CLINICAL PHARMACOLOGY
Mechanism Of Action
VITEKTA is an HIV-1
antiretroviral drug [see Microbiology].
Pharmacodynamics
Cardiac Electrophysiology
The effect of multiple doses of elvitegravir 125 mg (1.5
times the lowest recommended dosage) and 250 mg (1.7 times the maximum
recommended dosage) (coadministered with 100 mg ritonavir) on QT interval was
evaluated in a randomized, placebo-and active-controlled (moxifloxacin 400 mg)
parallel group thorough QT study in 126 healthy subjects. No clinically
meaningful changes in QTc interval were observed with either 125 mg dose or the
250 mg dose. The dose of 250 mg elvitegravir (with 100 mg ritonavir) is
expected to cover the high exposure clinical scenario.
Pharmacokinetics
Absorption
Following oral administration of VITEKTA and ritonavir
with food, in HIV-1 infected subjects, peak elvitegravir plasma concentrations
were observed approximately 4 hours post-dose. The steady-state mean
elvitegravir pharmacokinetic parameters are presented in Table 5. Elvitegravir
plasma exposures increased in a less than dose proportional manner, likely due
to solubility-limited absorption.
Table 5 : Pharmacokinetic Parameters of Elvitegravir
Following Oral Administration of VITEKTA in HIV-1 Infected Adults
Parameter Mean ± SD |
Elvitegravir 85 mg |
Elvitegravir 150 mg |
Cmax (mcg/mL) |
1.2 ± 0.36 |
1.5 ± 0.37 |
AUCtau (mcg•hr/mL) |
18 ± 7.1 |
18 ± 6.5 |
Ctrough (mcg/mL) |
0.42 ± 0.24 |
0.35 ± 0.20 |
Inhibitory Quotienta |
~ 5 |
~ 9 |
SD = Standard Deviation
a ratio
of Ctrough: protein binding-adjusted EC95 for wild-type HIV-1 virus |
VITEKTA must be taken with food.
Distribution
Elvitegravir is 98–99% bound to
human plasma proteins and the binding is independent of drug concentration over
the range of 1 ng/mL to 1.6 μg/mL. The mean plasma-toblood drug
concentration ratio is 1.37.
Metabolism and Elimination
Elvitegravir undergoes
primarily oxidative metabolism via CYP3A, and is secondarily glucuronidated via
UGT1A1/3 enzymes. Following oral administration of [14C]elvitegravir/ritonavir,
elvitegravir was the predominant species in plasma, representing ~94% of the
circulating radioactivity. Aromatic and aliphatic hydroxylation or
glucuronidation metabolites were present in very low levels, displayed
considerably lower anti-HIV activity and did not contribute to the
overall antiviral activity of elvitegravir.
Following oral administration of [14C]elvitegravir/ritonavir,
94.8% of the dose was recovered in feces, consistent with the hepatobiliary
excretion of elvitegravir; 6.7% of the administered dose was recovered in urine
as metabolites. The median terminal plasma half-life of elvitegravir following
administration of VITEKTA and ritonavir was approximately 8.7 hours.
Specific Populations
Race
Population pharmacokinetics analysis of elvitegravir in
HIV-1 infected subjects indicated that race had no clinically relevant effect
on the exposure of elvitegravir/ritonavir.
Gender
No clinically relevant pharmacokinetic differences have
been observed between men and women for elvitegravir/ritonavir.
Pediatric Patients
The pharmacokinetics of elvitegravir in pediatric
patients less than 12 years of age have not been established [see Use in
Specific Populations].
Exposures of elvitegravir in adolescents were comparable
to those in adults. The steady-state mean elvitegravir Cmax, AUCtau, and Ctrough
(mean ± SD) following multiple doses of boosted VITEKTA in HIV-1 infected
pediatric subjects 12 to less than 18 years were 2.1 ± 0.96 mcg/mL, 25 ± 11
mcg•hr/mL, and 0.63 ± 0.43 mcg/mL, respectively, for the 85 mg dose, and 2.1 ±
0.74 mcg/mL, 21 ± 7.6 mcg•hr/mL, and 0.32 ± 0.24 mcg/mL, respectively, for the
150 mg dose of elvitegravir, with inhibitory quotients of ~14 and ~7.1 (ratio
of Ctrough: protein binding-adjusted EC95 for wild-type HIV-1 virus for the 85
mg and 150 mg doses, respectively).
Geriatric Patients
Pharmacokinetics of elvitegravir have not been fully
evaluated in the elderly (65 years of age and older) [see Use in Specific
Populations].
