N2-Isobutyryl-5′-O-(4,4′-dimethoxytrityl)-2′-deoxyguanosine-3′-O-[O-(2-cyanoethyl)-N,N′-diisopropylphosphoramidite]

Endpoint summary

Description of key information

No data is available for the target substance Guanosine, 5′-O-[bis(4-methoxyphenyl)phenylmethyl]-2′-deoxy-N-(2-methyl-1-oxopropyl)-, 3′-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite]. Thus, data from a suitable read-across partner was used to assess the potential of the target substance to induce eye and skin irritation.

The potential of 5’-O-[bis(4-methoxyphenyl)phenylmethyl]-2’-deoxythymidine, 3’-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] (source substance) to induce skin irritation (OECD 439) and eye irritation (OECD 492) was tested in suitable in vitro test methods. In both tests, the source substance was tested as negative. Based on the results from the read-across partner, the target substance can be considered as non-irritant to the skin and eye.

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:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

mean of three tissues

Value:

94

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

For detailed results see Table 1 in box "Any other information on results incl. tables".

Results of the Pre-Experiments:

The mixture of 25 mg of the test item per 1 mL MTT medium showed no reduction of MTT compared to the solvent. The mixture did not turn blue/purple. Therefore, NSMTT was determined to be 0%.

The mixture of 25 mg of the test item per 300 µL aqua dest. or per 300 µL isopropanol showed no colouring detectable by unaided eye assessment. Therefore, NSC was determined to be 0%.

Results of the main experiment:

Table 1: Result of the Test Item 5’-O-[bis(4-methoxyphenyl)phenylmethyl]-2’-deoxythymidine, 3’-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite]

Name	Negative Control			Positive Control			Test Item
Tissue	1	2	3	1	2	3	1	2	3
Absolute OD570	1.518	1.533	1.619	0.123	0.119	0.112	1.483	1.444	1.461
	1.554	1.471	1.578	0.124	0.121	0.111	1.480	1.427	1.437
OD570(Blank Corrected)	1.475	1.489	1.576	0.080	0.075	0.068	1.439	1.400	1.418
	1.510	1.428	1.535	0.080	0.078	0.067	1.437	1.383	1.394
Mean OD570of the Duplicates (Blank Corrected)	1.493	1.459	1.555	0.080	0.076	0.068	1.438	1.392	1.406
Total Mean OD570of 3 Replicate Tissues (Blank Corrected)	1.502*			0.075			1.412
SD OD570	0.049			0.006			0.024
Relative Tissue Viability [%]	99.4	97.1	103.5	5.3	5.1	4.5	95.7	92.6	93.6
Mean Relative Tissue Viability [%]	100.0			5.0**			94.0
SD Tissue Viability [%]***	3.3			0.4			1.6
CV [% Viabilities]	3.3			8.4			1.7

* Blank-corrected mean OD_{570 nm} of the negative control corresponds to 100% absolute tissue viability.

**Mean relative tissue viability of the three positive control tissues is≤ 20%.

*** Standard deviation (SD) obtained from the three concurrently tested tissues is ≤ 18%.

Table 2:  Quality Criteria

	Value	Cut off	pass/fail
Mean Absolute OD570 nmNK	1.545	0.8 ≤ NK ≤ 2.8	pass
Relative Viability [%] PC	5.0	≤ 20%	pass
SD Viability[%]	0.4 -3.3	≤ 18%	pass

Interpretation of results:

GHS criteria not met

Conclusions:

In this study under the given conditions, 5’-O-[bis(4-methoxyphenyl)phenylmethyl]-2’-deoxythymidine, 3’-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] showed no irritant effects. The relative mean tissue viability after 60 min of exposure and 42 h post-incubation was > 50%. The test item is therefore classified as “non-irritant” in accordance with UN GHS “No Category”.

Executive summary:

In a primary dermal irritation study conducted according to OECD guideline 439, the EpiDerm™-Model (EPI-200-SIT) was topically exposed to 5’-O-[bis(4-methoxyphenyl)phenylmethyl]-2’-deoxythymidine, 3’-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] (purity 99.7%) for 60 mins followed by a 42 h post-incubation period. Irritant potential of the test item was predicted from the relative mean tissue viabilities obtained compared to the corresponding negative control tissues concurrently treated with DPBS. The mean relative tissue viability (% negative control) was > 50% (94.0%). Based on this result, the test item is classified as a non-irritant according to the UN GHS.

This information is used in a read-across approach in the assessment of the target substance.

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Irritation parameter:

other: Relative Tissue Viability [%]

Run / experiment:

Mean of replicates

Value:

64.7

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: First experiment, borderline results (60 +/- 5%)

Irritation parameter:

other: Relative Tissue Viability [%]

Run / experiment:

Mean of triplicates

Value:

92.7

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Experiment II, no indication of irritation

Other effects / acceptance of results:

The test item showed no irritant effects. The mean relative tissue viability (% negative control) was > 60% (64.7%). As the results were within the borderline values (60 ± 5%), a second experiment was performed to confirm the first results. The mean relative tissue viability (% negative control) of the second experiment was > 60% (92.7%). The controls confirmed the validity of the study. The mean absolute OD570 of the two negative control tissues was > 0.8 and < 2.5 (1.661 (Experiment 1), 1.480 (Repeated Experiment)). The mean relative tissue viability (% negative control) of the positive control was < 50% (18.6% (Experiment 1), 22.3% (Repeated Experiment)). The maximum inter tissue difference of replicate tissues of all dose groups was < 20% (19.2%). For detailed information please refer to Table 1 and Table 2 in box "Any other information on results incl. tables".

