Protein kinase, such as CHK-1, inhibiting tricyclic compounds of the following formula (wherein R.sup.2, R.sup.3 and R.sup.4 are as defined in the specification) ##STR00001## pharmaceutical compositions containing effective amounts of said compounds or their salts are useful as a single agent or in combination with an anti-neoplastic agent or therapeutic radiation having an anti-neoplastic effect for treating diseases or conditions such as cancers.