Patients with Renal Impairment
No clinically relevant differences in elvitegravir
pharmacokinetics were observed between subjects with severe renal impairment
(estimated creatinine clearance below 30 mL/min) and healthy subjects in a
clinical trial [see Use in Specific Populations].
Patients with Hepatic Impairment
Elvitegravir is primarily metabolized and eliminated by
the liver. No clinically relevant differences in elvitegravir pharmacokinetics
were observed between subjects with moderate hepatic impairment (Child-Pugh
Class B) and healthy subjects in a clinical trial. The effect of severe hepatic
impairment (Child-Pugh Class C) on the pharmacokinetics of elvitegravir has not
been studied [see Use in Specific Populations].
Hepatitis B and/or Hepatitis C Virus Co-infection
Limited data from population pharmacokinetic analysis
(N=56) indicated that hepatitis B and/or C virus infection had no clinically
relevant effect on the exposure of elvitegravir/ritonavir.
Drug Interaction Studies
The drug interaction studies described were conducted
with VITEKTA coadministered with ritonavir.
Elvitegravir is primarily metabolized by cytochrome
CYP3A. Coadministration of VITEKTA with drugs that induce CYP3A may result in
decreased plasma concentrations of elvitegravir.
In drug interaction studies conducted with elvitegravir
coadministered with ritonavir or cobicistat, there was no clinically
significant interaction observed between elvitegravir and abacavir,
emtricitabine, etravirine, famotidine, omeprazole, stavudine, tenofovir
disoproxil fumarate, or zidovudine. The effects of coadministered drugs on the
exposure of elvitegravir/ritonavir are shown in Table 6. The effects of
elvitegravir and ritonavir on the exposure of coadministered drugs are shown in
Table 7.
Table 6 : Drug Interactions: Changes in
Pharmacokinetic Parameters for Elvitegravir/Ritonavir in the Presence of the
Coadministered Druga
Coadministered Drug |
Dose of Coadministered Drug (mg) |
Elvitegravir Dose (mg) |
Ritonavir Dose (mg) |
N |
Mean Ratio of Elvitegravir/Ritonavir Pharmacokinetic Parametersb (90% CI); No Effect = 1.00 |
Cmax |
AUC |
Cmin |
|
20 mL single dose given 4 hours before elvitegravir |
|
|
8 |
0.95 (0.84, 1.07) |
0.96 (0.88, 1.04) |
1.04 (0.93, 1.17) |
Antacids |
20 mL single dose given 4 hours after elvitegravir |
50 once daily |
100 once daily |
10 |
0.98 (0.88, 1.10) |
0.98 (0.91, 1.06) |
1.00 (0.90, 1.11) |
20 mL single dose given 2 hours before elvitegravir |
11 |
0.82 (0.74, 0.91) |
0.85 (0.79, 0.91) |
0.90 (0.82, 0.99) |
|
20 mL single dose given 2 hours after elvitegravir |
|
|
10 |
0.79 (0.71, 0.88) |
0.80 (0.75, 0.86) |
0.80 (0.73, 0.89) |
Atazanavir |
300 once daily |
200 once daily |
100 once daily |
33 |
1.85 (1.69, 2.03) |
2.00 (1.85, 2.16) |
2.88 (2.53, 3.27) |
300 once daily |
85 once daily |
100 once daily |
20 |
0.91 (0.81, 1.02)c |
1.07 (0.95, 1.21)c |
1.38 (1.18, 1.61)c |
Carbamazepine |
200 twice daily |
150 daily |
150 once dailyd |
12 |
0.55 (0.49,0.61) |
0.31 (0.28,0.33) |
0.03 (0.02,0.04) |
Darunavir |
600 twice daily |
125 once daily |
100 twice daily |
21 |
1.13 (1.03, 1.24) |
1.10 (0.99, 1.22) |
1.18 (1.06, 1.31) |
Didanosine |
400 single dose |
200 once daily |
100 once daily |
32 |
0.95 (0.90, 1.01) |
0.97 (0.92, 1.01) |
1.06 (1.01, 1.12) |
Ketoconazole |
200 twice daily |
150 once daily |
100 once daily |
18 |
1.17 (1.04, 1.33) |
1.48 (1.36, 1.62) |
1.67 (1.48, 1.88) |
Lopinavir/ ritonavir |
400 twice daily |
125 once daily |
100 twice daily |
14 |
1.52 (1.29, 1.79) |
1.75 (1.50, 2.05) |
2.38 (1.81, 3.13) |
Maraviroc |
150 twice daily |
150 once daily |
100 once daily |
17 |
1.01 (0.89, 1.15) |
1.07 (0.96, 1.18) |
1.09 (0.95, 1.26) |
Rifabutin |
150 once every other day |
300 once daily |
100 once daily |
19 |
0.92 (0.84, 1.00) |
0.96 (0.90, 1.02) |
0.94 (0.82, 1.09) |
Rosuvastatin |
10 single dose |
150 single dose |
NAd,f |
10 |
0.94 (0.83, 1.07)e |
1.02 (0.91, 1.14)e |
0.98 (0.83, 1.16)e |
Tipranavir |
500 twice daily |
200 once daily |
200 twice daily |
26 |
1.06
(0.89, 1.26)e |
0.92
(0.79, 1.08)e |
0.90
(0.70, 1.17)e |
a All interaction studies conducted in healthy
volunteers
b The pharmacokinetic parameters of elvitegravir were compared with
elvitegravir coadministered with ritonavir 100 mg once daily unless specified
otherwise.
