Optimal recognition of neutral endopeptidase and angiotensin-converting enzyme active sites by mercaptoacyldipeptides as a means to design potent dual inhibitors

An interesting approach for the treatment of congestive heart failure and chronic hypertension could be to avoid the formation of angiotensin II by inhibiting angiotensin converting enzyme (ACE) and to protect atrial natriuretic factor by blocking neutral endopeptidase 24.11 (NEP). This is support-ed by recent results obtained with potent dual inhibitors of the two zinc metallopeptidases, such as RE 105, HSCH2CH(CH3)PhCONHCH(CH3)COOH (Fournie-Zaluski et rrl. Proc, Natl. Acad. Sci. U.S.A, 1994, 91, 4072-4076), which reduces blood pressure in experimental models of hypertension, independently of the stilt and renin angiotensin system status, In order to develop new dual inhibitors with improved affinities, long duration of action, and/or better bioavailabilities, various series of mercaptoacyldipeptides corresponding to the general formula HSCH(R(1))CONHCH(R(1)')CON(R)CH(R(2)')COOH have been si synthesized. The introduction of well-selected beta-branched chains in positions R(1) and R(1)', associated with a tyrosine or a cyclic amino acid in the C-terminal position, led to potent dual inhibitors of NEP and ACE; such as 21 [N-[(2S)-2-mercapto-3-methylbutanoyl]-Ile-Try] and 22 [N-[(2S)-2-mercapto-3-phenylpropanoyl]Ala-Pro] which have IC50 values in the nanomolar range for NEP and subnanomolar range for ACE, These compounds could have different modes of binding to the two peptidases. In NEP, the dual inhibitors seem to interact only with the S-1' and S-2' subsites, whereas additional interactions with the Si binding subsite of ACE probably account fbr their subnanomolar inhibitory potencies for this enzyme. The localization of the Pro residue of 22 outside the NEP active site is supported by biochemical data using (Arg(102),Glu)NEP and molecular modeling studies with thermolysin used as model of WE:P. One hour after oral administration in mice of a single dose (2.7 x 10(-5) mol/kg, 21 inhibited 80% and 36% of kidney NEP and lung ACE, respectively, while 22 inhibited 40% of kidney NEP and 56% of lung ACE.