KT 5720 (CAS 108068-98-0) is a cell-permeable reversible inhibitor of protein kinase A (PKA) that functions through ATP-competitive antagonism with an experimentally determined IC50 of 3 3 M This compound has been shown to counteract multidrug resistance in tumor cells mediated by MDR1 Additionally KT 5720 suppresses hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channel activity resulting in decreased intracellular calcium levels and reduced excitability in dorsal root ganglion (DRG) neurons KT 5720 is utilized in studies investigating mechanisms underlying hematological malignancies and HCN or DRG-related disorders