TRIPEPTIDE ALDEHYDE INHIBITORS OF HUMAN RHINOVIRUS 3C PROTEASE - DESIGN, SYNTHESIS, BIOLOGICAL EVALUATION, AND COCRYSTAL STRUCTURE SOLUTIONOF P-1 GLUTAMINE ISOSTERIC REPLACEMENTS

The investigation of tripeptide aldehydes as reversible covalent inhib itors of human rhinovirus (HRV) 3C protease (3CP) is reported. Molecul ar models based on the apo crystal structure of HRV-14 3CP and other t rypsin-like serine proteases were constructed to approximate the bindi ng of peptide substrates, generate transition state models of P-1-P-1' amide cleavage, and propose novel tripeptide aldehydes. Glutaminal de rivatives have limitations since they exist predominantly in the cycli c hemiaminal form. Therefore, several isosteric replacements for the P -1 carboxamide side chain were designed and incorporated into the trip eptide aldehydes. These compounds were found to be potent inhibitors o f purified HRV-14 3CP with K(i)s ranging from 0.005 to 0.64 mu M. Seve ral have low micromolar antiviral activity when tested against HRV-14- infected H1-HeLa cells. The N-acetyl derivative 3 was also shown to be active against HRV serotypes 2, 16, and 89. High-resolution cocrystal structures of HRV-8 3CP, covalently bound to compounds 3, 15, and 16, were solved. These cocrystal structures were analyzed and compared wi th our original HRV-14 3CP-substrate and inhibitor models.