Renin inhibitors: specific modulators of the renin-angiotensin system.
1. Angiotensin II (AII) acts as a potent pressor agent directly, by virtue of its vasoconstrictor activity and indirectly, by the volume expansion resulting from stimulation of aldosterone release from the adrenal cortex, leading to sodium and water retention. Various approaches of interfering with the enzymatic cascade leading to the production of AII have been made in an attempt to define therapeutic agents for the control of hypertension and heart failure. 2. AII receptor antagonists, to date, lack oral activity and have a relatively short duration of action, limiting their clinical usefulness. Inhibitors of angiotensin converting enzyme block AII production, are orally active and have been used successfully in the control of hypertension and in the treatment of congestive heart failure. 3. An ideal approach to the blockade of the renin-angiotensin system (RAS) is the inhibition of renin, an enzyme with only one known substrate (angiotensinogen) which catalyzes the first and rate-limiting step in the RAS. Early attempts to discover a renin inhibitor focused on immunologic inhibitors of renin, fragments of the prorenin sequence and compounds related to pepstatin, a potent pentapeptide inhibitor of pepsin and less potent inhibitor of renin. None of these approaches proved feasible for a variety of reasons including poor absorption, short duration of action and weak activity. 4. Substrate analogs offer the greatest promise for clinically useful renin inhibitors. Most recently, synthesis of compounds mimicking the enzyme transition state, the condition of greatest binding affinity, has resulted in renin inhibitors with potencies in the nanomolar range, which have shown hypotensive activity. These compounds contain at least one peptide bond and have limited oral activity.(ABSTRACT TRUNCATED AT 250 WORDS)