Pregn-4-ene-3,20-dione, 21-(acetyloxy)-6-fluoro-11-hydroxy-16-methyl-, (6.alpha.,11.beta.,16.alpha.)-

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Fluocortolone-A-acetate is negative with and without metabolic activation in a bacterial reverse mutation assay with the S. typhimurium strains TA 98, TA 100, TA1535, TA1537 and TA1538 (Reimann and Görke, 2000). Additionally, the mutagenic potential of Fluocortolone-A-Acetate was determined using the two QSAR models Leadscope and DEREK. There was no indication for a mutagnic potential in these QSAR predictions.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
Leadscope model applier (v3.0.2)

2. MODEL (incl. version number)
Leadscope model applier (v3.0.2)
3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CAS: 1176-81-4 ; Chemical name: Fluocortolon-A-Acetat

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: QMRF 4.10. Mutagenicity OECD 471 Bacterial Reverse Mutation Test

- Unambiguous algorithm:
A new ICH M7 compliant expert alert system to predict the mutagenic potential of impurities (white paper) http://www.leadscope.com/white_papers/ICHM7-WhitePaper-0314.pdf
The logic for matching alerts is detailed in "A new ICH M7 compliant expert alert system to predict the mutagenic potential of impurities" (white paper): http://www.leadscope.com/white_papers/ICHM7-WhitePaper-0314.pdf

- Defined domain of applicability: The applicability domain is defined as having at least one chemical in a reference set with at least 30% global similarity to the test structure (using the Leadscope 27,000 chemical fragments as descriptors and the Tanimoto similarity score).

- Appropriate measures of goodness-of-fit and robustness and predictivity: Chemicals/descriptor ratio: 241 alerts for 11,528 reference chemicals (ratio = 48); Alerts are run within the Leadscope model applier that provides the capability to specify one or more compounds (using SMILES, Mol files, SD files, or copying from the clipboard), select and run the alerts, assess the applicability domain, and view the results including an explanation for any prediction (such as a full description of any matched alerts). The performance was assessed using the Hansen dataset comprised of 3,700 chemicals (47% positive).
Concordance = 83%, Sensitivity = 92%, Specificity = 70%, Positive
Predictivity = 81%, Negative Predictivity = 86% , coverage = 95% were
obtained.

- Mechanistic interpretation: Accompanying any positive prediction, any alert(s) that match the test compounds are described including a description of the mechanistic basis from the literature reference that cites the alert.

5. APPLICABILITY DOMAIN

- Descriptor domain: The applicability domain is defined as having at least one chemical in a reference set with at least 30% global similarity to the test structure (using the Leadscope 27,000 chemical fragments as descriptors and the Tanimoto similarity score).

- Structural domain: Leadscope Predictive Data Miner is a software program for systematic sub‐structural analysis of a chemical using predefined structural features stored in a template library, training set‐dependent generated structural features (scaffolds) and calculated molecular descriptors. The feature library contains approximately 27,000 pre‐defined structural features and the structural features chosen for the library are motivated by those typically found in small molecules: aromatics, heterocycles, spacer groups, simple substituents. Leadscope allows for the generation of training set‐dependent structural features (scaffold generation), and these features can be added to the pre‐defined structural features from the library and be included in the descriptor selection process.

- Mechanistic domain: The global model identifies structural features and molecular descriptors which in the model development was found to be statistically significant associated with effect. Many predictions may indicate modes of action that are obvious for persons with expert knowledge for the endpoint

- Similarity with analogues in the training set: The original data set from Kazius et al. (2005) consisted of 4337 molecular structures with corresponding Ames test data.
The structural similarity of the test compound with respect to the training set compounds was analysed and quantified in terms of Tanimoto distance, which provides a quantitative measure of structural relatedness between the test compound and each training set compound. The 25 training set compounds found to be mostly similar to the test compound.

6. ADEQUACY OF THE RESULT
As can be seen from Annex A and B of the QPRF the result is considered adequate due to the presence of almost all structural features of the parent compound which can also be found in the training/validation dataset. Furthermore the prediction substantiate the experimental result for the substance of interest.

