CLINICAL PHARMACOLOGY
Mechanism Of Action
DUTREBIS is a fixed-dose
combination of HIV-1 antiviral drugs lamivudine and raltegravir [see Microbiology].
Pharmacodynamics
Cardiac Electrophysiology
DUTREBIS
No cardiac physiology studies
were performed with DUTREBIS.
Raltegravir
The effect of raltegravir 1600
mg (4 times the recommended dose) on QTc interval was evaluated in a
randomized, single-dose, placebo-controlled, crossover study in 31 healthy
subjects. At a dose 4 times the recommended dose, raltegravir did not prolong
the QTc interval to any clinically relevant extent.
Lamivudine
No cardiac physiology studies
have been performed with lamivudine.
Pharmacokinetics
DUTREBIS
In an open-label, single-dose,
randomized, two-period, crossover study in healthy subjects (n=108), one
DUTREBIS (150 mg lamivudine/300 mg raltegravir) fixed-dose combination tablet
was shown to provide comparable lamivudine and raltegravir exposures to one
EPIVIR 150 mg tablet plus one ISENTRESS 400 mg tablet.
Due to the higher
bioavailability of raltegravir contained in DUTREBIS, the exposures provided by
the 300 mg dose of raltegravir are comparable to 400 mg of raltegravir given as
the raltegravir poloxamer formulation (ISENTRESS), which accounts for the
difference in raltegravir dose.
Please refer to the full
prescribing information for raltegravir and lamivudine for additional
pharmacokinetic information.
Adults - Absorption
DUTREBIS
When DUTREBIS is administered
in the fasted state, raltegravir is absorbed with a T max of approximately 1
hour. The bioavailability of the raltegravir component of DUTREBIS in the
fasted state is approximately 60%. Once absorbed, lamivudine and raltegravir
distribution, metabolism, and excretion are similar to those of the reference
components administered individually as described in the full prescribing
information for lamivudine and raltegravir.
Effect of Food on Oral
Absorption
An open-label, single-dose,
randomized, two-period crossover study assessed the effect of a high fat meal
on DUTREBIS administered to 20 healthy male and female subjects. Similar AUC
values for fed vs. fasted and somewhat lower C max values (23% for raltegravir
and 21% for lamivudine) were observed with DUTREBIS. In addition, higher C 12h levels
(20% for raltegravir and 53% for lamivudine) were observed.
These changes are not considered clinically meaningful
and DUTREBIS can be taken without regard to a meal.
Distribution
Lamivudine
Binding of lamivudine to human plasma proteins is low
( < 36%). In vitro studies showed that over the concentration range of 0.1 to
100 mcg/mL, the amount of lamivudine associated with erythrocytes ranged from
53% to 57% and was independent of concentration.
Raltegravir
Raltegravir is approximately 83% bound to human plasma
protein over the concentration range of 2 to 10 μM.
Metabolism and Excretion
Lamivudine
Metabolism of lamivudine is a minor route of elimination.
Within 12 hours after a single oral dose of lamivudine in 6 HIV-1-infected
adults, 5.2% ± 1.4% (mean ± SD) of the dose was excreted as the transsulfoxide
metabolite in the urine.
Raltegravir
Studies using isoform-selective chemical inhibitors and
cDNA-expressed UDPglucuronosyltransferases (UGT) show that UGT1A1 is the main
enzyme responsible for the formation of raltegravir-glucuronide, the major
metabolite of raltegravir.
Elimination
Lamivudine
The majority of lamivudine is eliminated unchanged in
urine by active organic cationic secretion.
In most single-dose trials in HIV-1-infected subjects, HBV-infected
subjects, or healthy subjects with serum sampling for 24 hours after dosing,
the observed mean elimination half-life (t ½) ranged from 5 to 7 hours.
Raltegravir
Following administration of an oral dose of radiolabeled
raltegravir, approximately 51 and 32% of the dose was excreted in feces and
urine, respectively. The major circulating entity was raltegravir and
represented approximately 70% of the total radioactivity; the remaining
radioactivity in plasma was accounted for by raltegravir-glucuronide,
The apparent terminal half-life of raltegravir is
approximately 9 hours, with a shorter α-phase half-life (~1 hour)
accounting for much of the AUC.
