Sodium 3-mercaptopropanesulphonate

Endpoint summary

Description of key information

Due to the high structural similarity, similarity in organic functional groups, physico-chemical properties and similarity in reactivity to biomolecules, mesna (CAS 19767-45-4) is considered to be the most suitable chemical for read-across. Mesna did not produce any signs of toxicity in treated animals in two-year carcinogenicity study and therefore the dose of 350 mg/kg bw is considered to be a NOAEL. No C&L for systemic organ toxicity (STOT-RE) is required.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

chronic toxicity: oral

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: Read-across data (CAS 19767-45-4) found via OECD QSAR Toolbox. The publication is well documented and meets basic scientific principles.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 451 (Carcinogenicity Studies)

Deviations:

not specified

Principles of method if other than guideline:

92 male Sprague-Dawley rats, 8 weeks old, were divided into two groups. Group A received 70 mg/kg N-nitroso-N-butyl-N-(4-hydroxybutyl)amine (BBNOH) twice a week by gavage, whereas to Group B, BBNOH was administered at the same dose level together with 350 mg/kg Mesna given 5 times a week in drinking water. Two control groups of 40 animals each were given Mesna alone or were totally untreated.

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Süddeutsche Versuchstierfarm, Tuttlingen, F.R.G
- Age at study initiation: 8 weeks
- Weight at study initiation: no data (the weight was checked regularly during the entire period of the treatment).
- Housing: 2 per cage
- Diet (e.g. ad libitum): Altrominm pellets diet; ad libitum
- Water (e.g. ad libitum): tap water; ad libitum

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: 20 mL Mesna solutions were given to rats 5 days a week.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

39 weeks

Frequency of treatment:

5 times a week

Remarks:

Doses / Concentrations:
350 mg/kg bw
Basis:
nominal in water

No. of animals per sex per dose:

40

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: The high dose of Mesna was chosen in order to provide an excess amount that could interfere with the metabolites of BBNOH in the urinary bladder.

Positive control:

N-nitroso-N-butyl-N-(4-hydroxybutyl)amine (BBNOH) alone.

Observations and examinations performed and frequency:

The body weight was checked regularly during the entire period of the treatment.

Sacrifice and pathology:

At the end of the treatment animals were observed for life, with the exception of a few that were killed when moribund. After dissection, urinary bladders and all other organs showing macroscopical alterations were collected for histological examination.

Statistics:

Kaplan-Meier method.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
No significant differences were observed in the animals of the 4 experimental groups from a general point of view. Control animals did not show any pathological alteration at the end of the experiment. There were no signs of toxicity in the animals that received Mesna alone. A statistically significant increase of the lifespan of the Mesna treated animals was observed (P< 0.05).

BODY WEIGHT AND WEIGHT GAIN
Administration of Mesna did not have a significant effect on the weight; an increase in body weight was observed at the beginning of the treatment, up to the eighteenth week, followed by a slight decrease and a steady phase at the end of the experiment. Values ranged between 300 g and 500 g for all experimental groups.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
Mesna solutions were completely consumed within 24 h from the time of administration. The total Mesna consumption was 63.35 g/kg.

GROSS PATHOLOGY
No findings.

HISTOPATHOLOGY: NON-NEOPLASTIC
No findings.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
No findings.

Dose descriptor:

NOAEL

Effect level:

350 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

Conclusions:

The nearest analogue mesna was not carcinogenic in a two-year carcinogenicity study in rats. 350 mg/kg bw, which rats received daily during the exposure period of 39 weeks, can be considered as NOAEL since no clinical signs of toxicity and no findings of necropsy were noted in treated animals.

Executive summary:

Mesna is known as a cytoprotective agent that helps to prevent haemorrhagic cystitis caused by a widely used class of antineoplastic drugs, comprising cyclophosphamide, ifosfamide, and trofosfamide (Tacchi et al., 1984). A direct chemical interaction between Mesna and the active metabolites of antineoplastic drugs is supposed to be involved in the protective effects on the urinary bladder. In this respect, the influence of mesna on urinary bladder cancer induced by N-nitroso-N-butyl-N-(4 hydroxybutyl)amine (BBNOH) was studied in male Sprague-Dawley rats.
The treatment consisted of the administration of BBNOH alone per gavage, BBNOH with Mesna, Mesna alone and untreated control. The health effects in treated animals receiving Mesna alone is relevant for this endpoint. The group of 40 male animals (8-week old) received 350 mg/kg bw (total Mesna consumption was 63 g/kg bw (mean for all animals)) in drinking water over a period of 39 weeks. The rats received daily the dose in 20 mL water solution 5 days a week. Health condition of the animals and their body weights were checked regularly during the entire period of the treatment. At the end of the treatment animals were killed and dissected and urinary bladders and all other organs showing macroscopical alterations were collected for histological examination.
No significant differences were observed in the animals of the 4 experimental groups from a general point of view. Mesna solutions were completely consumed within 24 h from the time of administration. Administration of mesna did not have a significant effect on the weight; an increase in body weight was observed at the beginning of the treatment, up to the eighteenth week, followed by a slight decrease and a steady phase at the end of the experiment. Values ranged between 300 g and 500 g for all experimental groups. Control animals (untreated and receiving mesna alone) did not show any pathological alteration at the end of the experiment and there were no signs of toxicity. A statistically significant increase of the lifespan of the mesna treated animals was observed (P< 0.05).There were no findings at necropsy.
As no toxicological findings were observed in animals treated with mesna alone, 350 mg/kg bw can be considered as chronic NOAEL.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

