CLINICAL PHARMACOLOGY
Mechanism Of Action
Emtricitabine is an antiretroviral drug [see Microbiology].
Pharmacokinetics
Adults
The pharmacokinetic properties of FTC were evaluated in
healthy subjects and HIV-1-infected subjects. Emtricitabine pharmacokinetics
are similar between these populations.
Figure 1 shows the mean steady-state plasma FTC
concentration-time profile in 20 HIV-1-infected subjects receiving EMTRIVA
capsules.
Figure 1 : Mean (± 95% CI) Steady-State
Plasma FTC Concentrations in HIV-1 Infected Adults (N=20)
Absorption
Emtricitabine is rapidly and extensively absorbed
following oral administration, with peak plasma concentrations occurring at 1–2
hours postdose. Following multiple dose oral administration of EMTRIVA capsules
to 20 HIV-1 infected subjects, the (mean ± SD) steady-state plasma FTC
peak concentration (Cmax) was 1.8 ± 0.7 μg/mL and the area-under
the plasma concentration-time curve over a 24-hour dosing interval (AUC) was
10.0 ± 3.1 μg·hr/mL. The mean steady-state plasma trough
concentration at 24 hours postdose was 0.09 μg/mL. The mean absolute
bioavailability of EMTRIVA capsules was 93%, while the mean absolute
bioavailability of EMTRIVA oral solution was 75%. The relative bioavailability
of EMTRIVA oral solution was approximately 80% of EMTRIVA capsules.
The multiple dose pharmacokinetics of FTC are dose
proportional over a dose range of 25–200 mg.
Distribution
In vitro binding of FTC to human plasma proteins was less
than 4% and independent of concentration over the range of 0.02–200 μg/mL.
At peak plasma concentration, the mean plasma to blood drug concentration ratio
was ~1.0 and the mean semen to plasma drug concentration ratio was ~4.0.
Metabolism
Following administration of radiolabelled FTC, complete
recovery of the dose was achieved in urine (~86%) and feces (~14%). Thirteen
percent (13%) of the dose was recovered in urine as three putative metabolites.
The biotransformation of FTC includes oxidation of the thiol moiety to form the
3’-sulfoxide diastereomers (~9% of dose) and conjugation with glucuronic acid
to form 2’-O-glucuronide (~4% of dose). No other metabolites were identifiable.
Elimination
The plasma FTC half-life is approximately 10 hours. The
renal clearance of FTC is greater than the estimated creatinine clearance,
suggesting elimination by both glomerular filtration and active tubular
secretion. There may be competition for elimination with other compounds that
are also renally eliminated.
Effects Of Food On Oral Absorption
EMTRIVA capsules and oral solution may be taken with or
without food. Emtricitabine systemic exposure (AUC) was unaffected while Cmax
decreased by 29% when EMTRIVA capsules were administered with food (an
approximately 1000 kcal high-fat meal). Emtricitabine systemic exposure (AUC)
and Cmax were unaffected when 200 mg EMTRIVA oral solution was administered
with either a high-fat or low-fat meal.
Specific Populations
Geriatric Patients
The pharmacokinetics of FTC have not been fully evaluated
in the elderly (65 years of age and older).
Pediatric Patients
The pharmacokinetics of FTC at steady state were
determined in 77 HIV-1 infected pediatric subjects, and the pharmacokinetic
profile was characterized in four age groups (Table 6). The FTC exposure
achieved in pediatric subjects receiving a daily dose of 6 mg/kg up to a
maximum of 240 mg oral solution or a 200-mg capsule is similar to exposures
achieved in adult subjects receiving a once-daily dose of 200 mg.
The pharmacokinetics of FTC were studied in 20 neonates
born to HIV-1 positive mothers. Each mother received prenatal and intrapartum
combination antiretroviral therapy. Neonates received up to 6 weeks of AZT
prophylactically after birth. The neonates were administered two short courses
of FTC oral solution (each 3 mg/kg once daily > 4 days) during the first
3 months of life. The AUC observed in neonates who received a daily dose of 3
mg/kg of FTC was similar to the AUC observed in pediatric subjects aged 3
months to 17 years who received a daily dose of FTC as a 6 mg/kg oral solution
up to 240 mg or as a 200-mg capsule (Table 6).
