Protein kinase A (PKA), also known as cAMP-dependent protein kinase, is a serine-threonine kinase with a tetrameric structure consisting of regulatory and catalytic subunits. As its name suggests, PKA functions are dependent on cAMP and include metabolism, ion channel activation, cell growth and differentiation, gene expression and apoptosis. PKA inhibitors have been identified as potential targets for cancer therapy. Due to PKA’s structure, inhibitors are either inhibitory analogues of cAMP or structures that block the ATP binding site. H-89, the most well-known PKA inhibitor, acts via competitive inhibition to the binding site.