Specific Populations
Pediatric
DUTREBIS
The pharmacokinetics of DUTREBIS in the pediatric patient
population has not been studied in clinical trials. DUTREBIS should not be used
in children below 6 years of age or in patients weighing less than 30 kg due to
weight-based dose adjustments in this patient population [see Use in
Specific Populations].
Raltegravir
The raltegravir component in DUTREBIS (300 mg
raltegravir) fixed-dose combination tablet was shown to provide comparable
raltegravir exposures to ISENTRESS (400 mg raltegravir) tablet. Based on
modeling and simulation using raltegravir pharmacokinetic data in adults, the
pharmacokinetics of raltegravir in DUTREBIS in children was projected to result
in exposures that have been previously shown to be safe and efficacious in
adults.
Pregnancy
Lamivudine
Lamivudine pharmacokinetics were evaluated in 16 women at
36 weeks gestation using 150 mg lamivudine twice daily with zidovudine, 10
women at 38 weeks gestation using 150 mg lamivudine twice daily with
zidovudine, and 10 women at 38 weeks gestation using lamivudine 300 mg twice daily
without other antiretrovirals. These trials were not designed or powered to
provide efficacy information. Lamivudine pharmacokinetics in pregnant women
were similar to those seen in non-pregnant adults and in postpartum women. Lamivudine
concentrations were generally similar in maternal, neonatal, and umbilical cord
serum samples. In a subset of subjects, lamivudine amniotic fluid specimens
were collected following natural rupture of membranes. Amniotic fluid
concentrations of lamivudine were typically 2 times greater than maternal serum
levels and ranged from 1.2 to 2.5 mcg/mL (150 mg twice daily) and 2.1 to 5.2
mcg/mL (300 mg twice daily).
Age, Race, Gender
No studies have been performed to evaluate the effect of
age, race, or gender on the pharmacokinetics of DUTREBIS. Recommendations are
based on available data from lamivudine and raltegravir. No dosage adjustment
for DUTREBIS is required based on age, race, or gender.
Hepatic Impairment
DUTREBIS
No study has been performed with DUTREBIS in subjects
with hepatic insufficiency. Recommendations are based on available data from
lamivudine and raltegravir. No dosage adjustment for DUTREBIS is required for
patients with mild to moderate hepatic insufficiency.
Lamivudine
Lamivudine pharmacokinetic parameters were not altered by
diminishing hepatic function; therefore, no dose adjustment for lamivudine is
required for patients with impaired hepatic function. Safety and efficacy of
lamivudine have not been established in the presence of decompensated liver
disease.
Raltegravir
Raltegravir is eliminated primarily by glucuronidation in
the liver. A study of the pharmacokinetics of raltegravir was performed in
adult subjects with moderate hepatic impairment. Additionally, hepatic
impairment was evaluated in the composite pharmacokinetic analysis in clinical
studies of raltegravir. There were no clinically important pharmacokinetic
differences between subjects with moderate hepatic impairment and healthy subjects.
No dosage adjustment is necessary for patients with mild to moderate hepatic
impairment. The effect of severe hepatic impairment on the pharmacokinetics of
raltegravir has not been studied.
Renal Impairment
DUTREBIS
No study has been performed with DUTREBIS in subjects
with renal insufficiency. Recommendations are based on available data from the
individual components. DUTREBIS should not be given in patients with a
creatinine clearance of < 50 mL/min. Renal function should be monitored in
patients more likely to have decreased renal function. If creatinine clearance
decreases to < 50 mL/min, DUTREBIS should be switched to a regimen of
lamivudine and raltegravir. Please refer to the full prescribing information
for lamivudine and raltegravir for dosing instructions.
Lamivudine
The pharmacokinetic properties of lamivudine have been
determined in a small group of HIV-1-infected adults with impaired renal
function.
Exposure (AUC ∞), C max , and half-life increased
with diminishing renal function (as expressed by creatinine clearance).