350 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

High

Additional information

Long-term toxicity data on read-across substance Mesna (CAS 19767 -45 -4)

OECD QSAR Toolbox, v.3.0/Publication:

There is no repeated dose toxicity study available for sodium 3 -mercaptopropanesulfonate. Therefore a search for structurally similar substances with data on long-term toxicity was performed with the help of the OECD QSAR Toolbox (v.3.0, 2012). A structural analogue chemical sodium-2 -mercaptoethanesulfonate (mesna, CAS 19767 -45 -4) was identified (please refer to the Toolbox generated report attached in the section 7.7. of the IUCLID file). The read-across chemical and the target chemical are sodium salts of mercaptosulfonic acid; their hydrocarbon chains differ only in one methyl group. They have the same functional groups (thiol and sulfonic), similar reactivity to biomolecules (SN2 mechanism of binding to proteins and to DNA) and similar physico-chemical properties. Both substances are of similar molecular weight (178.21 and 164.18); they are soluble in water (estimated water solubility of 1E6 mg/L for both substances, EPIWIN) and possess negative logPow (-3.6 and -4.09 for the target and for the read-across substance, respectively). Therefore, the substances are expected to behave similarly in absorption and in distribution throughout the body, yielding similar metabolites.

Mesna is known as a cytoprotective agent that helps to prevent haemorrhagic cystitis caused by a widely used class of antineoplastic drugs, comprising cyclophosphamide, ifosfamide, and trofosfamide (Tacchi et al., 1984). A direct chemical interaction between mesna and the active metabolites of antineoplastic drugs is supposed to be involved in the protective effects on the urinary bladder. In this respect, the influence of mesna on urinary bladder cancer induced by N-nitroso-N-butyl-N-(4 hydroxybutyl)amine (BBNOH) was studied in male Sprague-Dawley rats.
The treatment consisted of the administration of BBNOH alone per gavage, BBNOH with mesna, mesna alone and untreated control. The health effects in treated animals receiving mesna alone is relevant for this endpoint. The group of 40 male animals (8-week old) received 350 mg/kg bw (total mesna consumption was 63 g/kg bw (mean for all animals)) in drinking water over a period of 39 weeks. The rats received daily the dose in 20 mL water solution 5 days a week. Health condition of the animals and their body weights were checked regularly during the entire period of the treatment. At the end of the treatment animals were killed and dissected and urinary bladders and all other organs showing macroscopical alterations were collected for histological examination.
No significant differences were observed in the animals of the 4 experimental groups from a general point of view. Mesna solutions were completely consumed within 24 h from the time of administration. Administration of mesna did not have a significant effect on the weight; an increase in body weight was observed at the beginning of the treatment, up to the eighteenth week, followed by a slight decrease and a steady phase at the end of the experiment. Values ranged between 300 g and 500 g for all experimental groups. Control animals (untreated and receiving mesna alone) did not show any pathological alteration at the end of the experiment and there were no signs of toxicity. A statistically significant increase of the lifespan of the mesna treated animals was observed (P< 0.05).There were no findings at necropsy.
As no toxicological findings were observed in animals treated with mesna alone, 350 mg/kg bw can be considered as chronic NOAEL.

Long-term toxicity data on Mesna from several publications

Mesna is a pharmacologically unremarkable, physiologically largely inert and almost totally non-toxic thio compound (Brock et al., 1982). In the frame of studies on prevention of urotoxicity induced by oxazaphosphorine, toxicity potential of mesna was studied in rats and dogs. In long-term experiments on BD II and BD IX rats (10 per dose and sex) mesna was administered orally for 6 months as a 40% solution in doses of 500, 1000 and 2000 mg/kg bw. The animals tolerated mesna up to 2000 mg/kg bw without compound-linked mortality and morbidity.

Repeated i.v. administration with mesna was carried out for six weeks on Sprague Dawley rats (10 per dose and sex) and on Beagle dogs (3 per dose and sex) with three dose levels, including one toxic dose. Low toxicity of mesna was confirmed in these experiments. The rats tolerated daily intravenous doses of up to 1000 mg/kg bw. The only sign of toxicity under the highest dosage was a retardation of the weights development. The beagle dogs tolerated daily intravenous doses of up to 316 mg/kg bw. The only toxic symptoms were vomiting and diarrhoea. No changes in body weights were observed. Haematological and haematochemical parameters were not affected. In the 100 mg/kg group these symptoms vanished after the first 2 weeks of administration, whilst in the 316 mg/kg group they occasionally persisted to the end of the experiment. No compound-specific effects were brought to light by macroscopic and histological examinations.

