Js. Kong et al., SYNTHESIS AND EVALUATION OF PEPTIDYL MICHAEL ACCEPTORS THAT INACTIVATE HUMAN RHINOVIRUS 3C PROTEASE AND INHIBIT VIRUS-REPLICATION, Journal of medicinal chemistry, 41(14), 1998, pp. 2579-2587
Human rhinovirus, the chief cause of the common cold, contains a posit
ive-sense strand of RNA which is translated into a large polyprotein i
n infected cells. Cleavage of the latter to produce the mature viral p
roteins required for replication is catalyzed in large part by a viral
ly encoded cysteine proteinase (3C(pro)) which is highly selective for
-Q similar to GP- cleavage sites. We synthesized peptidyl derivatives
of vinylogous glutamine or methionine sulfone esters (e.g., Boc-Val-L
eu-Phe-vGln-OR: R = Me, 1; R = Et, 2) and evaluated them as inhibitors
of HRV-14 3C protease (3C(pro)). Compounds 1 and 2 and several relate
d tetra- and pentapeptide analogues rapidly inactivated 3C(pro) with s
ubmicromolar IC50 values. Electrospray mass spectrometry confirmed the
expected 1:1 stoichiometry of 3C(pro) inactivation by 1, 2, and sever
al other analogues. Compound 2 also proved to be useful for active sit
e titration of 3C(pro), which has not been possible heretofore because
of the lack of a suitable reagent. In contrast to 1, 2, and congeners
, peptidyl Michael accepters lacking a Pq residue have greatly reduced
or negligible activity against 3C(pro), consistent with previously es
tablished structure-activity relationships for 3C(pro) substrates. Hyd
rolysis of the P-1 vinylogous grutamine ester to a carboxylic acid als
o decreased inhibitory activity considerably, consistent with the decr
eased reactivity of acrylic acids vs acrylic esters as Michael accepte
rs. Incorporating a vinylogous methionine sulfone ester in place of th
e corresponding glutamine derivative in 1 also reduced activity substa
ntially. Compounds 1 and 2 and several of their analogues inhibited HR
V replication in cell culture by 50% at low micromolar concentrations
while showing little or no evidence of cytotoxicity at 10-fold higher
concentrations. Peptidyl Michael acceptors and their analogues may pro
ve useful as therapeutic agents for pathologies involving cysteine pro
teinase enzymes.