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Software tool(s) used including version: Leadscope model applier (v3.0.2)
- Model(s) used: Leadscope model applier (v3.0.2)
- Model description: see field 'Attached justification'
- Justification of QSAR prediction: see field 'Attached justification'

GLP compliance:

no

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

other: Combination of results from the S. typhimurium histidine reversion gene mutation test using tester strains TA97, TA97a, TA1537, TA98, TA100, TA1535, TA102, E.coli (any variant)

Additional strain / cell type characteristics:

other: The QSAR prediction is based on results from all tester strains recommended by the OECD Test guideline

Evaluation criteria:

The model used was the Leadscope Applier which is a statistical model using structural fragments to set an alert. Only descrete organic compounds can be predicted. The model searches for structural fragments and combines them with eight molecular descriptors. Thus, a probability of either a negative or positive result is calculated. If experimental data are available the prediction of the statistical model may be overruled.

Key result

Species / strain:

bacteria, other: Not applicable for in silico study

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: Not applicable for in silico study

Vehicle controls validity:

not applicable

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

not applicable

Conclusions:

Based on the predictions performed with the statistical QSAR model Leadscope Applier Fluocortolone-A-Acetate is not mutagenic in a bacterial reverse mutation assay.

Executive summary:

In a QSAR prediction using Leadscope Model Applier (v3.0.2) the potential of Fluocortolone-A-Acetate to induce mutagenicity was assessed. Leadscope uses two parameters to guide the applicability of model domain: 1) having at least one structural feature defined in the model in addition to all the property descriptors; 2) having at least one chemical in a training neighbourhood with at least 30% global similarity to the test structure. In this case the prediction is within the applicability domain, since 37 training compounds were identified in the model training set being structurally similar to the test compound.

 

The query structure does not match structural alerts or examples for (bacterial in vitro) mutagenicity in Leadscope.

Based on these results Fluocortolone-A-Acetate is considered not mutagenic as predicted by Leadscope.

 

This study is classified as acceptable for assessment based on methodology and documentation. This study satisfy the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) and the data is part of an overall assessment.

Reference 2

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
DEREK Nexus 6.1
2. MODEL (incl. version number)
DEREK Nexus 6.1
3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CAS 1176-81-4
4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: TOX 7.6.1. Genetic toxicity in vitro
- Unambiguous algorithm: logic of argumentation. Derek Nexus makes qualitative predictions for and against toxicity through reasoning. For the endpoint of mutagenicity, predictions for toxicity decrease in confidence in the following order: certain>probable>plausible>equivocal. Predictions against toxicity increase in confidence in the following order: inactive (with unclassified and/or misclassified features) inactive
- Defined domain of applicability: The scopes of the structure-activity relationships describing the mutagenicity endpoint are defined by the developer to be the applicability domain for the model. Therefore, if a chemical activates an alert describing a structure-activity for mutagenicity it can be considered to be within the applicability domain. If a compound does not activate an alert or reasoning rule then Derek makes a negative prediction. The applicability of the negative prediction to the query compounds can be determined by an expert, if required, by investigating the presence (or absence) of misclassified and/or unclassified features. The applicability domain of each alert is defined by the alert developer on the basis of the training set data and expert judgement on the chemical and biological factors which affect the mechanism of action for each alert. For non-alerting compounds, users should determine the applicability of negative predictions by evaluating the information supplied by Derek (i.e. the presence or absence of misclassified and/or unclassified features).
- Appropriate measures of goodness-of-fit and robustness and predictivity: n/a
- Mechanistic interpretation: All alerts describing structure-activity relationships for the mutagenicity endpoint have a mechanistic basis wherever possible.
Mechanistic information is detailed in the comments associated with an alert and can include information on both the mechanism of action and biological target. The mechanistic basis of the model was developed a priori by examining the toxicological and mechanistic evidence before developing the structure-activity relationship.

5. APPLICABILITY DOMAIN

- Descriptor domain:
[1]Markush structures encoding activating and deactivating features (known as patterns in the Derek Nexus knowledge base)
[2]count of non-hydrogen atoms
[3]ClogP
[4]2D structural fragments
There is an a priori assumption that patterns and associated reasoning will be used to model toxicity within Derek Nexus. Further, experts identified that misclassified and unclassified features were useful descriptors for determining the reliability of negative predictions for non-alerting compounds.
- Similarity with analogues in the training set: Non-proprietary elements of the training set are available through the references, and illustrated by the examples, within Derek Nexus. The illustrative examples are not available, due to the proprietary nature of Derek Nexus.

