CLINICAL PHARMACOLOGY
Mechanism Of Action
Nelfinavir is an inhibitor of the HIV-1 protease [see
Microbiology].
Pharmacodynamics
Effects on Electrocardiogram
The effect of Viracept at the recommended dose of 1250 mg
twice daily on the QTcF interval administered with a low fat meal (20% fat) was
evaluated in a randomized, placebo and active (moxifloxacin 400 mg once daily)
controlled, crossover study in 66 healthy subjects. The maximum mean
time-matched (95% upper confidence bound) differences in QTcF interval from
placebo after baselinecorrection was below 10 milliseconds, the threshold of
clinical concern. This finding was unchanged when a single supratherapeutic dose
of Viracept 3125 mg was administered following a 3-day administration of
Viracept 1250 mg twice daily. The exposure at 3125 mg was 1.4-fold that at 1250
mg. The dose of 3125 mg in this study did not achieve the anticipated exposures
in patients taking a high fat meal (50% fat) or with concomitant administration
of drugs that could increase nelfinavir exposure [see Pharmacokinetics].
No subject in any group had an increase in QTcF of ≥ 60 milliseconds from
baseline. No subject experienced an interval exceeding the potentially
clinically relevant threshold of 500 milliseconds.
Pharmacokinetics
The pharmacokinetic properties of nelfinavir were
evaluated in healthy volunteers and HIV-infected patients; no substantial differences
were observed between the two groups.
Absorption
Pharmacokinetic parameters of nelfinavir (area under the
plasma concentration-time curve during a 24-hour period at steady-state [AUC24],
peak plasma concentrations [Cmax], morning and evening trough concentrations
[Ctrough]) from a pharmacokinetic study in HIV-positive patients after multiple
dosing with 1250 mg (five 250 mg tablets) twice daily (BID) for 28 days (10
patients) and 750 mg (three 250 mg tablets) three times daily (TID) for 28 days
(11 patients) are summarized in Table 7.
Table 7: Summary of a Pharmacokinetic Study in
HIV-positive Patients With Multiple Dosing of 1250 mg (Five 250 mg Tablets) BID
for 28 Days and 750 mg (Three 250 mg Tablets) TID for 28 Days
Regimen |
AUC24
mg•h/L |
Cmax
mg/L |
Ctrough
Morning
mg/L |
Ctrough
Afternoon or Evening
mg/L |
1250 mg BID |
52.8 ± 15.7 |
4.0 ± 0.8 |
2.2 ± 1.3 |
0.7 ± 0.4 |
750 mg TID |
43.6 ± 17.8 |
3.0 ± 1.6 |
1.4 ± 0.6 |
1.0 ± 0.5 |
Data are mean ± SD |
The difference between morning and afternoon or evening
trough concentrations for the TID and BID regimens was also observed in healthy
volunteers who were dosed at precisely 8- or 12-hour intervals.
In healthy volunteers receiving a single 1250 mg dose,
the 625 mg tablet was not bioequivalent to the 250 mg tablet formulation. Under
fasted conditions (n=27), the AUC and Cmax were 34% and 24% higher,
respectively, for the 625 mg tablets. In a relative bioavailability assessment
under fed conditions (n=28), the AUC was 24% higher for the 625 mg tablet; the
Cmax was comparable for both formulations. In HIV-1 infected subjects (N=21)
receiving multiple doses of 1250 mg BID under fed conditions, the 625 mg formulation
was bioequivalent to the 250 mg formulation based on similarity in steady state
exposure (Cmax and AUC).
Table 8 shows the summary of the steady state
pharmacokinetic parameters (mean ± SD) of nelfinavir after multiple dose administration
of 1250 mg BID (2 x 625 mg tablets) to HIV-infected patients (N=21) for 14
days.
Table 8: Summary of the Steady State Pharmacokinetic
Parameters (Mean ± SD) of Nelfinavir After Multiple Dose Administration of 1250
mg BID (2 x 625 mg Tablets) to HIV-infected Patients (N=21) for 14 Days.
Regimen |
AUC12
mg•h/L |
Cmax
mg/L |
Cmin
mg/L |
1250 mg BID |
35.3 (16.4) |
4.7 (1.9) |
1.5 (1.0) |
AUC12: Steady state AUC
Cmax: Maximum plasma concentration at steady state
Cmin: Minimum plasma concentration at steady state |
In healthy volunteers receiving a single 750 mg dose
under fed conditions, nelfinavir concentrations were similar following administration
of the 250 mg tablet and oral powder.
