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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 supported by
recent results obtained with potent dual inhibitors of the two zinc
metallopeptidases, such as RB 105, HSCH2CH(CH3)PhCONHCH(CH3)COOH
(Fournié-Zaluski et al. Proc. Natl. Acad. Sci. U.S.A. 1994, 91, 4072-4076),
which reduces blood pressure in experimental models of hypertension,
independently of the salt 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(R1)CONHCH(R1')CON(R)CH(R2')COOH have
been synthesized. The introduction of well-selected beta-branched chains in
positions R1 and R1', 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-Tyr] 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 S1' and S2' subsites, whereas
additional interactions with the S1 binding subsite of ACE probably account for
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 (Arg102,Glu)NEP and molecular modeling studies with thermolysin used as
model of NEP. 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.
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