CLINICAL PHARMACOLOGY
Mechanism Of Action
Maraviroc is an HIV-1 antiviral drug [see Microbiology].
Pharmacodynamics
Exposure-Response Relationship In Treatment-Experienced Adult Subjects
The relationship between maraviroc, modeled plasma trough concentration (Cmin) (1 to 9 samples
per subject taken on up to 7 visits), and virologic response was evaluated in
973 treatment-experienced HIV-1–infected subjects with varied optimized background
antiretroviral regimens in Trials A4001027 and A4001028. The Cmin, baseline viral load, baseline
CD4+ cell count, and overall sensitivity score (OSS) were found to be important predictors of
virologic success (defined as viral load less than 400 copies per mL at 24 weeks). Table 9
illustrates the proportions of subjects with virologic success (%) within each Cmin quartile for
150-mg twice-daily and 300-mg twice-daily groups.
Table 9. Treatment-Experienced Subjects with Virologic Success by Cmin Quartile (Q1-
Q4)
|
150 mg Twice Daily
(with CYP3A Inhibitors) |
300 mg Twice Daily
(without CYP3A Inhibitors) |
n |
Median
Cmin |
% Subjects with
Virologic Success |
n |
Median
Cmin |
% Subjects with
Virologic Success |
Placebo |
160 |
- |
30.6 |
35 |
- |
28.6 |
Q1 |
78 |
33 |
52.6 |
22 |
13 |
50.0 |
Q2 |
77 |
87 |
63.6 |
22 |
29 |
68.2 |
Q3 |
78 |
166 |
78.2 |
22 |
46 |
63.6 |
Q4 |
78 |
279 |
74.4 |
22 |
97 |
68.2 |
Exposure-Response Relationship In Treatment-Naive Adult Subjects
The relationship between maraviroc, modeled plasma trough concentration (Cmin) (1 to
12 samples per subject taken on up to 8 visits), and virologic response was evaluated in
294 treatment-naive HIV-1–infected subjects receiving maraviroc 300 mg twice daily in
combination with lamivudine/zidovudine in Trial A4001026. Table 10 illustrates the proportion
(%) of subjects with virologic success less than 50 copies per mL at 48 weeks within each Cmin
quartile for the 300-mg twice-daily dose.
Table 10. Treatment-Naive Subjects with Virologic Success by Cmin Quartile (Q1-Q4)
|
300 mg Twice Daily |
n |
Median Cmin |
% Subjects with Virologic Success |
Q1 |
75 |
23 |
57.3 |
Q2 |
72 |
39 |
72.2 |
Q3 |
73 |
56 |
74.0 |
Q4 |
74 |
81 |
83.8 |
Eighteen of 75 (24%) subjects in Q1 had no measurable maraviroc concentration on at least one
occasion versus 1 of 73 and 1 of 74 in Q3 and Q4, respectively.
Effects On Electrocardiogram
A placebo-controlled, randomized, crossover trial to evaluate the effect on the QT interval of
healthy male and female volunteers was conducted with 3 single oral doses of maraviroc and
moxifloxacin. The placebo-adjusted mean maximum (upper 1-sided 95% CI) increases in QTc
from baseline after 100, 300, and 900 mg of maraviroc were -2 (0), -1 (1), and 1 (3) msec,
respectively, and 13 (15) msec for moxifloxacin 400 mg. No subject in any group had an
increase in QTc of greater than or equal to 60 msec from baseline. No subject experienced an
interval exceeding the potentially clinically relevant threshold of 500 msec.
Pharmacokinetics
Table 11. Mean Maraviroc Pharmacokinetic Parameters in Adults
Patient Population |
Maraviroc Dose |
n |
AUC12
(ng.h/mL) |
Cmax
(ng/mL) |
Cmin
(ng/mL) |
Healthy volunteers
(Phase 1) |
300 mg twice daily |
64 |
2,908 |
888 |
43.1 |
Asymptomatic HIV
subjects (Phase 2a) |
300 mg twice daily |
8 |
2,550 |
618 |
33.6 |
Treatment-experienced
HIV subjects (Phase 3)a |
300 mg twice daily |
94 |
1,513 |
266 |
37.2 |
150 mg twice daily
(+ CYP3A inhibitor) |
375 |
2,463 |
332 |
101 |
Treatment-naive HIV
subjects (Phase 2b/3)a |
300 mg twice daily |
344 |
1,865 |
287 |
60 |
a The estimated exposure is lower compared with other trials possibly due to sparse sampling,
food effect, compliance, and concomitant medications. |
Absorption
Peak maraviroc plasma concentrations are attained 0.5 to 4 hours following single oral doses of 1
to 1,200 mg administered to uninfected volunteers. The pharmacokinetics of oral maraviroc are
not dose proportional over the dose range.
The absolute bioavailability of a 100-mg dose is 23% and is predicted to be 33% at 300 mg.
Maraviroc is a substrate for the efflux transporter P-gp.
Effect of Food on Oral Absorption:
Coadministration of a 300-mg tablet with a high-fat breakfast
reduced maraviroc Cmax and AUC by 33% and coadministration of 75 mg of oral solution with a
high-fat breakfast reduced maraviroc AUC by 73% in healthy adult volunteers. Studies with the
tablet formulation demonstrated a reduced food effect at higher doses.
There were no food restrictions in the adult trials (using the tablet formulation) or in the pediatric
trial (using both tablet and oral solution formulations) that demonstrated the efficacy/antiviral
activity and safety of maraviroc [see Clinical Studies].
Distribution
Maraviroc is bound (approximately 76%) to human plasma proteins, and shows moderate
affinity for albumin and alpha-1 acid glycoprotein. The volume of distribution of maraviroc is
approximately 194 L.
