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Quantitative Structure-Activity Relationship, Activity Prediction, and Molecular Dynamics of Non-nucleotide Reverse Transcriptase Inhibitors

Quantitative Structure-Activity Relationship, Activity Prediction, and Molecular Dynamics of Non-nucleotide Reverse Transcriptase Inhibitors

Published on: May 9, 2025

Derivatives of mesoxalic acid block translocation of HIV-1 reverse transcriptase

Jean A Bernatchez¹, Rakesh Paul², Egor P Tchesnokov³

¹From the Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada.

The Journal of Biological Chemistry

|October 31, 2014

Abstract:

The pyrophosphate mimic and broad spectrum antiviral phosphonoformic acid (PFA, foscarnet) was shown to freeze the pre-translocational state of the reverse transcriptase (RT) complex of the human immunodeficiency virus type 1 (HIV-1). However, PFA lacks a specificity domain, which is seen as a major reason for toxic side effects associated with the clinical use of this drug. Here, we studied the mechanism of inhibition of HIV-1 RT by the 4-chlorophenylhydrazone of mesoxalic acid (CPHM) and demonstrate that this compound also blocks RT translocation. Hot spots for inhibition with PFA or CPHM occur at template positions with a bias toward pre-translocation. Mutations at active site residue Asp-185 compromise binding of both compounds. Moreover, divalent metal ions are required for the formation of ternary complexes with either of the two compounds. However, CPHM contains both an anchor domain that likely interacts with the catalytic metal ions and a specificity domain. Thus, although the inhibitor binding sites may partly overlap, they are not identical. The K65R mutation in HIV-1 RT, which reduces affinity to PFA, increases affinity to CPHM. Details with respect to the binding sites of the two inhibitors are provided on the basis of mutagenesis studies, structure-activity relationship analyses with newly designed CPHM derivatives, and in silico docking experiments. Together, these findings validate the pre-translocated complex of HIV-1 RT as a specific target for the development of novel classes of RT inhibitors.

Insights

Phosphonoformic acid (PFA) inhibits HIV-1 reverse transcriptase (RT) but causes toxicity. A new compound, CPHM, also blocks RT translocation and shows potential for developing specific HIV-1 RT inhibitors with fewer side effects.

Area of Science:

Virology
Drug Discovery
Molecular Biology

Background:

Phosphonoformic acid (PFA) is a broad-spectrum antiviral that inhibits HIV-1 reverse transcriptase (RT) by freezing its pre-translocational state.
PFA's lack of a specificity domain contributes to its clinical toxicity.
Developing specific HIV-1 RT inhibitors is crucial for effective antiviral therapy.

Purpose of the Study:

To investigate the mechanism of HIV-1 RT inhibition by 4-chlorophenylhydrazone of mesoxalic acid (CPHM).
To compare the inhibition mechanism of CPHM with PFA.
To explore CPHM as a potential lead for developing novel, specific RT inhibitors.

Main Methods:

Mutagenesis studies targeting the Asp-185 residue.
Structure-activity relationship (SAR) analyses of novel CPHM derivatives.
In silico docking experiments.
Analysis of inhibitor binding in the presence of divalent metal ions.

Main Results:

CPHM, like PFA, inhibits HIV-1 RT by blocking translocation, with a preference for pre-translocational states.
CPHM possesses both an anchor domain for metal ion interaction and a specificity domain, unlike PFA.
The K65R mutation in HIV-1 RT enhances affinity for CPHM while reducing it for PFA, indicating distinct binding sites.
Mutagenesis and SAR studies elucidated inhibitor binding sites.

Conclusions:

The pre-translocated complex of HIV-1 RT is a validated target for specific inhibitor development.
CPHM represents a promising scaffold for designing novel HIV-1 RT inhibitors with improved specificity and reduced toxicity.
Understanding the distinct binding mechanisms of PFA and CPHM provides a foundation for rational drug design.

Read full analysis

Keywords:

Antiviral Agent Drug Action Drug Resistance Human Immunodeficiency Virus (HIV)Reverse Transcription

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