SELZENTRY Film-coated tablet / Oral solution Ref.[50720] Active ingredients: Maraviroc

Exposure-Response Relationship in Treatment-Experienced Adult Subjects

The relationship between maraviroc, modeled plasma trough concentration (C_min) (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 C_min, 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 C_min quartile for 150-mg twice-daily and 300-mg twice-daily groups.

Table 9. Treatment-Experienced Subjects with Virologic Success by C_min Quartile (Q1-Q4):

Exposure-Response Relationship in Treatment-Naive Adult Subjects

The relationship between maraviroc, modeled plasma trough concentration (C_min) (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 C_min quartile for the 300-mg twice-daily dose.

Table 10. Treatment-Naive Subjects with Virologic Success by C_min Quartile (Q1-Q4):

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.

Table 11. Mean Maraviroc Pharmacokinetic Parameters in Adults:

^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 C_max 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 (14.1, 14.2)].

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 C_max 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 (5.1)].

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 C_max and AUC_inf 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 (2.3), Warnings and Precautions (5.3)].

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 AUC_tau, C_max, and C_min were 50% higher, 20% higher, and 43% lower, respectively, for subjects with mild renal impairment (dosed every 24 hours). Geometric mean ratios for maraviroc AUC_tau, C_max, and C_min 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 (2.3)].

Pediatric Patients

Aged 2 to Less Than 18 Years: 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 dose-finding stage of Trial A4001031, doses were administered with food on intensive pharmacokinetic 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 pharmacokinetic 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 aged 2 to less than 18 years receiving potent CYP3A inhibitors with or without a potent CYP3A inducer were similar to those observed in adults (Table 12).

Table 12. Maraviroc Pharmacokinetic Parameters in Treatment-Experienced Pediatric Patients Receiving SELZENTRY with Potent CYP3A Inhibitors (with or without a Potent CYP3A Inducer):

^a Model-predicted steady-state pharmacokinetic parameters are presented.

Aged from Birth to Less Than 6 Weeks: The pharmacokinetics of maraviroc were evaluated in 38 of 47 enrolled HIV-1–exposed neonates (born to HIV-1–infected mothers) aged from birth up to 6 weeks [see Adverse Reactions (6.1)]. In the IMPAACT P2007 trial, 13 neonates received weight-based maraviroc dosing as single doses at birth and approximately 7 days, and 25 neonates received maraviroc twice daily up to 6 weeks of age without exposure to potent CYP3A inhibitors and/or inducers. Maraviroc pharmacokinetic parameters in neonates weighing at least 2 kg at birth (Table 13) were similar to those observed in adults. Exposure to maternal efavirenz both in utero (for a minimum of 2 weeks immediately prior to delivery) and after birth while breastfeeding did not have a meaningful impact on maraviroc pharmacokinetic parameters.

Table 13. Maraviroc Pharmacokinetic Parameters in Full-Term Neonates (Birth Up to 6 Weeks of Age) Receiving SELZENTRY with Noninteracting Concomitant Medications^a:

^a Noninteracting concomitant medications include all medications that are not potent CYP3A inhibitors or inducers.
^b AUC_inf calculated for single-dose pharmacokinetics.

Clinical pharmacokinetic data with maraviroc in pediatric patients aged older than 6 weeks to less than 2 years are not available and clinical pharmacokinetic data in pediatric patients aged 2 to less than 18 years receiving noninteracting concomitant medications are limited. Based on population pharmacokinetic modeling and simulation, the recommended dosing regimen of SELZENTRY for this population is predicted to result in similar maraviroc exposures when compared with exposures achieved in adults receiving SELZENTRY 300 mg twice daily (with noninteracting concomitant medications) [see Dosage and Administration (2.4)].

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 (8.5)].

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, lopinavir/ritonavir, ritonavir, darunavir/ritonavir, saquinavir/ritonavir, and atazanavir ± ritonavir all increased the C_max and AUC of maraviroc (Table 14). The CYP3A and/or P-gp inducers rifampin, etravirine, and efavirenz decreased the C_max 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:

^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 C_min 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 C_min and AUC of amprenavir 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, zidovudine, or lamivudine. Maraviroc decreased the C_min 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.

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: 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), through resistance to background therapy drugs (Table 15), or due to low exposure to maraviroc [see Clinical Pharmacology (12.2)].

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:

^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.

Carcinogenesis

Long-term oral carcinogenicity studies of maraviroc were carried out in rasH2 transgenic mice (6 months) and in rats for up to 96 weeks (females) and 104 weeks (males). No drug-related increases in tumor incidence were found in mice at 1,500 mg per kg per day and in male and female rats at 900 mg per kg per day. The highest exposures in rats were approximately 11 times those observed in humans at the therapeutic dose of 300 mg twice daily for the treatment of HIV-1 infection.

Mutagenesis

Maraviroc was not genotoxic in the reverse mutation bacterial test (Ames test in Salmonella and E. coli), a chromosome aberration test in human lymphocytes, and mouse bone marrow micronucleus test.

Impairment of Fertility

Maraviroc did not impair mating or fertility of male or female rats and did not affect sperm of treated male rats at approximately 20-fold higher exposures (AUC) than in humans given the recommended 300-mg twice-daily dose.

14.1 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:

NNRTI = Non-nucleoside reverse transcriptase inhibitors; NRTI = nucleoside reverse transcriptase inhibitors; OBT = optimized background therapy; PI = protease inhibitor.
^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:

^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:

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 Assay^a:

^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.

14.2 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%).