Elimination
Metabolism:
Trials in humans and in vitro studies using human liver microsomes and expressed
enzymes have demonstrated that maraviroc is principally metabolized by the cytochrome P450
system to metabolites that are essentially inactive against HIV-1. In vitro studies indicate that
CYP3A is the major enzyme responsible for maraviroc metabolism. In vitro studies also indicate
that polymorphic enzymes CYP2C9, CYP2D6, and CYP2C19 do not contribute significantly to
the metabolism of maraviroc.
Maraviroc is the major circulating component (~42% drug-related radioactivity) following a
single oral dose of 300 mg [14C]-maraviroc. The most significant circulating metabolite in
humans is a secondary amine (~22% radioactivity) formed by N-dealkylation. This polar
metabolite has no significant pharmacological activity. Other metabolites are products of
mono-oxidation and are only minor components of plasma drug-related radioactivity.
Excretion:
The terminal half-life of maraviroc following oral dosing to steady state in healthy
subjects was 14 to 18 hours. A mass balance/excretion trial was conducted using a single 300-mg
dose of 14C-labeled maraviroc. Approximately 20% of the radiolabel was recovered in the urine
and 76% was recovered in the feces over 168 hours. Maraviroc was the major component present
in urine (mean of 8% dose) and feces (mean of 25% dose). The remainder was excreted as
metabolites.
Specific Populations
Patients With Hepatic Impairment
Maraviroc is primarily metabolized and eliminated by the
liver. A trial compared the pharmacokinetics of a single 300-mg dose of SELZENTRY in
subjects with mild (Child-Pugh Class A, n = 8) and moderate (Child-Pugh Class B, n = 8)
hepatic impairment with pharmacokinetics in healthy subjects (n = 8). The mean Cmax and AUC
were 11% and 25% higher, respectively, for subjects with mild hepatic impairment, and 32% and
46% higher, respectively, for subjects with moderate hepatic impairment compared with subjects
with normal hepatic function. These changes do not warrant a dose adjustment. Maraviroc
concentrations are higher when SELZENTRY 150 mg is administered with a potent CYP3A
inhibitor compared with following administration of 300 mg without a CYP3A inhibitor, so
patients with moderate hepatic impairment who receive SELZENTRY 150 mg with a potent
CYP3A inhibitor should be monitored closely for maraviroc-associated adverse events. The
pharmacokinetics of maraviroc have not been studied in subjects with severe hepatic impairment
[see WARNINGS AND PRECAUTIONS].
Patients With Renal Impairment
A trial compared the pharmacokinetics of a single 300-mg dose
of SELZENTRY in adult subjects with severe renal impairment (CrCl less than 30 mL per
minute, n = 6) and ESRD (n = 6) with healthy volunteers (n = 6). Geometric mean ratios for
maraviroc Cmax and AUCinf were 2.4-fold and 3.2-fold higher, respectively, for subjects with
severe renal impairment, and 1.7-fold and 2.0-fold higher, respectively, for subjects with ESRD
as compared with subjects with normal renal function in this trial. Hemodialysis had a minimal
effect on maraviroc clearance and exposure in subjects with ESRD. Exposures observed in
subjects with severe renal impairment and ESRD were within the range observed in previous
300-mg single-dose trials of SELZENTRY in healthy volunteers with normal renal function.
However, maraviroc exposures in the subjects with normal renal function in this trial were 50%
lower than those observed in previous trials. Based on the results of this trial, no dose adjustment
is recommended for patients with renal impairment receiving SELZENTRY without a potent
CYP3A inhibitor or inducer. However, if patients with severe renal impairment or ESRD
experience any symptoms of postural hypotension while taking SELZENTRY 300 mg twice
daily, their dose should be reduced to 150 mg twice daily [see DOSAGE AND ADMINISTRATION, WARNINGS AND PRECAUTIONS].
In addition, the trial compared the pharmacokinetics of multiple-dose SELZENTRY in
combination with saquinavir/ritonavir 1,000/100 mg twice daily (a potent CYP3A inhibitor
combination) for 7 days in subjects with mild renal impairment (CrCl greater than 50 and less
than or equal to 80 mL per minute, n = 6) and moderate renal impairment (CrCl greater than or
equal to 30 and less than or equal to 50 mL per minute, n = 6) with healthy volunteers with
normal renal function (n = 6). Subjects received 150 mg of SELZENTRY at different dose
frequencies (healthy volunteers – every 12 hours; mild renal impairment – every 24 hours;
moderate renal impairment – every 48 hours). Compared with healthy volunteers (dosed every
12 hours), geometric mean ratios for maraviroc AUCtau, Cmax, and Cmin were 50% higher, 20%
higher, and 43% lower, respectively, for subjects with mild renal impairment (dosed every
24 hours). Geometric mean ratios for maraviroc AUCtau, Cmax, and Cmin were 16% higher, 29%
lower, and 85% lower, respectively, for subjects with moderate renal impairment (dosed every
48 hours) compared with healthy volunteers (dosed every 12 hours). Based on the data from this
trial, no adjustment in dose is recommended for patients with mild or moderate renal impairment
[see DOSAGE AND ADMINISTRATION].
Pediatric Patients
The pharmacokinetics of maraviroc were evaluated in CCR5-tropic, HIV-1–
infected, treatment-experienced pediatric subjects aged 2 to less than 18 years. In the dosefinding
stage of Trial A4001031, doses were administered with food on intensive PK evaluation
days and optimized to achieve an average concentration over the dosing interval (Cavg) of greater
than 100 ng per mL. Throughout the trial, on non-intensive PK evaluation days maraviroc was
taken with or without food. The initial dose of maraviroc was based on BSA and concomitant
medication category (i.e., presence of CYP3A inhibitors and/or inducers). The conversion of
dosing to a weight (kg)-band basis in children provides comparable exposures with those
observed in the trial at the corresponding BSA.