Table 6 : Mean ± SD Pharmacokinetic
Parameters by Age Groups for Pediatric Subjects and Neonates Receiving EMTRIVA
Capsules or Oral Solution
Age |
HIV-1- exposed Neonates |
HIV-1 Infected Pediatric Subjects |
0-3 mo
(N=20) a |
3-24 mo
(N=14) |
25 mo-6 yr
(N=19) |
7-12yr
(N=17) |
13-17 yr
(N=27) |
Formulation Capsule (n) |
0 |
0 |
0 |
10 |
26 |
Oral Solution (n) |
20 |
14 |
19 |
7 |
1 |
Dose (mg/kg)b |
3.1 (2.9-3.4) |
6.1 (5.5-6.8) |
6.1 (5.6-6.7) |
5.6 (3.1-6.6) |
4.4 (1.8-7.0) |
Cmax (μg/mL) |
1.6 ± 0.6 |
1.9 ± 0.6 |
1.9 ± 0.7 |
2.7 ± 0.8 |
2.7 ± 0.9 |
AUC (μg•;hr/mL) |
11.0 ± 4.2 |
8.7 ± 3.2 |
9.0 ± 3.0 |
12.6 ± 3.5 |
12.6 ± 5.4 |
T½ (hr) |
12.1 ± 3.1 |
8.9 ± 3.2 |
11.3 ± 6.4 |
8.2 ± 3.2 |
8.9 ± 3.3 |
a Two pharmacokinetic evaluations were
conducted in 20 neonates over the first 3 months of life. Median (range) age of
infant on day of pharmacokinetic evaluation was 26 (5–81) days.
b Mean (range). |
Gender
FTC pharmacokinetics are similar in adult male and female
subjects.
Race
No pharmacokinetic differences due to race have been
identified.
Patients With Renal Impairment
The pharmacokinetics of FTC are altered in subjects with
renal impairment [see WARNINGS AND PRECAUTIONS]. In adult subjects with
creatinine clearance below 50 mL/min or with end-stage renal disease (ESRD)
requiring dialysis, Cmax and AUC of FTC were increased (Table 7). The effects
of renal impairment on FTC pharmacokinetics in pediatric patients are not
known.
Table 7 : Pharmacokinetic Parameters (Mean ±
SD) of FTC in Adult Subjects with Varying Degrees of Renal Function
Creatinine Clearance (mL/min) |
>80
(N=6) |
50-80
(N=6) |
30-49
(N=6) |
<30
(N=5) |
ESRDa <30
(N=5) |
Baseline creatinine clearance (mL/min) |
107 ± 21 |
59.8 ± 6.5 |
40.9 ± 5.1 |
22.9 ± 5.3 |
8.8 ± 1.4 |
Cmax (ag/mL) |
2.2 ± 0.6 |
3.8 ± 0.9 |
3.2 ± 0.6 |
2.8 ± 0.7 |
2.8 ± 0.5 |
AUC (μg•hr/mL) |
11.8 ± 2.9 |
19.9 ± 1.2 |
25.1 ± 5.7 |
33.7± 2.1 |
53.2 ± 9.9 |
CL/F (μL/min) |
302 ± 94 |
168 ± 10 |
138 ± 28 |
99 ± 6 |
64 ± 12 |
CLr (mL/min) |
213 ± 89 |
121 ± 39 |
69 ± 32 |
30 ± 11 |
NAb |
a ESRD subjects requiring dialysis
b NA = Not Applicable |
Patients With Hepatic Impairment
The pharmacokinetics of FTC have not been studied in
subjects with hepatic impairment; however, FTC is not significantly metabolized
by liver enzymes, so the impact of liver impairment should be limited.
Assessment Of Drug Interactions
At concentrations up to 14-fold higher than those
observed in vivo, FTC did not inhibit in vitro drug metabolism mediated by any
of the following human CYP isoforms: CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19,
CYP2D6, and CYP3A4. FTC did not inhibit the enzyme responsible for
glucuronidation (uridine-5’-disphosphoglucuronyl transferase). Based on the
results of these in vitro experiments and the known elimination pathways of
FTC, the potential for CYP-mediated interactions involving FTC with other
medicinal products is low.
EMTRIVA has been evaluated in healthy volunteers in
combination with TDF, AZT, indinavir, famciclovir, and d4T. Tables 8 and 9
summarize the pharmacokinetic effects of coadministered drug on FTC
pharmacokinetics and effects of FTC on the pharmacokinetics of coadministered
drug.
