Abstract
The compound ICI 65,709 is a substituted guanidine which has antiviral activity in human embryo lung cells (Bucknall et al. 1973). We have found that ICI 65,709 reversibly inhibits the synthesis of RNA by rhinovirus type 2. The three species of virus RNA were equally affected. Comparison of the effect with that of guanidine, a well known inhibitor of picornavirus RNA synthesis, showed that ICI 65,709 and guanidine mediated their antiviral effects in different ways. This conclusion was supported by the failure of ICI 65,709 to inhibit multiplication of a bovine enterovirus which was inhibited by guanidine. ICI 65,709 also inhibited the multiplication of poliovirus type 1.