Pharmacotherapeutic group: Antivirals for systemic use, other antivirals, ATC code: J05AX09
Mechanism of action
Maraviroc is a member of a therapeutic class called CCR5 antagonists. Maraviroc selectively binds to the human chemokine receptor CCR5, preventing CCR5-tropic HIV-1 from entering cells.
Antiviral activity in vitro
Maraviroc has no antiviral activity in vitro against viruses which can use CXCR4 as their entry co-receptor (dual-tropic or CXCR4-tropic viruses, collectively termed 'CXCR4-using' virus below). The serum adjusted EC90 value in 43 primary HIV-1 clinical isolates was 0.57 (0.06 – 10.7) ng/mL without significant changes between different subtypes tested. The antiviral activity of maraviroc against HIV-2 has not been evaluated. For details please refer to the pharmacology section of the CELSENTRI European Public Assessment Report (EPAR) on the European Medicines Agency (EMA) website.
When used with other antiretroviral medicinal products in cell culture, the combination of maraviroc was not antagonistic with a range of NRTIs, NNRTIs, PIs or the HIV fusion inhibitor enfuvirtide.
Virologic Escape
Virologic escape from maraviroc can occur via 2 routes: the emergence of pre-existing virus which can use CXCR4 as its entry co-receptor (CXCR4-using virus) or the selection of virus that continues to use exclusively drug-bound CCR5 (CCR5-tropic virus).
In vitro
HIV-1 variants with reduced susceptibility to maraviroc have been selected in vitro, following serial passage of two CCR5-tropic viruses (0 laboratory strains, 2 clinical isolates). The maraviroc-resistant viruses remained CCR5-tropic and there was no conversion from a CCR5-tropic virus to a CXCR4-using virus.
Phenotypic resistance
Concentration response curves for the maraviroc-resistant viruses were characterized phenotypically by curves that did not reach 100% inhibition in assays using serial dilutions of maraviroc (<100% maximal percentage inhibition (MPI)). Traditional IC50/IC90 fold-change was not a useful parameter to measure phenotypic resistance, as those values were sometimes unchanged despite significantly reduced sensitivity.
Genotypic resistance
Mutations were found to accumulate in the gp120 envelope glycoprotein (the viral protein that binds to the CCR5 co-receptor). The position of these mutations was not consistent between different isolates. Hence, the relevance of these mutations to maraviroc susceptibility in other viruses is not known.
Cross-resistance in vitro
HIV-1 clinical isolates resistant to NRTIs, NNRTIs, PIs and enfuvirtide were all susceptible to maraviroc in cell culture. Maraviroc-resistant viruses that emerged in vitro remained sensitive to the fusion inhibitor enfuvirtide and the PI, saquinavir.
In vivo
Treatment-Experienced Adult Patients
In the pivotal studies (MOTIVATE 1 and MOTIVATE 2), 7.6% of patients had a change in tropism result from CCR5-tropic to CXCR4-tropic or dual/mixed-tropic between screening and baseline (a period of 4-6 weeks).
Failure with CXCR4-using virus
CXCR4-using virus was detected at failure in approximately 60% of subjects who failed treatment on maraviroc, as compared to 6% of subjects who experienced treatment failure in the placebo + OBT arm. To investigate the likely origin of the on-treatment CXCR4-using virus, a detailed clonal analysis was conducted on virus from 20 representative subjects (16 subjects from the maraviroc arms and 4 subjects from the placebo + OBT arm) in whom CXCR4-using virus was detected at treatment failure. This analysis indicated that CXCR4-using virus emerged from a pre-existing CXCR4-using reservoir not detected at baseline, rather than from mutation of CCR5-tropic virus present at baseline. An analysis of tropism following failure of maraviroc therapy with CXCR4-using virus in patients with CCR5 virus at baseline, demonstrated that the virus population reverted back to CCR5 tropism in 33 of 36 patients with more than 35 days of follow-up.
At the time of failure with CXCR4-using virus, the resistance pattern to other antiretrovirals appears similar to that of the CCR5-tropic population at baseline, based on available data. Hence, in the selection of a treatment regimen, it should be assumed that viruses forming part of the previously undetected CXCR4 -using population (i.e. minor viral population) harbours the same resistance pattern as the CCR5-tropic population.
Failure with CCR5-tropic virus
Phenotypic resistance
In patients with CCR5-tropic virus at time of treatment failure with maraviroc, 22 out of 58 patients had virus with reduced sensitivity to maraviroc. In the remaining 36 patients, there was no evidence of virus with reduced sensitivity as identified by exploratory virology analyses on a representative group. The latter group had markers correlating to low compliance (low and variable drug levels and often a calculated high residual sensitivity score of the OBT). In patients failing therapy with CCR5-tropic virus only, maraviroc might be considered still active if the MPI value is ≥95% (PhenoSense Entry assay). Residual activity in vivo for viruses with MPI-values <95% has not been determined.