Maraviroc pharmacokinetic parameters in pediatric subjects receiving potent CYP3A inhibitors
with or without a potent CYP3A inducer (Table 12) and in subjects weighing greater than or
equal to 30 kg and receiving noninteracting concomitant medications (Table 13) were similar to
those observed in adults. Insufficient pharmacokinetic data are available to make a comparison
between adults and pediatric subjects weighing less than 30 kg and receiving noninteracting
concomitant medications or between adult and pediatric subjects receiving concomitant
medications consisting of a potent CYP3A inducer without CYP3A inhibitor.
Table 12. Maraviroc Pharmacokinetic Parameters in Treatment-Experienced Pediatric
Patients Receiving SELZENTRY with Potent CYP3A Inhibitors (with or without a
Potent CYP3A Inducer)
Weight |
Dose of
SELZENTRY |
Maraviroc Pharmacokinetic Parametera
Geometric Mean |
AUC12
(ng.h/mL) |
Cavg
(ng/mL) |
Cmax
(ng/mL) |
Cmin
(ng/mL) |
10 kg to <20 kg |
50 mg
twice daily |
2,349 |
196 |
324 |
78 |
20 kg to <30 kg |
75 mg
twice daily |
3,020 |
252 |
394 |
118 |
30 kg to <40 kg |
100 mg
twice daily |
3,229 |
269 |
430 |
126 |
≥40 kg |
150 mg
twice daily |
4,044 |
337 |
563 |
152 |
a The covariate distribution of the study population of 85 subjects on CYP3A-inhibitorcontaining
regimens was randomly sampled with replacement to obtain 1,000 subjects. Shown
in the table are model-predicted steady-state PK parameters for the 1,000 subjects in the
simulation dataset. |
Table 13. Maraviroc Pharmacokinetic Parameters in Treatment-Experienced Pediatric
Patients Receiving SELZENTRY with Noninteracting Concomitant Medicationsa
Weight (n) |
Dose of
SELZENTRY |
Maraviroc Pharmacokinetic Parameter
Geometric Mean |
AUC12
(ng.h/mL) |
Cavg
(ng/mL) |
Cmax
(ng/mL) |
Cmin
(ng/mL) |
<30 kg |
Insufficient data |
≥30 kg (n = 5)b |
300 mg
twice daily |
1,998 |
167 |
413 |
50.6 |
a Noninteracting concomitant medications include all medications that are not potent CYP3A
inhibitors or inducers.
b Nine observations from 5 subjects. |
Geriatric Patients
Pharmacokinetics of maraviroc have not been fully evaluated in the elderly
(aged 65 years and older). Based on population pharmacokinetic analyses, age did not have a
clinically relevant effect on maraviroc exposure in subjects up to age 65 years [see Use In Specific Populations].
Race And Gender
Based on population pharmacokinetics and 2 clinical CYP3A5 genotype
analyses for race, no dosage adjustment is recommended based on race or gender.
Drug Interaction Studies
Effect Of Concomitant Drugs On The Pharmacokinetics Of Maraviroc
Maraviroc is a substrate of
CYP3A and P-gp and hence its pharmacokinetics are likely to be modulated by inhibitors and
inducers of these enzymes/transporters. The CYP3A/P-gp inhibitors ketoconazole, boceprevir,
lopinavir/ritonavir, ritonavir, darunavir/ritonavir, saquinavir/ritonavir, and atazanavir ± ritonavir
all increased the Cmax and AUC of maraviroc (Table 14). The CYP3A and/or P-gp inducers
rifampin, etravirine, and efavirenz decreased the Cmax and AUC of maraviroc (Table 14). While
not studied, potent CYP3A and/or P-gp inducers carbamazepine, phenobarbital, and phenytoin
are expected to decrease maraviroc concentrations. Based on in vitro study results, maraviroc is
also a substrate of OATP1B1 and MRP2; its pharmacokinetics may be modulated by inhibitors
of these transporters.
Tipranavir/ritonavir (net CYP3A inhibitor/P-gp inducer) did not affect the steady-state
pharmacokinetics of maraviroc (Table 14). Cotrimoxazole and tenofovir did not affect the
pharmacokinetics of maraviroc.
Table 14. Effect of Coadministered Agents on the Pharmacokinetics of Maraviroc
Coadministered Drug
and Dose |
n |
Dose of
SELZENTRY |
Ratio (90% CI) of Maraviroc Pharmacokinetic
Parameters with/without Coadministered Drug
(No Effect = 1.00) |
Cmin |
AUCtau |
Cmax |
CYP3A and/or P-gp Inhibitors |
Ketoconazole
400 mg q.d. |
12 |
100 mg b.i.d. |
3.75
(3.01, 4.69) |
5.00
(3.98, 6.29) |
3.38
(2.38, 4.78) |
Ritonavir
100 mg b.i.d. |
8 |
100 mg b.i.d. |
4.55
(3.37, 6.13) |
2.61
(1.92, 3.56) |
1.28
(0.79, 2.09) |
Saquinavir (soft gel
capsules) /ritonavir
1,000 mg/100 mg b.i.d. |
11 |
100 mg b.i.d. |
11.3
(8.96, 14.1) |
9.77
(7.87, 12.14) |
4.78
(3.41, 6.71) |
Lopinavir/ritonavir
400 mg/100 mg b.i.d. |
11 |
300 mg b.i.d. |
9.24
(7.98, 10.7) |
3.95
(3.43, 4.56) |
1.97
(1.66, 2.34) |
Atazanavir
400 mg q.d. |
12 |
300 mg b.i.d. |
4.19
(3.65, 4.80) |
3.57
(3.30, 3.87) |
2.09
(1.72, 2.55) |
Atazanavir/ritonavir
300 mg/100 mg q.d. |
12 |
300 mg b.i.d. |
6.67
(5.78, 7.70) |
4.88
(4.40, 5.41) |
2.67
(2.32, 3.08) |
Darunavir/ritonavir
600 mg/100 mg b.i.d. |
12 |
150 mg b.i.d. |
8.00
(6.35, 10.1) |
4.05
(2.94, 5.59) |
2.29
(1.46, 3.59) |
Boceprevir
800 mg t.i.d. |
14 |
150 mg b.i.d. |
2.78
(2.40, 3.23) |
3.02
(2.53, 3.59) |
3.33
(2.54, 4.36) |
Elvitegravir/ritonavir
150 mg/100 mg q.d. |
11 |
150 mg b.i.d. |
4.23
(3.47, 5.16) |
2.86
(2.33, 3.51) |
2.15
(1.71, 2.69) |
CYP3A and/or P-gp Inducers |
Efavirenz
600 mg q.d. |
12 |
100 mg b.i.d. |
0.55
(0.43, 0.72) |
0.55
(0.49, 0.62) |
0.49
(0.38, 0.63) |
Efavirenz
600 mg q.d. |
12 |
200 mg b.i.d.
