In Vivo Emergence of Vicriviroc Resistance in a Human Immunodeficiency Virus Type 1 Subtype C-Infected Subject

Abstract

Little is known about the in vivo development of resistance to human immunodeficiency virus type 1 (HIV-1) CCR5 antagonists. We studied 29 subjects with virologic failure from a phase IIb study of the CCR5 antagonist vicriviroc (VCV) and identified one individual with HIV-1 subtype C who developed VCV resistance. Studies with chimeric envelopes demonstrated that changes within the V3 loop were sufficient to confer VCV resistance. Resistant virus showed VCV-enhanced replication, cross-resistance to another CCR5 antagonist, TAK779, and increased sensitivity to aminooxypentane-RANTES and the CCR5 monoclonal antibody HGS004. Pretreatment V3 loop sequences reemerged following VCV discontinuation, implying that VCV resistance has associated fitness costs.The human immunodeficiency virus type 1 (HIV-1) envelope third variable loop (V3) is the major structural element of gp120 that determines coreceptor recognition and specificity (9,15,16). Vicriviroc (VCV; Schering-Plough) and maraviroc (Selzentry; Pfizer) are allosteric noncompetitive antagonists that bind to similar sites on CCR5 and antagonize the gp120-CCR5 interaction (19). To date, data on resistance to these agents have come largely from in vitro selection studies. Phenotypically, resistance manifests as a plateau in the maximum achievable suppression of viral replication (19). This plateau, referred to as the percent maximal inhibition, correlates with viral adaptation to the use of the inhibitor-bound form of CCR5 for entry (13,21). Genotypically, VCV resistance has been associated with a variety of amino-acid-changing mutations throughout the envelope gene (env) that most often involve V3 but whose effect on drug susceptibility depends on the env backbone into which they are introduced (5). In vitro data suggest that resistance to the closely related CCR5 antagonist AD101 does not confer a significant loss of viral fitness (1, 8). In vivo resistance to the CCR5 antagonists remains poorly defined.To study the emergence of VCV resistance in vivo, we monitored subjects enrolled in ACTG 5211, a 48-week study of VCV in 118 HIV-1-infected, treatment-experienced subjects (3). Among the 90 subjects receiving VCV, we studied all 29 who experienced protocol-defined virologic failure. We amplified full-length HIV-1 env from plasma samples collected during the period from study entry through week 48. These env sequences were used to generate pseudovirions for examining VCV susceptibility and coreceptor usage in the PhenoSense entry susceptibility and Trofile assays (Monogram Biosciences), respectively (20,22). In 28 of 29 subjects analyzed, no evidence of decreased VCV susceptibility was observed (data not shown). Samples from the remaining subject demonstrated increasing VCV resistance over 28 weeks (Fig. 1). This subject, randomly assigned to receive 10 mg of VCV daily, experienced protocol-defined virologic failure at week 16 but continued VCV treatment through week 28 (see Fig. S1 in the supplemental material). Samples from 13 of the 29 subjects showed the emergence...

HIV-1 Resistance to CCR5 Antagonists Associated with Highly Efficient Use of CCR5 and Altered Tropism on Primary CD4 + T Cells

“…Passaging HIV-1 in the presence of increasing concentrations of a CCR5 antagonist in vitro can result in the development of mutations in Env that enable it to recognize the drugbound conformation of CCR5 (22,33,51,56). A similar resistance pathway can occur in vivo or, as we have shown, can even occur in the absence of drug selection (48,53). This resistance pathway often, but not always, results in a virus that is resistant to multiple CCR5 antagonists (22,33,39,53,56).…”

“…A similar resistance pathway can occur in vivo or, as we have shown, can even occur in the absence of drug selection (48,53). This resistance pathway often, but not always, results in a virus that is resistant to multiple CCR5 antagonists (22,33,39,53,56). The CCR5 antagonists that have been used clinically all seem to bind to a hydrophobic region in the transmembrane helices of CCR5 and induce conformational alterations in the extracellular domains of the coreceptor that inhibit recognition by gp120 (13,31,32,46,52).…”

“…Viral determinants critical for CCR5 antagonist resistance are often localized to the V3 loop, consistent with the role of this domain in mediating coreceptor interactions (22,33,53,56). However, while V3 loop mutations appear to be a common though not universal theme underlying resistance to CCR5 antagonists, the specific changes can vary and are often context dependent in that mutations important for CCR5 antagonist resistance often fail to impart complete resistance when introduced into a heterologous background (22,37).…”

“…Because all Env clones isolated from this patient were resistant to complete suppression by aplaviroc, we performed a protein BLAST search on the Env clone demonstrating the greatest resistance to aplaviroc (clone pre5.2) and identified JRFL as a closely related, commonly studied HIV strain that is sensitive to inhibition by aplaviroc and other CCR5 antagonists. Since mutations in the V3 loop are commonly associated with resistance to CCR5 antagonists (22,33,53,56), we constructed chimeric viruses in which the V3 loops of pre5.2 and JRFL were exchanged. Pseudotype infection assays were performed on NP2/CD4/CCR5 cells in the presence or absence of 10 M aplaviroc, a level empirically determined to be 3 log units higher than required to saturate CCR5 receptors on this cell line.…”

Reduction of CCR5 with low-dose rapamycin enhances the antiviral activity of vicriviroc against both sensitive and drug-resistant HIV-1

“…Results from both VCV and maraviroc trials in patients infected with R5 HIV-1 indicate that X4 variants can be detected in some patients who do not respond to antagonist treatment. However, genotypic analyses suggest that such X4 variants already were present, although at an undetectable frequency, before treatment, and that their presence became evident after suppression of the dominant R5 strains (36,37). Thus, therapy with a CCR5 antagonist may select for pre-existing X4 strains but does not seem to induce evolution of R5 to X4 strains.…”