Effect of Food on Oral Absorption
Food increases nelfinavir exposure and decreases
nelfinavir pharmacokinetic variability relative to the fasted state. In one
study, healthy volunteers received a single dose of 1250 mg of VIRACEPT 250 mg
tablets (5 tablets) under fasted or fed conditions (three different meals). In
a second study, healthy volunteers received single doses of 1250 mg VIRACEPT (5
x 250 mg tablets) under fasted or fed conditions (two different fat content
meals). The results from the two studies are summarized in Table 9 and Table
10, respectively.
Table 9: Increase in AUC, Cmax and Tmax for Nelfinavir
in Fed State Relative to Fasted State Following 1250 mg VIRACEPT (5 x 250 mg
Tablets)
Number of Kcal |
% Fat |
Number of subjects |
AUC fold increase |
Cmax fold increase |
Increase in Tmax (hr) |
125 |
20 |
n=21 |
2.2 |
2.0 |
1.00 |
500 |
20 |
n=22 |
3.1 |
2.3 |
2.00 |
1000 |
50 |
n=23 |
5.2 |
3.3 |
2.00 |
Table 10: Increase in Nelfinavir AUC, Cmax and Tmax in
Fed Low Fat (20%) versus High Fat (50%) State Relative to Fasted State
Following 1250 mg VIRACEPT (5 x 250 mg Tablets)
Number of Kcal |
% Fat |
Number of subjects |
AUC fold increase |
Cmax fold increase |
Increase in Tmax (hr) |
500 |
20 |
n=22 |
3.1 |
2.5 |
1.8 |
500 |
50 |
n=22 |
5.1 |
3.8 |
2.1 |
Nelfinavir exposure can be increased by increasing the
calorie or fat content in meals taken with VIRACEPT.
A food effect study has not been conducted with the 625
mg tablet. However, based on a cross-study comparison (n=26 fed vs. n=26 fasted)
following single dose administration of nelfinavir 1250 mg, the magnitude of
the food effect for the 625 mg nelfinavir tablet appears comparable to that of
the 250 mg tablets. VIRACEPT should be taken with a meal.
Distribution
The apparent volume of distribution following oral
administration of nelfinavir was 2-7 L/kg. Nelfinavir in serum is extensively protein-bound
( > 98%).
Metabolism
Unchanged nelfinavir comprised 82-86% of the total plasma
radioactivity after a single oral 750 mg dose of 14C-nelfinavir. In vitro, multiple
cytochrome P-450 enzymes including CYP3A and CYP2C19 are responsible for
metabolism of nelfinavir. One major and several minor oxidative metabolites
were found in plasma. The major oxidative metabolite has in vitro antiviral
activity comparable to the parent drug.
Elimination
The terminal half-life in plasma was typically 3.5 to 5
hours. The majority (87%) of an oral 750 mg dose containing 14C-nelfinavir was recovered
in the feces; fecal radioactivity consisted of numerous oxidative metabolites
(78%) and unchanged nelfinavir (22%). Only 1-2% of the dose was recovered in
urine, of which unchanged nelfinavir was the major component.
Specific Populations
Hepatic Impairment
The steady-state pharmacokinetics of nelfinavir (1250 mg
BID for 2 weeks) was studied in HIV-seronegative subjects with mild (Child-Pugh
Class A; n=6) or moderate (Child-Pugh Class B; n=6) hepatic impairment. When
compared with subjects with normal hepatic function, the Cmax and AUC of
nelfinavir were not significantly different in subjects with mild hepatic
impairment but were increased by 22% and 62%, respectively, in subjects with
moderate hepatic impairment. The steady-state pharmacokinetics of nelfinavir
has not been studied in HIV-seronegative subjects with severe hepatic
impairment.
The steady-state pharmacokinetics of nelfinavir has not
been studied in HIV-positive patients with any degree of hepatic impairment.
Renal Impairment
The pharmacokinetics of nelfinavir have not been studied
in patients with renal impairment.
Gender and Race
No significant pharmacokinetic differences have been
detected between males and females. Pharmacokinetic differences due to race have
not been evaluated.