(+ efavirenz):
100 mg b.i.d.
(alone) |
1.09
(0.89, 1.35) |
1.15
(0.98, 1.35) |
1.16
(0.87, 1.55) |
Rifampicin
600 mg q.d. |
12 |
100 mg b.i.d. |
0.22
(0.17, 0.28) |
0.37
(0.33, 0.41) |
0.34
(0.26, 0.43) |
Rifampicin
600 mg q.d. |
12 |
200 mg b.i.d.
(+ rifampicin):
100 mg b.i.d.
(alone) |
0.66
(0.54, 0.82) |
1.04
(0.89, 1.22) |
0.97
(0.72, 1.29) |
Etravirine
200 mg b.i.d. |
14 |
300 mg b.i.d. |
0.61
(0.53, 0.71) |
0.47
(0.38, 0.58) |
0.40
(0.28, 0.57) |
Nevirapinea
200 mg b.i.d.
(+ lamivudine 150 mg b.i.d.,
tenofovir 300 mg q.d.) |
8 |
300 mg single
dose |
– |
1.01
(0.65, 1.55) |
1.54
(0.94, 2.51) |
CYP3A and/or P-gp Inhibitors and Inducers |
Lopinavir/ritonavir +
efavirenz
400 mg/100 mg b.i.d. +
600 mg q.d. |
11 |
300 mg b.i.d. |
6.29
(4.72, 8.39) |
2.53
(2.24, 2.87) |
1.25
(1.01, 1.55) |
Saquinavir(soft gel
capsules) /ritonavir +
efavirenz
1,000 mg/100 mg b.i.d. +
600 mg q.d. |
11 |
100 mg b.i.d. |
8.42
(6.46, 10.97) |
5.00
(4.26, 5.87) |
2.26
(1.64, 3.11) |
Darunavir/ritonavir +
etravirine
600 mg/100 mg b.i.d. +
200 mg b.i.d. |
10 |
150 mg b.i.d. |
5.27
(4.51, 6.15) |
3.10
(2.57, 3.74) |
1.77
(1.20, 2.60) |
Fosamprenavir/ritonavir
700 mg/100 mg b.i.d. |
14 |
300 mg b.i.d. |
4.74
(4.03, 5.57) |
2.49
(2.19, 2.82) |
1.52
(1.27, 1.82) |
Fosamprenavir/ritonavir
1,400 mg/100 mg q.d. |
14 |
300 mg q.d. |
1.80
(1.53, 2.13) |
2.26
(1.99, 2.58) |
1.45
(1.20, 1.74) |
Tipranavir/ritonavir
500 mg/200 mg b.i.d. |
12 |
150 mg b.i.d. |
1.80
(1.55, 2.09) |
1.02
(0.85, 1.23) |
0.86
(0.61, 1.21) |
Other |
Raltegravir
400 mg b.i.d. |
17 |
300 mg b.i.d. |
0.90
(0.85, 0.96) |
0.86
(0.80, 0.92) |
0.79
(0.67, 0.94) |
a Compared with historical data. |
Effect Of Maraviroc On The Pharmacokinetics Of Concomitant Drugs
Maraviroc is unlikely to
inhibit the metabolism of coadministered drugs metabolized by the following cytochrome P
enzymes (CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and CYP3A) or to inhibit the
uptake of OATP1B1 or the export of MRP2 because maraviroc did not inhibit activity of those
enzymes or transporters at clinically relevant concentrations in vitro. Maraviroc does not induce
CYP1A2 in vitro. Additionally, in vitro studies have shown that maraviroc is not a substrate for,
and does not inhibit, any of the major renal uptake inhibitors (organic anion transporter [OAT]1,
OAT3, organic cation transporter [OCT]2, novel organic cation transporter [OCTN]1, and
OCTN2) at clinically relevant concentrations.
In vitro results suggest that maraviroc could inhibit P-gp in the gut. However, maraviroc did not
significantly affect the pharmacokinetics of digoxin in vivo, indicating maraviroc may not
significantly inhibit or induce P-gp clinically.
Drug interaction trials were performed with maraviroc and other drugs likely to be
coadministered or commonly used as probes for pharmacokinetic interactions (Table 14).
Coadministration of fosamprenavir 700 mg/ritonavir 100 mg twice daily and maraviroc 300 mg
twice daily decreased the Cmin and AUC of amprenavir by 36% and 35%, respectively.
Coadministration of fosamprenavir 1,400 mg/ritonavir 100 mg once daily and maraviroc 300 mg
once daily decreased the Cmin and AUC by 15% and 30%, respectively. No dosage adjustment is
necessary when SELZENTRY is dosed 150 mg twice daily in combination with
fosamprenavir/ritonavir dosed once or twice daily. Fosamprenavir should be given with ritonavir
when coadministered with SELZENTRY.
