Sodium 1-amino-9,10-dihydro-4-[5-[(2-hydroxyethyl)sulphamoyl]-3,4-xylidino]-9,10-dioxoanthracene-2-sulphonate

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics

Type of information:

other: Expert Statement

Adequacy of study:

weight of evidence

Study period:

2014

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

The absorption, distribution, metabolism and excretion of FAT 20033 have been predicted in the absence of toxicokinetic studies. There are no guidelines on how to conduct this type of modelling, but the methods described are well accepted scientifically.

Principles of method if other than guideline:

The absorption, distribution, metabolism and excretion of FAT 20033/L have been predicted in the absence of toxicokinetic studies. There are no guidelines on how to conduct this type of modelling, but the methods described are well accepted scientifically.

Details on absorption:

Oral route:
A combined repeated dose oral toxicity study with the reproduction/ developmental toxicity screening test was performed in Wistar rats. No mortality occurred in the control or any of the dose groups during the study period and there were no adverse effects of toxicological relevance on any of the parameters investigated (clinical signs, FOB, body weight, food consumption, haematology, blood coagulation, clinical biochemistry, urine, organ weights, gross lesions, histopathology, reproduction, development of the pups, gross external abnormalities, macroscopic findings). Although there were no obvious signs of toxicity exhibited during the study, dose-dependent macroscopic findings related to the test item were found to be bluish or greenish discolouration of various organs (oesophagus, stomach, small and large intestines, Peyer’s patches, mesenteric lymph node, and/or trachea) in males of the high dose group. This observation was considered to reflect the colour of the test item or the colour was formed by the test item mixing with the intestinal contents. However, there was no histologic alteration that correlated with the macroscopic appearances. The discolouration of the organs investigated indicates that all or part of FAT 20033 L has been absorbed following oral intake. However, there is insufficient information available to determine how much of the substance is absorbed and in what form. The lack of oral toxicity seen in the repeated dose study is supported by the acute oral toxicity study. The OECD QSAR application toolbox was used to apply Lipinski's Rule of Five. FAT 20033 L was predicted to be not orally bioavailable based on these rules, although it is clear that it (or possibly its coloured metabolites) is bioavailable from the repeated dose toxicity study. The toolbox is also designed to predict possible metabolites that can be produced by phase 1 (e.g., oxidation/reduction) and phase 2 (e.g., conjugation) biotransformations in the liver, based on the structure of the parent molecule. This biotransformation can occur during the first pass effect but can also occur if the unmetabolised molecule passes into the systemic circulation and returns through the liver.

In conclusion, it is clear from the repeated dose toxicity study that absorption of FAT 20033 L (or possibly one or more of its predicted metabolites, also expected to be blue) must have occurred.

Inhalation route:
There is no information available regarding the absorption or toxicity of FAT 20033/L via inhalation. The vapour pressure of FAT 20033/L is predicted to be low indicating that inhalation exposure from volatilisation is unlikely to be a potential route of exposure. The particle size distribution (L50D = 11.0 µm, L10D = 2.3 µm) of the test material indicates the presence of inhalable and respirable particles. REACH endpoint specific guidance (R.7c) states that respirable particles are < 15 µm. However, according to other REACH guidance (chapter R.14) respirable particles are regarded as being < 10 µm. According to the particle size distribution study, more than 47% of particles are < 10 µm, and 26% are < 5 µm. Therefore, there is potential for deposition in the alveoli, where dissolution in the alveolar fluid could occur followed by absorption. Inhalable particles are likely to be cleared from the lungs by the mucociliary escalator, but then swallowed making them potentially available for absorption via the GI tract.
In conclusion, uptake via the inhalation route is expected to be low to moderate based on the particle size distribution but any particles that reach the alveoli would be expected to be absorbed to a relatively high degree based on the observed absorption via the oral route.

Dermal route:
There is no information available regarding the absorption or toxicity of FAT 20033 L following dermal exposure. Dermal absorption is influenced inter alia by water solubility, log Pow and molecular weight. REACH endpoint specific guidance (R.7c) indicates that the water solubility of FAT 20033 L is within the optimum range of 100-10000 mg/L and thereby favours dermal absorption, but the molecular weight above 500 and log Pow of 0.05 (limiting penetration into stratum corneum) reduces the likelihood. Therefore, dermal absorption is expected to be low.
Although local effects were seen in the acute dermal toxicity study, there was no systemic toxicity reported which provides additional evidence that dermal absorption is low.

Details on distribution in tissues:

In the repeated dose oral toxicity study, macroscopic examination indicated that there was a bluish or greenish discolouration of various organs including the oesophagus, stomach, small and large intestines, Peyer’s patches, mesenteric lymph node, and/or trachea. This indicates that FAT 20033 L and/or its coloured metabolites are distributed extensively throughout the body. The extent to which this absorption and distribution occurs is unknown as it is possible that only a very small amount of the test substance or coloured metabolites can lead to the appearance of blue or green coloured tissue. Based on the very low log Pow of FAT 20033 L, the substance is unlikely to bioaccumulate in fat. In conclusion, FAT 20033 L and/or its metabolites are distributed extensively throughout the body, despite the OECD toolbox prediction of non-bioavailability.