Apparent total oral clearance (Cl/F) of lamivudine decreased as creatinine
clearance decreased. T max was not significantly affected by renal function. When
administered as an individual component, the lamivudine dose should be adjusted
for patients with creatinine clearance < 50 mL/min. If creatinine clearance
decreases to < 50 mL/min, DUTREBIS should be switched to a regimen of
lamivudine and raltegravir. Please refer to the full prescribing information
for lamivudine and raltegravir for dosing instructions. [See DOSAGE AND
ADMINISTRATION]
Raltegravir
Renal clearance of unchanged drug is a minor pathway of
elimination. A study of the pharmacokinetics of raltegravir was performed in
adult subjects with severe renal impairment. Additionally, renal impairment was
evaluated in the composite pharmacokinetic analysis in clinical studies of
raltegravir. There were no clinically important pharmacokinetic differences
between subjects with severe renal impairment and healthy subjects. No dosage
adjustment is necessary.
UGT1A1 Polymorphism
Raltegravir
There is no evidence that common UGT1A1 polymorphisms
alter raltegravir pharmacokinetics to a clinically meaningful extent. In a
comparison of 30 adult subjects with *28/*28 genotype (associated with reduced
activity of UGT1A1) to 27 adult subjects with wild-type genotype, the geometric
mean ratio (90% CI) of AUC was 1.41 (0.96, 2.09).
Drug Interactions
[see DRUG INTERACTIONS]
DUTREBIS
One drug interaction study was conducted for DUTREBIS and
etravirine. In addition, drug interaction studies were conducted with
lamivudine or raltegravir coadministered with other commonly used drugs. The
results of the drug interaction studies are summarized in Tables 2, 3 and 4.
For information regarding clinical recommendations, see DRUG INTERACTIONS).
Table 2: Effect of Etravirine on the Pharmacokinetics
of Lamivudine/Raltegravir in Adults
Coadministered Drug |
Coadministered Drug Dose/ Schedule |
Lamivudine/ Raltegravir Dose/Schedule |
Ratio (90% Confidence Interval) of Raltegravir Pharmacokinetic Parameters with/without Coadministered Drug; Prespecified bounds: 0.5, 2.0 |
N |
C12 hr |
Etravirine |
200 mg etravirine twice daily for 15 days (Period 2) |
Lamivudine/raltegravir tablet (150 mg/300 mg) as a single dose on Day 1, Period 1, and on Day 14, Period 2 |
18 |
0.86 (0.63, 1.17) No dosage adjustment necessary |
Lamivudine
Interferon Alfa
There was no significant
pharmacokinetic interaction between lamivudine and interferon alfa in a trial
of 19 healthy male subjects [see WARNINGS AND PRECAUTIONS].
Ribavirin
In vitro data indicate ribavirin reduces phosphorylation of
lamivudine, stavudine, and zidovudine. However, no pharmacokinetic (e.g.,
plasma concentrations or intracellular triphosphorylated active metabolite
concentrations) or pharmacodynamic (e.g., loss of HIV-1/HCV virologic
suppression) interaction was observed when ribavirin and lamivudine (n=18),
stavudine (n=10), or zidovudine (n=6) were coadministered as part of a
multi-drug regimen to HIV-1/HCV co-infected subjects [see WARNINGS
AND PRECAUTIONS].
Trimethoprim/Sulfamethoxazole
Table 3: Effect of Trimethoprim/Sulfamethoxazole on
the Pharmacokinetics of Lamivudine
Coadministered Drug and Dose |
Drug and Dose |
N |
Concentrations of Lamivudine (% Change) |
Concentration of coadministered drug |
AUC Mean (SD) |
Oral CL Mean (SD) |
Renal CL Mean (SD) |
Trimethoprim 160 mg/ Sulfamethoxazole 800 mg daily x 5 days |
Lamivudine Single 300 mg |
14 |
Increase 43% (23%) |
Decrease 29% (13%) |
Decrease 30% (36%) |
Not altered |
Zidovudine
No clinically significant
alterations in lamivudine or zidovudine pharmacokinetics were observed in 12
asymptomatic HIV-1-infected adult patients given a single dose of zidovudine
(200 mg) in combination with multiple doses of lamivudine (300 mg q 12 hr) [see
DRUG INTERACTIONS].
Raltegravir
The results of the drug
interaction studies represented in the following table were conducted with
raltegravir.