6. ADEQUACY OF THE RESULT
Based on the common structure of the substance, the result is considered reliable.

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Software tool(s) used including version: DEREK Nexus 6.1
- Model(s) used: DEREK Nexus 6.1
- Model description: see field 'Attached justification'
- Justification of QSAR prediction: see field 'Attached justification'

GLP compliance:

no

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

bacteria, other: Predictions are made for the domain of bacteria and can be broken down into species (e.g. Salmonella typhimurium and Escherichia coli)

Additional strain / cell type characteristics:

other: The prediction is based on results from all tester strains recommended by the OECD Test Guideline

Evaluation criteria:

Two types of models were used to predict the mutagenic potential of the test item.
The DEREK Nexus model was used as a rule-based model which is based on the training set data and expert judgement on the chemical and biological factors which affect the mechanism of action for each alert. The second model used was the Leadscope Applier which is a statistical model using structural fragments to set an alert. If experimental data are available the prediction of the statistical model may be overruled.

Key result

Species / strain:

bacteria, other: Not applicable for in silico study

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: Not applicable for in silico study

Vehicle controls validity:

not applicable

Untreated negative controls validity:

not applicable

True negative controls validity:

not applicable

Positive controls validity:

not applicable

Conclusions:

Based on the predictions performed with the statistical QSAR model Leadscope Applier and the rule-based model DEREK Nexus Fluocortolone-A-Acetate is not mutagenic in a bacterial reverse mutation assay.

Executive summary:

In a QSAR prediction using DEREK Nexus v6.1 the potential of Fluocortolone-A-Acetate to induce mutagenicity was assessed. Derek Nexus makes qualitative predictions for and against toxicity through reasoning. For the endpoint of mutagenicity, predictions for toxicity decrease in confidence in the following order: certain>probable>plausible>equivocal. Predictions against toxicity increase in confidence in the following order: inactive (with unclassified and/or misclassified features)<inactive<improbable. Likelihood levels have been shown to correlate with predictivity [Judson et al, 2013]. Multiple data sources (e.g. toxicity data from multiple assays and mechanistic evidence) are synthesised into the structure-activity relationships that underpins Derek Nexus predictions. An appreciation of the assay units applied by alert writers when building the alert training set. However, predictions are not quantitative and, as a result, do not include units.

 

The query structure does not match a structural alert or examples for (bacterial in vitro) mutagenicity in Derek.

Based on these results Fluocortolone-A-Acetate is not considered mutagenic as predicted by DEREK Nexus.

This study is classified as acceptable for assessment based on methodology and documentation. This study satisfy the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) and the data is part of an overall assessment.

Reference 3

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Mar to Apr 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

21 July 1997

Deviations:

yes

Remarks:

no E. coli WP2 or S. typhimurium TA102 strain tested; only one experiment (direct plate incorporation procedure) was performed

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine gene locus

Species / strain / cell type:

S. typhimurium TA 1538

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

S. typhimurium TA 1537

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

S. typhimurium TA 1535

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

S. typhimurium TA 100

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

S. typhimurium TA 98

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced male rat liver S9 mix
Type and composition of metabolic activation system:
- source of S9: Liver homogenates (S9:9000xg fraction), derived from male Sprague-Dawley rats pre-treated with Aroclor 1254, was obtained from CN/Cappel Pharmaceuticals, Inc., Aurora, Ohio, USA, [S9 batch no. 99554; protein content 37.3 mg/mL; EROD activity: 2627.3 pmoles 7-hydroxyresorufin/min/mg S9 protein].

- concentration or volume of S9 mix and S9 in the final culture medium: 0.5 mL of S9 mix were added to each bacterial culture with a volume of approx. 2.55 mL

Test concentrations with justification for top dose:

0.1, 0.25, 0.5, 1.0, 2.5, 5.0 mg/plate

Vehicle / solvent:

DMSO

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

sodium azide

benzo(a)pyrene

cyclophosphamide

other: 4-nitro-o-phenylenediamine (only TA 1537) 10 µg/plate without S9, 2-aminoanthracene (all strains) 5 µg/plate with S9

Details on test system and experimental conditions:

NUMBER OF REPLICATIONS:
- Number of cultures per concentration triplicate
- Number of independent experiments one

METHOD OF TREATMENT/ EXPOSURE:
- Cell density at seeding (if applicable): Aliquots of a E-06 dilution of the overnight culture were spread onto complete agar to measure the viability and cell densityof each culture.
- Test substance added in agar (plate incorporation)

METHODS FOR MEASUREMENT OF CYTOTOXICITY
- Method, e.g.: background growth inhibition


METHODS FOR MEASUREMENTS OF GENOTOXICITY
The plates were scored for the number of mutant colonies with an automated colony counter (Artek M 982B, Artek Systems Corporation, Farmingdale, NY, USA). In exceptional cases, where reliable automatic counting is not possible, e.g. due to distinct precipitates of the test compound, the colonies are scored manually.

