Synthesis, Enantiomeric Resolution and Biological Evaluation of HIV Capsid Inhibition Activity for Racemic, (S)- and (R)-PF74.

Stuart Ruddell,David J France,Lorna Mae Hellam,Sarah Memarzadeh,Sam J Wilson,Elena Sugrue

doi:10.3390/molecules26133919

Abstract

PF74 is a capsid-targeting inhibitor of HIV replication that effectively perturbs the highly sensitive viral uncoating process. A lack of information regarding the optical purity (enantiomeric excess) of the single stereogenic centre of PF74 has resulted in ambiguity as to the potency of different samples of this compound. Herein is described the synthesis of enantiomerically enriched (S)- and (R)-PF74 and further enrichment of the samples (≥98%) using chiral HPLC resolution. The biological activities of each enantiomer were then evaluated, which determined (S)-PF74 (IC50 1.5 µM) to be significantly more active than (R)-PF74 (IC50 19 µM). Computational docking studies were then conducted to rationalise this large discrepancy in activity, which indicated different binding conformations for each enantiomer. The binding energy of the conformation adopted by the more active (S)-PF74 (ΔG = −73.8 kcal/mol) was calculated to be more favourable than the conformation adopted by the less active (R)-enantiomer (ΔG = −55.8 kcal/mol) in agreement with experimental observations.

Highlights

Human Immunodeficiency Virus (HIV) is a pathogenic retrovirus that infects cells of the human immune system and, if left untreated, can result in Acquired Immunodeficiency Syndrome (AIDS)
Combination antiretroviral therapy currently provides effective viral suppression for most patients, but concerns including drug resistance and adverse drug events provide a powerful motivation for investigation into new mechanisms to treat HIV-1 infection [3]
The small molecule PF74 was the first to be co-crystallised with capsid protein (CA), and has been widely studied [5,6,7]

Summary

Introduction

Human Immunodeficiency Virus (HIV) is a pathogenic retrovirus that infects cells of the human immune system and, if left untreated, can result in Acquired Immunodeficiency Syndrome (AIDS). Nine methyl ester hydrochloride (2a, 2b and 2c, respectively) was utilised to generate the amide containing methyl ester 3 (Scheme 1) Yields for these amidations were greater when using PyBop than those obtained using HATU [13]. A3,dgdreiteinon).aAlldy,dwitihoennaltlhye, wcehlelsnwtheerecetlrlesawteedrewtritehat1e0dμwMithsy10ntμhMetiscy(nrtahceetmicic) PF74, effective inhibition of viral infectivity was observed, as indicated by decrease in the percentage of cells infected for a given dose of CSGW (Figure 3, blue). 2021, 26, x (racemic) PF74, effective inhibition of viral infectivity was observed, as indicated by decrease in the percentage of cells infected for a given dose of CSGW (Figure 3, blue). Molecules 2021, 26, 39(1r9acemic) PF74, effective inhibition of viral infectivity was observed, as indicated by de-4 of 12 crease in the percentage of cells infected for a given dose of CSGW (Figure 3, blue). The results of these computational studies constitute a reasonable explanation as to why the efficacy of (S)-PF74 was approximately 15-fold greater than that of (R)-PF74

General Chemical Methods

Virus Titrations

Molecular Docking Methods

Findings

Conclusions