Pediatrics
The pharmacokinetics of nelfinavir have been investigated
in 5 studies in pediatric patients from birth to 13 years of age either receiving
VIRACEPT three times or twice daily. The dosing regimens and associated AUC24
values are summarized in Table 11.
Table 11: Summary of Steady-state AUC24 of Nelfinavir
in Pediatric Studies
Protocol number |
Dosing regimen* |
N† |
Age |
AUC24 (mg•hr/L) arithmetic mean ± SD |
AG1343-524 |
20 (19-28) mg/kg TID |
14 |
2-13 years |
56.1 ± 29.8 |
PACTG-725 |
55 (48-60) mg/kg BID |
6 |
3-11 years |
101.8 ± 56.1 |
PENTA 7 |
40 (34-43) mg/kg TID |
4 |
2-9 months |
33.8 ± 8.9 |
PENTA 7 |
75 (55-83) mg/kg BID |
12 |
2-9 months |
37.2 ± 19.2 |
PACTG-353 |
40 (14-56) mg/kg BID |
10 |
6 weeks |
44.1 ± 27.4 |
1 week |
45.8 ± 32.1 |
* Protocol specified dose (actual dose range)
† N: number of subjects with evaluable pharmacokinetic results
Ctrough values are not presented in the table because they are not available
for all studies |
Pharmacokinetic data are also available for 86 patients
(age 2 to 12 years) who received VIRACEPT 25-35 mg/kg TID in Study AG1343-556.
The pharmacokinetic data from Study AG1343-556 were more variable than data
from other studies conducted in the pediatric population; the 95% confidence
interval for AUC24 was 9 to 121 mg·hr/L.
Overall, use of VIRACEPT in the pediatric population is
associated with highly variable drug exposure. The high variability may be due
to inconsistent food intake in pediatric patients [see DOSAGE AND
ADMINISTRATION].
Geriatric Patients
The pharmacokinetics of nelfinavir have not been studied
in patients over 65 years of age.
Drug Interactions
CYP3A and CYP2C19 appear to be the predominant enzymes
that metabolize nelfinavir in humans. The potential ability of nelfinavir to
inhibit the major human cytochrome P450 enzymes (CYP3A, CYP2C19, CYP2D6,
CYP2C9, CYP1A2 and CYP2E1) has been investigated in vitro. Only CYP3A was
inhibited at concentrations in the therapeutic range. Specific drug interaction
studies were performed with nelfinavir and a number of drugs. Table 12 summarizes
the effects of nelfinavir on the geometric mean AUC, Cmax and Cmin of
coadministered drugs. Table 13 shows the effects of coadministered drugs on the
geometric mean AUC, Cmax and Cmin of nelfinavir.
Table 12: Drug Interactions: Changes in Pharmacokinetic
Parameters for Coadministered Drug in the Presence of VIRACEPT
Coadministered Drug |
Nelfinavir Dose |
N |
% Change of Coadministered Drug Pharmacokinetic Parameters* (90% CI) |
AUC |
Cmax |
Cmin |
HIV-Protease Inhibitors |
Indinavir 800 mg Single Dose |
750 mg q8h x 7 days |
6 |
↑51%
(↑29-↑77%) |
↓10%
(↓28-↑13%) |
NA |
Ritonavir 500 mg Single Dose |
750 mg q8h x 5 doses |
10 |
↔ |
↔ |
NA |
Saquinavir 1200 mg Single Dose† |
750 mg TID x 4 days |
14 |
↑392%
(↑291-↑521%) |
↑179%
(↑117-↑259%) |
NA |
Amprenavir 800 mg TID x 14 days |
750 mg TID x 14 days |
6 |
↔ |
↓14%
(↓38-↑20%) |
↑189%
(↑52-↑448%) |
Nucleoside Reverse Transcriptase Inhibitors |
