| Reference | 1. J Clin Virol. 2012 Oct;55(2):134-9. doi: 10.1016/j.jcv.2012.06.021. Epub 2012 Jul 21.<br />
Detection of HIV-1 CXCR4 tropism and resistance in treatment experienced subjects receiving CCR5 antagonist-Vicriviroc.<br />
McNicholas P(1), Vilchez RA, Greaves W, Kumar S, Onyebuchi C, Black T, Strizki JM.<br />
Author information:<br />
(1)Merck Research Laboratories, Kenilworth, NJ, USA.<br />
BACKGROUND: Vicriviroc (VCV), a small-molecule antagonist of the C-C chemokine receptor 5 (CCR5), blocks HIV's entry into CD4+ cells. Small studies have suggested that resistance to CCR5 antagonists is slow to develop.<br />
OBJECTIVES: To examine resistance to VCV in isolates from treatment experienced patients who experienced virologic failure in two phase 3 trials.<br />
STUDY DESIGN: Genotypic and phenotypic susceptibility to VCV, and other antiretroviral drugs were evaluated at baseline and at defined intervals during the study. In a post hoc analysis, viral tropism at baseline was evaluated using the Trofile-ES assay. Only subjects with R5-tropic virus were included in the analysis. Viral envelope sequencing was performed on samples from subjects with emergent VCV resistance defined using a relative MPI cutoff.<br />
RESULTS: 71/486 subjects treated with VCV for 48 weeks met the protocol-defined virologic failure criteria. 7/71 (10%) had DM/X4 virus at the time of virologic failure; VCV resistance was identified in 4/486 treated subjects (1%). No control subject had detectable DM/X4 virus or VCV resistance at virologic failure. Clonal analysis of envelope sequences from VCV-resistant virus identified 2-5 amino acid substitutions at or near the crown of the V3 loop; however, no signature V3 mutations were identified. Changes outside the V3 loop were also observed in resistant clones; no consistent variant pattern was observed.<br />
CONCLUSIONS: In these trials, use of a sensitive tropism assay and potent antiretroviral drug combinations contributed to the infrequent detection of X4-tropic virus and VCV resistance. Substitutions in the V3 loop were associated with VCV resistance, however, no specific pattern of amino acid changes were sufficient to reliably predict VCV susceptibility.<br />
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2. Virology. 2012 Jun 5;427(2):158-65. doi: 10.1016/j.virol.2012.02.006. Epub 2012 Mar 16.<br />
V3 determinants of HIV-1 escape from the CCR5 inhibitors Maraviroc and Vicriviroc.<br />
Berro R(1), Klasse PJ, Jakobsen MR, Gorry PR, Moore JP, Sanders RW.<br />
Author information:<br />
(1)Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10065, USA.<br />
Erratum in<br />
Virology. 2012 Jun 20;428(1):76. Jakobsen, Martin R [added]; Gorry, Paul R [added].<br />
HIV-1 develops resistance to CCR5 antagonists such as Maraviroc (MVC) and Vicriviroc (VVC) both in vitro and in vivo, with most changes arising in the gp120 V3 region. Both compounds bind to the same hydrophobic cavity in CCR5 in subtly different ways. Here, we investigated which V3 sequence changes are most associated with MVC and VVC resistance and how they affect the interaction between gp120 and the CCR5 NT. We found that VVC- and MVC-selected amino acid changes map to different V3 locations and involve residues that interact with the CCR5 NT in different ways. Changes in VVC-selected, but not MVC-selected, variants often involve charged residues. Although the overall V3 charge tends not to change, the introduction or removal of charged residues at specific positions affects the local electrostatic potential and could have structural and functional implications. In summary, VVC and MVC trigger the evolution of distinct HIV-1 resistance patterns in V3.<br />
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3. Clin Ther. 2011 Oct;33(10):1503-14. doi: 10.1016/j.clinthera.2011.08.012. Epub 2011 Oct 19.<br />
Effect of vicriviroc with or without ritonavir on oral contraceptive pharmacokinetics: a randomized, open-label, parallel-group, fixed-sequence crossover trial in healthy women.<br />
Kasserra C(1), Li J, March B, O'Mara E.<br />
Author information:<br />
(1)Schering-Plough, Merck & Co., Inc., Kenilworth, New Jersey, USA. [email protected]<br />
BACKGROUND: Because women of childbearing potential represent 20% to 25% of the HIV population, it is important to determine any potential drug interactions between vicriviroc, an antiretroviral agent, and an oral contraceptive (OC) to provide guidance on any potential dose adjustments.<br />
