New Class of Inhibitors Specific for Human Renin

Abstract
Seven active tetrapeptide amides characterized by a C-terminal phenylalanyl aminoadamantane (PheNHAd) sequence, were identified by selective testing for human renin inhibitory activity among compounds with adjacent hydrophobic groups and molecular size equivalent to 3–5 amino acid residues. The new inhibitors were compared with known renin inhibitors (RIP, pepstatin, H-77) and opioid analgesic agents (Met-enkephalin, morphine), with the following results: The new inhibitors were active against human renin (IC50 ∼10−5M), but inactive against rat renin and pepsin. Although active in opiate receptor binding studies (IC50–10−7M), they were, with few exceptions, inactive in the mouse writhing and hot plate tests for analgesia. SAR studies suggested a separation of the renin inhibitory from the analgesic activity of enkephalin analogs. Preliminary experiments with sodium-depleted rhesus monkeys indicated hypotensive activity for three of the new inhibitors at 3 mg/kg i.v., and RIP at 1 mg/kg. The recently reported clinical hypotensive properties of RIP (Zusman et al., Trans. Assoc. Am. Physicians 96:365, 1983) along with the present comparative studies suggest that the new inhibitors may lead to clinically useful agents.

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