Lamivudine 150 mg Single Dose |
750 mg q8h x 7-10 days |
11 |
↑10%
(↑2-↑18%) |
↑31%
(↑9-↑56%) |
NA |
Zidovudine 200 mg Single Dose |
750 mg q8h x 7-10 days |
11 |
↓35%
(↓29-↓40%) |
↓31%
(↓13-↓46%) |
NA |
Non-nucleoside Reverse Transcriptase Inhibitors |
Efavirenz 600 mg qd x 7 days |
750 mg q8h x 7 days |
10 |
↓12%
(↓31-↑12%) |
↓12%
(↓29-↑8%) |
↓22%
(↓54-↑32%) |
Delavirdine 400 mg q8h x 14 days |
750 mg q8h x 7 days |
7 |
↓31%
(↓57-↑10%) |
↓27%
(↓49-↑4%) |
↓33%
(↓70-↑49%) |
Anti-infective Agents |
Rifabutin 150 mg qd x 8 days§ |
750 mg q8h x 7-8 days1 |
12 |
↑83%
(↑72-↑96%) |
↑19%
(↑11-↑28%) |
↑177%
(↑144-↑215%) |
Rifabutin 300 mg qd x 8 days |
750 mg q8h x 7-8 days |
10 |
↑207%
(↑161-↑263%) |
↑146%
(↑118-↑178%) |
↑305%
(↑245-↑375%) |
Azithromycin 1200 mg Single Dose |
750 mg TID x 11 days |
12 |
↑112%
(↑80-↑150%) |
↑136%
(↑77-↑215%) |
NA |
HMG-CoA Reductase Inhibitors |
Atorvastatin 10 mg qd x 28 days |
1250 mg BID x 14 days |
15 |
↑74%
(↑41-↑116%) |
↑122%
(↑68-↑193%) |
↑39%
(↓21-↑145%) |
Simvastatin 20 mg qd x 28 days |
1250 mg BID x 14 days |
16 |
↑505%
(↑393-↑643%) |
↑517%
(↑367-↑715%) |
ND |
Other Agents |
Ethinyl estradiol 35 |ag qd x 15 days |
750 mg q8h x 7 days |
12 |
↓47%
(↓42-↓52%) |
↓28%
(↓16-↓37%) |
↓62%
(↓57-↓67%) |
Norethindrone 0.4 mg qd x 15 days |
750 mg q8h x 7 days |
12 |
↓18%
(↓13-↓23%) |
↔ |
↓46%
(↓38-↓53%) |
Methadone 80 mg ± 21 mg qd# > 1 month |
1250 mg BID x 8 days |
13 |
↓47%
(↓42-↓51%) |
↓46%
(↓42-↓49%) |
↓53%
(↓49-↓57%) |
Phenytoin 300 mg qd x 14 daysÞ |
1250 mg BID x 7 days |
12 |
↓29%
(↓17-↓39%) |
↓21%
(↓12-↓29%) |
↓39%
(↓27-↓49%) |
NA: Not relevant for single-dose treatment; ND: Cannot be
determined
* ↑ Indicates increase; ↓ Indicates decrease; ↔ Indicates no
change (geometric mean exposure increased, or decreased < 10%)
† Using the soft-gelatin capsule formulation of saquinavir 1200 mg
§ Rifabutin 150 mg qd changes are relative to Rifabutin 300 mg qd x 8 days
without coadministration with nelfinavir
¶Comparable changes in rifabutin concentrations were observed with VIRACEPT
1250 mg q12h x 7 days
# Changes are reported for total plasma methadone; changes for the individual
R-enantiomer and S-enantiomer were similar
Þ Phenytoin exposure measures are reported for total phenytoin exposure. The
effect of nelfinavir on unbound phenytoin was similar |
Table 13: Drug Interactions: Changes in
Pharmacokinetic Parameters for Nelfinavir in the Presence of the Coadministered
Drug
Coadministered Drug |
Nelfinavir Dose |
N |
% Change of Nelfinavir Pharmacokinetic Parameters* (90% CI) |
AUC |
C max |
C min |
HIV-Protease Inhibitors |
Indinavir 800 mg q8h x 7 days |
750 mg Single Dose |
6 |
↑83%
(↑42-↑137%) |
↑31%
(↑16-↑48%) |
NA |
Ritonavir 500 mg q12h x 3 doses |
750 mg Single Dose |
10 |
↑152%
(↑96-↑224%) |
↑44%
(↑28-↑63%) |
NA |
Saquinavir 1200 mg TID x 4 dayst |
750 mg Single Dose |
14 |
↑18%
(↑7-↑30%) |
↔ |
NA |
Nucleoside Reverse Transcriptase Inhibitors |
Didanosine 200 mg Single Dose |
750 mg Single Dose |
9 |
↔ |
↔ |
NA |