Mesna is known as protective agent against damage induced by aggressive anti-neoplastic drugs cyclophosphamide and ifosphamide in the kidney and lower urinary and genital tracts (Son et al., 2003). Ochratoxin A (OTA) is a potent nephrotoxin in several species. In order to elucidate whether mesna has curative or preventive effects on OTA-induced renal damage or renal tumour development, OTA, OTA together with mesna, mesna alone and vehicle sodium bicarbonate were administered to both DA and Lewis rats for their life-time and examined kidney, urethra and urinary bladder histologically. For the assessment of the toxicological profile of mesna, effects in animals from the mesna control group are relevant.

There were no effects of mesna administration at concentration of 1000 mg/L in drinking water on mortality, body weight, gross pathology, histology, non-neoplastic and neoplastic lesions in DA and Lewis rats compared to vehicle control.

Read-across based on grouping of substances in categories (OECD QSAR Toolbox, v.3.0)

Structurally similar substances to 3-mercaptopropanesulfonic acid, sodium salt (CAS 17636 -10 -1) with data on repeated dose toxicity have been searched with the help of the OECD QSAR Toolbox (v.3.0). The prediction was based on the experimental values of chemicals assigned into the category.The target chemical was profiled as "Thiols "Acute toxicity" by the "US EPA New Chemical Categories" and as "High reactive (Thiols)" by the general mechanistic profiling method "DPRA Cysteine peptide depletion".Thiols in general are known to conjugate with proteins via a protein-thiol-disulfide-interchange-mechanism. They are also capable to bind covalently proteins via a SN2 reaction at a sulphur atom leading to disulfide bridges. These mechanisms of action are relevant for the investigated endpoint. Therefore, a search for chemicals with the same profiling results was performed and two categories have been created. In each category, the chemicals with the most data points were taken for the read-across.

In both categories, the nearest read-across chemicals contain thiol functional groups but no sulfonic groups in their structure. Sulfonic group, however, is not associated with high reactivity as it thiol group does i.e. generation of reactive oxygen species in cells, cysteine peptide depletion or interaction with DNA leading to mutations. Therefore, the category members with thiol groups were considered to be worst case for the target substance. The chemicals containing other chemical elements in their structure and/or other organic functional groups have not been removed from the domain since it would destroy the categories. Moreover, the read-across chemicals were similar with the target chemical regarding their mechanistic and endpoint specific profiling (= similar reactivity to biomolecules).The predicted NOAEL for the target chemical were 79.9 mg/kg bw and 137 mg/kg bw in both predictions, respectively.

A third category has been created in order to find chemicals containing sulfonic and thiol functional groups in their structure. However, no chemicals with repeated dose toxicity data were found using "Organic functional groups" as grouping method. Three structurally similar chemicals (2 -propene-1 -sulfonic acid (CAS 2495 -39 -8), sulfamic acid, monosodium salt (CAS 13845 -18 -6) and sodium 2 -hydroxyethane sulfonate CAS 1562 -001) were identified by the calculation method of Dice using standard settings implemented in the Toolbox. The chemicals in the category contained only sulfonic group in their structures and no thiol group. In place of thiol group, amino,- allyl,- and hydroxyl groups are positioned. Sulfonic group, however, is not associated with high reactivity like thiol group it does i.e. generation of reactive oxygen species in cells, cysteine peptide depletion or interaction with DNA leading to mutations. Therefore, the category members with only sulfonic groups can be used for read-across on a limited basis (a detailed assessment of the toxicity pattern is required). The endpoint and mechanistic profiling results of the chemicals in this category differed from those of the target chemical. The category was not refined since it is based on structural similarity principle only and the toxicity data of the structural analogues are intended to be used for comparison with those of other created categories. NOAEL of 733 mg/kg bw was predicted for the target chemical.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The test result originates from an old study published (1984) conducted with the nearest analogue to the target chemical. The publication has been found via OECD QSAR Toolbox (v.3.0) by searching for structurally similar chemicals with long-term toxicity data. The publication is well documented and meets basic scientific principles. The justification on suitability of the analogue substance for the read-across purposes is presented in the section 7.5 (Endpoint summary on repeated dose toxicity) or in the chapter 5.6.3. of CSR.

Justification for classification or non-classification

Based on the results of the key repeated dose toxicity study conducted with the nearest analogue mesna (CAS 19767 -45 -4) and considering the chronic NOEL of 350 mg/kg bw without toxic effects, sodium 3 -mercaptopropanesulfonic acid is not subject to classification and labelling as STOT-RE according to the Regulation No 1272/2008 (CLP).