Disodium 3,3'-dithiobis[propanesulphonate]

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable well-documented publication which meets basic scientific principles.

Remarks:

read-across

Justification for type of information:

REPORTING FORMAT FOR THE CATEGORY APPROACH
For details, please refer to the attached read-across justification. In brief:

1. HYPOTHESIS FOR THE CATEGORY APPROACH (ENDPOINT LEVEL)
There are two category approaches relevant for all human health associated endpoints: Chain-length category and similar metabolic pathway.
Chain-length Category: Both SPS and Dimesna are sodium salts of two sulphonated alkanes connected via a disulphide group. SPS contains two propane moieties, Dimesna ethane ones, hence, these chemicals only differ minor in their hydrocarbon chains in one –CH2– group. The same applies to the carbon chain in MPS and MESNA, connecting the sodium sulfonate with the sulfhydryl moiety. The reactivity and toxicological relevance of this difference in chain length is considered to be minor compared to the chemicals properties triggered by the two remaining respective functional groups. Comparing the actually available information on the substances with regard to their physico-chemical properties, the minor influence of the hydrocarbon chain length becomes obvious. The melting points for the disulphide compounds and the sulfhydryl ones are consistent, and the ones for the ethane derivatives are as expected slightly lower. All compounds are very soluble in water, and similar consistencies are noted with regard to vapour pressure and partition coefficient.
Metabolic pathway: Here it is aimed to justify the read-across from both MPS to SPS and Mensa to Dimesna, and Dimesna to SPS and Mesna to MPS (and vice versa) based on the available information on their metabolism.
Generally, Mesna and Dimesna are considered to be a metabolite of each other. Also, other metabolites of Mesna were identified, besides Mesna-Mesna (i.e., Dimesna), such as Mesna-Cys, Mesna-homocysteine, Mesna-cysteinylglutamate, Mesna-cysteinylglycine, and Mesna-GSH which have been collectively termed “Dimesna” in some studies, while others refer to the mixed disulfides containing a single Mesna moiety as “Mesna”, quantifying Dimesna separately. The relevant functional groups for the enzymatic and non-enzymatic metabolism of Dimesna and Mesna are the disulphide resp. thiol functional groups. Those are both contained in the related substances SPS and MPS, which only differ from the former in their hydrocarbon chains in one –CH2– group, the basic structure and functional groups are however identical. Hence, only taking into account the given functional groups, a similar toxicodynamic behaviour of SPS and MPS compared to Dimesna and Mesna can be expected.

2. CATEGORY APPROACH JUSTIFICATION (ENDPOINT LEVEL)
As shown above, Mesna, MPS, Dimesna and SPS can be used for read-across to each other by grouping of chemicals. Mesna and MPS and Dimesna and SPS share similar physico-chemical properties as well as they exhibit similar toxicological properties, where data is available. Their alkyl side chains differ only in one –CH2- group, so it can be concluded that e.g. absorption, distribution patterns, or excretion from organ systems and body are comparable. Furthermore, Dimesna and Mesna are considered a metabolite of each other, which allows the conclusion that the same also applies for SPS and MPS. Conclusively, data for Mesna, MPS, and Dimesna can be used to cover data gaps for SPS; especially for the required endpoints for human health assessment.
Freely available toxicological information on Dimesna is lacking, so the available information on SPS, MPS and Mesna will be compared in order to obtain contributing information for the read-across justification, as set out in the attachment
The available data indicate that SPS, MPS and Mesna do not need to be classified as acute toxic according to Regulation (EC) No 1272/2008, all available LD50 (oral or dermal) values are greater than 2000 mg/kg bw, clearly indicating the comparability of the substances and the relative harmlessness of all group members including the target chemical SPS with regard to acute toxicity.
All available Ames tests on SPS, MPS and Mesna are consistently negative. Furthermore, the available in vitro micronucleus test on MPS, the SCE assay and in vivo micronucleus test on Mesna do also not give any indication that this group of substances bears any genotoxic properties. Here, gene mutation as well as chromosome mutation and clastogenicity endpoints are covered. In addition, the SCE assay is indicative for an enhanced repair activity upon genotoxic damage, which may result in several outcomes, e.g. point mutations, chromosome breaks etc., which support additionally the hypothesis that this group does not bear genotoxic properties of any kind.
In the available publications on carcinogenicity, both Mesna and its dimer Dimesna did not trigger any signs of toxicity or carcinogenic activity up to the highest dose tested, i.e., 15 resp. 35 mg/kg bw/d with lifetime exposure. Data on Mesna alone indicate that both doses could have been chosen much higher without resulting in any effects, as e.g. a NOAEL was determined to be 350 mg/kg bw/d over an exposure period of 39 weeks. Again this indicates that this group of chemicals does not trigger any relevant adverse effects upon repeated dosage. Last but not least, Mesna was not identified to be a developmental and or reproductive toxicant in several available studies on that endpoint, up to and including limit dosages of 2000 mg/kg bw/d.