Maraviroc had no significant effect on the pharmacokinetics of elvitegravir, boceprevir,
zidovudine, or lamivudine. Maraviroc decreased the Cmin and AUC of raltegravir by 27% and
37%, respectively, which is not clinically significant. Maraviroc had no clinically relevant effect
on the pharmacokinetics of midazolam, the oral contraceptives ethinylestradiol and
levonorgestrel, no effect on the urinary 6β-hydroxycortisol/cortisol ratio, suggesting no induction
of CYP3A in vivo. Maraviroc had no effect on the debrisoquine metabolic ratio (MR) at 300 mg
twice daily or less in vivo and did not cause inhibition of CYP2D6 in vitro until concentrations
greater than 100 microM. However, there was 234% increase in debrisoquine MR on treatment
compared with baseline at 600 mg once daily, suggesting potential inhibition of CYP2D6 at
higher doses.
Microbiology
Mechanism Of Action
Maraviroc is a member of a therapeutic class called CCR5 co-receptor antagonists. Maraviroc
selectively binds to the human chemokine receptor CCR5 present on the cell membrane,
preventing the interaction of HIV-1 gp120 and CCR5 necessary for CCR5-tropic HIV-1 to enter
cells. CXCR4-tropic and dual-tropic HIV-1 entry is not inhibited by maraviroc.
Antiviral Activity In Cell Culture
Maraviroc inhibits the replication of CCR5-tropic laboratory strains and primary isolates of
HIV-1 in models of acute peripheral blood leukocyte infection. The mean EC50 value (50%
effective concentration) for maraviroc against HIV-1 group M isolates (subtypes A to J and
circulating recombinant form AE) and group O isolates ranged from 0.1 to 4.5 nM (0.05 to
2.3 ng per mL) in cell culture.
When used with other antiretroviral agents in cell culture, the combination of maraviroc was not
antagonistic with non-nucleoside reverse transcriptase inhibitors (NNRTIs: delavirdine,
efavirenz, and nevirapine), NRTIs (abacavir, didanosine, emtricitabine, lamivudine, stavudine,
tenofovir, zalcitabine, and zidovudine), or protease inhibitors (PIs: amprenavir, atazanavir,
darunavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, and tipranavir). Maraviroc was
not antagonistic with the HIV-1 gp41 fusion inhibitor enfuvirtide. Maraviroc was not active
against CXCR4-tropic and dual-tropic viruses (EC50 value greater than 10 microM). The
antiviral activity of maraviroc against HIV-2 has not been evaluated.
Resistance in Cell Culture:
HIV-1 variants with reduced susceptibility to maraviroc have been
selected in cell culture following serial passage of 2 CCR5-tropic viruses (CCl/85 and RU570).
The maraviroc-resistant viruses remained CCR5-tropic with no evidence of a change from a
CCR5-tropic virus to a CXCR4-using virus. Two amino acid residue substitutions in the V3-loop
region of the HIV-1 envelope glycoprotein (gp160), A316T, and I323V (HXB2 numbering),
were shown to be necessary for the maraviroc-resistant phenotype in the HIV-1 isolate CCl/85.
In the RU570 isolate a 3-amino acid residue deletion in the V3 loop, ΔQAI (HXB2 positions 315
to 317), was associated with maraviroc resistance. The relevance of the specific gp120
substitutions observed in maraviroc-resistant isolates selected in cell culture to clinical maraviroc
resistance is not known. Maraviroc-resistant viruses were characterized phenotypically by
concentration-response curves that did not reach 100% inhibition in phenotypic drug assays,
rather than increases in EC50 values.
Cross-Resistance in Cell Culture:
Maraviroc had antiviral activity against HIV-1 clinical isolates
resistant to NNRTIs, NRTIs, PIs, and the gp41 fusion inhibitor enfuvirtide in cell culture (EC50
values ranged from 0.7 to 8.9 nM [0.36 to 4.57 ng per mL]). Maraviroc-resistant viruses that
emerged in cell culture remained susceptible to enfuvirtide and the protease inhibitor saquinavir.
Clinical Resistance:
Virologic failure on maraviroc can result from genotypic and phenotypic
resistance to maraviroc, through outgrowth of undetected CXCR4-using virus present before
maraviroc treatment (see Tropism below), through resistance to background therapy drugs (Table
15), or due to low exposure to maraviroc [see CLINICAL PHARMACOLOGY].
Antiretroviral Treatment-Experienced Adult Subjects (Trials A4001027 and A4001028):
Week
48 data from treatment-experienced subjects failing maraviroc-containing regimens with
CCR5-tropic virus (n = 58) have identified 22 viruses that had decreased susceptibility to
maraviroc characterized in phenotypic drug assays by concentration-response curves that did not
reach 100% inhibition. Additionally, CCR5-tropic virus from 2 of these treatment-failure
subjects had greater than or equal to 3-fold shifts in EC50 values for maraviroc at the time of
failure.
Fifteen of these viruses were sequenced in the gp120 encoding region and multiple amino acid
substitutions with unique patterns in the heterogeneous V3 loop region were detected. Changes at
either amino acid position 308 or 323 (HXB2 numbering) were seen in the V3 loop in 7 of the
subjects with decreased maraviroc susceptibility. Substitutions outside the V3 loop of gp120 may
also contribute to reduced susceptibility to maraviroc.
Antiretroviral Treatment-Naive Adult Subjects (Trial A4001026):
Treatment-naive subjects
receiving SELZENTRY had more virologic failures and more treatment-emergent resistance to
the background regimen drugs compared with those receiving efavirenz (Table 15).