Table 1: Main results first experiment
Name	Negative Control		Positive Control		Test item
Tissue	1	2	1	2	1	2
OD570values	1.823	1.516	0.314	0.380	0.927	1.246
	1.801	1.505	0.308	0.377	0.943	1.247
OD570values (blank-corrected)	1.780	1.473	0.271	0.337	0.884	1.203
	1.758	1.462	0.265	0.334	0.900	1.204
mean of the duplicates	1.769	1.468	0.268	0.336	0.892	1.203
mean OD	1.618*		0.302		1.048
TODTT	-		-		1.045
SD of mean OD	0.213		0.048		0.220
tissue viability [%]	109.3	90.7	16.6	20.7	55.1	74.4
relative tissue viability difference [%]^***	18.6		4.2		19.2
mean tissue viability [%]	100.0		18.6**		64.7
mean tissue viability [%] - NSClivingcorrected	-		-		64.5

Table 2: Main results second experiment
Name	Negative Control		Positive Control		Test item
Tissue	1	2	1	2	1	2
OD570values	1.352	1.606	0.316	0.413	1.381	1.402
	1.366	1.598	0.319	0.405	1.298	1.420
OD570values (blank-corrected)	1.308	1.563	0.273	0.369	1.338	1.359
	1.323	1.554	0.276	0.362	1.254	1.377
mean of the duplicates	1.769	1.468	0.274	0.365	1.296	1.368
mean OD	1.437*		0.320		1.332
TODTT	-		-		1.330
SD of mean OD	0.172		0.064		0.051
tissue viability [%]	91.5	108.5	19.1	25.4	90.2	95.2
relative tissue viability difference [%]^***	16.9		6.3		5.0
mean tissue viability [%]	100.0		22.3**		92.7
mean tissue viability [%] - NSClivingcorrected	-		-		92.5

* corrected mean OD570 of the negative control corresponds to 100% absolute tissue viability

* corrected mean OD570 of the negative control corresponds to 100% absolute tissue viability

** mean relative tissue viability of the positive control is < 50%

*** relative tissue viability difference of replicate tissues is < 20%

Table 2: Acceptance Criteria
		Value	Cut-off	pass/fail
Mean absolute OD570 NK		1.661 (Experiment 1) 1.480 (Experiment 2)	0.8 < NK < 2.5	pass
Mean relative viability PC [%]		18.6 (Experiment 1) 22.3 (Experiment II)	< 50%	pass
Max difference of % viability [%]		19.2	< 20%	pass

Interpretation of results:

GHS criteria not met

Conclusions:

In this study under the given conditions the test item showed no irritant effects. The test item is classified as “non-irritant“ in accordance with UN GHS “No Category” for eye irritation.

Executive summary:

In the present study the eye irritant potential of 5′-O-[bis(4-methoxyphenyl)phenylmethyl]-2′-deoxythymidine, 3′-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] (99.7% purity) was analysed according to OECD 492 using the three-dimensional human corneal epithelium model EpiOcular, consisting of normal, human-derived epidermal keratinocytes mimicking characteristics of the corneal epithelium. Hereby, 50 mg of the test item was applied directly atop the EpiOcular™ tissue. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT after a 6 hours exposure and 18-hour post-incubation period and compared to those of the concurrent negative controls. The mixture of 50 mg test item per 1 mL Aqua dest. showed colouring as compared to the solvent. Thus, coloured tissue controls were included and used for quantitative correction of results. The test item showed no irritant effects. The mean relative tissue viability of two replicates (% negative control) was > 60% (64.7%). As the results were within the borderline range of 60 +/- 5%, a second experiment was performed to confirm the results. The mean relative tissue viability (% negative control) of the second experiment was > 60% (92.7%). Based on the results, the test item is considered to be non-irritating to the eye in accordance with UN GHS “No Category”.

This information is used in a read-across approach in the assessment of the target substance.

For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No data is available for the target substance Guanosine, 5′-O-[bis(4-methoxyphenyl)phenylmethyl]-2′-deoxy-N-(2-methyl-1-oxopropyl)-, 3′-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite]. Thus, data from a suitable read-across partner was used to assess the potential of the target substance to induce eye and skin irritation. Details on the read-across rationale are provided in IUCLID section 13.

The potential of 5’-O-[bis(4-methoxyphenyl)phenylmethyl]-2’-deoxythymidine, 3’-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] (source substance) to induce skin irritation (OECD 439) and eye irritation (OECD 492) was tested in suitable in vitro test methods. In both tests, the source substance was tested as negative. Based on the results from the read-across partner, the target substance can be considered as non-irritant to the skin and eye.

Justification for classification or non-classification

Based on available data from a suitable read-across partner, no classification for skin and/or eye irritation is warranted for the target substance.