Tetra(sodium/potassium)-7-[(E)-{2-acetamido-4-[(E)-(4-{[4-chlor-6-({2-[(4-fluor-6-{[4-(vinylsulfonyl)phenyl]amino}-1,3,5-triazin-2-yl)amino]propyl}amino)-1,3,5-triazin-2-yl]amino}-5-sulfonato-1-naphthyl)diazenyl]-5-methoxyphenyl}diazenyl]-1,3,6-naphthalintrisulfonate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics, other

Type of information:

other: Basic assessment based on phys.-chem. properties and available toxicological data

Adequacy of study:

weight of evidence

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Materials and methods

Principles of method if other than guideline:

Basic assessment based on physchem properties and available tox data

GLP compliance:

no

Test material

Test material information

Constituent 1

Test material form:

other: Solid

Details on test material:

Colour: Black
Purity: Content of organic part (Na-salt): approx. 80 %;Oligomers: 13 %;Main component: approx. 53 %
Stability in Solvent: Stable for 7 days in water, saline, polyethylene glycol, and CMC at room temperature
Storage: At room temperature in the desiccator

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Oral/gastrointestinal absorption:
Based on the molecular weight of 1272.65 g/mol for Reactive Brown 051, it can be assumed to have low oral absorption. However, substances with such high molecular weights can get absorbed to some extent via pinocytosis and/or persorption. With high water solubility of >306 g/L, Reactive Brown 051 may readily dissolve into the gastrointestinal fluids and may get absorbed via passive diffusion, which may be limited by the rate at which the substance partitions out of the gastrointestinal fluid. No findings signifying absorption were reported in an acute oral toxicity study conducted in rats. In the 28-days repeated dose oral toxicity study, discolored faeces and urine were seen with animals treated at high dose group (1000 mg/kg bw/day). The urine discoloration was also reported in females treated at 200 mg/kg bw/day. Both the findings were reversible during the recovery period. In the reproductive and developmental toxicity screening test conducted using oral gavage, decreased fertility and conception indices, and decreased numbers of corpora lutea and implantation sites were the adverse effects observed at the high dose of 1000 mg/kg bw/day. At 300 mg/kg bw/day, the mean number of living pups at first litter check was decreased. These findings support the hypothesis that some absorption is to be expected via gastrointestinal tract. In an erythrocyte micronucleus test, red to orange discoloration of urine was seen with the treated animals. Hence, the systemic distribution and the bioavailability of the test substance could be confirmed. Thus, the high water solubility and the findings of the oral toxicity studies suggests that Reactive Brown 051 may get absorbed to an extent when administered via oral route at high doses.

Dermal absorption:
The molecular weight 1272.65 g/mol for Reactive Brown 051, indicates it being too large for dermal absorption. With high solubility in water (>306 g/L) and low partition coefficient (<-5.4), dermal uptake is expected to be low as Reactive Brown 051 is considered to be too hydrophilic to cross the lipid rich environment of the stratum corneum. The substance is not irritating to skin, and therefore an enhancement of dermal absorption can be ruled out. In support of this low dermal absorption hypothesis, the systemic toxicity of the test substance via the skin is low (acute dermal toxicity, LD50 value of >2000 mg/kg bw for rats). Taking into account the findings from oral dose toxicity studies as discussed under oral absorption section, Reactive Brown 051 can be expected to get absorbed to limited extent when administered via dermal route at sufficiently high doses.

Respiratory absorption:
No experimental data is available concerning the respiratory absorption of Reactive Brown 051. However, it has low vapour pressure (3.06E-37 Pa) and high melting point >250 °C, hence low volatility is to be expected, which implies that the substance may not be available for inhalation as dust/aerosol. The median particle size for Reactive Brown 051 was determined to be <5.5 µm, which indicates possibility of of Reactive Brown 051 reaching lower respiratory tract, when inhaled. However, the high water solubility (>306 g/L), indicates if dust is produced, it may get trapped in the mucus. Thus, Reactive Brown 051 can be expected to be cleared from the respiratory system if it gets inhaled. However, as seen with oral route, absorption via respiratory exposure may take place to a limited extent at sufficiently high doses.

Details on distribution in tissues:

The systemic distribution due to high water solubility would most likely occur via the serum. Owing to the high molecular size and hydrophilic nature of the substance (low n-octanol/water partition coefficient and high water solubility), access of Reactive Brown 051 to the central nervous system (CNS) or testes is likely to be restricted by the blood-brain and blood-testes barriers, while accumulation in body fat is unlikely to occur. In an in vivo micronucleus test in mouse, urine of the animals treated with Reactive Brown 051 was discolored red to orange. Similar, urine discoloration was seen with the animals treated at 1000 mg/kg bw/day and females treated at 200 mg/kg bw/day in the 28 days repeated dose oral toxicity study. These findings indicate the systemic distribution of the test item and its bioavailability.

Details on excretion:

The route of excretion for Reactive Brown 051 has not been investigated. However, owing to the hydrophilic nature of the substance, it will be expected to be predominantly excreted via urine, while any unabsorbed remaining fraction being excreted in the faeces. The urine discoloration reported in the 28 days repeated dose oral toxicity study as well as the micronucleus assay supports the conclusion that excretion through urine will play major role in excretion of this hydrophilic substance. Excretion via faeces was confirmed in the 28-day repeated dose oral toxicity study , wherein, dark discoloration of the faeces was reported in animals at high dose group (1000 mg/kg bw/day), which might be the result of unabsorbed portion of Reactive Brown 051 being excreted through the faecal matter.

Metabolite characterisation studies

Metabolites identified:

no

Details on metabolites:

Currently no investigation regarding metabolism of Reactive Brown 051 is available. There was no evidence to indicate Reactive Brown 051 or metabolite influenced hepatic metabolism in the available genetic toxicity studies. Hence, the high-water solubility of Reactive Brown 051 along with absence of supporting findings for hepatic metabolism suggests that metabolism would be limited and mostly not required to facilitate renal excretion.

Applicant's summary and conclusion

Conclusions:

Reactive Brown 051 would have some degree of absorption from gastrointestinal tract when administered via oral route at sufficiently high doses, while low absorption is expected on dermal and inhalation exposure. The systemic distribution would most likely occur via the serum, while metabolism is expected to occur but would be limited and not required to facilitate renal excretion.