Table 8 : Drug Interactions: Change in Pharmacokinetic
Parameters for FTC in the Presence of the Coadministered Druga
Coadministered Drug |
Dose of Coadministered Drug (mg) |
FTC Dose (mg) |
N |
% Change of FTC Pharmacokinetic Parametersb (90% CI) |
Cmax |
AUC |
Cmin |
Famciclovir |
500 x 1 |
200 x 1 |
12 |
⇔ |
⇔ |
NA |
Indinavir |
800 x 1 |
200 x 1 |
12 |
⇔ |
⇔ |
NA |
Stavudine |
40 x 1 |
200 x 1 |
6 |
⇔ |
⇔ |
NA |
Tenofovir DF |
300 once daily x 7 days |
200 once daily x 7 days |
17 |
⇔ |
⇔ |
↑ 20
(↑ 12 to ↑ 29) |
Zidovudine |
300 twice daily x 7 days |
200 once daily x 7 days |
27 |
⇔ |
⇔ |
⇔ |
a All interaction trials conducted in healthy
volunteers.
b ↑ = Increase; ⇔ = No Effect; NA = Not Applicable |
Table 9 : Drug Interactions: Change in Pharmacokinetic
Parameters for Coadministered Drug in the Presence of FTCa
Coadministered Drug |
Dose of Coadministered Drug (mg) |
FTC Dose (mg) |
N |
% Change of Coadministered Drug Pharmacokinetic Parametersb (90% CI) |
Cmax |
AUC |
Cmin |
Famciclovir |
500 x 1 |
200 x 1 |
12 |
⇔ |
⇔ |
NA |
Indinavir |
800 x 1 |
200 x 1 |
12 |
⇔ |
⇔ |
NA |
Stavudine |
40 x 1 |
200 x 1 |
6 |
⇔ |
⇔ |
NA |
Tenofovir DF |
300 once daily x 7 days |
200 once daily x 7 days |
17 |
⇔ |
⇔ |
⇔ |
Zidovudine |
300 twice daily x 7 days |
200 once daily x 7 days |
27 |
↑ 17 (↑ 0 to ↑ 38) |
↑ 13 (↑ 5 to↑ 20) |
⇔ |
a All interaction trials conducted in healthy
volunteers.
b ↑ = Increase; ⇔ = No Effect; NA = Not Applicable |
Microbiology
Mechanism Of Action
FTC, a synthetic nucleoside analog of cytidine, is
phosphorylated by cellular enzymes to form emtricitabine 5'-triphosphate
(FTC-TP), which inhibits the activity of the HIV-1 reverse transcriptase (RT)
by competing with the natural substrate deoxycytidine 5'-triphosphate and by
being incorporated into nascent viral DNA resulting in chain termination.
FTC-TP is a weak inhibitor of mammalian DNA polymerases α, β,
ε, and mitochondrial DNA polymerase γ.
Antiviral Activity
The antiviral activity of FTC against laboratory and
clinical isolates of HIV-1 was assessed in lymphoblastoid cell lines, the
MAGI-CCR5 cell line, and peripheral blood mononuclear cells. The 50% effective
concentration (EC50) values for FTC were in the range of 0.0013–0.64 μM
(0.0003–0.158 μg/mL). The median EC50, range, and number of isolates for
the laboratory isolates were 0.07, 0.009-0.62, 10; 0.011,
0.002-0.03, 12; 0.055, 0.0015-0.09, 4 respectively for
lymphoblastoid, PBMC, and reporter cells. The median EC50, range, and number of
isolates for the clinical isolates were 0.05, 0.0105-0.64, 15; 0.015,
0.004-0.028, 6 respectively for lymphoblastoid cells and PBMCs. No
antagonism was observed in drug combination studies of emtricitabine with
nucleoside reverse transcriptase inhibitors (NRTIs) (abacavir, lamivudine,
stavudine, tenofovir, zidovudine), non-nucleoside reverse transcriptase
inhibitors (NNRTIs) (delavirdine, efavirenz, nevirapine), and protease
inhibitors (amprenavir, nelfinavir, ritonavir, saquinavir). FTC displayed
antiviral activity in cell culture against HIV-1 clades A, B, C, D, E, F, and G
(EC50 values ranged from 0.007–0.075 μM) and showed strain-specific
activity against HIV-2 (EC50 values ranged from 0.007–1.5 μM in PBMCs
and MAGI cells).
Resistance
FTC-resistant isolates of HIV-1 have been selected in
cell culture and in vivo. Genotypic analysis of these isolates showed that the
reduced susceptibility to FTC was associated with a valine or isoleucine
(M184V/I) substitution in the HIV-1 RT.