Table 15. Development of Resistance to Maraviroc or Efavirenz and Background Drugs
in Antiretroviral Treatment-Naive Trial A4001026 for Patients with Only CCR5-Tropic
Virus at Screening Using Enhanced Sensitivity TROFILE Assay
|
Maraviroc |
Efavirenz |
Total N in dataset (as-treated) |
273 |
241 |
Total virologic failures (as-treated) |
85 (31%) |
56 (23%) |
Evaluable virologic failures with post baseline
genotypic and phenotypic data |
73 |
43 |
Lamivudine resistance |
39 (53%) |
13 (30%) |
Zidovudine resistance |
2 (3%) |
0 |
Efavirenz resistance |
– |
23 (53%) |
Phenotypic resistance to maraviroca |
19 (26%) |
– |
a Includes subjects failing with CXCR4- or dual/mixed-tropism because these viruses are not
intrinsically susceptible to maraviroc. |
In an as-treated analysis of treatment-naive subjects at 96 weeks, 32 subjects failed a
maraviroc-containing regimen with CCR5-tropic virus and had a tropism result at failure; 7 of
these subjects had evidence of maraviroc phenotypic resistance defined as
concentration-response curves that did not reach 95% inhibition. One additional subject had a
greater than or equal to 3-fold shift in the EC50 value for maraviroc at the time of failure. A
clonal analysis of the V3 loop amino acid envelope sequences was performed from 6 of the
7 subjects. Changes in V3 loop amino acid sequence differed between each of these different
subjects, even for those infected with the same virus clade, suggesting that there are multiple
diverse pathways to maraviroc resistance. The subjects who failed with CCR5-tropic virus and
without a detectable maraviroc shift in susceptibility were not evaluated for genotypic resistance.
Of the 32 maraviroc virologic failures failing with CCR5-tropic virus, 20 (63%) also had
genotypic and/or phenotypic resistance to background drugs in the regimen (lamivudine,
zidovudine).
Tropism:
In both treatment-experienced and treatment-naive subjects, detection of CXCR4-using
virus prior to initiation of therapy has been associated with a reduced virologic response to
maraviroc.
Antiretroviral Treatment-Experienced Subjects (Trials A4001027 and A4001028):
In the
majority of cases, treatment failure on maraviroc was associated with detection of CXCR4-using
virus (i.e., CXCR4- or dual/mixed-tropic) which was not detected by the tropism assay prior to
treatment. CXCR4-using virus was detected at failure in approximately 55% of subjects who
failed treatment on maraviroc by Week 48, as compared with 9% of subjects who experienced
treatment failure in the placebo 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 arm) in whom
CXCR4-using virus was detected at treatment failure. From analysis of amino acid sequence
differences and phylogenetic data, it was determined that CXCR4-using virus in these subjects
emerged from a low level of pre-existing CXCR4-using virus not detected by the tropism assay
(which is population-based) prior to treatment rather than from a co-receptor switch from
CCR5-tropic virus to CXCR4-using virus resulting from mutation in the virus.
Detection of CXCR4-using virus prior to initiation of therapy has been associated with a reduced
virological response to maraviroc. Furthermore, subjects failing twice-daily maraviroc at Week
48 with CXCR4-using virus had a lower median increase in CD4+ cell counts from baseline
(+41 cells per mm3) than those subjects failing with CCR5-tropic virus (+162 cells per mm3).
The median increase in CD4+ cell count in subjects failing in the placebo arm was +7 cells per
mm3.
Antiretroviral Treatment-Naive Subjects (Trial A4001026):
In a 96-week trial of antiretroviral
treatment-naive subjects, 14% (12 of 85) who had only CCR5-tropic virus at screening with an
enhanced sensitivity tropism assay (TROFILE) and failed therapy on maraviroc had
CXCR4-using virus at the time of treatment failure. A detailed clonal analysis was conducted in
2 previously antiretroviral treatment-naive subjects enrolled in a Phase 2a monotherapy trial who
had CXCR4-using virus detected after 10 days’ treatment with maraviroc. Consistent with the
detailed clonal analysis conducted in treatment-experienced subjects, the CXCR4-using variants
appear to emerge from outgrowth of a pre-existing undetected CXCR4-using virus. Screening
with an enhanced sensitivity tropism assay reduced the number of maraviroc virologic failures
with CXCR4- or dual/mixed-tropic virus at failure to 12 compared with 24 when screening with
the original tropism assay. All but one (11 of 12; 92%) of the maraviroc failures failing with
CXCR4- or dual/mixed-tropic virus also had genotypic and phenotypic resistance to the
background drug lamivudine at failure and 33% (4 of 12) developed zidovudine-associated
resistance substitutions.
Subjects who had only CCR5-tropic virus at baseline and failed maraviroc therapy with
CXCR4-using virus had a median increase in CD4+ cell counts from baseline of +113 cells per
mm3 while those subjects failing with CCR5-tropic virus had an increase of +135 cells per mm3.
The median increase in CD4+ cell count in subjects failing in the efavirenz arm was + 95 cells
per mm3.
Antiretroviral Treatment-Experienced Pediatric Subjects (Trial A4001031):
In the Week 48
analysis of Trial A4001031 (n = 103), the mechanisms of resistance to maraviroc observed in the
treatment-experienced pediatric population were similar to those observed in adult populations:
reasons for virologic failure included failing with CXCR4- or dual/mixed-tropic virus, evidence
of reduced maraviroc susceptibility as measured by a decrease in maximal percentage inhibition
(MPI), and emergence of resistance to background drug in the regimen.
Clinical Studies
Clinical Studies In Adult Subjects
The clinical efficacy and safety of SELZENTRY are derived from analyses of data from 3 trials
in adult subjects infected with CCR5-tropic HIV-1: Trials A4001027 and A4001028 in
antiretroviral treatment-experienced adult subjects and Trial A4001026 in treatment-naive
subjects. These trials were supported by a 48-week trial in antiretroviral treatment-experienced
adult subjects infected with dual/mixed-tropic HIV-1, Trial A4001029.
Trials In CCR5-Tropic, Treatment-Experienced Subjects
Trials A4001027 and A4001028 were double-blind, randomized, placebo-controlled, multicenter
trials in subjects infected with CCR5-tropic HIV-1. Subjects were required to have an HIV-1
RNA greater than 5,000 copies per mL despite at least 6 months of prior therapy with at least
1 agent from 3 of the 4 antiretroviral drug classes (greater than or equal to 1 NRTI, greater than
or equal to 1 NNRTI, greater than or equal to 2 PIs, and/or enfuvirtide) or documented resistance
to at least 1 member of each class. All subjects received an optimized background regimen
consisting of 3 to 6 antiretroviral agents (excluding low-dose ritonavir) selected on the basis of
the subject’s prior treatment history and baseline genotypic and phenotypic viral resistance
measurements. In addition to the optimized background regimen, subjects were then randomized
in a 2:2:1 ratio to SELZENTRY 300 mg once daily, SELZENTRY 300 mg twice daily, or
placebo. Doses were adjusted based on background therapy as described in Dosage and
Administration (2), Table 1.