Genotypic resistance
A relatively small number of individuals receiving maraviroc-containing therapy have failed with phenotypic resistance (i.e. the ability to use drug-bound CCR5 with MPI <95%). To date, no signature mutation(s) have been identified. The gp120 amino acid substitutions identified so far are context dependent and inherently unpredictable with regards to maraviroc susceptibility.
Treatment-Experienced Paediatric and Adolescent Patients
In the Week 48 analysis (N=103), non-CCR5 tropic-virus was detected in 5/23 (22%) subjects at virologic failure. One additional subject had CCR5 tropic-virus with reduced susceptibility to maraviroc at virologic failure, although this was not retained at the end of treatment. Subjects with virologic failure generally appeared to have low compliance to both maraviroc and the background antiretroviral elements of their regimens. Overall, the mechanisms of resistance to maraviroc observed in this treatment-experienced paediatric population were similar to those observed in adult populations.
Clinical results
Studies in Treatment-Experienced Adult Patients Infected with CCR5-tropic Virus
The clinical efficacy of maraviroc (in combination with other antiretroviral medicinal products) on plasma HIV RNA levels and CD4+ cell counts have been investigated in two pivotal randomized, double blind, multicentre studies (MOTIVATE 1 and MOTIVATE 2, n=1076) in patients infected with CCR5 tropic HIV-1 as determined by the Monogram Trofile Assay.
Patients who were eligible for these studies had prior exposure to at least 3 antiretroviral medicinal product classes [≥1 NRTIs, ≥1 NNRTIs, ≥2 PIs, and/or enfurvirtide] or documented resistance to at least one member of each class. Patients were randomised in a 2:2:1 ratio to maraviroc 300 mg (dose equivalence) once daily, twice daily or placebo in combination with an optimized background consisting of 3 to 6 antiretroviral medicinal products (excluding low-dose ritonavir). The OBT was selected on the basis of the subject's prior treatment history and baseline genotypic and phenotypic viral resistance measurements.
Table 5: Demographic and baseline characteristics of patients (pooled studies MOTIVATE 1 and MOTIVATE 2)
| Demographic and Baseline Characteristics | Maraviroc 300 mg twice daily + OBT N = 426 | Placebo + OBT N = 209 |
| Age (years) (Range, years) | 46.3 21-73 | 45.7 29-72 |
| Male Sex | 89.7% | 88.5% |
| Race (White/Black/Other) | 85.2% / 12% / 2.8% | 85.2% / 12.4% / 2.4% |
| Mean Baseline HIV-1 RNA (log10 copies/mL) | 4.85 | 4.86 |
| Median Baseline CD4+ Cell Count (cells/mm3) (range, cells/mm3) | 166.8 (2.0-820.0) | 171.3 (1.0-675.0) |
| Screening Viral Load ≥100,000 copies/mL | 179 (42.0%) | 84 (40.2%) |
| Baseline CD4+ Cell Count ≤200 cells/mm3 | 250 (58.7%) | 118 (56.5%) |
| Number (Percentage) of patients with GSS score1: 0 1 2 ≥3 | 102 (23.9%) 138 (32.4%) 80 (18.8%) 104 (24.4%) | 51 (24.4%) 53 (25.4%) 41 (19.6%) 59 (28.2%) |
1Based on GeneSeq resistance assay.
Limited numbers of patients from ethnicities other than Caucasian were included in the pivotal clinical studies, therefore very limited data are available in these patient populations.
The mean increase in CD4+ cell count from baseline in patients who failed with a change in tropism result to dual/mixed tropic or CXCR4, in the maraviroc 300 mg twice daily + OBT (+56 cells/mm3) group was greater than that seen in patients failing placebo + OBT (+13.8 cells/mm3) regardless of tropism.
Table 6: Efficacy Outcomes at week 48 (pooled studies MOTIVATE 1 and MOTIVATE 2)
| Outcomes | Maraviroc 300 mg twice daily + OBT N=426 | Placebo + OBT N=209 | Difference1 (Confidence Interval2) |
| HIV-1 RNA Mean change from baseline (log copies/mL) | -1.837 | -0.785 | -1.055 (-1.327, -0.783) |
| Percentage of patients with HIV-1 RNA <400 copies/mL | 56.1% | 22.5% | Odds ratio: 4.76 (3.24, 7.00) |
| Percentage of patients with HIV-1 RNA <50 copies/mL | 45.5% | 16.7% | Odds ratio: 4.49 (2.96, 6.83) |
| CD4+ cell count Mean change from baseline (cells/µL) | 122.78 | 59.17 | 63.13 (44.28, 81.99)2 |
1 p-values < 0.0001
2 For all efficacy endpoints the confidence intervals were 95%, except for HIV-1 RNA Change from baseline, which was 97.5%
In a retrospective analysis of the MOTIVATE studies with a more sensitive assay for screening of tropism (Trofile ES), the response rates (<50 copies/mL at week 48) in patients with only CCR5-tropic virus detected at baseline was 48.2% in those treated with maraviroc + OBT (n=328), and 16.3% in those treated with placebo + OBT (n=178).