Details on excretion:

Excretion:
The repeated dose toxicity study reports that the faeces were stained a blue colour. This indicates several possibilities; the parent and/or its coloured metabolites were absorbed and then passed through the biliary duct and/or the unmetabolised parent and/or its coloured metabolites (formed in the intestine) passed through the GI tract unabsorbed. Colourless or yellow urine was observed in the test animals and the control during the study. There was no observed blue discolouration of the urine which could indicate that either excretion via urine is minimal or the parent molecule is being metabolised into smaller molecules (e.g., M2, M8, M9) which are colourless and which could pass into the urine undetected. The molecular weights of the parent and unfragmented metabolites are greater than 300 which increases the likelihood of excretion via the biliary duct rather than via urine. This could also explain the lack of blue colouration in the urine. In summary, excretion of FAT 20033/L is expected via bile and GI tract, but not via urine. Excretion via bile is expected for metabolites with molecular weights greater than 300. Excretion of smaller non-coloured metabolites (M3, M9 and M10) via urine is possible.

Details on metabolites:

Metabolism:
Potential metabolites of FAT 20033 L in the liver and skin have been predicted using OECD Toolbox (Table 1). Nine metabolites were predicted for liver metabolism (4 are bioavailable and 5 not bioavailable) and twelve metabolites for skin metabolism (1 is bioavailable and 11 are not bioavailable). Three metabolites were common in both liver and skin (M1, M5 and M6).
The OECD Toolbox has predicted that FAT 20033 L will undergo phase I transformations (reductions, hydroxylation). Some of these transformations, such as reductions, may also occur in the intestine due to action by microflora. Metabolites M2, M8, M9, M13 and M14 were identified by the OECD QSAR application toolbox or by the websites PubChem and ChemSpider.

Toxicologically relevant metabolites:
The toolbox predicts that the parent molecule undergoes minimal biotransformations and remains largely intact. Therefore, the toxicity of these unfragmented metabolites will be similar to the parent.

Glycol acid (M8, glycolic acid):
According to a NICNAS report (Priority Existing Chemical Assessment Report No. 12, 2000), glycolic acid is harmful by single-dose ingestion or inhalation and depending on concentration and pH, it may be either corrosive or irritating to the skin, eyes and respiratory system. Furthermore, it is toxic to the kidneys by prolonged or repeated oral administration. Therefore, it is possible that effects in the kidneys may be seen following oral intake of FAT 20033 L. However, this molecule would be expected to be rapidly excreted.

Glyoxylic acid (M9):
The CCRIS database indicated a number of positive Ames tests on various Salmonella strains. Therefore, formation of this metabolite may exhibit mutagenic potential in humans. However, this molecule would be expected to be rapidly excreted.

Conclusions:

There is insufficient information available to be able to determine the rate and extent of any absorption that may occur and the true toxicokinetic pathway of FAT 20033 L

Executive summary:

The absorption, distribution, metabolism and excretion of FAT 20033 L have been predicted in the absence of toxicokinetic studies. FAT 20033/L (and/or blue-coloured metabolites formed in the GI tract) is absorbed via the oral route, based on blue colouration of tissues/organs. FAT 20033/L uptake via inhalation is expected to be low. FAT 20033/L is expected to have low dermal absorption. FAT 20033/L and/or its predicted metabolites are widely distributed throughout the body, as indicated by blue/ green colouration of organs and tissues. The OECD toolbox predicts that FAT 20033/L will undergo typical phase I biotransformations but these transformations lead to only minimal fragmentation of the molecule. Excretion of FAT 20033/L and any of its predicted metabolites is expected to be via bile and the GI tract, but not via urine. Although there is clear evidence that FAT 20033/L is being systemically absorbed, there was no noticeable toxicity seen in the acute oral, acute dermal and the repeated dose oral toxicity studies.

Description of key information

In accordance with REACH Regulation (EC) No 1907/2006 Annex VIII section 8.8.1, a toxicokinetics study is not required as assessment of the toxicokinetic behaviour of the substance has been derived from the relevant available information.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

5

Absorption rate - inhalation (%):

100

Additional information

No ADME studies are available for FAT 20033/L. Therefore, the toxicokinetic assessment of FAT 20033/L is predicted based on its physico-chemical properties and available toxicological study data. The OECD QSAR application toolbox v3.2 was also utilized to make a qualitative prediction of metabolites formed in the liver and skin. FAT 20033/L (and/or blue-coloured metabolites formed in the GI tract) is absorbed via the oral route, based on blue colouration of tissues/organs. FAT 20033/L uptake via inhalation is expected to be low. FAT 20033 L is expected to have low dermal absorption. FAT 20033/L and/or its predicted metabolites are widely distributed throughout the body, as indicated by blue/ green colouration of organs and tissues. The OECD toolbox predicts that FAT 20033/L will undergo typical phase I biotransformations but these transformations lead to only minimal fragmentation of the molecule. Excretion of FAT 20033/L and any of its predicted metabolites is expected to be via bile and the GI tract, but not via urine. Although there is clear evidence that FAT 20033/L is being systemically absorbed, there was no noticeable toxicity seen in the acute oral, acute dermal and the repeated dose oral toxicity studies.