In the pooled analysis for Trials A4001027 and A4001028, the demographics and baseline
characteristics of the treatment groups were comparable (Table 16). Of the 1,043 subjects with a
CCR5-tropism result at screening, 7.6% had a dual/mixed-tropism result at the baseline visit 4 to
6 weeks later. This illustrates the background change from CCR5- to dual/mixed-tropism result
over time in this treatment-experienced population, prior to a change in antiretroviral regimen or
administration of a CCR5 co-receptor antagonist.
Table 16. Demographic and Baseline Characteristics of Subjects in Trials A4001027
and A4001028
|
SELZENTRY
Twice Daily
(n = 426) |
Placebo
(n = 209) |
Age (years) |
|
|
Mean (range) |
46.3 (21-73) |
45.7 (29-72) |
Sex: |
|
|
Male |
382 (89.7%) |
185 (88.5%) |
Female |
44 (10.3%) |
24 (11.5%) |
Race: |
|
|
White |
363 (85.2%) |
178 (85.2%) |
Black |
51 (12.0%) |
26 (12.4%) |
Other |
12 (2.8%) |
5 (2.4%) |
Region: |
|
|
U.S. |
276 (64.8%) |
135 (64.6%) |
Non-U.S. |
150 (35.2%) |
74 (35.4%) |
Subjects with previous enfuvirtide use |
142 (33.3%) |
62 (29.7%) |
Subjects with enfuvirtide as part of OBT |
182 (42.7%) |
91 (43.5%) |
Baseline plasma HIV-1 RNA (log10 copies/mL) |
|
|
Mean (range) |
4.85 (2.96-6.88) |
4.86 (3.46-7.07) |
Subjects with screening viral load ≥100,000 copies/mL |
179 (42.0%) |
84 (40.2%) |
Baseline CD4+ cell count (cells/mm3) |
|
|
Median (range) |
167 (2-820) |
171 (1-675) |
Subjects with baseline CD4+ cell count ≤200 cells/mm3) |
250 (58.7%) |
118 (56.5%) |
Subjects with Overall Susceptibility Score (OSS):a |
|
|
0 |
57 (13.4%) |
35 (16.7%) |
1 |
136 (31.9%) |
44 (21.1%) |
2 |
104 (24.4%) |
59 (28.2%) |
≥3 |
125 (29.3%) |
66 (31.6%) |
Subjects with enfuvirtide resistance substitutions |
90 (21.2%) |
45 (21.5%) |
Median number of resistance-associated:b |
|
|
PI substitutions |
10 |
10 |
NNRTI substitutions |
1 |
1 |
NRTI substitutions |
6 |
6 |
a OSS - Sum of active drugs in OBT based on combined information from genotypic and
phenotypic testing.
b Resistance substitutions based on IAS guidelines.1 |
The Week 48 results for the pooled Trials A4001027 and A4001028 are shown in Table 17.
Table 17. Outcomes of Randomized Treatment at Week 48 in Trials A4001027 and
A4001028
Outcome |
SELZENTRY
Twice Daily
(n = 426) |
Placebo
(n = 209) |
Mean
Difference |
Mean change from Baseline to Week 48 in
HIV-1 RNA (log10 copies/mL) |
-1.84 |
-0.78 |
-1.05 |
<400 copies/mL at Week 48 |
239 (56%) |
47 (22%) |
34% |
<50 copies/mL at Week 48 |
194 (46%) |
35 (17%) |
29% |
Insufficient clinical response |
97 (23%) |
113 (54%) |
– |
Adverse events |
19 (4%) |
11 (5%) |
– |
Other |
27 (6%) |
18 (9%) |
– |
Subjects with treatment-emergent CDC
Category C events |
22 (5%) |
16 (8%) |
– |
Deaths (during trial or within 28 days of
last dose) |
9 (2%)a |
1 (0.5%) |
– |
a One additional subject died while receiving open-label therapy with SELZENTRY subsequent
to discontinuing double-blind placebo due to insufficient response. |
After 48 weeks of therapy, the proportions of subjects with HIV-1 RNA less than 400 copies per
mL receiving SELZENTRY compared with placebo were 56% and 22%, respectively. The mean
changes in plasma HIV-1 RNA from baseline to Week 48 were –1.84 log10 copies per mL for
subjects receiving SELZENTRY + OBT compared with –0.78 log10 copies per mL for subjects
receiving OBT only. The mean increase in CD4+ cell count was higher on SELZENTRY twice
daily + OBT (124 cells per mm3) than on placebo + OBT (60 cells per mm3).
Trial In Dual/Mixed-Tropic, Treatment-Experienced Subjects
Trial A4001029 was an exploratory, randomized, double-blind, multicenter trial to determine the
safety and efficacy of SELZENTRY in subjects infected with dual/mixed co-receptor tropic
HIV-1. The inclusion/exclusion criteria were similar to those for Trials A4001027 and
A4001028 above and the subjects were randomized in a 1:1:1 ratio to SELZENTRY once daily,
SELZENTRY twice daily, or placebo. No increased risk of infection or HIV-1 disease
progression was observed in the subjects who received SELZENTRY. Use of SELZENTRY 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.
