A number of aromatic mono- and bis-amidines are capable of
blocking cell fusion induced by Respiratory Syncytial (RS) virus.
Suitable amidino compounds include those selected from the group
consisting of 1-4-di(4-amidinophenoxy)-2-butanol;
1,2-bis(5-amidino-2-benzimidazolyl )ethane; 5-amidino-indole;
5-amidinobenzimidazole, 5-amidino-1-methylindole and
5-amidino-1-(4-amidinobenzyl)indole. The most powerful of the
compounds, bis(5-amidino-2-benzimidazolyl)methane (BABIM), is able
to achieve complete suppression of syncytium formation at a
concentration of 1 .mu.M. Inhibition occurs in RS virus-infected
Hep-2 cells as well as CV-1 cells. BABIM also causes a significant
retardation of RS virus penetration, but does not interfere with
adsorption. Addition of the amidines after the penetration of RS
virus does not affect single cycle yields. The compounds may be
used in the prophylactic control of RS virus in man.