Table 4: Effect of Other
Agents on the Pharmacokinetics of Raltegravir in Adults
Coadministered Drug |
Coadministered Drug Dose/Schedule |
Raltegravir Dose/Schedule |
Ratio (90% Confidence Interval) of Raltegravir Pharmacokinetic Parameters with/without Coadministered Drug; No Effect = 1.00 |
n |
Cmax |
AUC |
Cmin |
aluminum and magnesium hydroxide antacid |
20 mL single dose given with raltegravir |
400 mg twice daily |
25 |
0.56 (0.42, 0.73) |
0.51 (0.40, 0.65) |
0.37 (0.29, 0.48) |
20 mL single dose given 2 hours before raltegravir |
23 |
0.49 (0.33, 0.71) |
0.49 (0.35, 0.67) |
0.44 (0.34, 0.55) |
20 mL single dose given 2 hours after raltegravir |
23 |
0.78 (0.53, 1.13) |
0.70 (0.50, 0.96) |
0.43 (0.34, 0.55) |
atazanavir |
400 mg daily |
100 mg single dose |
10 |
1.53 (1.11, 2.12) |
1.72 (1.47, 2.02) |
1.95 (1.30, 2.92) |
atazanavir/ritonavir |
300 mg/100 mg daily |
400 mg twice daily |
10 |
1.24 (0.87, 1.77) |
1.41 (1.12, 1.78) |
1.77 (1.39, 2.25) |
boceprevir |
800 mg three times daily |
400 mg single dose |
22 |
1.11 (0.91-1.36) |
1.04 (0.88-1.22) |
0.75 (0.45-1.23) |
calcium carbonate antacid |
3000 mg single dose given with raltegravir |
400 mg twice daily |
24 |
0.48 (0.36, 0.63) |
0.45 (0.35, 0.57) |
0.68 (0.53, 0.87) |
efavirenz |
600 mg daily |
400 mg single dose |
9 |
0.64 (0.41, 0.98) |
0.64 (0.52, 0.80) |
0.79 (0.49, 1.28) |
etravirine |
200 mg twice daily |
400 mg twice daily |
19 |
0.89 (0.68, 1.15) |
0.90 (0.68, 1.18) |
0.66 (0.34, 1.26) |
omeprazole |
20 mg daily |
400 mg single dose |
14 (10 for AUC) |
4.15 (2.82, 6.10) |
3.12 (2.13, 4.56) |
1.46 (1.10, 1.93) |
rifampin |
600 mg daily |
400 mg single dose |
9 |
0.62 (0.37, 1.04) |
0.60 (0.39, 0.91) |
0.39 (0.30, 0.51) |
rifampin |
600 mg daily |
400 mg twice daily when administered alone; 800 mg twice daily when administered with rifampin |
14 |
1.62 (1.12, 2.33) |
1.27 (0.94, 1.71) |
0.47 (0.36, 0.61) |
ritonavir |
100 mg twice |
400 mg single |
10 |
0.76 |
0.84 |
0.99 |
Microbiology
Mechanism of Action
Lamivudine
Lamivudine is an HIV-1
nucleoside analogue reverse transcriptase inhibitor (NRTI). Intracellularly, lamivudine
is phosphorylated to its active 5'-triphosphate metabolite, lamivudine
triphosphate (3TC-TP). The principal mode of action of 3TC-TP is the inhibition
of HIV-1 reverse transcriptase (RT) via DNA chain termination after
incorporation of the nucleotide analogue into viral DNA.
Raltegravir
Raltegravir inhibits the strand
transfer activity of HIV-1 integrase (integrase strand transfer inhibitor;
INSTI), an HIV-1 encoded enzyme that is required for viral replication.
Inhibition of integrase prevents the covalent insertion, or integration, of
unintegrated linear HIV-1 DNA into the host cell genome preventing the
formation of the HIV-1 provirus. The provirus is required to direct the
production of progeny virus, so inhibiting integration prevents propagation of
the viral infection.