Maraviroc 300 mg twice daily + OBT was superior to placebo + OBT across all subgroups of patients analysed (see Table 7). Patients with very low CD4+ count at baseline (i.e. <50 cells/µL) had a less favourable outcome. This subgroup had a high degree of bad prognostic markers, i.e. extensive resistance and high baseline viral loads. However, a significant treatment benefit for maraviroc compared to placebo + OBT was still demonstrated (see Table 7).
Table 7: Proportion of patients achieving <50 copies/mL at Week 48 by subgroup (pooled Studies MOTIVATE 1 and MOTIVATE 2)
| Subgroups | HIV-1 RNA <50 copies/mL |
| Maraviroc 300 mg twice daily + OBT N=426 | Placebo + OBT N=209 |
| Screening HIV-1 RNA (copies /mL): <100,000 ≥100,000 | 58.4% 34.7% | 26.0% 9.5% |
| Baseline CD4+ (cells/µL): <50 50-100 101-200 201-350 ≥ 350 | 16.5% 36.4% 56.7% 57.8% 72.9% | 2.6% 12.0% 21.8% 21.0% 38.5% |
| Number of active ARVs in OBT1: 0 1 2 ≥3 | 32.7% 44.5% 58.2% 62% | 2.0% 7.4% 31.7% 38.6% |
1Based on GSS.
Studies in Treatment-Experienced Adult Patients Infected with Non-CCR5-tropic Virus
Study A4001029 was an exploratory study in patients infected with dual/mixed or CXCR4 tropic HIV-1 with a similar design as the studies MOTIVATE 1 and MOTIVATE 2. Use of maraviroc was not associated with a significant decrease in HIV 1 RNA compared with placebo in these subjects and no adverse effect on CD4+ cell count was noted.
Studies in Treatment-Naïve Adult Patients Infected with CCR5-tropic Virus
A randomised, double-blinded study (MERIT), explored maraviroc versus efavirenz, both in combination with zidovudine/lamivudine (n=721, 1:1). After 48 weeks of treatment, maraviroc did not reach non-inferiority to efavirenz for the endpoint of HIV-1 RNA < 50 copies/mL (65.3 vs. 69.3 % respectively, lower confidence bound -11.9%). More patients treated with maraviroc discontinued due to lack of efficacy (43 vs.15) and among patients with lack of efficacy, the proportion acquiring NRTI resistance (mainly lamivudine) was higher in the maraviroc arm. Fewer patients discontinued maraviroc due to adverse events (15 vs. 49).
Studies in Adult Patients Co-infected with Hepatitis B and/or Hepatitis C virus
The hepatic safety of maraviroc in combination with other antiretroviral agents in CCR5-tropic HIV-1-infected subjects with HIV RNA <50 copies/mL, co-infected with Hepatitis C and/or Hepatitis B Virus was evaluated in a multicentre, randomized, double blinded, placebo-controlled study. 70 subjects (Child-Pugh Class A, n=64; Child-Pugh Class B, n=6) were randomized to the maraviroc group and 67 subjects (Child-Pugh Class A, n=59; Child-Pugh Class B, n=8) were randomized to the placebo group.
The primary objective assessed the incidence of Grade 3 and 4 ALT abnormalities (>5x upper limit of normal (ULN) if baseline ALT ≤ ULN; or >3.5x baseline if baseline ALT > ULN) at Week 48. One subject in each treatment arm met the primary endpoint by Week 48 (at Week 8 for placebo and Week 36 for the maraviroc arm).
Studies in Treatment-Experienced Paediatric and Adolescent Patients Infected with CCR5-tropic Virus
Study A4001031 is an open-label, multicenter trial in paediatric and adolescent patients (aged 2 years to less than 18 years) infected with CCR5-tropic HIV-1, determined by the enhanced-sensitivity Trofile assay.
Subjects were required to have HIV-1 RNA greater than 1,000 copies per mL at Screening.
All subjects (n = 103) received maraviroc twice daily and OBT. Maraviroc dosing was based on body surface area and doses were adjusted based on whether the subject was receiving potent CYP3A inhibitors and/or inducers.
In paediatric and adolescent patients with a successful tropism test, dual mixed/CXCR4-tropic virus was detected in around 40% of screening samples (8/27, 30% in 2-6 year-olds, 31/81, 38% in 6-12 year-olds and 41/90, 46% in 12-18 year-olds), underscoring the importance of tropism testing also in the paediatric population.
The population was 52% female and 69% black, with mean age of 10 years (range: 2 years to 17 years). At baseline, mean plasma HIV-1 RNA was 4.3 log10 copies/mL (range 2.4 to 6.2 log10 copies per mL), mean CD4+ cell count was 551 cells/mm3 (range 1 to 1654 cells/mm3) and mean CD4+ % was 21% (range 0% to 42%).
At 48 weeks, using a missing, switch or discontinuation equals failure analysis, 48% of subjects treated with maraviroc and OBT achieved plasma HIV-1 RNA less than 48 copies/mL and 65% of subjects achieved plasma HIV-1 RNA less than 400 copies per mL. The mean CD4+ cell count (percent) increase from baseline to Week 48 was 247 cells/mm3 (5%).