title: A low-molecular-weight entry inhibitor of both CCR5- and CXCR4-tropic strains of human immunodeficiency virus type 1 targets a novel site on gp41.
abstract: A low-molecular-weight human immunodeficiency virus type 1 (HIV-1) inhibitor, PF-68742 (molecular weight, 573), has been identified in a high-throughput screen for compounds that block HIV-1 envelope glycoprotein (Env)-mediated fusion. The compound is shown to be potent against R5 and X4 isolates in both cell-cell fusion and antiviral assays (50% effective concentrations of approximately 0.1 to 1 muM). Postfusion and HIV-1 pseudotyping control experiments confirm that PF-68742 is an entry inhibitor with Env as the specific target for antiviral action. PF-68742 was not able to block binding of monomeric gp120 to soluble CD4 or the binding of gp120:CD4 complexes to cell-associated CCR5, thus distinguishing PF-68742 from described gp120 antagonists and coreceptor binders. Escape variants of HIV-1(NL4-3) were selected, and all resistant viruses were found to contain a common G514R (HxB2 numbering) mutation in Env, located proximal to the furin cleavage site in the fusion peptide of gp41. When introduced into wild-type NL4-3 gp41, G514R conferred resistance to PF-68742. Resistance via G514R is shown to be associated with enhancement of virion infectivity by PF-68742 that may result from altered properties of inhibitor-bound Env, rather than from a loss of compound binding. Wild-type viruses and those with substitutions in the disulfide loop (DSL) region of gp41 were also examined for PF-68742 sensitivity. Here, complete resistance to PF-68742 was found to occur through changes outside of position 514, including in the gp41 DSL region. The results highlight PF-68742 as a starting point for novel therapies against HIV-1 and provide new insights into models of Env-mediated fusion.
authors.affiliation: Antiviral Research Unit, IPC 424, Pfizer PGRD, Discovery Biology, Sandwich Laboratories, Sandwich, Kent CT13 9NJ, United Kingdom. ted.murray@pfizer.com
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Murray
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Leaman
authors.forename: Nishant
authors.initials: N
authors.lastname: Pawa
authors.forename: Hannah
authors.initials: H
authors.lastname: Perkins
authors.forename: Chris
authors.initials: C
authors.lastname: Pickford
authors.forename: Manos
authors.initials: M
authors.lastname: Perros
authors.forename: Michael B
authors.initials: MB
authors.lastname: Zwick
authors.forename: Scott L
authors.initials: SL
authors.lastname: Butler
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D065100:CCR5 Receptor Antagonists; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015699:HIV Envelope Protein gp120 / Q000378:metabolism; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D023581:HIV Fusion Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D009154:Mutation; D011728:Pyridones / Q000494:pharmacology*; D019713:Receptors, CCR5 / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016415:Sequence Alignment; D013449:Sulfonamides / Q000494:pharmacology*; D053586:Virus Internalization / Q000187:drug effects*
chemical_list: D065100:CCR5 Receptor Antagonists; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D023581:HIV Fusion Inhibitors; C551246:PF 68742; D011728:Pyridones; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; D013449:Sulfonamides