PDE1

Class

inhibitor

PDE1 (phosphodiesterase 1) is an enzyme family that breaks down two intracellular signaling molecules, cyclic AMP (cAMP) and cyclic GMP (cGMP), which relay messages from cell-surface receptors to downstream effectors controlling contraction, growth, and neuronal signaling. A distinguishing feature of PDE1 is that its activity depends on calcium bound to a protein called calmodulin, linking cyclic nucleotide signaling to calcium fluxes within the cell. PDE1 is expressed in the heart, blood vessels, kidney, and brain. Inhibiting PDE1 slows the breakdown of cAMP and cGMP, prolonging their signaling effects, which include vascular smooth muscle relaxation, modulation of cardiac muscle function, and changes in neuronal excitability. This mechanism is of interest across several disease areas: in cardiovascular disease, where cyclic nucleotide signaling influences blood pressure and heart muscle performance; in neurodegenerative and movement disorders, where dopaminergic signaling in the brain intersects with cyclic nucleotide pathways; and in kidney disease, where similar signaling affects renal blood flow and fluid handling. By acting on a calcium-regulated enzyme rather than a single receptor, PDE1 inhibition offers a way to amplify existing physiological signals in tissues where PDE1 is enriched, rather than introducing an entirely new signal.