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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
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 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes
Type of assay:
micronucleus 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%

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: well known breeder
- Age at study initiation:
- Weight at study initiation:
- Assigned to test groups randomly: [no/yes, under following basis: ]
- Fasting period before study:
- Housing:
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C):18-26°C
- Humidity (%):30% to 70%
- Photoperiod (hrs dark / hrs light):12hrs dark /12 hrs light

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle(s)/solvent(s) used: corn oil
- Concentration of test material in vehicle:
- Amount of vehicle (if gavage or dermal): 10ml/kg
- Lot/batch no. (if required):lot no. 12-394
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Test article wasdissolved in corn oil
Duration of treatment / exposure:
24h and 48h
Frequency of treatment:
single dose
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
62.5 mg/kg
Basis:
actual ingested
Remarks:
Doses / Concentrations:
125 mg/kg
Basis:
actual ingested
Remarks:
Doses / Concentrations:
250 mg/kg
Basis:
actual ingested
No. of animals per sex per dose:
5 males/dose for the negative and positive control and the 62.5 and 125 mg/kg and 10/sex/dose for the 250 mg/kg
Control animals:
yes, concurrent vehicle
Positive control(s):
cyclophosphamide in sterile deionized water
- Route of administration: gavage
- Doses / concentrations: 80mg/kg

Examinations

Tissues and cell types examined:
Bone marrow. micronuclei in polychromatic erythrocytes (PCEs) and norchromatic erythrocytes (NCEs)
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION:Based upon the result of the dose range-finding study, the estimated maximum tolerated doses was 250 mglkg after one oral gavage administration

SAMPLING TIMES ( in addition to information in specific fields): 24h and 48h

DETAILS OF SLIDE PREPARATION:Bone marrow smears were prepared and allowed to air dry. The slides were then fixed in methanol, stained in May-Grunwald-Giemsa stain and protected by permanently mounted cover slips.

METHOD OF ANALYSIS:The slides were blind scored for micronuclei in polychromatic erythrocytes (PCEs) and norchromatic erythrocytes (NCEs) and determination of PCE/NCE ratios to access possible bone marrow cytotoxicity.
The micronucleus frequency (expressed as percent micronucleated cell) wasdetennlned by analyzing number of micronucleated PCEs from at least 2000 PCEs per animal. The PCE:NCE ratio was determined by scoring the number of PCEs and NCEs observed while scoring at least the first 500 erythrocytes per animal.

Evaluation criteria:
The criteria for the identification of micronuclei were those of Schmid (1976).
Statistics:
Yes but no details

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Remarks:
no significant decreases in the PCE:NCE ratios observed at any RDX dose or bone marrow sampling time point
Toxicity:
no effects
Remarks:
RDX at doses 62.5, 125, and 250 mg/kg were not cytotoxic to bone marrow (i.e.no statistically significant decrease in PCE:NCE ratios)
Vehicle controls validity:
valid
Negative controls validity:
not specified
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY
- Dose range: up to 500 mg/kg
- Clinical signs of toxicity in test animals: Mice dosed at all dose levels showed neurotoxic signs (hyperactive) and deaths at high dose of 500 mg/kg.


Any other information on results incl. tables

Summary data from micronuleus assay for RDX in bone marrow of CD-l mouse

 Treatment  Dose  Harvest time  % Micronucleated PCE (mean of 2000 per animal ±SE)  Ratio PCE:NCE (mean ± S.E.)
     
  Positive control   CP 80 mg/kg  24h   2.39 ± 0.31*  0.57 ± 0.05
  Test article   62.5 mg/kg  24h 0.04 ± 0.02 0.47 ± 0.07 
    125 mg/kg  24h  0.03 ± 0.01  0.36 ± 0.04
    250 mg/kg 24  0.02 ± 0.01  0.60 ± 0.05
     48h  0.10 ± 0.02  0.69 ± 0.11
   Vehicle control   Corn oil 24h    0.05 ± 0.02    0.50 ± 0.07
     48h    0.08 ± 0.03   0.71 ± 0.06

*Significantly greater than the corresponding vehicle control, P =0.01

CP = cyclophosphamide.

PCE = polychromatic erythrocyte.

NCE = normochromatic erythrocyte.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
RDX was found to be negative in the in vivo mouse bone marrow micronucleus assay.
Executive summary:

HMX and RDX, which is tested for its genotoxicity in a mouse micronucleus 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.