FTC-resistant isolates of HIV-1 have been recovered from
some subjects treated with FTC alone or in combination with other antiretroviral
agents. In a clinical trial of treatment-naive subjects treated with EMTRIVA,
didanosine, and efavirenz (EFV) [see Clinical Studies], viral isolates
from 37.5% of subjects with virologic failure showed reduced susceptibility to
FTC. Genotypic analysis of these isolates showed that the resistance was due to
M184V/I substitutions in the HIV-1 RT.
In a clinical trial of treatment-naive subjects treated
with either EMTRIVA, TDF, and EFV or AZT/3TC and EFV [see Clinical Studies],
resistance analysis was performed on HIV-1 isolates from all confirmed
virologic failure subjects with greater than 400 copies/mL of HIV-1 RNA at Week
144 or early discontinuation. Development of EFV resistance-associated
substitutions occurred most frequently and was similar between the treatment
arms. The M184V amino acid substitution, associated with resistance to EMTRIVA
and 3TC, was observed in 2/19 analyzed subject isolates in the EMTRIVA + TDF
group and in 10/29 analyzed subject isolates in the AZT/3TC group. Through 144
weeks of Trial 934, no subjects have developed a detectable K65R substitution
in their HIV-1 as analyzed through standard genotypic analysis.
Cross Resistance
Cross-resistance among certain NRTIs has been recognized.
FTC-resistant isolates (M184V/I) were cross-resistant to 3TC but retained
susceptibility in cell culture to AZT, didanosine, d4T, and tenofovir, and to
NNRTIs (delavirdine, EFV, and nevirapine). HIV-1 isolates containing the K65R
substitution, selected in vivo by abacavir, didanosine, and tenofovir,
demonstrated reduced susceptibility to inhibition by FTC. Viruses harboring
substitutions conferring reduced susceptibility to AZT and d4T (M41L, D67N,
K70R, L210W, T215Y/F, K219Q/E) or didanosine (L74V) remained sensitive to FTC.
HIV-1 containing the K103N substitution associated with resistance to NNRTIs
was susceptible to FTC.
Clinical Studies
Overview Of Clinical Trials
The efficacy and safety of EMTRIVA were evaluated in the
trials summarized in Table 10.
Table 10 : Trials Conducted with EMTRIVA in Adult and
Pediatric Subjects
Trial |
Population |
Trial Arms (N)a |
Timepoint (Weeks) |
Trial 934b (NCT00112047) |
HIV-1 treatment-naive adults |
EMTRIVA+TDF+EFV (227) AZT/3TC+EFV (229) |
144 |
Trial 301Ac (NCT00006208) |
EMTRIVA+didanosine+EFV (286) d4T+didanosine+EFV (285) |
48 |
Trial 303b (NCT00002416) |
HIV-1 treatment-experienced adults |
EMTRIVA+AZT/d4T+NNRTI/PI (294) 3TC+AZT/d4T+NNRTI/PI (146) |
48 |
Trial 202d (NCT00016718) |
HIV-1 treatment-naive and experienced pediatrics |
EMTRIVA+didanosine+EFV (43) |
48 |
Trial 203d (NCT00743340) |
EMTRIVA+d4T+lopinavir/ritonavir (116) |
48 |
Trial 211d (NCT00642291) |
EMTRIVA+didanosine+EFV (16) |
48 |
a Randomized and dosed.
b Randomized, open-label, active-controlled trial.
c Randomized, double-blind, active-controlled trial.
d Nonrandomized, open-label trial. |
Clinical Trial Results In Treatment-Naive Adults
Trial 934
Data through 144 weeks are reported for Trial 934, a
randomized, open-label, active-controlled multicenter clinical trial comparing
EMTRIVA + TDF administered in combination with EFV versus AZT/3TC fixed-dose
combination administered in combination with EFV in 511 antiretroviral-naive
subjects. From Weeks 96 to 144 of the trial, subjects received FTC/TDF
fixed-dose combination with EFV in place of EMTRIVA + TDF with EFV. Subjects
had a mean age of 38 years (range 18–80); 86% were male, 59% were Caucasian,
and 23% were Black. The mean baseline CD4+ cell count was 245 cells/mm³ (range
2–1191) and median baseline plasma HIV-1 RNA was 5.01 log10 copies/mL (range
3.56–6.54). Subjects were stratified by baseline CD4+ cell count (< or ≥200
cells/mm³); 41% had CD4+ cell counts <200 cells/mm³ and 51% of subjects had
baseline viral loads >100,000 copies/mL. Table 11 provides treatment
outcomes through 48 and 144 weeks for those subjects who did not have EFV
resistance at baseline.
