The H series isoquinolinesulfonamide protein kinase (PK) inhibitors are widely used to block signaling pathways to elucidate mechanisms of cellular regulation and signal transduction. H-8, an isoquinolinesulfonamide protein kinase (PK) inhibitor, is a potent inhibitor of PKA and PKG and shows moderate inhibition for PKC and MLCK with Ki values of 1.2, 0.48, 15, and 68 μM, respectively. H-8 can disrupt transcriptional elongation by inhibiting cyclin C/Cdk8 and cyclin H/Cdk7/p36 CTD kinase activity with IC50 values of 47 and 6.2 μM, respectively.
