In prosecution of an anti-Flaviviridae project a new series of variously 
substituted 2-diphenyl-benzimidazoles were synthesized and tested in vitro for 
antiviral and antiproliferative activities. Compounds were tested in cell-based 
assays against viruses representative of: i) two of the three genera of the 
Flaviviridae family, i.e. Flaviviruses and Pestiviruses; ii) other RNA virus 
families, such as Retroviridae, Picornaviridae, Paramyxoviridae, Rhabdoviridae 
and Reoviridae; iii) two DNA virus families (Herpesviridae and Poxviridae). The 
5-Acetyl-2-(4'-nitrobiphenyl-4-yl)-1H-benzimidazole (24) emerged as potent 
active lead compound against Yellow Fever Virus (a Flavivirus) (EC(50) = 0.5 
microM) and CVB-2 at 1 microM and was not cytotoxic, whereas the other title 
benzimidazoles showed no antiviral activity at concentrations not cytotoxic for 
the resting cell monolayers. Among the examined series, the most cytotoxic 
derivatives (11,12,14,16,18,19,20,21,23,25-30) against mock-infected MT-4 cells 
(CC50 < 8.0 microM) were evaluated against a panel of human cell lines derived 
from haematological and solid tumours,using 6-mercaptopurine (6-MP) and 
etoposide as reference drugs. In particular, compounds 26 and 28 showed a 
similar potency of 6-MP and etoposide.