Renin inhibitors. Dipeptide analogs of angiotensinogen utilizing a structurally modified phenylalanine residue to impart proteolytic stability

Abstract

A series of renin inhibitors have been prepared and evaluated for their susceptibility to cleavage by the serine protease chymotrypsin. The compounds were designed by consideration of the structural requirements in the active-site region of renin and chymotrypsin. By systematic alteration of the P3 phenylalanine residue, compounds with varying degrees of renin inhibitory potency and chymotrypsin susceptibility were obtained. Selected analogues from this group were examined in vivo for both their hypotensive effects and metabolic patterns.

Prodrugs of Peptides and Proteins for Improved Formulation and Delivery

“…However, as in other peptide analogs (18), simple proteolytic resistance toward chymotrypsin may not result in adequate oral absorption. Consequently, in vivo bioavailability studies are essential for adequate evaluation of this prodrug concept.…”

“…Methods to diminish the proteolytic degradation of polypeptides through irreversible chemical modifications (analog design) have received considerable attention (18,19). Despite prodigious effort, our understanding of the structural modification requirements to impart complete metabolic stability for peptide and peptide mimetic agents remains incomplete.…”

“…In absence of external stimuli to facilitate absorption, use of these alternative routes has had limited success. Various strategies have been implemented to promote bioavailability of polypeptides, including supplemental administration of protease inhibitors (11)(12)(13), use of absorption enhancers (14,15), novel formulation strategies (16,17), and irreversible (analogs) ( 18,19) or reversible (prodrug) chemical modifications.…”

Prodrugs of Peptides and Proteins for Improved Formulation and Delivery

“…delivery (18). Such observations suggest that in vivo studies are pivotal evaluating the therapeutic potential of such prodrugs.…”

Discovery of a well-absorbed, efficacious renin inhibitor, A-74273.

“…Several in vitro techniques for the determination of potency and specificity based on inhibition of activity have been described previously: purified human renal renin, pH 6.0, 13 human plasma renin, pH 7.4, 14 bovine cathepsin D, 13 porcine pepsin, 13 human gastricsin, 15 and human pepsin. 15 The IQo values for animal plasma renins determined at pH 7.4 were quantified by a modification of the human plasma assay in the presence of 3 mM ethylenediaminetetraacetic acid (EDTA), 1.4 mM phenylmethylsulfonyl fluoride (PMSF), and 1% dimethyl sulfoxide 14 ; the respective incubation times at 37°C and the fractions of incubate used for the radioimmunoassay of angiotensin I (Ang I) were 1 hour and 100% for the monkey, 1 hour and 50% for the ferret, 1 hour and 40% for the dog, and 1 hour and 100% for the rat. To avoid possible overestimation of activity, 8-hydroxyquinoline was omitted from the assay.…”