5-chloro-3-nitro-pyrazolo[1,5-a]pyrimidine

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

other information

Study period:

October 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2021

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

June 2020

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: refrigerator
- Solubility and stability of the test substance in the solvent/vehicle: According to ICH Draft Consensus Guideline M7, formulations were prepared freshly prior to start of treatment. Thus, no stability test in the solvent was performed.


TREATMENT OF TEST MATERIAL PRIOR TO TESTING

- Final preparation: clear colorless solution (only used at the same day) - The purity of the test item was not taken into account for the calculation of the dosages.

Method

Target gene:

Histidine gene locus

Species / strain

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254 induced male Sprague Dawley rat liver S9 mix

Test concentrations with justification for top dose:

0, 16, 50, 160, 500, 1600, 5000 µg/plate (+/-S9 mix, all strains)

Vehicle / solvent:

DMSO

Controls

Untreated negative controls:

not specified

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: sodium azide (TA 1535, TA 100), 4-nitro-1,2-phenylene diamine (TA 1537), 2-Nitrofluoren (TA 98), Cumene hydroperoxide (TA 102), 2-aminoanthracene (all strains).

Details on test system and experimental conditions:

METHOD: each concentration including the controls was tested in triplicate.

Evaluation criteria:

A reproducible and dose-related increase in mutant counts of at least one strain is considered to be a positive result. For TA1535, TA100, TA1537 and TA98 this increase should be about twofold as compared to the solvent controls. For TA102 an increase of about 100 mutants should be reached. Otherwise, the result is evaluated as negative. However, these criteria may be overruled by good scientific judgment. In case of questionable results, investigations should continue, possibly with modifications, until a final evaluation is possible.

Results and discussion

Test results

Key result

Species / strain:

S. typhimurium, other: TA1535, TA100, TA1537, TA98 and TA102

Metabolic activation:

with and without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not specified

Positive controls validity:

valid

Additional information on results:

test item precipitation was not observed.

Any other information on results incl. tables

Table 1: Summary of results from the Salmonella mutagenicity assay with FMA (mean values of revertants per plate)

 

Dose (µg per plate)	Without metabolic activation
	TA 1535	TA 100	TA 1537	TA 98	TA 102
solvent control	7	94	7	16	246
16	6	220	20	22	252
50	0	249	23	20	227
160	0	0	0	0	0
500	0	0	0	0	0
1600	0	0	0	0	0
5000	0	0	0	0	0
Positive control	874	1323	51	879	472
Dose ( µg per plate )	With metabolic activation (liver S9 mix)
	TA 1535	TA 100	TA 1537	TA 98	TA 102
solvent control	8	104	7	22	345
16	8	102	14	21	400
50	7	270	12	19	395
160	0	0	0	0	0
500	0	0	0	0	0
1600	0	0	0	0	0
5000	0	0	0	0	0
Positive control	123	3115	216	2345	1081

 

 

 

Historical negative control data demonstrated that no deleterious or mutagenic effects were induced by the chosen solvent. The positive controls sodium azide, 4-nitro-1,2 -phenylene diamine, 2-nitrofluoren, cumene hydroperoxide and 2-aminoanthracene increased mutant counts to well over those of the solvent controls, and thus demonstrated the system's sensitivity and the activity of the S9 mix.

None of the five strains used showed a dose-related and biologically relevant increase inmutant counts over those of the solvent controls in the preincubation test. This applied both to the tests with and without S9 mix.

 

 

Applicant's summary and conclusion

Conclusions:

Evidence of mutagenic activity.

Executive summary:

The test item Chloro nitro PP, dissolved in DMSO, was administered in doses of up to and including 5000 μg per plate without and with S9 mix on five Salmonella typhimurium LT2 mutants. These comprised the histidine-auxotrophic strains TA1535, TA100, TA1537, TA98 and TA102.
Doses up to and including 16 μg per plate did not cause any bacteriotoxic effects. At higher doses the test item induced a strain-specific bacteriotoxic effect. This range could also be used strain specific up to 160 μg per plate for assessment purposes. Test item precipitation did not occur.
Evidence of mutagenic activity of the test item was seen. In the preincubation modification, biologically relevant increase in the mutant count, in comparison to the solvent controls, was observed in two of the strains tested, without and with S9 mix, under the experimental conditions applied.
The employed positive controls induced a marked mutagenic effect, as was seen by a biologically relevant increase in mutant colonies compared to the corresponding solvent controls.
Therefore, the test item is considered to be mutagenic in the preincubation modification of the Salmonella/microsome test.