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Twelve aminoarylazocompounds (A-C) and 46 aryltriazene 7 derivatives (D-G) have been synthesized and evaluated in cell-based assays for cytotoxicity and antiviral activity against a panel of 10 RNA and DNA viruses. Eight aminoazocompounds and 27 aryltriazene derivatives exhibited antiviral activity, sometimes of high level, against one or more viruses. A marked activity against BVDV and YFV was prevailing among the former compounds, while the latter type of compounds affected mainly CVB-2 and RSV. None of the active compounds inhibited the multiplication of HIV-1, VSV and VV. Arranged in order of decreasing potency and selectivity versus the host cell lines, the best compounds are the following; BVDV: 1>7>8>4; YFV: 7>5; CVB-2: 25>56>18; RSV: 14>20>55>38>18>19; HSV-1: 2. For these compounds the EC(50) ranged from 1.6 microM (1) to 12 microM (18), and the S. I. from 19.4 (1) to 4.2 (2). Thus the aminoarylazo and aryltriazene substructures appear as interesting molecular component for developing antiviral agents against ss RNA viruses, particularly against RSV and BVDV, which are important human and veterinary pathogens. Finally, molecular modeling investigations indicated that compounds of structure A-C, active against BVDV, could work targeting the viral RNA-dependent RNA-polymerase (RdRp), having been observed a good agreement between the trends of the estimated IC(50) and the experimental EC(50) values.

We have identified a series of 1-aryl-4,6-diamino-1,2-dihydrotriazines, structurally related to the antimalarial drug cycloguanil, as new inhibitors of influenza A and B virus and respiratory syncytial virus (RSV) via targeting of the host dihydrofolate reductase (DHFR) enzyme. Most analogues proved active against influenza B virus in the low micromolar range, and the best compounds (11, 13, 14 and 16) even reached the sub-micromolar potency of zanamivir (EC = 0.060 μM), and markedly exceeded (up to 327 times) the antiviral efficacy of ribavirin. Activity was also observed for two influenza A strains, including a virus with the S31N mutant form of M2 proton channel, which is the most prevalent resistance mutation for amantadine. Importantly, the compounds displayed nanomolar activity against RSV and a superior selectivity index, since the ratio of cytotoxic to antiviral concentration was >10,000 for the three most active compounds 11, 14 and 16 (EC ∼0.008 μM), far surpassing the potency and safety profile of the licensed drug ribavirin (EC = 5.8 μM, SI > 43).

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Forty-three 2-[(benzotriazol-1/2-yl)methyl]benzimidazoles, bearing either linear (dialkylamino)alkyl- or bulkier (quinolizidin-1-yl)alkyl moieties at position 1, were evaluated in cell-based assays for cytotoxicity and antiviral activity against viruses representative of two of the three genera of the Flaviviridae family, i.e. Flaviviruses (Yellow Fever Virus (YFV)) and Pestiviruses (Bovine Viral Diarrhoea Virus (BVDV)), as Hepaciviruses can hardly be used in routine cell-based assays. Compounds were also tested against representatives of other virus families. Among ssRNA+ viruses were a retrovirus (Human Immunodeficiency Virus type 1 (HIV-1)), two picornaviruses (Coxsackie Virus type B2 (CVB2), and Poliovirus type-1, Sabin strain (Sb-1)); among ssRNA- viruses were a Paramyxoviridae (Respiratory Syncytial Virus (RSV)) and a Rhabdoviridae (Vesicular Stomatitis Virus (VSV)) representative. Among double-stranded RNA (dsRNA) viruses was a Reoviridae representative (Reo-1). Two representatives of DNA virus families were also included: Herpes Simplex type 1, (HSV-1; Herpesviridae) and Vaccinia Virus (VV; Poxviridae). Most compounds exhibited potent activity against RSV, with EC(50) values as low as 20 nM. Moreover, some compounds, in particular when bearing a (quinolizidin-1-yl)alkyl residue, were also moderately active against BVDV, YFV, and CVB2.