Data source

Reference

Reference Type:

publication

Title:

Studies on the Urotoxicity of Oxazaphosphorine Cytostatics and its Prevention. 2. Comparative Study on the Uroprotective Efficacy of Thiols and Other Sulfur Compounds

Author:

Brock, N., Pohl, J., Stekar, J.

Year:

1981

Bibliographic source:

Eur J. Cancer Clin. Oncol., Vol. 17, No. 11, pp, 1155-1163, 1981.

Materials and methods

Objective of study:

excretion

other: protective efficacy against ifosfamide induced urotoxicity

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Mesna was tested for its uroprotective efficacy in 10 (per dose level) Sprague Dawley rats treated with 68 mg/kg ifosfamide that is known to induce haemorrhagic cystitis. Mesna was administered by i. v. administration 15 min before the injection of ifosfamide at dose levels of 6.81, 10.0, 14.7 and 21.5 mg/kg bw. The uroprotective efficacy of Mesna was evaluated 24 hours after the administration of ifosfamide. The rats were killed and the urinary bladder were evaluated (inflammation, bleeding and weight). The pharmakokinetic behaviour of mesna was also studied.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Disodium 3,3'-dithiobis[propanesulphonate]

EC Number:

248-324-3

EC Name:

Disodium 3,3'-dithiobis[propanesulphonate]

Cas Number:

27206-35-5

Molecular formula:

C6H14O6S4.2Na

IUPAC Name:

disodium 3,3'-disulfanediyldipropane-1-sulfonate

Test material form:

solid

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Asta-Werke, Bielefeld, and Mus Rattus AG, Brunnthal
- Weight at study initiation: 250 g
- Housing: standard conditions
- Diet (e.g. ad libitum): ad libitum (altromin ® 1324, no deprivation)
- Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS: not reported

Administration / exposure

Route of administration:

intravenous

Vehicle:

physiological saline

Details on exposure:

No details reported

Duration and frequency of treatment / exposure:

single treatment

Doses / concentrations

Remarks:

Doses / Concentrations:
Screening dose: 100 mg/kg bw;
Further doses: 6.81, 10.0, 14.7 and 21.5 mg/kg bw

No. of animals per sex per dose / concentration:

10

Control animals:

yes, concurrent no treatment

Positive control reference chemical:

Ifosfamide (68 mg/kg bw)

Details on study design:

- Dose selection rationale: screening dose 100 mg/kg, raised or lowered in steps with a factor of 2.15.

Details on dosing and sampling:

PHARMACOKINETIC STUDY (excretion)
- Tissues and body fluids sampled: urine
- Time and frequency of sampling: not reported in details (most likely: every hour)

Statistics:

No data

Results and discussion

Main ADME results

Type:

excretion

Results:

After i.v. administration of 21.5 mg/kg to the rat, about 40% of the administered dose is excreted with the urine as the sulfhydryl compound within the first hour.

Toxicokinetic / pharmacokinetic studies

Details on excretion:

Within the first 3 hour about 50% of the dose is excreted as the sulfhydryl compound and a further 30% of the dose as the disulphide. Rapid renal excretion of sulfhydryl groups is also observed after oral administration of mesna to rats. Similar findings have also been made on the dog. The behaviour of dimesna after intravenous and after oral administration to rats and dogs is very similar to that of mesna. After i.v. administration of 42.4 mg/kg to rats, 28% of the dose was excreted with the urine as the free sulfhydryl compound within 3 hours.

Any other information on results incl. tables

The severity of the inflammation of the bladder after i.v. administration of ifosfamide was dose-dependent. An ifosfamide dose of 68 mg/kg always induced an approximately 2- fold increase in the wet weight of the bladder and a damage score of about 2. Some of the rats also showed bladder haemorrhages. The scoring system used takes into account two parameters: firstly, increased capillary permeability (which is demonstrable objectively by the extravasal occurrence of intravenously injected trypan blue) and secondly, the increase in the weight of the bladder, which can also be assessed macroscopically as a swelling of the bladder. In some selected groups the bladder damage and the extent of bladder protection were also investigated histologically. The uroprotective effect of mesna was dose-dependent. It was reflected in a reduced increase in the bladder weight and reduced extravasation of trypan blue, and it was also demonstrable histologically. In the case of mesna, the lowest dose ensuring reliable uroprotection was determined. The results of these investigations of the uroprotective efficacy of MPS and mesna (as well as it dimer dimesna) are summarized in the following table:

Table 1.  Uroprotective action of mercapto-alkane sulfonates and analogues
					Assessment of urinary bladder
Compound	Structural formula	Dose (mg/kg)		Animals (n)	Inflamm. (x/n)	Bleeding	Weight (mg)		Score (0-3)
						x/n	Mean+S.E.
Untreated controls		—		105	0	0	81.0±12.0		0
Ifosfamide		68.1	i.v.	100	100	63	165.0±35.0		2.3
Mesna	HS-CH2-CH2 -SO3Na	6.81	i.v.	10	6	1	97.3±22.6		1.5
		10.0	i.v.	10	2	0	88.8±5.4		0.5
		14.7	i.v.	10	0	0	77.5±10.9		0.3
		21.5	i.v.	10	0	0	72.6±10.3		0
Dimesna	S-CH2CH2-S03Na S-CH2CH2-S03Na	21.5	i.v.	10	6	3	137.5±29.1		1.4
		31.6	i.v.	10	3	0	101.6±12.4		0.3
		46.4	i.v.	10	1	0	86.6±12.4		0.1
		68.1	i.v.	10	0	0	77.5±10.9		0
Asta 7100	HS-(CH2)3-SO3Na	21.5	i.v.	5	5	0	138.4±26.5		2.0
		68.1	i.v.	5	3	0	80.4±7.4		0.5
		215.0	i.v.	5	1	0	77.0±10.1		0.1

The longer chain homologue of mesna, Asta 7100 (= MPS), was also effective in protection of urinary bladder against ifosfamide induced urotoxicity.

Applicant's summary and conclusion

Conclusions:

Interpretation of results: no bioaccumulation potential based on study results
Mesna protected completely ifosfamide induced urotoxicity in rats. Mesna was rapidly excreted in the urine. Data is taken from an acceptable well documented publication which meets basic scientific principles on a suitable Read-Across substance. Hence, data can be considered to be reliable within an WoE approach to conclude that no potential to bioaccumulate is given for Mesna or its category members.

Executive summary:

Mesna was tested for its uroprotective efficacy in 10 (per dose level) Sprague Dawley rats treated with 68 mg/kg ifosfamide that is known to induce haemorrhagic cystitis (Brock et al., 1981). Mesna was administered by i. v. administration 15 min before the injection of ifosfamide at dose levels of 6.81, 10.0, 14.7 and 21.5 mg/kg bw. The uroprotective efficacy of Mesna was evaluated 24 hours after the administration of ifosfamide. The rats were killed and the urinary bladder were evaluated (inflammation, bleeding and weight). The pharmakokinetic behaviour of mesna was also studied.

The severity of the inflammation of the bladder after i.v. administration of ifosfamide was dose-dependent. An ifosfamide dose of 68 mg/kg always induced an approximately 2- fold increase in the wet weight of the bladder and a damage score of about 2. Some of the rats also showed bladder haemorrhages. The scoring system used takes into account two parameters: firstly, increased capillary permeability (which is demonstrable objectively by the extravasal occurrence of intravenously injected trypan blue) and secondly, the increase in the weight of the bladder, which can also be assessed macroscopically as a swelling of the bladder. In some selected groups the bladder damage and the extent of bladder protection were also investigated histologically. The uroprotective effect of mesna was dose-dependent. It was reflected in a reduced increase in the bladder weight and reduced extravasation of trypan blue, and it was also demonstrable histologically. In the case of mesna, the lowest dose ensuring reliable uroprotection was determined (10 mg/kg bw). The longer chain homologue of mesna, MPS, the proposed metabolite of SPS, was also effective in protection of urinary bladder against ifosfamide induced urotoxicity. Regrading excretion of mesna, after i.v. administration of 21.5 mg/kg to the rat, about 40% of the administered dose is excreted with the urine as the sulfhydryl compound within the first hour. Within the first 3 hour about 50% of the dose is excreted as the sulfhydryl compound and a further 30% of the dose as the disulfide. Rapid renal excretion of sulfhydryl groups is also observed after oral administration of mesna to rats. Similar findings have also been made on the dog. The behaviour of dimesna after intravenous and after oral administration to rats and dogs is very similar to that of mesna. After i.v. administration of 42.4 mg/kg to rats, 28% of the dose was excreted with the urine as the free sulfhydryl compound within 3 hours.

Mesna is a suitable Read-Across substance for SPS asDimesna and Mesna could be considered a metabolite of each other, which allows the conclusion that the same also applies for SPS and MPS, and their respective alkyl side chains differ only in one –CH₂- group, so it can reasonably concluded that e.g. absorption, distribution patterns, or excretion from organ systems and body in total are comparable, which is in detail outlined in the read-across justification.