Design of Novel Mercapto-3-phenylpropanoyl Dipeptides as Dual Angiotensin-Converting Enzyme C-Domain-Selective/Neprilysin Inhibitors.

Dual angiotensin-converting enzyme (ACE) and neprilysin (NEP) inhibitors such as omapatrilat showed promise as potent treatments for hypertension but produced adverse effects due to their high affinity for both domains of ACE (nACE and cACE). This led to the search for compounds that retained NEP potency but selectively inhibit cACE, leaving nACE active to degrade other peptides such as bradykinin. Lisinopril-tryptophan (LisW) has previously been reported to have cACE selectivity. Three mercapto-3-phenylpropanoyl inhibitors were synthesized, combining features of omapatrilat and LisW to probe structural characteristics required for potent dual cACE/NEP inhibition. We report the synthesis of these inhibitors, enzyme inhibition data, and high-resolution crystal structures in complex with nACE and cACE. This provides valuable insight into factors driving potency and selectivity and shows that the mercapto-3-phenylpropanoyl backbone is significantly better for NEP potency than a P(1) carboxylate. Future chemistry efforts could be directed at identifying alternative chemotypes for optimization of cACE/NEP inhibitors.