Table 11 : Virologic Outcomes of Randomized Treatment
at Week 48 and 144 (Trial 934)
Outcomes |
Week 48 |
Week 144 |
EMTRIVA +TDF +EFV
(N=244) |
AZT/3TC +EFV
(N=243) |
EMTRIVA +TDF +EFV
(N=227)a |
AZT/3TC +EFV
(N=229)a |
Responderb |
84% |
73% |
71% |
58% |
Virologic failurec |
2% |
4% |
3% |
6% |
Rebound |
1% |
3% |
2% |
5% |
Never suppressed |
0% |
0% |
0% |
0% |
Change in antiretroviral regimen |
1% |
1% |
1% |
1% |
Death |
<1% |
1% |
1% |
1% |
Discontinued due to adverse event |
4% |
9% |
5% |
12% |
Discontinued for other reasonsd |
10% |
14% |
20% |
22% |
a Subjects who were responders at Week 48 or
Week 96 (HIV-1 RNA <400 copies/mL) but did not consent to continue in the
trial after Week 48 or Week 96 were excluded from analysis.
b Subjects achieved and maintained confirmed HIV-1 RNA <400
copies/mL through Weeks 48 and 144.
c Includes confirmed viral rebound and failure to achieve confirmed
<400 copies/mL through Weeks 48 and 144.
d Includes lost to follow-up, subject withdrawal, noncompliance,
protocol violation and other reasons. |
Through Week 48, 84%, and 73% of subjects in the EMTRIVA
+ TDF group and the AZT/3TC group, respectively, achieved and maintained HIV-1
RNA <400 copies/mL (71% and 58% through Week 144). The difference in the
proportion of subjects who achieved and maintained HIV-1 RNA <400 copies/mL
through 48 weeks largely results from the higher number of discontinuations due
to adverse events and other reasons in the AZT/3TC group in this open-label
trial. In addition, 80% and 70% of subjects in the EMTRIVA + TDF group and the
AZT/3TC group, respectively, achieved and maintained HIV-1 RNA <50 copies/mL
through Week 48 (64% and 56% through Week 144). The mean increase from baseline
in CD4+ cell count was 190 cells/mm³ in the EMTRIVA + TDF group and 158
cells/mm³ in the AZT/3TC group at Week 48 (312 and 271 cells/mm³ at Week 144).
Through 48 weeks, 7 subjects in the EMTRIVA + TDF group
and 5 subjects in the AZT/3TC group experienced a new CDC Class C event (10 and
6 subjects through 144 weeks).
Trial 301A
Trial 301A was a 48-week double-blind, active-controlled,
multicenter clinical trial comparing EMTRIVA (200 mg once daily) administered
in combination with didanosine and EFV versus d4T, didanosine, and EFV in 571
antiretroviral naive adult subjects. Subjects had a mean age of 36 years (range
18–69); 85% were male, 52% Caucasian, 16% African-American, and 26% Hispanic.
Subjects had a mean baseline CD4+ cell count of 318 cells/mm³ (range 5–1317)
and a median baseline plasma HIV-1 RNA of 4.9 log10 copies/mL (range 2.6–7.0).
Thirty-eight percent of subjects had baseline viral loads >100,000 copies/mL
and 31% had CD4+ cell counts <200 cells/mL. Table 12 provides treatment
outcomes through 48 weeks.
Table 12 : Virologic Outcomes of Randomized Treatment
at Week 48 (Trial 301A)
Outcomes |
EMTRIVA + Didanosine + EFV
(N=286) |
d4T + Didanosine + EFV
(N=285) |
Respondera |
81% (78%) |
68% (59%) |
Virologic Failureb |
3% |
11% |
Death |
0% |
<1% |
Discontinuation Due to Adverse Event |
7% |
13% |
Discontinuation for Other Reasonsc |
9% |
8% |
a Subjects achieved and maintained confirmed
HIV RNA <400 copies/mL (<50 copies/mL) through Week 48.
b Includes subjects who failed to achieve virologic suppression or
rebounded after achieving virologic suppression.
c Includes lost to follow-up, subject withdrawal, non-compliance,
protocol violation, and other reasons. |
The mean increase from baseline in CD4+ cell count was
168 cells/mm³ for the EMTRIVA arm and 134 cells/mm³ for the d4T arm.
