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Toxicokinetic parameters such as uptake, distribution, metabolism and excretion form the essential toxicological profile of a substance. An approximate indication of the toxicokinetic pattern can be gained from the physico-chemical properties (solubility in solvents, log POW, hydrolytic stability) and the results of basic toxicity testing of the test article. The assessment of the toxicokinetic properties of DYNS 2246 given below is based on the results obtained for, the following toxicological endpoints:


·        Acute oral toxicity in rats

·        Acute dermal toxicity in rats

·        In vivo skin irritation in rabbits

·        In vivo eye irritation in rabbits

·        Local lymphnode assay in mice

·        Subacute (28-day) oral toxicity in rats

·        Bacterial reverse mutation test

·        In vitro mammalian cell gene mutation test (HPRT-assay)

·        Chromosome aberration study with mammalian cells in vitro


All studies were carried out according to the principles of Good Laboratory Practice and met the requirements of the OECD and EU-Guideline for the Testing of Chemicals.



Physico-chemical properties

Name:                            DYNS 2246

Chemical name:         beta.-Alanine, N-[4-[2-(2-cyano-4-nitrophenyl)diazenyl]phenyl]-N-(phenylmethyl)-, 2-oxopropyl ester

CAS Number:             1021394-33-1

Physical state:              dark brown fine crystalline solid with a green gleam

Empirical formula:   C26H23N5O5

Molecular weight:     485.5 g/mol

Water solubility:        < 8.45 µg/L (low)

Partition coefficient: log Po/w = 4.5 (relatively high)




Toxicological Profile


After single oral administration of DYNS 2246 at a dose level of 2000 mg/kg body weight to female rats neither deaths nor significant adverse symptoms occurred. Similarly, single dermal application of 2000 mg/kg body weight onto male and female rats produced no deaths or symptoms of systemic toxicity. Test item relatedpurple staining of the treated area was observed up to and including Day 8.The median lethal dose (LD50) of DYNS 2246 after oral and dermal administration to rats is greater than 2000 mg/kg body weight.

Testing for skin irritating properties of DYNS 2246 in rabbits led to a minimal erythema or edema (score 1) up to 24 hours after test item administration.

The administration of DYNS 2246 into the conjunctival sac of rabbit eyes did not result in significant irritation of the conjunctiva. Based on the system of evaluation defined by the EEC, the following group mean scores after 24, 48 and 72 hours were calculated: conjunctiva redness: 1.55, chemosis: 0.0, discharge: 0.0; cornea opacity: 0.0, iris: 0.0. Consequently, DYNS 2246 is not irritating to skin or eyes according to the classification criteria of Directive 2001/59/EC orRegulation (EC) No 1272/2008.

Testing for sensitizing properties of DYNS 2246 was performed in the Local Lymphnode Assay (LLNA) in female mice. Dose levels tested were 5%, 10%, and 25%. No evidence of skin sensitizing properties was found.


To assess the toxicity of DYNS 2246 after repeated administration, male and female rats received the test substance at dose levels of 62.5, 250, or 1000 mg/kg body weight per day for a period of 28 days by oral gavage. 14-day recovery groups (controls and high dose animals) were included in the study.

There was no mortality. Dark colored feces occurred in both sexes from the second treatment day to the end of the treatment period.As further consequence of the staining effect of the test item, dark discoloration of the bedding was observed in males at 1000 mg/kg/day from Day 7 onwards and light pink discoloration of the fur in males and females at 250 and/or 1000 mg/kg/day from Day 19 onwards were recorded. Following completion of the treatment at 1000 mg/kg bw/day (recovery animals), the dark discoloration of the bedding observed in the cages of the male animals ceased as of Day 28, while the light pink staining of the animal fur – observed in 250- and 1000‑mg/kg/day males and 1000-mg/kg/day females – persisted during the first week of post-treatment observation in both sexes. All the animals were normal at the end of the 14-day recovery period.There were no other test item related clinical signs and no functional observation battery effects were found. There were no test item related differences in the body weight development and in the mean food consumption between any dose levels. There were no test item related differences in the examined hematological and clinical chemistry parameters.

At necropsy of the main animals on Day 28, test item-related brown discoloration of the digestive content was observed in 3 rats at 250‑mg/kg/day and all rats at 1000 mg/kg bw/day. Pink-brown discoloration of the whole body in 1 male at 250 mg/kg/day and all males at 1000 mg/kg/day males was suggestive of a secondary effect (staining) of DYNS 2246. No similar effect was noted in the females. At the end of the 14-day recovery period, no DYNS 2246-related macroscopic findings were noted. There were no microscopic changes, or changes in the organ weights related to DYNS 2246 administration in either main or recovery animals examined.

In conclusion, treatment of CRL:(WI) BR rats with DYNS 2246 for 28 days at 1000 mg/kg bw/day did not cause any adverse effects. The only effect of treatment was discoloration of feces, urine and/or skin, attributed to the attaining effect of the dye.

DYNS 2246 was tested for bacterial mutagenicity. The experiments were carried out using histidine-requiring auxotroph strains ofSalmonella typhimurium(TA98, TA100, TA1535 and TA1537), and the tryptophan-requiring auxotroph strain ofEscherichia coli(WP2 uvrA) in the presence and absence of a metabolic activation system, which is a cofactor-supplemented post-mitochondrial S9 fraction prepared from rat liver.

Biologically relevant increases in the number of revertant colonies compared to the solvent control plates were observed in all Salmonella strains with and without metabolic activation.

The observed substantial increases were higher in tester strains sensitive to frameshifts than in tester strains sensitive to base pair substitutions. Higher numbers of revertants were observed in experiments carried out without metabolic activation than in experiments with metabolic activation.

The potential of DYNS 2246 to induce gene mutations in mammalian cells was tested at the HPRT locus in Chinese hamster ovary (CHO KI)cells in vitro using concentrations up to 800 µg/mL. The test substance proved to be non-mutagenic in this test system in the presence and in the absence of a metabolic activation system (S9-mix).

DYNS 2246 has been assessed for its clastogenic potential in a chromosome aberration study in vitro with V79 cells of Chinese hamster lung fibroblasts. In summary, DYNS 2246 tested both with and without metabolic activation did not induce structural chromosome aberrations in this test system. DYNS 2246 is considered non-clastogenic in this system.

Evaluation and Assessment

Examination of the data of the acute dermal toxicity, dermal irritation and skin sensitization studies gave no indication of there being any evidence for skin penetration of the test item. In the rat dermal toxicity study, the remaining color on the skin was not present by about 9 days. Oral bioavailability of DYNS 2246 is plausible due to the log Po/w of 4.5, since substances with a log Po/w > 0.5 might be significantly absorbed. Bioavailability of DYNS 2246 after oral administration was not demonstrated in the subacute 28-day study (at 1000 mg/kg bw) or in any other study, there was no indication of bioaccumulation.

Based on the available data, elimination of test compound probably occurs primarily via feces.

This corresponds to the fact that substances with a molecular weight above 300 g/mol are generally preferentially excreted via the feces in rodents.


In summary, based on the results obtained in various toxicological examinations and in the absence of any significant signs of accumulation it can be concluded that DYNS 2246 does not show any toxicokinetic peculiarity.