Non-structural protein NS4B: HCV replication web inducer

Synthesis of novel derivatives of 7,8-dihydro-6H-imidazo[2,1-b][1,3]benzothiazol-5-one and their virus-inhibiting activity against influenza A virus

Influenza remains a highly pathogenic and hardly controlled human infection. The ability of selecting drug-resistant variants necessitates the search and development of novel anti-influenza drugs. Herein, we describe the synthesis and evaluation of a series of novel 2-substituted 7,8-dihydro-6H-imidazo[2,1-b][1,3]benzothiazol-5-ones 3a-k for their virus-inhibiting activity against influenza A virus. The new analogues 3a-k prepared in two steps from commercially available cyclohexane-1,3-diones were fully characterized by their NMR and mass spectral data. Among the new derivatives screened for cytotoxicity and in vitro antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells, three analogues 3i-k containing a thiophene unit were found to exhibit high virus-inhibiting activity (high SI values) and a favorable toxicity profile. The compound 3j (CC₅₀ : >1000 μM, SI = 77) with higher potency is the best anti-influenza hit analogue for further structural optimization and drug development. The most active compounds did not inhibit viral neuraminidase and possess therefore other targets and mechanisms of activity than the currently used neuraminidase inhibitors.

Inhibition of HCV replication by humanized-single domain transbodies to NS4B

NS4B of hepatitis C virus (HCV) initiates membrane web formation, binds RNA and other HCV proteins for viral replication complex (RC) formation, hydrolyses NTP, and inhibits innate anti-viral immunity. Thus, NS4B is an attractive target of a novel anti-HCV agent. In this study, humanized-nanobodies (VHs/VHHs) that bound to recombinant NS4B were produced by means of phage display technology. The nanobodies were linked molecularly to a cell penetrating peptide, penetratin (PEN), for making them cell penetrable (become transbodies). Human hepatic (Huh7) cells transfected with HCV JFH1-RNA that were treated with transbodies from four Escherichia coli clones (PEN-VHH7, PEN-VHH9, PEN-VH33, and PEN-VH43) had significant reduction of HCV RNA amounts in their culture fluids and intracellularly when compared to the transfected cells treated with control transbody and medium alone. The results were supported by the HCV foci assay. The transbody treated-transfected cells also had upregulation of the studied innate cytokine genes, IRF3, IFNβ and IL-28b. The transbodies have high potential for testing further as a novel anti-HCV agent, either alone, adjunct of existing anti-HCV agents/remedies, or in combination with their cognates specific to other HCV enzymes/proteins.