HALOPERIDOL-BASED IRREVERSIBLE INHIBITORS OF THE HIV-1 AND HIV-2 PROTEASES

The proteases expressed by the HIV-1 and HIV-2 viruses process the pol yproteins encoded by the viral genomes into the mature proteins requir ed for virion replication and assembly. Eight analogs of haloperidol h ave been synthesized that cause time-dependent inactivation of the HIV -I protease and, in six cases, HIV-2 protease. The IC50 values for the analogues are comparable to that of haloperidol itself. Enzyme inacti vation is due to the presence of an epoxide in two of the analogues an d carbonyl-conjugated double or triple bonds in the others. Irreversib le inactivation is confirmed by the failure to recover activity when o ne of the inhibitors is removed from the medium.` At pH 8.0, the agent s inactivate the HIV-1 protease 4-80 times more rapidly than the HIV-2 protease. Faster inactivation of the HIV-1 protease is consistent wit h alkylation of cysteine residues because the HIV-1 protease has four such residues whereas the HIV-2 protease has none. Inactivation of the HIV-2 protease requires modification of non-cysteine residues. The si milarities in the rates of inactivation of the HIV-2 protease by six a gents that have intrinsically different reactivities toward nucleophil es suggest that the rate-limiting step in the inactivation process is not the alkylation reaction itself. At least five of the agents inhibi t polyprotein processing in an ex vivo cell assay system, but they are also toxic to the cells.