Evaluation criteria:

The arithmetic means of the number of mutant colonies of the 3 parallel plates in the negative control groups were compared with those of the compound groups. A positive. response was considered if the number of revertants of the compound groups compared to the number of revertants of the negative group was reproducibly higher than 2-fold. A dose-dependent increase in the number of revertants was also considered to indicate a mutagenic effect.

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

growth inhibition at 5.0 mg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

growth inhibition at 5.0 mg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

growth inhibition at 5.0 mg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

growth inhibition at 5.0 mg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

growth inhibition at 5.0 mg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

The total colony counts of the 10 -6 dilution of bacterial suspension culture confirmed the viability and high cell density of the cultures of the individual strains.The colony counts recorded on appropriate negative control plates confirmed the characteristically spontaneous reversion rates of the tester strains. Appropriate positive control chemicals induced marked increases in revertant colony numbers with all strains.

 

None of the five tester strains showed increased reversion to prototrophy with ZK 47525 (fluocortolone-A-acetate) at the concentrations tested between 0.1 and 5.0 mg/plate, either in the absence or presence of S9 mix.

 

Precipitates in the agar were found starting at 1.0 mg/plate onwards. Growth inhibition of the background lawn was observed at the highest concentration tested.

 

TA 1535		Revertants per plate						Quotient
Dose/Plate		-S9	M	SD	+S9	M	SD	-S9	+S9
DMSO	50µL	35	41	6	15	15	1	1.0	1.0
		46			15
		41			14
Phosphate Buffer	50µL	52	55	8	16	15	1	1.4	1.0
		64			15
		49			14
Test item	0.10mg	52	52	10	14	13	1	1.3	0.9
		42			13
		61			13
	0.25mg	62	60	2	17	19	2	1.5	1.3
		60			18
		59			21
	0.50mg	42	49	6	18	19	2	1.2	1.3
		51			21
		54			17
	1.0mg	41P	45	3	21P	20	1	1.1	1.3
		46P			19P
		47P			19P
	2.5mg	40 mP	37	3	17 mP	17	2	0.9	1.1
		35 mP			18mP
		37 mP			15 mP
	5.0mg	30 mPB	31	2	18 mPB	17	2	0.8	1.1
		33 mPB			15 mPB
		30 mPB			17 mPB
2-AA	5µg	55	58	2	113	129	20	1.4	8.8
		59			151
		59			124
CP	400µg	101	96	8	195	205	9	2.4	14.0
		101			207
		87			212
NaN3	5µg	361	365	7	39	46	8	9.0	3.1
		373			55
		360			44
TA 100		Revertants per plate						Quotient
Dose/Plate		-S9	M	SD	+S9	M	SD	-S9	+S9
DMSO	50µL	128	144	14	111	105	5	1.0	1.0
		147			103
		156			101
Phosphate Buffer	50µL	135	139	12	110	113	16	1.0	1.1
		129			131
		153			99
Test item	0.10mg	147	148	14	113	112	6	1.0	1.1
		135			118
		162			106
	0.25mg	113	131	15	103	107	5	0.9	1.0
		138			112
		141			107
	0.50mg	145	147	2	100	105	5	1.0	1.0
		147			109
		149			107
	1.0mg	147P	138	12	117P	115	10	1.0	1.1
		142P			104P
		125P			123P
	2.5mg	145 mP	145	6	111 mP	124	13	1.0	1.2
		139 mP			123 mP
		150 mP			137 mP
	5.0mg	150 mPB	137	12	109 mPB	105	5	1.0	1.0
		129 mPB			100 mPB
		131 mPB			106 mPB
2-AA	5µg	229	220	16	1554	1602	56	1.5	15.3
		202			1589
		230			1664
