HIV-1 protease inhibitors with a P1 phosphonate modification maintain potency against drug-resistant variants by increased interactions with flap residues.

Protease inhibitors are the most potent antivirals against HIV-1, but they still lose efficacy against resistant variants. Improving the resistance profile is key to developing more robust inhibitors, which may be promising candidates for simplified next-generation antiretroviral therapies. In this study, we explored analogs of darunavir with a P1 phosphonate modification in combination with increasing size of the P1' hydrophobic group and various P2' moieties to improve potency against resistant variants.

Inhibiting HTLV-1 Protease: A Viable Antiviral Target.

Human T-cell lymphotropic virus type 1 (HTLV-1) is a retrovirus that can cause severe paralytic neurologic disease and immune disorders as well as cancer. An estimated 20 million people worldwide are infected with HTLV-1, with prevalence reaching 30% in some parts of the world. In stark contrast to HIV-1, no direct acting antivirals (DAAs) exist against HTLV-1.

Drug Design Strategies to Avoid Resistance in Direct-Acting Antivirals and Beyond.

Drug resistance is prevalent across many diseases, rendering therapies ineffective with severe financial and health consequences. Rather than accepting resistance after the fact, proactive strategies need to be incorporated into the drug design and development process to minimize the impact of drug resistance. These strategies can be derived from our experience with viral disease targets where multiple generations of drugs had to be developed to combat resistance and avoid antiviral failure.

Structural Analysis of Potent Hybrid HIV-1 Protease Inhibitors Containing Bis-tetrahydrofuran in a Pseudosymmetric Dipeptide Isostere.

The design, synthesis, and X-ray structural analysis of hybrid HIV-1 protease inhibitors (PIs) containing bis-tetrahydrofuran (bis-THF) in a pseudo-C-symmetric dipeptide isostere are described. A series of PIs were synthesized by incorporating bis-THF of darunavir on either side of the Phe-Phe isostere of lopinavir in combination with hydrophobic amino acids on the opposite P2/P2' position. Structure-activity relationship studies indicated that the bis-THF moiety can be attached at either the P2 or P2' position without significantly affecting potency.

HIV-1 Protease Inhibitors Incorporating Stereochemically Defined P2' Ligands To Optimize Hydrogen Bonding in the Substrate Envelope.

A structure-guided design strategy was used to improve the resistance profile of HIV-1 protease inhibitors by optimizing hydrogen bonding and van der Waals interactions with the protease while staying within the substrate envelope. Stereoisomers of 4-(1-hydroxyethyl)benzene and 4-(1,2-dihydroxyethyl)benzene moieties were explored as P2' ligands providing pairs of diastereoisomers epimeric at P2', which exhibited distinct potency profiles depending on the configuration of the hydroxyl group and size of the P1' group. While compounds with the 4-(1-hydroxyethyl)benzene P2' moiety maintained excellent antiviral potency against a panel of multidrug-resistant HIV-1 strains, analogues with the polar 4-(1,2-dihydroxyethyl)benzene moiety were less potent, and only the ()-epimer incorporating a larger 2-ethylbutyl P1' group showed improved potency.

Structural Adaptation of Darunavir Analogues against Primary Mutations in HIV-1 Protease.

HIV-1 protease is one of the prime targets of agents used in antiretroviral therapy against HIV. However, under selective pressure of protease inhibitors, primary mutations at the active site weaken inhibitor binding to confer resistance. Darunavir (DRV) is the most potent HIV-1 protease inhibitor in clinic; resistance is limited, as DRV fits well within the substrate envelope.

Quinoxaline-Based Linear HCV NS3/4A Protease Inhibitors Exhibit Potent Activity against Drug Resistant Variants.

A series of linear HCV NS3/4A protease inhibitors was designed by eliminating the P2-P4 macrocyclic linker in grazoprevir, which, in addition to conferring conformational flexibility, allowed structure-activity relationship (SAR) exploration of diverse quinoxalines at the P2 position. Biochemical and replicon data indicated preference for small hydrophobic groups at the 3-position of P2 quinoxaline for maintaining potency against resistant variants R155K, A156T, and D168A/V. The linear inhibitors, though generally less potent than the corresponding macrocyclic analogues, were relatively easier to synthesize and less susceptible to drug resistance.

Dengue Virus NS2B/NS3 Protease Inhibitors Exploiting the Prime Side.

The mosquito-transmitted dengue virus (DENV) infects millions of people in tropical and subtropical regions. Maturation of DENV particles requires proper cleavage of the viral polyprotein, including processing of 8 of the 13 substrate cleavage sites by dengue virus NS2B/NS3 protease. With no available direct-acting antiviral targeting DENV, NS2/NS3 protease is a promising target for inhibitor design.

Design and synthesis of potent macrocyclic HIV-1 protease inhibitors involving P1-P2 ligands.

A series of potent macrocyclic HIV-1 protease inhibitors have been designed and synthesized. The compounds incorporated 16- to 19-membered macrocyclic rings between a nelfinavir-like P2 ligand and a tyrosine side chain containing a hydroxyethylamine sulfonamide isostere. All cyclic inhibitors are more potent than their corresponding acyclic counterparts.