Trial In Treatment-Naive Subjects
Trial A4001026 was a randomized, double-blind, multicenter trial in subjects infected with
CCR5-tropic HIV-1 classified by the original TROFILE tropism assay. Subjects were required to
have plasma HIV-1 RNA greater than or equal to 2,000 copies per mL and could not have: 1)
previously received any antiretroviral therapy for greater than 14 days, 2) an active or recent
opportunistic infection or a suspected primary HIV-1 infection, or 3) phenotypic or genotypic
resistance to zidovudine, lamivudine, or efavirenz. Subjects were randomized in a 1:1:1 ratio to
SELZENTRY 300 mg once daily, SELZENTRY 300 mg twice daily, or efavirenz 600 mg once
daily, each in combination with lamivudine/zidovudine. The efficacy and safety of
SELZENTRY are based on the comparison of SELZENTRY twice daily versus efavirenz. In a
pre-planned interim analysis at 16 weeks, SELZENTRY 300 mg once daily failed to meet the
pre-specified criteria for demonstrating non-inferiority and was discontinued.
The demographic and baseline characteristics of the maraviroc and efavirenz treatment groups
were comparable (Table 18). Subjects were stratified by screening HIV-1 RNA levels and by
geographic region. The median CD4+ cell counts and mean HIV-1 RNA at baseline were similar
for both treatment groups.
Table 18. Demographic and Baseline Characteristics of Subjects in Trial A4001026
|
SELZENTRY
300 mg Twice Daily +
Lamivudine/ Zidovudine
(n = 360) |
Efavirenz
600 mg Once Daily +
Lamivudine/ Zidovudine
(n = 361) |
Age (years): |
|
|
Mean |
36.7 |
37.4 |
Range |
20-69 |
18-77 |
Female, n% |
104 (29) |
102 (28) |
Race, n%: |
|
|
White |
204 (57) |
198 (55) |
Black |
123 (34) |
133 (37) |
Asian |
6 (2) |
5 (1) |
Other |
27 (8) |
25 (7) |
Median (range) CD4+ cell count
(cells/microL) |
241 (5-1,422) |
254 (8-1,053) |
Median (range) HIV-1 RNA
(log10 copies/mL) |
4.9 (3-7) |
4.9 (3-7) |
The treatment outcomes at 96 weeks for Trial A4001026 are shown in Table 19. Treatment
outcomes are based on reanalysis of the screening samples using a more sensitive tropism assay,
enhanced sensitivity TROFILE HIV tropism assay, which became available after the Week 48
analysis; approximately 15% of the subjects identified as CCR5-tropic in the original analysis
had dual/mixed- or CXCR4-tropic virus. Screening with enhanced sensitivity version of the
TROFILE tropism assay reduced the number of maraviroc virologic failures with CXCR4- or
dual/mixed-tropic virus at failure to 12 compared with 24 when screening with the original
TROFILE HIV tropism assay.
Table 19. Trial Outcome (Snapshot) at Week 96 Using Enhanced Sensitivity Assaya
Outcome at Week 96b |
SELZENTRY
300 mg Twice Daily +
Lamivudine/ Zidovudine
(n = 311)
n (%) |
Efavirenz
600 mg Once Daily +
Lamivudine/ Zidovudine
(n = 303)
n (%) |
Virologic Responders:
(HIV-1 RNA <400 copies/mL) |
199 (64) |
195 (64) |
Virologic Failure: |
|
|
Non-sustained HIV-1 RNA
suppression |
39 (13) |
22 (7) |
HIV-1 RNA never suppressed |
9 (3) |
1 (<1) |
Virologic Responders:
(HIV-1 RNA <50 copies/mL) |
183 (59) |
190 (63) |
Virologic Failure: |
|
|
Non-sustained HIV-1 RNA
suppression |
43 (14) |
25 (8) |
HIV-1 RNA never suppressed |
21 (7) |
3 (1) |
Discontinuations due to: |
|
|
Adverse events |
19 (6) |
47 (16) |
Death |
2 (1) |
2 (1) |
Otherc |
43 (14) |
36 (12) |
a The total number of subjects (311, 303) in Table 19 represents the subjects who had a
CCR5-tropic virus in the reanalysis of screening samples using the more sensitive tropism
assay. This reanalysis reclassified approximately 15% of subjects shown in Table 18 as having
dual/mixed- or CXCR4-tropic virus. These numbers are different than those presented in Table
18 because the numbers in Table 18 reflect the subjects with CCR5-tropic virus according to
the original tropism assay.
b Week 48 results: Virologic responders (less than 400): 228 of 311 (73%) in SELZENTRY, 219
of 303 (72%) in efavirenz;
Virologic responders (less than 50): 213 of 311 (69%) in SELZENTRY, 207 of 303 (68%) in
efavirenz.
c Other reasons for discontinuation include lost to follow-up, withdrawn, protocol violation, and
other. |
The median increase from baseline in CD4+ cell counts at Week 96 was 184 cells per mm3 for
the arm receiving SELZENTRY compared with 155 cells per mm3 for the efavirenz arm.
Clinical Studies In Pediatric Subjects
Trial In CCR5-Tropic, Treatment-Experienced Subjects
Trial A4001031 is an open-label, multicenter trial in pediatric subjects aged 2 to less than
18 years infected with only CCR5-tropic HIV-1. Subjects were required to have HIV-1 RNA
greater than 1,000 copies per mL at screening. All subjects (n = 103) received SELZENTRY
twice daily and OBT. Dosing of SELZENTRY was based on BSA and doses were adjusted
based on whether the subject was receiving potent CYP3A inhibitors and/or inducers.
The population was 52% female and 69% black, with mean age of 10 years (range: 2 to
17 years). At baseline, mean plasma HIV-1 RNA was 4.4 log10 copies per mL (range: 2.4 to
6.2 log10 copies per mL), mean CD4+ cell count was 551 cells per mm3 (range: 1 to
1,654 cells per mm3), and mean CD4+ percent was 21% (range: 0% to 42%).
At 48 weeks, 48% of subjects treated with SELZENTRY and OBT achieved plasma HIV-1 RNA
less than 48 copies per 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 per mm3 (5%).