B[a]P	2.5µg	135	130	7	1153	1007	165	0.9	9.6
		122			1040
		134			828
NaN3	5µg	1109	1023	77	294	348	49	7.1	3.3
		960			360
		999			389
TA 1537		Revertants per plate						Quotient
Dose/Plate		-S9	M	SD	+S9	M	SD	-S9	+S9
DMSO	50µL	13	20	6	18	19	4	1.0	1.0
		23			23
		24			16
Phosphate Buffer	50µL	28	24	4	15	17	4	1.2	0.9
		21			14
		23			21
Test item	0.10mg	25	21	9	16	15	1	1.1	0.8
		11			15
		27			15
	0.25mg	19	23	4	7	15	8	1.1	0.8
		23			17
		26			22
	0.50mg	19	19	1	14	13	3	1.0	0.7
		20			10
		18			15
	1.0mg	22P	21	3	12P	13	1	1.1	0.7
		24P			14P
		18P			13P
	2.5mg	19P	19	5	10 mP	11	2	1.0	0.6
		15 mP			9 mP
		24 mP			13 mP
	5.0mg	25 mPB	17	7	9 mPB	13	4	0.9	0.7
		13 mPB			15 mPB
		14 mPB			16 mPB
2-AA	5.0 µg	24	29	6	155	137	16	1.5	7.2
		35			127
		28			128
4-NPDA	10.0 µg	71	72	1	33	32	2	3.6	1.7
		73			33
		73			30
TA 1538		Revertants per plate						Quotient
Dose/Plate		-S9	M	SD	+S9	M	SD	-S9	+S9
DMSO	50µL	11	12	1	19	17	3	1.0	1.0
		12			13
		12			19
Phosphate Buffer	50µL	9	12	3	31	28	3	1.1	1.7
		14			28
		14			26
Test item	0.10mg	11	16	5	23	23	1	1.4	1.3
		16			23
		21			22
	0.25mg	13	10	3	20	20	9	0.9	1.2
		7			12
		11			29
	0.50mg	14	15	2	19	21	2	1.3	1.3
		14			22
		18			23
	1.0mg	14 mP	13	1	26P	19	6	1.1	1.1
		13 mP			15 mP
		12 mP			16 mP
	2.5mg	10 mP	11	3	18 mP	16	3	0.9	1.0
		14 mP			13 mP
		9 mP			18 mP
	5.0mg	9 mPB	12	3	17 mPB	16	3	1.0	1.0
		12 mPB			13 mPB
		14 mPB			19 mPB
2-NF	10µg	23	24	2	959	1114	150	2.1	65.5
		26			1123
		23			1259
2-AA	5µg	1303	1326	75	598	530	67	113.7	31.2
		1266			465
		1410			526
TA 98		Revertants per plate						Quotient
Dose/Plate		-S9	M	SD	+S9	M	SD	-S9	+S9
DMSO	50µL	30	35	5	32	34	2	1.0	1.0
		35			34
		40			36
Phosphate Buffer	50µL	30	41	11	32	33	1	1.2	1.0
		42			34
		51			33
Test item	0.10mg	33	36	3	28	24	4	1.0	0.7
		38			21
		37			23
	0.25mg	41	43	4	20	25	4	1.2	0.7
		40			28
		48			26
	0.50mg	30	37	6	25	27	8	1.0	0.8
		40			20
		40			35
	1.0mg	45 mP	36	8	22 mP	24	2	1.0	0.7
		29 mP			26 mP
		33 mP			25 mP
	2.5mg	41 mP	38	5	25 mP	21	3	1.1	0.6
		33 mP			19 mP
		41 mP			20 mP
	5.0mg	34 mPB	38	5	25 mPB	22	4	1.1	0.6
		37 mPB			17 mPB
		43 mPB			24 mPB
2-AA	5.0 µg	47	53	6	1770	1805	57	1.5	53.1
		59			1871
		54			1775
B[a]P	2.5 µg	42	42	4	280	265	21	1.2	7.8
		45			241
		38			273
2-NF	10µg	726	760	37	318	373	56	21.7	11.0
		753			430
		800			371
M  : Mean  SD  : Standard-deviation  Quotient  =  Mean revertants (test substance) p  : Precipitation  +S9  : With S9 mix  -S9  : Without S9 mix m  :-Manually scored  C  : Contamination  / : Not tested B  : Background lawn reduced R  : Repeat experiment

 

 

 

Conclusions:

The mutagenic potential of the test substance was evaluated in a Salmonella/microsome test with the S. typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and TA 1538 in the presence and absence of S9 mix according to OECD TG 471. Evidence of mutagenic activity was not seen up to the maximum recommended dose level of 5.0 mg/plate. No substantial increases in revertant colony numbers of any of the five tester strains were observed at any dose level in the presence and absence of metabolic activation. Therefore, ZK 47525 (fluocortolone-A-acetate) was considered to be non-mutagenic in the Salmonella typhimurium reverse mutation assay.

