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Toxicological information

Genetic toxicity: in vitro

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Administrative data

Endpoint:
in vitro gene mutation study in mammalian cells
Remarks:
Type of genotoxicity: gene mutation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
It is a GLP study following international guidelines and has been published in a peer reviewed journal. The restriction is also due to the use of the read across approach: the test was performed not with HMX but with RDX, a substance which has been demonstrated to be very similar in structure, physical/chemical properties and toxicological profile .

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2005
Report Date:
2005

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Deviations:
not specified
GLP compliance:
yes
Type of assay:
mammalian cell gene mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
- Name of test material (as cited in study report): Hexahydro-l,3,5-trinitro-1,3,5-triazine and RDX
- Molecular formula (if other than submission substance):C3H6N6O6
- Molecular weight (if other than submission substance): 222.26
- Smiles notation (if other than submission substance):N(=O)(=O)N(CN(N(=O)(=O))CN1N(=O)(=O))C1
- InChl (if other than submission substance):
- Structural formula attached as image file (if other than submission substance): see Fig.
- Substance type: Explosive
- Physical state: crystal
- Analytical purity: 99.99%

Method

Target gene:
Thymidine kinase locus
Species / strain
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
S-9 mix
Test concentrations with justification for top dose:
3.93, 7.85, 15.7, 31.3, 62.5, 125, 250 and 500 μg/ml
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
Controls
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
3-methylcholanthrene
methylmethanesulfonate
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium; in agar (plate incorporation);

DURATION
- Exposure duration: 4 hours
- Expression time (cells in growth medium): 2 days
- Selection time (if incubation with a selection agent): 10 to 14 days

SELECTION AGENT (mutation assays):Trifluorothymidine

NUMBER OF REPLICATIONS: 2 independant tests

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth

Evaluation criteria:
The results are considered positive if dose-dependent increases of two-fold or greater in mutant frequency are obtained over the concurrent background mutant frequency (average mutant frequency of the vehicle control cultures). The two-fold or greater increase is based on extensive experience
that indicates such responses are repeatable in additional trials. The test article is evaluated as negative if a two-fold increase in mutant frequency is not observed for (1) a range of doses that extends to toxicities causing 10% to 20% relative total growth (RTG); (2) for relatively non toxic test articles,a range of doses extending to the maximum concentration of 5 mg/ml or 10mM (which ever is lower); (3) a range of doses that extends to a level approximately twice the solubility limit in culture medium; (4) the increase(s) are not repeatable in a confirmatory trial.

Results and discussion

Test results
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
other: No cytotoxicity to weak cytotoxicity was induced when tested up to precipitating concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: in treatment medium at concentrations as low as 250 ug/ml

RANGE-FINDING/SCREENING STUDIES: yes

COMPARISON WITH HISTORICAL CONTROL DATA: the negative control mutant frequencies were within historical range for all trials in the absence and presence of S9 activation.

ADDITIONAL INFORMATION ON CYTOTOXICITY:No cytotoxicity to weak cytotoxicity was induced. Higher concentrations were not included in this study because a precipitate was observed in treatment medium at concentrations as low as 250 ug/ml. Higher concentrations would have interfered with the performance of the assay.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information):
negative

Under the conditions of this mouse lymphoma TK locus assay, RDX showed no evidence of mutagenic activity in any of the strains tested, either in the presence or absence of metabolic activation at concentrations up to 500 μg/ml.
Executive summary:

HMX and RDX, which is tested for its genotoxicity in a mouse lymphoma TK locus assay, are both explosive compounds used in military munitions formulations.

These substances have been demonstrated to be very similar in structure, physical/chemical properties and toxicological profile in the Analogue Approach - Read Across High Melting Explosive (HMX) (2013) document (see Section 13). Due to the fact that HMX and RDX have nearly the same chemical structure, the same mode of interaction with bio-macromolecules, living cells and tissue and metabolic pathway is expected. Therefore, a read-across from HMX to data obtained with RDX is scientifically justified.