The heterotrimeric influenza virus polymerase performs replication and transcription of viral RNA in the nucleus of infected cells. Transcription by "cap-snatching" requires that host-cell pre-mRNAs are bound via their 5' cap to the PB2 subunit. Thus, the PB2 cap-binding site is potentially a good target for new antiviral drugs that will directly inhibit viral replication. Docking studies using the structure of the PB2 cap-binding domain suggested that 7-alkylguanine derivatives substituted at position N-9 and N-2 could be good candidates. Four series of 7,9-di- and 2,7,9-trialkyl guanine derivatives were synthesized and evaluated by an AlphaScreen assay in competition with a biotinylated cap analogue. Three synthesized compounds display potent in vitro activity with IC50 values lower than 10 μM. High-resolution X-ray structures of three inhibitors in complex with the H5N1 PB2 cap-binding domain confirmed the binding mode and provide detailed information for further compound optimization.

The design of N-phenylbenzo[d]oxazolamines as CYP26A1 inhibitors involved ligand docking experiments using molecular modeling (FlexX) and analysis of ligand interactions at the binding domain. The synthesis of the benzooxazol-2-yl-[phenyl-imidazol-1-yl-methyl)phenyl]amines was achieved by cyclisation of the corresponding isothiocyanates with subsequent introduction of the haem-binding heterocycle. Triazole and tetrazole derivatives were also prepared for comparison with the lead imidazole derivative. The benzooxazol-2-yl-[phenyl-imidazol-1-yl-methyl)phenyl]amines with small substituents in the phenyl ring were moderately potent CYP26A1 inhibitors (IC50 8 and 12 μM) and comparable with liarozole (IC50 7 μM).

Methodology previously described by our group was applied to the preparation of a series of 4-alkyl/aryl-substituted 1-[benzofuran-2-yl-phenylmethyl]-1H-triazoles. The [1,2,4]-triazole derivatives were prepared for a range of alkyl and aryl substituents, and for the 4-methyl, 4-ethyl, 4-'propyl, 4-'butyl, 4-phenyl and 4-chlorophenyl derivatives, the minor [1,3,4]-triazole isomer also isolated. All the triazole derivatives were evaluated for CYP26A1 inhibitory activity using a MCF-7 cell-based assay. The 4-ethyl and 4-phenyl-1,2,4-triazole derivatives displayed inhibitory activity (IC50 4.5 and 7 mu M, respectively) comparable with that of the CYP26 inhibitor liarozole (IC50 7 mu M). Using a CYP26A1 homology model (based on CYP3A4) template, docking experiments were performed with MOE with multiple hydrophobic interactions observed in addition to coordination between the triazole nitrogen and the haem transition metal. (c) 2006 Elsevier Ltd. All rights reserved.