The permeability was determined by measuring the amount of fluorescein sodium which diffused through all cell layers of the cornea. The measurement was carried out at a wavelength of 490 nm (OD490) by an ELISA - Reader (Bio-Tek EL 808, Software Gen5).

SCORING SYSTEM: In Vitro Irritancy Score (IVIS)

DECISION CRITERIA:decision criteria as indicated in the OECD TG 437

Irritation parameter:

in vitro irritation score

Run / experiment:

mean

Value:

11.7

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Table 1: Individual values of opacity, permeability and IVIS

Cornea No.	Opacity per cornea	Permeability per cornea	IVIS per cornea	IVIS per group
				mean		SD
Negative control                   1	-2.7	0.007	-2.6
0.9 % NaCl                          2	2.5	0.004	2.6	0.7		2.9
3	2.2	0.005	2.2
Positive Control                     4	87.2	0.900	100.8
20 % Imidazole                      5	80.5	0.847	93.2	94.2		6.1
6	72.8	1.053	88.6
Test item                                7	6.5	0.005	6.6
20% Cyano-Naphthyridin       8	17.5	0.004	17.5	11.7		5.5
9	11.1	0.001	11.1

 

Interpretation of results:

other: negative

Executive summary:

The test item (20 % (w/v) in physiologic saline) was tested in the BCOP test according to OECD TG 437. For determination of corneal damage opacity as well as tissue permeability was measured after a 4 hour exposure time. Based on these data, in comparison to the vehicle control, the In Vitro Irritancy Score (IVIS) value was calculated to be 11.7 which is below the IVIS cut-off threshold of 55 and thus identifying the test item as not inducing serious eye damage. The results of the positive (20 % imidazole solution) and negative (physiologic saline solution) controls confirmed the validity of the test system.

Reference 2

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

November 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Version / remarks:

July 2015

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

other: reconstucted human cornea-like epithelium (RhCE)

Strain:

other: not applicable

Details on test animals or tissues and environmental conditions:

- Justification of the test method and considerations regarding applicability
The EpiOcular™ eye irritation test (EIT) follows international OECD test guidelines. The EIT measures the ocular irritation potential of a test item by determination of cytotoxic effects on a reconstructed human cornea epithelium (RhCE) tissue model to discriminate chemicals not requiring classification for eye irritancy (UN GHS No Category) from those requiring classification. The EpiOcular™ EIT is not intended to differentiate between UN GHS Category 1 (serious eye damage) and UN GHS Category 2 (eye irritation).
- Description of the cell system used, incl. certificate of authenticity and the mycoplasma status of the cell line
The EpiOcular™ RhCE tissue construct consists of 3 viable layers of cells and a non-keratinized surface as recommended by the test guidelines. The model is standardized and commercially available. The cell viability and barrier function as well as sterility of each batch of the RhCE tissue construct used is adequate, as has been demonstrated by the supplier (MatTek Corporation, Slovakia).

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 50 mg per tissue insert in duplicate
- Concentration (if solution): neat test item
POSITIVE CONTROL
- Amount(s) applied (volume or weight with unit): 50 μL methyl acetate per tissue insert in duplicate
- Concentration (if solution): neat
- Lot/batch no. (if required): 091916MHB
- Purity: 99.0 %

Duration of treatment / exposure:

6 hours under cell culture conditions (at 37°± 2°C, 5% CO2 and maximal humidity in an incubator) followed by a post-soak immersion period of about 25 min

Duration of post- treatment incubation (in vitro):

18 hours under cell culture conditions

Number of animals or in vitro replicates:

tissue inserts were used in duplicate for test item, negative and positive control

Details on study design:

RhCE tissue construct used, including batch number: EpiOcular RhCE tissue supplied by MatTek
Corporation, Lot-No. 23746
- Pre-check for potential optical interferences of the test item
Optical properties of the test item or its chemical action on MTT may interfere with the measurement of MTT formazan leading to a false estimate of tissue viability.
The test item was therefore tested in advance for a potential direct influence on the test results not related to cytotoxic effects on tissue cells. For this pre-check the following parameters were tested:
1. Assessment of potential direct MTT-reduction of the test item
In case of a direct MTT-reduction of the test item a killed tissue control (inserts, which were killed by freezing) was used in the main assay
2. Assessment of potential interference of colored or staining test items, which become colored after application to the tissues, with OD read out
2.1. Assessment of the color reaction with water
2.2. Assessment of the color reaction with isopropanol
In case of an influence of test item color on OD measurement, a color control was used in the main assay.
The evaluation criteria for the pre-check were:
- For MTT reduction (visual assessment): If the MTT solution color turns blue/purple, the test item is presumed to have reduced the MTT. A killed control must be conducted.
- For color reaction (measurement of the OD): If, after subtraction of the OD for water or isopropanol the OD of the test item solution is >0.08 a Color Control must be conducted.

Procedure for killed control or color control
Killed control and color control not required.

- Description of the method used to quantify MTT formazan
For viability testing the inserts were placed in new plates containing MTT solution (1 mg/ml in Maintenance medium at 37°C, or Assay medium for the color control inserts). The tissues were incubated for 180 ± 10 min. under cell culture conditions. The extraction of blue formazan was performed in isopropanol on a vertical shaker for 2-3 hours at room temperature or overnight in the dark at 2-8°C. The concentration of formazan was measured by determination of the OD of the isopropanol-extracts in duplicate at 570 nm in an automatic reader of a spectrophotometer (EL808, Bio-Tek; 96 well format, 200 μl). Data acquisition and evaluation were performed with the software "Gen5" (Bio-Tek).
- Assay acceptance criteria:
The following acceptance criteria determine the validity of an assay:
- mean OD 570 nm negative control (NC) is > 0.8 and < 2.5
- mean relative viability of the positive control (PC) is < 50 % (relative to negative control)
- the difference of viability between the two replicates is < 20 %.

Irritation parameter:

other: final cell viability in %

Value:

ca. 140

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

OTHER EFFECTS:
- Visible damage on test system: none
DEMONSTRATION OF TECHNICAL PROFICIENCY:
ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes
- Acceptance criteria met for positive control: yes

Interpretation of results:

other: negative

Executive summary:

An in vitro study for assessing ocular irritation properties of the solid test item was performed using the reconstructed human cornea-like epithelium (RhCE) cell model EpiOcularTM. The model used is standardized and commercially available. The EpiOcularTM Eye Irritation Test (EIT) was conducted in accordance with OECD 492. The solid test item was applied topically to the RhCE tissue surface in duplicate for 6 hours, followed by an 18 hour post-treatment incubation period. Cell viability was measured in a spectrophotometer by assessing the extent of MTT (methylthiazole tetrazolium) reduction. The optical density value obtained for the test item was used to calculate the percentage of viability relative to the negative control, which was set at 100 %. The results of the concurrent negative control (NC, deionized water) and positive control (PC, neat methyl acetate) demonstrated the viability (NC) and sensitivity (PC) of the tissue model.

The final mean percent tissue viability recorded for the test item is 140 % (rounded).

According to the results of this study the test item was identified as not requiring classification for eye irritation according to UN GHS (No Category).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Due to the results of the described studies no classification is required according to Regulation (EC) 1272/2008/EC (CLP), Annex I.