DPC 681 and DPC 684: potent, selective inhibitors of human immunodeficiency virus protease active against clinically relevant mutant variants.

Human immunodeficiency virus (HIV) protease inhibitors (PIs) are important components of many highly active antiretroviral therapy regimens. However, development of phenotypic and/or genotypic resistance can occur, including cross-resistance to other PIs. Development of resistance takes place because trough levels of free drug are inadequate to suppress preexisting resistant mutant variants and/or to inhibit de novo-generated resistant mutant variants. There is thus a need for new PIs, which are more potent against mutant variants of HIV and show higher levels of free drug at the trough. We have optimized a series of substituted sulfonamides and evaluated the inhibitors against laboratory strains and clinical isolates of HIV type 1 (HIV-1), including viruses with mutations in the protease gene. In addition, serum protein binding was determined to estimate total drug requirements for 90% suppression of virus replication (plasma IC(90)). Two compounds resulting from our studies, designated DPC 681 and DPC 684, are potent and selective inhibitors of HIV protease with IC(90)s for wild-type HIV-1 of 4 to 40 nM. DPC 681 and DPC 684 showed no loss in potency toward recombinant mutant HIVs with the D30N mutation and a fivefold or smaller loss in potency toward mutant variants with three to five amino acid substitutions. A panel of chimeric viruses constructed from clinical samples from patients who failed PI-containing regimens and containing 5 to 11 mutations, including positions 10, 32, 46, 47, 50, 54, 63, 71, 82, 84, and 90 had mean IC(50) values of <20 nM for DPC 681 and DPC 681, respectively. In contrast, marketed PIs had mean IC(50) values ranging from 200 nM (amprenavir) to >900 nM (nelfinavir).

Identification of selective inhibitors of cyclin dependent kinase 4.

A new structural type of kinase inhibitor, containing a benzocarbazole nucleus, has been identified. Members of the series are selective for inhibition of the cyclin dependent kinase family of enzymes. Although the cdks are highly homologous, representatives of the series showed intra-cdk selectivities, especially for cdk4. SAR studies elucidated the important features of the molecules for inhibition.

Increased antiviral activity of cyclic urea HIV protease inhibitors by modifying the P1/P1' substituents.

A series of alkyl substituted P1/P1' analogs was prepared in an attempt to increase translation of the 3-aminoindazole class of HIV protease inhibitors. Increasing the lipophilicity of the P1/P1' residues dramatically improved translation of enzyme activity to antiviral activity in the whole cell assay.

Stereoisomers of cyclic urea HIV-1 protease inhibitors: synthesis and binding affinities.

We have synthesized stereoisomers of cyclic urea HIV-1 protease inhibitors to study the effect of varying configurations on binding affinities. Four different synthetic approaches were used to prepare the desired cyclic urea stereoisomers. The original cyclic urea synthesis using amino acid starting materials was used to prepare three isomers. Three additional isomers were prepared by synthetic routes utilizing L-tartaric acid and D-sorbitol as chiral starting materials. A stereoselective hydroxyl inversion of the cyclic urea trans-diol was used to prepare three additional isomers. In all 9 of the 10 possible cyclic urea stereoisomers were prepared, and their binding affinities are described.

The synthesis of symmetrical and unsymmetrical P1/P1' cyclic ureas as HIV protease inhibitors.

Cyclic urea SD146, a potent HIV protease inhibitor bearing a flat resistance profile, possessed poor solubility and bioavailability, which precluded further development of the compound. In an effort to improve upon the pharmacokinetic profile of the compound, several analogs modified at the P1/P1' residues were prepared and evaluated. Several of those compounds displayed significant improvement of physical properties.

Preparation and structure-activity relationship of novel P1/P1'-substituted cyclic urea-based human immunodeficiency virus type-1 protease inhibitors.

A series of novel P1/P1'-substituted cyclic urea-based HIV-1 protease inhibitors was prepared. Three different synthetic schemes were used to assemble these compounds. The first approach uses amino acid-based starting materials and was originally used to prepare DMP 323. The other two approaches use L-tartaric acid or L-mannitol as the starting material. The required four contiguous R,S,S,R centers of the cyclic urea scaffold are introduced using substrate control methodology. Each approach has specific advantages based on the desired P1/P1' substituent. Designing analogs based on the enzyme's natural substrates provided compounds with reduced activity. Attempts at exploiting hydrogen bond sites in the S1/S1' pocket, suggested by molecular modeling studies, were not fruitful. Several analogs had better binding affinity compared to our initial leads. Modulating the compound's physical properties led to a 10-fold improvement in translation resulting in better overall antiviral activity.

Phospholipase C inhibitors: a new class of cytotoxic agents.

A series of nitrocoumarin and nitrochromene derivatives have been prepared and shown to inhibit the phosphatidylinositol-specific phospholipase C(PLC)(IC50 < 10 micrograms/mL) isolated from human melanoma. The inhibition of PLC by nitrocoumarin 4a was time-dependent and irreversible. The inhibition of PLC was shown to interfere with inositide metabolism in whole cells (IC50 = 4 micrograms/mL) in a manner consistent with their proposed mode of activity. Finally, the compounds were shown to be growth inhibitory to cultured melanoma cells (ID50 = 2 micrograms/mL), suggesting that PLC may be an attractive new target for chemotherapeutic intervention.