Zidovudine 200 mg + Lamivudine 150 mg Single Dose |
750 mg q8h x 7-10 days |
11 |
↔ |
↔ |
↔ |
Non-nucleoside Reverse Transcriptase Inhibitors |
Efavirenz 600 mg qd x 7 days |
750 mg q8h x 7 days |
7 |
↑20%
(↑8-↑34%) |
↑21%
(↑10-↑33%) |
↔ |
Nevirapine 200 mg qd x 14 days followed by 200 mg BID x 14 days |
750 mg TID x 36 days |
23 |
↔ |
↔ |
↓32%
(↓50-↑5%) |
Delavirdine 400 mg q8h x 7 days |
750 mg q8h x 14 days |
12 |
↑107%
(↑83-↑135%) |
↑88%
(↑66-↑113%) |
↑136%
(↑103-↑175%) |
Anti-infective Agents |
Ketoconazole 400 mg qd x 7 days |
500 mg q8h x 5-6 days |
12 |
↑35%
(↑24-↑46%) |
↑25%
(↑11-↑40%) |
↑14%
(↓23-↑69%) |
Rifabutin 150 mg qd x 8 days |
750 mg q8h x 7-8 days |
11 |
↓23%
(↓14-↓31%) |
↓18%
(↓8-↓27%) |
↓25%
(↓8-↓39%) |
1250 mg q12h x 7-8 days |
11 |
↔ |
↔ |
↓15%
(↓43-↑27%) |
Rifabutin 300 mg qd x 8 days |
750 mg q8h x 7-8 days |
10 |
↓32%
(↓15-↓46%) |
↓24%
(↓10-↓36%) |
↓53%
(↓15-↓73%) |
Rifampin 600 mg qd x 7 days |
750 mg q8h x 5-6 days |
12 |
↓83%
(↓79-↓86%) |
↓76%
(↓69-↓82%) |
↓92%
(↓86-↓95%) |
Azithromycin 1200 mg Single Dose |
750 mg tid x 9 days |
12 |
↓15%
(↓7-↓22%) |
↓10%
(↓19-↑1%) |
↓29%
(↓19-↓38%) |
Other Agents |
Phenytoin 300 mg qd x 7 days |
1250 mg BID x 14 days |
15 |
↔ |
↔ |
↓18%
(↓45-↑23%) |
Omeprazole 40 mg qd x 4 days administered 30 minutes before nelfinavir |
1250 mg BID x 4 days |
19 |
↓36%
(↓20-↓49%) |
↓37%
(↓23-↓49%) |
↓39%
(↓15-↓57%) |
NA: Not relevant for single-dose treatment
* ↑ Indicates increase; ↓ Indicates decrease; ↔ Indicates no
change (geometric mean exposure increased or decreased < 10%)
† Using the soft-gelatin capsule formulation of saquinavir 1200 mg |
Microbiology
Mechanism of Action
Nelfinavir is an inhibitor of the HIV-1 protease.
Inhibition of the viral protease prevents cleavage of the gag and gag-pol polyprotein
resulting in the production of immature, non-infectious virus.
Antiviral Activity in Cell Culture
The antiviral activity of nelfinavir has been
demonstrated in both acute and/or chronic HIV infections in lymphoblastoid cell
lines, peripheral blood lymphocytes, and monocytes/macrophages. Nelfinavir was
found to be active against several laboratory strains and clinical isolates of
HIV-1, and the HIV-2 strain ROD. The EC95 (95% effective concentration) of
nelfinavir ranged from 7 to 196 nM. Drug combination studies with other HIV-1
protease inhibitors showed nelfinavir had antagonistic interactions with
indinavir, additive interactions with ritonavir or saquinavir, and synergistic
interactions with amprenavir and lopinavir. Minimal to no cellular cytotoxicity
was observed with any of these protease inhibitors alone or in combination with
nelfinavir. In combination with reverse transcriptase inhibitors, nelfinavir
demonstrated additive (didanosine or stavudine) to synergistic (abacavir,
delavirdine, efavirenz, emtricitabine, lamivudine, nevirapine, tenofovir,
zalcitabine, or zidovudine) antiviral activity without enhanced cytotoxicity. Nelfinavir's
anti-HIV activity was not antagonized by the anti-HCV drug ribavirin.
