Aziridine inhibitors of HIV-1 protease

Betsy Diann Leverett, Purdue University

Abstract

The HIV-1 Protease (HIV1PR) is an aspartyl protease responsible for the critical proteolytic processing step in the HIV-1 viral life cycle. Though many examples of noncovalent inhibition of HIV1PR have been reported, few attempts have been made to covalently modify this enzyme. In designing a covalent inhibitor for HIV1PR it is advantageous to avoid targeting the catalytically essential Asp25 and Asp25$\sp\prime$ residues as these residues share mechanistic identity with the mammalian aspartyl proteases. Instead, four other conserved, nonessential aspartic acid residues at positions 29, 29$\sp\prime,$ 30, and 30$\sp\prime$ in the HIV1PR active site, which are conserved as Ser and Thr in mammalian enzymes, can serve as potential targets for active site modification. Beginning with the noncovalent inhibitor MVT-101 as a structural template, aziridine-containing peptides have been developed as potential covalent inhibitors of HIV1PR targeting these residues. Computer-assisted design of aziridine inhibitors has provided a series of peptidomimetic structures as targets for synthesis. The inhibitors were derived from MVT-101, either by substitution of the N- or C-terminal residue with an aziridine-containing amino acid, or by addition of aziridine-2-carbonyl to the N-terminus, to give the following three general formulas where X is an aziridine-containing amino acid:(UNFORMATTED TABLE OR EQUATION FOLLOWS)$$\vbox{\halign{#\hfil&&\quad#\hfil\cr{\it type 1\/}: &Ac-{\bf X}-I-Nle-\lbrack CH$\sb2$-NH\rbrack-Nle-Q-R-NH$\sb2$\cr {\it type 2\/}: &Ac-T-I-Nle-\lbrack CH$\sb2$-NH\rbrack-Nle-Q-{\bf X}-NH$\sb2$\cr {\it type 3\/}: &{\bf X}-T-I-Nle-\lbrack CH$\sb2$-NH\rbrack-Nle-Q-R-NH$\sb2.$\cr}}$$(TABLE/EQUATION ENDS) Synthesis of these inhibitors has been initiated with preparation of key intermediates and an investigation of several approaches to representative compounds. A chromogenic assay has been employed to investigate inhibitor activity against HIV1PR. Low micromolar $K\sb{\rm i}$ values have been obtained for MVT-101 and representative compounds in the series. In addition, covalent inactivation of HIV1PR by these inhibitors has been investigated with three types of preincubation experiments. The results of these studies have concurrently indicated a time-dependent loss of activity that is consistent with covalent inhibition.

Degree

Ph.D.

Advisors

Loudon, Purdue University.

Subject Area

Biochemistry|Pharmacology|Pharmacology

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