Synthesis and antiviral activity of a new series of 4-isothiazolecarbonitriles

A series of 4-isothiazolecarbonitriles was synthesized and screened for in vitro antiviral activity. The effect of various substituents on the phenyl ring, as well as the substitution of the phenyl for other aromatic and heteroaromatic rings, was examined to establish the requirements for optimum activity. The most active member of the series, 3-methylthio-S-phenyl-4-isothiazolecarbonitrile, exhibited a high level of activity against enteroviruses polio 1 and ECHO 9. Preliminary studies on its mechanism of action indicated that this compound had an effect on an early event in the replication of poliovirus type 1.