Description: Nepicastat (SYN-117 and RS-25560-197) is a potent and selective inhibitor of both bovine and human dopamine-β-hydroxylase with IC50 of 8.5 nM and 9 nM, with negligible affinity for twelve other enzymes and thirteen neurotransmitter receptors. Dopamine beta-hydroxylase is an enzyme that catalyzes the conversion of dopamine to norepinephrine.Nepicastat has been studied as a possible treatment for congestive heart failure, and appears to be well tolerated.