c Comparison based on elvitegravir/ritonavir 150/100 mg once daily.
d Study was conducted in the presence of 150 mg cobicistat.
e Comparison based on elvitegravir/cobicistat 150/150 mg once daily.
f NA = Not Applicable |
Table 7 : Drug Interactions:
Changes in Pharmacokinetic Parameters for Coadministered Drug in the Presence
of Elvitegravir/Ritonavira
Coadministered Drug |
Dose of Coadministered Drug (mg) |
Elvitegravir Dose (mg) |
Ritonavir Dose (mg) |
N |
Mean Ratio of Coadministered Drug Pharmacokinetic Parametersb (90% CI); No Effect = 1.00 |
Cmax |
AUC |
Cmin |
Atazanavir |
300 once daily |
200 once daily |
100 once daily |
33 |
0.84 (0.78, 0.91) |
0.79 (0.74, 0.85) |
0.65 (0.59, 0.73) |
300 once daily |
85 once daily |
100 once daily |
20 |
0.97 (0.87, 1.08) |
0.89 (0.80, 0.99) |
0.83 (0.72, 0.95) |
Buprenorphine |
16 - 24 once daily |
150 once daily |
150 once dailyd |
17 |
1.12 (0.98, 1.27) |
1.35 (1.18, 1.55) |
1.66 (1.43, 1.93) |
Norburprenorphine |
1.24 (1.03, 1.49) |
1.42 (1.22, 1.67) |
1.57 (1.31, 1.88) |
Carbamazepine |
200 twice daily |
150 once daily |
150 once dailyd |
12 |
1.40 (1.32,1.49) |
1.43 (1.36,1.52) |
1.51 (1.41,1.62) |
Carbamazepine- 10,11-epoxide |
0.73 (0.70,0.78) |
0.65 (0.63,0.66) |
0.59 (0.57,0.61) |
Darunavir |
600 twice daily |
125 once daily |
100 twice daily |
22 |
0.89 (0.85, 0.94) |
0.89 (0.82, 0.96) |
0.83 (0.74, 0.93) |
Didanosine |
400 single dose |
200 once daily |
100 once daily |
32 |
0.84 (0.67, 1.05) |
0.86 (0.75, 0.99) |
NCe |
Lopinavir/ ritonavir |
400 twice daily |
125 once daily |
100 twice daily |
13 |
0.99 (0.88, 1.12) |
0.97 (0.85, 1.09) |
0.92 (0.79, 1.08) |
Maraviroc |
150 twice daily |
150 once daily |
100 once daily |
11 |
2.15 (1.71, 2.69) |
2.86 (2.33, 3.51) |
4.23 (3.47, 5.16) |
Naloxone |
4 - 6 once daily |
150 once daily |
150 once dailyd |
17 |
0.72 (0.61, 0.85) |
0.72 (0.59, 0. 87) |
NC |
Rifabutin |
150 once every other day |
300 once daily |
100 once daily |
18 |
0.92 (0.83, 1.02)c |
0.94 (0.86, 1.03)c |
1.16 (1.02, 1.31 )c |
25-O-desacetyl- rifabutin |
5.40 (4.66, 6.25)c |
9.51 (8.09, 11.18)c |
19.36 (15.85, 23.65)c |
Rosuvastatin |
10 single dose |
150 single dose |
NAd,e |
10 |
1.89 (1.48, 2.42) |
1.38 (1.14, 1.67) |
1.43 (1.08, 1.89) |
Tipranavir |
500 twice daily |
200 once daily |
200 twice daily |
26 |
0.92 (0.84, 1.00) |
0.89 (0.80, 0.99) |
0.89 (0.77, 1.02) |
a All interaction studies conducted in healthy
volunteers
b The pharmacokinetic parameters of the protease inhibitors
presented in this table were assessed in the presence of ritonavir.