Executive summary:

In a reverse gene mutation assay in bacteria according to OECD test guideline 471, strains TA 98, TA 100, TA 1535, TA 1537 and TA 1538 of S. typhimurium were exposed to Fluocortolone acetate (100% a.i.), in DMSO at concentrations of 0.1, 0.25, 0.5, 1.0, 2.5, 5.0 mg/plate in the presence and absence of mammalian metabolic activation with the plate co-incubation method.

 

Fluocortolone acetate was tested up to cytotoxic and insoluble concentrations. None of the five tester strains TA 1535, TA 100, TA 1537, TA 1538 and TA98 showed increased reversion to prototrophy in assays with ZK 47525 at the doses tested between 0.1 and·5.0 mg/plate, either in the absence or presence of S9 mix. In the present study ZK 47525 was tested up to the highest recommended dose of 5 mg/plate. Precipitates in the agar were found starting at 1.0 mg/plate onwards. Growth inhibition of the background lawn was observed at the highest dose tested. The positive controls induced the appropriate responses in the corresponding strains.   There was no evidence of induced mutant colonies over background.

 

This study satisfies the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

 

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In a reverse gene mutation assay in bacteria according to OECD test guideline 471, strains TA 98, TA 100, TA 1535, TA 1537 and TA 1538 of S. typhimurium were exposed to Fluocortolone acetate (100% a.i.), in DMSO at concentrations of 0.1, 0.25, 0.5, 1.0, 2.5, 5.0 mg/plate in the presence and absence of mammalian metabolic activation with the plate co-incubation method.

Fluocortolone acetate was tested up to cytotoxic and insoluble concentrations. None of the five tester strains TA 1535, TA 100, TA 1537, TA 1538 and TA98 showed increased reversion to prototrophy in assays with ZK 47525 at the doses tested between 0.1 and·5.0 mg/plate, either in the absence or presence of S9 mix. In the present study ZK 47525 was tested up to the highest recommended dose of 5 mg/plate. Precipitates in the agar were found starting at 1.0 mg/plate onwards. Growth inhibition of the background lawn was observed at the highest dose tested. The positive controls induced the appropriate responses in the corresponding strains.   There was no evidence of induced mutant colonies over background.

This study satisfies the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

 

In a QSAR prediction using Leadscope Model Applier (v3.0.2) the potential of Fluocortolone-A-Acetate to induce mutagenicity was assessed. Leadscope uses two parameters to guide the applicability of model domain: 1) having at least one structural feature defined in the model in addition to all the property descriptors; 2) having at least one chemical in a training neighbourhood with at least 30% global similarity to the test structure. In this case the prediction is within the applicability domain, since 37 training compounds were identified in the model training set being structurally similar to the test compound.

The query structure does not match structural alerts or examples for (bacterial in vitro) mutagenicity in Leadscope.

Based on these results Fluocortolone-A-Acetate is considered not mutagenic as predicted by Leadscope.

 

This study is classified as acceptable for assessment based on methodology and documentation. This study satisfy the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) and the data is part of an overall assessment.

In a QSAR prediction using DEREK Nexus v6.1 the potential of Fluocortolone-A-Acetate to induce mutagenicity was assessed. Derek Nexus makes qualitative predictions for and against toxicity through reasoning. For the endpoint of mutagenicity, predictions for toxicity decrease in confidence in the following order: certain>probable>plausible>equivocal. Predictions against toxicity increase in confidence in the following order: inactive (with unclassified and/or misclassified features)<inactive<improbable. Likelihood levels have been shown to correlate with predictivity [Judson et al, 2013]. Multiple data sources (e.g. toxicity data from multiple assays and mechanistic evidence) are synthesised into the structure-activity relationships that underpins Derek Nexus predictions. An appreciation of the assay units applied by alert writers when building the alert training set. However, predictions are not quantitative and, as a result, do not include units.

The query structure does not match a structural alert or examples for (bacterial in vitro) mutagenicity in Derek.

Based on these results Fluocortolone-A-Acetate is not considered mutagenic as predicted by DEREK Nexus.

This study is classified as acceptable for assessment based on methodology and documentation. This study satisfy the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) and the data is part of an overall assessment.

Justification for classification or non-classification

Based on the study results a classification according to Regulation (EC) No. 1272/2008 (CLP) is not required.