In this study we describe an extension of our previous studies on cis- benzylidenemalononitrile tyrphostins. We have introduced S-aryl substituents in the 5 position (meta vis-a-vis the malononitrile moiety). We find that these compounds are potent blockers of EGFR kinase and its homolog HER-2 kinase. Interestingly, we find that certain S- aryltyrphostins discriminate between EGFR and HER-2 kinase in favor of the HER-2 ...