c Comparison based on rifabutin 300 mg once daily. Total
antimycobacterial activity was increased by 50%.
d Study was conducted in the presence of 150 mg cobicistat.
e NA = Not Applicable; NC = Not Calculated |
Microbiology
Mechanism of Action
Elvitegravir is an HIV-1
integrase strand transfer inhibitor (INSTI). Integrase is an HIV-1 encoded
enzyme that is required for viral replication. Inhibition of integrase prevents
the integration of HIV-1 DNA into host genomic DNA, blocking the formation of
the HIV-1 provirus and propagation of the viral infection. Elvitegravir does
not inhibit human topoisomerases I or II.
Antiviral Activity in Cell
Culture
The antiviral activity of
elvitegravir against laboratory and clinical isolates of HIV-1 was assessed in
T lymphoblastoid cells, monocyte/macrophage cells, and primary peripheral blood
lymphocytes. The 50% effective concentration (EC50) values ranged from 0.02 to 1.7
nM. Elvitegravir displayed antiviral activity in cell culture against HIV-1
clades A, B, C, D, E, F, G, and O (EC50 values ranged from 0.1 to 1.3 nM) and
activity against HIV-2 (EC50 value of 0.53 nM). The antiviral activity of
elvitegravir with antiretroviral drugs in two-drug combination studies was not
antagonistic when combined with the INSTI raltegravir, NNRTIs (efavirenz,
etravirine, or nevirapine), NRTIs (abacavir, didanosine, emtricitabine,
lamivudine, stavudine, tenofovir, or zidovudine), PIs (amprenavir, atazanavir,
darunavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, or
tipranavir), the fusion inhibitor enfuvirtide, or the CCR5 co-receptor
antagonist maraviroc.
Elvitegravir did not show
inhibition of replication of HBV or HCV in cell culture.
Resistance
In Cell Culture
HIV-1 isolates with reduced
susceptibility to elvitegravir were selected in cell culture. Reduced
susceptibility to elvitegravir was associated with the primary integrase
substitutions T66A/I, E92G/Q, S147G, and Q148R. Additional integrase
substitutions observed in cell culture selection included D10E, S17N, H51Y,
F121Y, S153F/Y, E157Q, D232N, R263K, and V281M.
Clinical Studies
Pooled resistance analysis was
performed on virus samples from subjects receiving elvitegravir-containing
regimens in 6 clinical trials of elvitegravir (as single drug in combination
with a regimen containing a protease inhibitor/ritonavir or as the fixed dose
combination STRIBILD) who were viremic with HIV-1 RNA greater than 400
copies/mL at the time of efficacy evaluation (up to 192 weeks). Development of
substitutions T66A/I/K, E92G/Q, T97A, S147G, Q148H/K/R, and N155H in the HIV-1
integrase protein was primarily associated with resistance to elvitegravir. In
addition to these primary elvitegravir resistance-associated substitutions,
E92A, F121C/Y, P145S, Q146I/L/R, and N155S were also occasionally observed and
were shown to confer reduced susceptibility to elvitegravir. Substitutions at
positions E92 and N155 were the most frequently observed (39% and 27% of those
evaluated subjects, respectively). In virus isolates harboring the observed
primary elvitegravir resistance-associated substitutions, additional
substitutions in integrase were detected including H51Y, L68I/V, G70R,
V72A/N, I73V, Q95K/R, S119R, E138A/K, G140A/C/S, E157Q, K160N, E170A, S230R,
and D232N.
Treatment-Experienced HIV-1-Infected Subjects
By Week 96, evidence of emerging primary elvitegravir
resistance-associated substitutions T66A/I, E92G/Q, T97A, S147G, Q148R, or
N155H was observed in 23 of the 74 subjects with evaluable genotypic data in
Study 145. Post-baseline virus isolates harboring primary elvitegravir
resistance-associated substitutions had median decreases in susceptibility to
elvitegravir of 8-fold (29 isolates, ranging from 2-to greater than 158-fold)
and of 5-fold (26 isolates, ranging from 1-to greater than 58-fold) compared to
wild-type reference HIV-1 and to their respective baseline isolates,
respectively.
