CCR5 antagonists: host-targeted antivirals for the treatment of HIV infection.
The human chemokine receptors, CCR5 and CXCR4, are potential host targets for exogenous, small-molecule antagonists for the inhibition of HIV-1 infection. HIV-1 strains can be categorised by co-receptor tropism - their ability to utilise CCR5 (CCR5-tropic), CXCR4 (CXCR4-tropic) or both (dual-tropic) as a co-receptor for entry into susceptible cells. CCR5 may be the more suitable co-receptor target for small-molecule antagonists because a natural deletion in the CCR5 gene preventing its expression on the cell surface is not associated with any obvious phenotype, but can confer resistance to infection by CCR5-tropic strains - the most frequently sexually-transmitted strains. The current leading CCR5 antagonists in clinical development include maraviroc (UK-427,857, Pfizer), aplaviroc (873140, GlaxoSmithKline) and vicriviroc (SCH-D, Schering-Plough), which have demonstrated efficacy and tolerability in HIV-infected patients. Pharmacodynamic data also suggest that these compounds have a long plasma half-life and/or prolonged CCR5 occupancy, which may explain the delay in viral rebound observed following compound withdrawal in short-term monotherapy studies. A switch from CCR5 to CXCR4 tropism occurs spontaneously in approximately 50% of HIV-infected patients and has been associated with, but is not required for, disease progression. The possibility of a co-receptor tropism switch occurring under selection pressure by CCR5 antagonists is discussed. The completion of ongoing Phase lib/Ill studies of maraviroc, aplaviroc and vicriviroc will provide further insight into co-receptor tropism, HIV pathogenesis and the suitability of CCR5 antagonists as a potent new class of antiyirals for the treatment of HIV infection.
Westby
Mike
M
Pfizer Global R&D, Kent, UK. mike.westby@pfizer.com
van der Ryst
Elna
E
D000577:Amides / Q000627:therapeutic use; D019380:Anti-HIV Agents / Q000627:therapeutic use; D000998:Antiviral Agents / Q000627:therapeutic use*; D065100:CCR5 Receptor Antagonists; D002986:Clinical Trials as Topic; D015658:HIV Infections / Q000188:drug therapy*; D015497:HIV-1 / Q000187:drug effects; D006801:Humans; D000644:Quaternary Ammonium Compounds / Q000627:therapeutic use
D000577:Amides; D019380:Anti-HIV Agents; D000998:Antiviral Agents; D065100:CCR5 Receptor Antagonists; D000644:Quaternary Ammonium Compounds; C119369:TAK 779