Resistance
HIV-1 isolates with reduced susceptibility to nelfinavir
have been selected in cell culture. HIV-1 isolates from selected patients
treated with nelfinavir alone or in combination with reverse transcriptase
inhibitors were monitored for phenotypic (n=19) and genotypic (n=195, 157 of
which were evaluable) changes in clinical trials over a period of 2 to 82
weeks. One or more viral protease mutations at amino acid positions 30, 35, 36,
46, 71, 77, and 88 were detected in the HIV-1 of > 10% of patients with
evaluable isolates. The overall incidence of the D30N substitution in the viral
protease of evaluable isolates (n=157) from patients receiving nelfinavir
monotherapy or nelfinavir in combination with zidovudine and lamivudine or
stavudine was 54.8%. The overall incidence of other substitutions associated
with primary protease inhibitor resistance was 9.6% for the L90M substitution,
whereas substitutions at 48, 82, or 84 were not observed. Of the 19 clinical
isolates for which both phenotypic and genotypic analyses were performed, 9
showed reduced susceptibility (5- to 93-fold) to nelfinavir in cell culture.
All 9 isolates possessed one or more mutations in the viral protease gene. Amino
acid position 30 appeared to be the most frequent mutation site.
Cross-resistance
Non-clinical Studies: Patient-derived recombinant
HIV-1 isolates containing the D30N substitution (n=4) and demonstrating
highlevel ( > 10-fold) nelfinavir-resistance remained susceptible
( < 2.5-fold resistance) to amprenavir, indinavir, lopinavir, and saquinavir
in cell culture. Patient-derived recombinant HIV-1 isolates containing the L90M
substitution (n=8) demonstrated moderate to high-level resistance to nelfinavir
and had varying levels of susceptibility to amprenavir, indinavir, lopinavir,
and saquinavir in cell culture. Most patient-derived recombinant isolates with
phenotypic and genotypic evidence of reduced susceptibility ( > 2.5-fold) to
amprenavir, indinavir, lopinavir, and/or saquinavir demonstrated high-level
cross-resistance to nelfinavir. Amino acid substitutions associated with resistance
to other protease inhibitors (e.g., G48V, V82A/F/T, I84V, L90M) appeared to
confer high-level cross-resistance to nelfinavir. Following ritonavir therapy 6
of 7 clinical isolates with decreased ritonavir susceptibility (8- to 113-fold)
compared to baseline also exhibited decreased susceptibility to nelfinavir (5-
to 40-fold). Cross-resistance between nelfinavir and reverse transcriptase
inhibitors is unlikely because different enzyme targets are involved. Clinical
isolates (n=5) with decreased susceptibility to lamivudine, nevirapine, or
zidovudine remain fully susceptible to nelfinavir.
Clinical Studies: There have been no controlled or
comparative studies evaluating the virologic response to subsequent protease inhibitor-containing
regimens in subjects who have demonstrated loss of virologic response to a
nelfinavir-containing regimen. However, virologic response was evaluated in a
single-arm prospective study of 26 subjects with extensive prior antiretroviral
experience with reverse transcriptase inhibitors (mean 2.9) who had received
nelfinavir for a mean duration of 59.7 weeks and were switched to a ritonavir
(400 mg BID)/saquinavir hard-gel (400 mg BID)-containing regimen after a
prolonged period of nelfinavir failure (median 48 weeks). Sequence analysis of
HIV-1 isolates prior to switch demonstrated a D30N or an L90M substitution in
18 and 6 subjects, respectively. Subjects remained on therapy for a mean of 48
weeks (range 40 to 56 weeks) where 17 (65%) and 13 (50%) of the 26 subjects
were treatment responders with HIV-1 RNA below the assay limit of detection
( < 500 HIV-1 RNA copies/mL, Chiron bDNA) at 24 and 48 weeks, respectively.
Clinical Studies
Description of Clinical Studies
The efficacy of VIRACEPT is based on analyses of multiple
clinical studies in HIV-1 infected antiretroviral treatment-naïve and experienced
adult patients. In the adult clinical studies described below, efficacy was
evaluated by the percent of patients with plasma HIV RNA < 400 copies/mL
(Studies 511 and 542), < 500 copies/mL (Study ACTG 364), or < 50 copies/mL
(Study Avanti 3). In the analysis presented in each figure, patients who
terminated the study early for any reason, switched therapy due to inadequate
efficacy or who had a missing HIV-RNA measurement that was either preceded or
followed by a measurement above the limit of assay quantification were
considered to have HIV-RNA above 400 copies/mL, above 500 copies/mL, or above
50 copies/mL at subsequent time points, depending on the study's definition of
virologic failure.