OBJECTIVE: The primary study objective was to determine the effect of vicriviroc, a C-C chemokine receptor type 5 inhibitor, alone or in the presence of ritonavir, on the pharmacokinetics (AUC and C(max)) of the study OC (ethinyl estradiol [EE] 0.035 mg + norethindrone [NET] 1 mg). A secondary objective was to monitor the safety and tolerability of vicriviroc plus an OC with and without ritonavir. METHODS: This was a randomized, open-label, parallel-group, single-center study with a fixed-sequence crossover design. Female subjects were randomized into 2 groups and treated for 2 menstrual cycles. In cycle 1, all received the OC alone, per standard 28-day pack instructions. On the first 10 days of cycle 2, group 1 received OC + vicriviroc and group 2 received OC + ritonavir; on the following 11 days, both groups received OC + vicriviroc + ritonavir. Blood samples were collected up to 24 hours after dosing on prespecified days. Pharmacokinetic parameters, including AUC(0-24), C(max), and C(min), were calculated using noncompartmental methods, and drug interactions were evaluated using an ANOVA model by treatment group. Adverse events were collected using physical examination, vital sign measurements, clinical laboratory analysis, electrocardiography, and questioning at predefined time points throughout the study to assess the safety profile.<br />
RESULTS: Twenty-seven subjects were enrolled (26 white, 1 black). The median age and body mass index were 21 years (range, 18-36 years) and 24.5 kg/m(2) (range, 19.1-31.3 kg/m(2)), respectively. Twenty-one subjects completed the study and were included in the pharmacokinetic analysis; 4 discontinued for reasons unrelated to study drug and 2 discontinued because of adverse events. Vicriviroc had little effect on the pharmacokinetics of the OC. EE mean ratio estimates for C(max) and AUC(0-24) compared with OC administered alone were 91% and 97%, respectively, and for NET were 106% and 93%. Subjects receiving ritonavir, alone or with vicriviroc, experienced decreases in exposure of EE (C(max) mean ratio estimates, 89% and 76%; AUC(0-24) mean ratio estimates, 71% each, for ritonavir alone and ritonavir with vicriviroc, respectively) and, to a lesser extent, decreases in NET (C(max) mean ratio estimates 89% each; AUC(0-24) mean ratio estimates: 93% and 83%, for ritonavir alone and ritonavir with vicriviroc, respectively). Twenty-two of 27 (81%) subjects reported ≥1 treatment-emergent adverse event (TEAE). During cycle 1, TEAEs were reported for 18 of 27 (67%) subjects while receiving OC alone and for 3 of 24 (13%) subjects while receiving placebo OC. During cycle 2, TEAEs were reported for 8 of 12 (67%) subjects while receiving vicriviroc with OC, 4 of 12 (33%) subjects while receiving ritonavir with OC, 7 of 22 (32%) subjects while receiving vicriviroc + ritonavir with OC, and 2 of 22 (9%) subjects while receiving placebo OC. The most commonly reported TEAE was headache (vicriviroc + OC, n = 1; ritonavir + OC, n = 3; vicriviroc + ritonavir + OC, n = 2; OC alone, n = 12; placebo OC, n = 2). No TEAEs were considered severe.<br />
CONCLUSIONS: In this population of healthy female subjects, vicriviroc had little effect on the pharmacokinetics of EE or NET, whereas ritonavir, alone or with vicriviroc, was associated with consistent decrease in exposure of EE and a lesser decrease in NET.<br />
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4. Expert Opin Drug Metab Toxicol. 2010 Sep;6(9):1139-50. doi: 10.1517/17425255.2010.510833.<br />
Vicriviroc, a new CC-chemokine receptor 5 inhibitor for treatment of HIV: properties, promises and challenges.<br />
Lenz JC(1), Rockstroh JK.<br />
Author information:<br />
(1)University of Bonn, Medicine I, Sigmund-Freudstr. 25, Bonn 53105, Germany.<br />
IMPORTANCE OF THE FIELD: Although HIV has become a treatable disease with near to normal life expectancy, the quest for the development of better tolerated drugs with simple dosing schedules and a high barrier to the emergence of drug resistance remains. Vicriviroc is a small-molecule chemokine receptor antagonist that inhibits the binding of R5-tropic HIV-1 to host cells at the CC-chemokine receptor 5 (CCR5) co-receptor, thus, preventing viral entry. CCR5 inhibitors are believed to possibly decrease inflammation from the immune system and thereby offer additional properties further to their antiretroviral efficacy. AREAS COVERED IN THIS REVIEW: This review is based on a PubMed search covering the years 2005 – 2010 for pharmacokinetic, pharmacological and clinical data of vicriviroc.<br />
WHAT THE READER WILL GAIN: In this review, the pharmacokinetic, pharmacological and clinical data of vicriviroc are presented. Moreover, the potential role of vicriviroc in the growing HIV armamentarium is discussed.<br />
TAKE HOME MESSAGE: Vicriviroc is being developed to be administered in combination with a ritonavir-boosted protease inhibitor for patients with R5-tropic virus. Early clinical trials have established the safety of vicriviroc in both treatment-naive and -experienced R5-tropic HIV-1 infected individuals. Recently, two Phase III clinical trials in treatment-experienced patients failed to prove its superiority over available HIV medications. Phase III trials for treatment-naive patients are still under planning. Clearly, more favorable study results are needed to move vicriviroc into drug registration and approval.<br />
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