Cross-Resistance
Cross-resistance has been observed among INSTIs. Among
the 23 subjects who developed genotypic resistance to elvitegravir with
evidence of emerging primary elvitegravir resistance-associated substitutions
in Study 145, 12/21 (57%) subjects with evaluable drug susceptibility data had
HIV-1 with reduced susceptibility to raltegravir (greater than 1.5-fold, above
the biological cutoff for raltegravir).
Elvitegravir-resistant viruses showed varying degrees of
cross-resistance in cell culture to raltegravir in the INSTI class depending on
the type and number of substitutions in HIV-1 integrase. Of the primary
elvitegravir resistance-associated substitutions tested (T66A/I/K, E92G/Q,
T97A, S147G, Q148H/K/R, and N155H), all but three (T66I, E92G, and S147G)
conferred greater than 1.5-fold reduced susceptibility to raltegravir when
introduced individually into a wild-type virus by site-directed mutagenesis. Of
the primary raltegravir resistance-associated substitutions tested (Y143C/H/R,
Q148H/K/R, and N155H), all but one (Y143H) conferred greater than 2.5-fold
reductions in susceptibility to elvitegravir (above the biological cutoff for
elvitegravir).
Clinical Studies
Treatment-Experienced Adults With HIV-1 Infection
The efficacy of VITEKTA in treatment-experienced adult
patients with HIV-1 infection is based on the analyses through 96 weeks from
one randomized, double-blind, active-controlled trial, Study 145, in treatment-experienced,
HIV-1 infected subjects (N=702). In Study 145, subjects were randomized in a
1:1 ratio to receive either VITEKTA (150 mg or 85 mg) once daily or raltegravir
400 mg twice daily, each administered with a background regimen (BR) containing
a fully active protease inhibitor coadministered with ritonavir and a second
antiretroviral drug. The BR was selected by the investigator based on
genotypic/phenotypic resistance testing and prior antiretroviral treatment
history.
The mean age of subjects was 45 years (range 19–78); 82%
were male, 62% were White, and 34% were Black. The mean baseline plasma HIV-1
RNA was 4.3 log10 copies/mL (range 1.7–6.6) and 26% of subjects had baseline
viral loads greater than 100,000 copies/mL. The mean duration of prior HIV-1
treatment was 9.4 years. The mean baseline CD4+ cell count was 262 cells/mm³ (range 1–1497), 45% had CD4+ cell counts ≤ 200 cells/mm³,
and 85% had a baseline genotypic sensitivity score ≥ 2.
Virologic outcomes were similar across the treatment arms
through 96 weeks as presented in Table 8. The mean increase from baseline in
CD4+ cell count at Week 96 was 205 cells/mm³ in VITEKTA-treated
subjects and 198 cells/mm³ in raltegravir-treated subjects.
Table 8 : Virologic Outcomes of Randomized Treatment
of Study 145 in HIV-1 Infected Treatment-Experienced Adults (Week 96a Analysis)
|
VITEKTA + Protease Inhibitor/Ritonavir + Another Antiretroviral Drug
(N=351) |
Raltegravir + Protease Inhibitor/Ritonavir + Another Antiretroviral Drug
(N=351) |
HIV-1 RNA < 50 copies/mLb |
52% |
53% |
HIV-1 RNA ≥ 50 copies/mLc |
36% |
31% |
No Virologic Data at Week 96 |
12% |
16% |
Discontinued Study Drug Due to AE or Deathd |
3% |
7% |
Discontinued Study Drug Due to Other Reasons and Last Available HIV-1 RNA < 50 copies/mLe |
8% |
9% |
Missing Data During Window but on Study Drug |
1% |
1% |
a The Week 96 analysis window is between Day
645 and 700 (inclusive).
b Difference (95% CI) of response rate is –0.5% (–7.9%, 6.8%) at
Week 96.
c Includes subjects who had ≥ 50 copies/mL in the Week 96
window; subjects who discontinued early due to lack or loss of efficacy;
subjects who had a viral load ≥ 50 copies/mL at the time of change in
background regimen; subjects who discontinued for reasons other than an adverse
event, death, or lack or loss of efficacy, and at the time of discontinuation
had a viral value of ≥ 50 copies/mL.
d Includes subjects who discontinued due to adverse event or death
at any time point from Day 1 through the time window, if this resulted in no
virologic data on treatment during the specified window.
e Includes subjects who discontinued for reasons other than an
adverse event, death, or lack or loss of efficacy; eg, withdrew consent, loss
to follow-up, etc. |