key: cord-0771743-5l749f7o
authors: Pokrovskii, A. G.; Il'icheva, T. N.; Kotovskaya, S. K.; Romanova, S. A.; Charushin, V. N.; Chupakhin, O. N.
title: Fluorinated Derivatives of Benz[4,5]imidazo[1,2-b][1,3] thiazole—Inhibitors of Reproduction of Measles Virus
date: 2004
journal: Dokl Biochem Biophys
DOI: 10.1023/b:dobi.0000046638.99138.e2
sha: bdd1ae2ed69133d4fd4b545622e0fa9c6565ef3c
doc_id: 771743
cord_uid: 5l749f7o

nan

Currently, designing antiviral drugs remains a topical problem because of a wide distribution of HIV infection, viral hepatites, and appearance of new viral infections (including those induced by coronaviruses). The special attention of researchers is attracted by the fluorine-containing heterocyclic compounds, which exhibit a unique set of proportions, because the presence of the fluorine atom increases their solubility in lipids and ability to penetrate across cell membranes [1] . The compounds of the benzimidazole series occupy a key position among the known drugs. For example, the spasmolytic dibazol, neuroleptics pimozide and droperidol, antihistamine drug astemizol, and highly effective antiulcerogenic drug omeprazol are widely used in medicine [2] . Benzimidazole derivatives (including fluorine-containing compounds) that exhibit antiviral activity against herpes virus were found [3] [4] [5] .

In this work, we studied the antiviral activity of new fluorine-containing derivatives of benz [4, 5] imidazo [1,2b ] [1, 3] thiazoles ( 1a-1n ) against the measles virus. The synthesis of the compounds analyzed was described by us earlier [6] . Antiviral activity of these compounds was studied in vitro in Vero green marmoset kidney cells against the measles virus strain Leningrad 16. Cells were cultured in 96-well plates (Costar, the United States) in a DMEM nutrient medium supplemented with 2% bovine fetal serum (ICN, the United States), 100 µ g/ml gentamycin, and 60 µ g/ml lincomycin at 37°ë in 5% ëé 2 . When monolayer was formed, the virus (infection multiplicity, 0.2-0.5 infective units per cell) and the compound tested (concentration, 0.1-400 µ g/ml) were added to wells. Cells were incubated at 37°ë for 5 days in 5% ëé 2 and then stained with crystalline violet (1.3 g of the dye, 50 ml of ethanol, water to 700 ml, and 300 ml of 40% formalin) for 1.5 h. Optical density was determined on a spectrophotometer at a wavelength of 570 nm. Based of the data obtained, 50% toxic ( CD 50 ) and effective ( ED 50 ) doses of compounds were calculated [7] ; the therapeutic index (IS) was determined as CD 50 /ED 50 .

The results of study of antiviral activity and cytotoxicity of 2-aroyl-3-methyl-6,7-difluorobenz [4, 5] imidazo[2,1b ] [1, 3] thiazoles ( 1a-1n ) are summarized in Table 1 . Ribavirin (1-( β -d-ribofuranosyl-10-1,2,4-triazol-3-carboxamide)), which is commonly used for treating infections induced by RNA-containing viruses (including heavy forms of measles) [8] , was used as a reference drug. However, the use of this drug is limited by its high toxicity. Out of 14 compounds studied, compound 1a exhibited the greatest activity: its therapeutic index was much greater than that of ribavirin (245.5 and 14.4, respectively). Lower activity was exhibited by compound 1b ; the other compounds had low activity or were ineffective.

We studied the antiviral activity of compound 1a depending on the time of its addition to culture medium. The tested compound was added one day before virus adsorption, simultaneously with the virus, immediately after virus adsorption, and 6 h and one day after virus adsorption. The results of this experiment are shown in Table 2 . It is seen that preliminary treatment of cells with the compound did not protect cells

against subsequent infection with the measles virus. However, addition of the tested compound simultaneously with the virus or after infecting only slightly affected its antiviral activity: ÖD 50 in the case of simultaneous addition was only in 3, 4 times greater than ÖD 50 determined when the drug was added one day after infecting.

Thus, the study of antiviral activity of 2-aroyl-3methyl-6,7-difluorobenz [4, 5] imidazo [2,1b ] [1, 3] thiazoles ( 1a-1n ) in vitro showed that 2-phenyl-3-methyl-6,7-difluorobenz [4, 5] imidazo[2,1b ][1,3]thiazole ( 1a ) exhibits a pronounced activity against the measles virus and a low toxicity for Vero cells. The antiviral activity slightly changed depending on the time of its addition to culture medium, when the compound was added simultaneously with the virus or within one day after infecting. Apparently, the antiviral activity of compound 1a is related to blocking late stages of measles virus reproduction (synthesis or assembling of viral proteins). In view of this, the drug based on this compound may be used both as a therapeutic and prophylactic agent.

Thus, further study of compound 1a and the whole group of fluorine-containing benzimidazole derivatives show promise for designing novel drugs effective against viral infections. Table 1 . Antiviral activity and cytotoxicity of 2-aroyl-3-methyl-6,7-difluorobenz [4, 5] imidazo [2,1- 

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