Antiviral Activity in Cell
Culture
Lamivudine
The antiviral activity of
lamivudine against HIV-1 was assessed in a number of cell lines (including
monocytes and fresh human peripheral blood lymphocytes) using standard
susceptibility assays. EC 50 values (50% effective concentrations) were in the
range of 0.003 to 15 μM (1 μM=0.23 mcg/mL). HIV-1 from therapy-naïve
subjects with no amino acid substitutions associated with resistance gave
median EC50 values of 0.429 μM (range: 0.200 to 2.007 μM) from Virco
(n=92 baseline samples from COLA40263) and 2.35 μM (1.37 to 3.68 μM)
from Monogram Biosciences (n=135 baseline samples from ESS30009). The EC 50 values
of lamivudine against different HIV-1 clades (A-G) ranged from 0.001 to 0.120
μM, and against HIV-2 isolates from 0.003 to 0.120 μM in peripheral
blood mononuclear cells. Ribavirin (50 μM) decreased the anti-HIV-1
activity of lamivudine by 3.5 fold in MT-4 cells. In HIV-1infected MT-4 cells,
lamivudine in combination with zidovudine at various ratios exhibited
synergistic antiretroviral activity.
Raltegravir
Raltegravir at concentrations
of 31 ± 20 nM resulted in 95% inhibition (EC 95 ) of viral spread (relative to
an untreated virus-infected culture) in human T-lymphoid cell cultures infected
with the cell-line adapted HIV-1 variant H9IIIB. In addition, 5 clinical
isolates of HIV-1 subtype B had EC 95 values ranging from 9 to 19 nM in cultures
of mitogen-activated human peripheral blood mononuclear cells. In a
single-cycle infection assay, raltegravir inhibited infection of 23 HIV-1
isolates representing 5 non-B subtypes (A, C, D, F, and G) and 5 circulating
recombinant forms (AE, AG, BF, BG, and cpx) with EC 50 values ranging from 5 to
12 nM. Raltegravir also inhibited replication of an HIV-2 isolate when tested
in CEMx174 cells (EC 95 value=6 nM). Additive to synergistic antiretroviral
activity was observed when human T-lymphoid cells infected with the H9IIIB
variant of HIV-1 were incubated with raltegravir in combination with
nonnucleoside reverse transcriptase inhibitors (delavirdine, efavirenz, or
nevirapine); nucleoside reverse transcriptase inhibitors (abacavir, didanosine,
lamivudine, stavudine, tenofovir, or zidovudine); protease inhibitors
(amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, or
saquinavir); or the entry inhibitor enfuvirtide.
Resistance
Lamivudine
Lamivudine-resistant variants
of HIV-1 have been selected in cell culture and in subjects treated with
lamivudine. Genotypic analysis showed that the resistance was due to a specific
amino acid substitution in the HIV-1 reverse transcriptase at codon 184
changing the methionine to either isoleucine or valine (M184V/I).
Raltegravir
The mutations observed in the HIV-1 integrase coding
sequence that contributed to raltegravir resistance (evolved either in cell
culture or in subjects treated with raltegravir) generally included an amino
acid substitution at either Y143 (changed to C, H, or R) or Q148 (changed to H,
K, or R) or N155 (changed to H) plus one or more additional substitutions
(i.e., L74M, E92Q, Q95K/R, T97A, E138A/K, G140A/S, V151I, G163R, H183P,
Y226C/D/F/H, S230R, and D232N). E92Q and F121C are occasionally seen in the
absence of substitutions at Y143, Q148, or N155 in raltegravir-treatment
failure subjects.
Cross Resistance
Lamivudine
Cross-resistance has been observed among NRTIs. The
M184I/V lamivudine resistance substitution confers resistance to emtricitabine.
Lamivudine-resistant HIV-1 mutants were also cross-resistant to didanosine
(ddI). In some subjects treated with zidovudine plus didanosine, isolates
resistant to multiple reverse transcriptase inhibitors, including lamivudine,
have emerged.
Raltegravir
Cross-resistance has been observed among INSTIs. Amino
acid substitutions in HIV-1 integrase conferring resistance to raltegravir
generally also confer resistance to elvitegravir. Substitutions at amino acid Y143
confer greater reductions in susceptibility to raltegravir than to
elvitegravir, and the E92Q substitution confers greater reductions in
susceptibility to elvitegravir than to raltegravir. Viruses harboring a
substitution at amino acid Q148, along with one or more other raltegravir
resistance substitutions, may also have clinically significant resistance to
dolutegravir.
Clinical Studies
Clinical trials have not been specifically performed with
DUTREBIS. The indication of DUTREBIS is based on efficacy and safety data
demonstrated in clinical trials with lamivudine [see lamivudine full
prescribing information] and with raltegravir [see raltegravir full
prescribing information].