Through 48 weeks, 5 subjects (1.7%) in the EMTRIVA group
experienced a new CDC Class C event compared to 7 subjects (2.5%) in the d4T
group.
Clinical Trial Results In Treatment-Experienced Adults
Trial 303
Trial 303 was a 48-week, open-label, active-controlled,
multicenter clinical trial comparing EMTRIVA (200 mg once daily) to 3TC, in
combination with d4T or AZT and a protease inhibitor or NNRTI in 440 adult
subjects who were on a 3TC-containing triple-antiretroviral drug regimen for at
least 12 weeks prior to trial entry and had HIV-1 RNA ≤400 copies/mL.
Subjects were randomized 1:2 to continue therapy with 3TC
(150 mg twice daily) or to switch to EMTRIVA (200 mg once daily). All subjects
were maintained on their stable background regimen. Subjects had a mean age of
42 years (range 22–80); 86% were male, 64% Caucasian, 21% African-American, and
13% Hispanic. Subjects had a mean baseline CD4+ cell count of 527 cells/mm³
(range 37–1909), and a median baseline plasma HIV-1 RNA of 1.7 log10 copies/mL
(range 1.7–4.0).
The median duration of prior antiretroviral therapy was
27.6 months. Table 13 provides treatment outcomes through 48 weeks.
Table 13 : Virologic Outcomes of Randomized Treatment
at Week 48 (Trial 303)
Outcomes |
EMTRIVA + AZT/d4T + NNRTI/PI
(N=294) |
3TC + AZT/d4T + NNRTI/PI
(N=146) |
Respondera |
77% (67%) |
82% (72%) |
Virologic Failureb |
7% |
8% |
Death |
0% |
<1% |
Discontinuation Due to Adverse Event |
4% |
0% |
Discontinuation for Other Reasonsc |
12% |
10% |
a Subjects achieved and maintained confirmed
HIV RNA <400 copies/mL (<50 copies/mL) through Week 48.
b Includes subjects who failed to achieve virologic suppression or
rebounded after achieving virologic suppression.
c Includes lost to follow-up, subject withdrawal, non-compliance,
protocol violation, and other reasons. |
The mean increase from baseline in CD4+ cell count was 29
cells/mm³ for the EMTRIVA arm and 61 cells/mm³ for the 3TC arm.
Through 48 weeks, in the EMTRIVA group 2 subjects (0.7%)
experienced a new CDC Class C event compared to 2 subjects (1.4%) in the 3TC
group.
Clinical Trial Results In Pediatrics
In three open-label, nonrandomized clinical trials, FTC
was administered to 169 HIV-1 infected treatment-naive and experienced (defined
as virologically suppressed on a 3TC-containing regimen for which FTC was
substituted for 3TC) subjects between 3 months and 21 years of age. Subjects
received once-daily EMTRIVA oral solution (6 mg/kg to a maximum of 240 mg/day)
or EMTRIVA capsules (a single 200 mg capsule once daily) in combination with at
least two other antiretroviral agents.
Subjects had a mean age of 7.9 years (range 0.3–21); 49%
were male, 15% Caucasian, 61% Black, and 24% Hispanic. Subjects had a median
baseline HIV-1 RNA of 4.6 log10 copies/mL (range 1.7–6.4) and a mean baseline
CD4+ cell count of 745 cells/mm³ (range 2–2650). Through 48 weeks of therapy,
the overall proportion of subjects who achieved and sustained an HIV-1 RNA
<400 copies/mL was 86%, and <50 copies/mL was 73%. The mean increase from
baseline in CD4+ cell count was 232 cells/mm³ (-945, +1512). The adverse
reaction profile observed during these clinical trials was similar to that of
adult subjects, with the exception of the occurrence of anemia and higher
frequency of hyperpigmentation in children [see ADVERSE REACTIONS].
The pharmacokinetics of FTC were studied in 20 neonates
born to HIV-1 positive mothers. Each mother received prenatal and intrapartum
combination antiretroviral therapy. Neonates received up to 6 weeks of AZT
prophylactically after birth. The neonates were administered two short courses
of FTC oral solution (each 3 mg/kg once daily > 4 days) during the first
3 months of life. FTC exposures in neonates were similar to the exposures
achieved in subjects aged 3 months to 17 years [see CLINICAL PHARMACOLOGY].
During the two short dosing periods on FTC, there were no safety issues identified
in the treated neonates. All neonates were HIV-1 negative at the end of the
trial; the efficacy of FTC in preventing or treating HIV-1 could not be
determined.