Studies In Antiretroviral Treatment Naïve Adult Patients
Study 511: VIRACEPT + zidovudine + lamivudine versus
zidovudine + lamivudine
Study 511 is a double-blind, randomized,
placebo-controlled trial comparing treatment with zidovudine (ZDV; 200 mg TID)
and lamivudine (3TC; 150 mg BID) plus 2 doses of VIRACEPT (750 mg and 500 mg
TID) to zidovudine (200 mg TID) and lamivudine (150 mg BID) alone in 297
antiretroviral naïve HIV-1 infected patients. The median age was 35 years
[range 21 to 63]; 89% were male and 78% were Caucasian. Mean baseline CD4 cell
count was 288 cells/mm³ and mean baseline plasma HIV RNA was 5.21 log10 copies/mL
(160,394 copies/mL). The proportion of patients with plasma HIV RNA < 400
copies/mL at Week 48 was 86%, as summarized in Figure 1. The mean change in CD4
cell count at Week 48 was 207.6 cells/mm³.
Figure 1: Study 511: Percentage of Patients With HIV
RNA Below 400 Copies/mL
Study 542: VIRACEPT BID + stavudine + lamivudine compared
to VIRACEPT TID + stavudine + lamivudine
Study 542 is a, randomized, open-label trial comparing
the HIV RNA suppression achieved by VIRACEPT 1250 mg BID versus VIRACEPT 750 mg
TID in patients also receiving stavudine (d4T; 30-40 mg BID) and lamivudine
(3TC; 150 mg BID). Patients had a median age of 36 years (range 18 to 83), were
84% male, and were 91% Caucasian. Patients had received less than 6 months of therapy
with nucleoside transcriptase inhibitors and were naïve to protease inhibitors.
Mean baseline CD4 cell count was 296 cells/mm³ and mean baseline plasma HIV RNA
was 5.0 log10 copies/mL (100,706 copies/mL).
Results showed that there was no significant difference
in mean CD4 cell count among treatment groups; the mean increases from baseline
for the BID and TID arms were 150 cells/mm³ at 24 weeks and approximately 200
cells/mm³ at 48 weeks.
The percent of patients with HIV RNA < 400 copies/mL
and the outcomes of patients through 48 weeks of treatment are summarized in
Table 14.
Table 14: Outcomes of Randomized Treatment Through 48
Weeks
Outcome |
VIRACEPT 1250 mg BID Regimen |
VIRACEPT 750 mg TID Regimen |
Number of patients evaluable* |
323 |
192 |
HIV-1 RNA < 400 copies/mL |
198 (61%) |
111 (58%) |
HIV-1 RNA ≥ 400 copies/mL |
46 (14%) |
22 (11%) |
Discontinued due to VIRACEPT toxicity** |
9 (3%) |
2 (1%) |
Discontinued due to other antiretroviral agents’ toxicity** |
3 (1%) |
3 (2%) |
Others*** |
67 (21%) |
54 (28%) |
* Twelve patients in the BID
arm and fourteen patients in the TID arm had not yet reached 48 weeks of therapy.
** These rates only reflect dose-limiting toxicities that were counted as the
initial reason for treatment failure in the analysis [see ADVERSE REACTIONS].
*** Consent withdrawn, lost to follow-up, intercurrent illness, noncompliance
or missing data; all assumed as failures. |
Study Avanti 3: VIRACEPT TID +
zidovudine + lamivudine compared to zidovudine + lamivudine
Study Avanti 3 was a
placebo-controlled, randomized, double-blind study designed to evaluate the
safety and efficacy of VIRACEPT (750 mg TID) in combination with zidovudine
(ZDV; 300 mg BID) and lamivudine (3TC; 150 mg BID) (n=53) versus placebo in combination
with ZDV and 3TC (n=52) administered to antiretroviral-naïve patients with HIV
infection and a CD4 cell count between 150 and
500 cells/μL. Patients had a mean age of 35 (range 22-59), were 89% male, and 88% Caucasian. Mean baseline CD4
cell count was 304 cells/mm³ and mean baseline plasma HIV RNA was 4.8 log10
copies/mL (57,887 copies/mL). The percent of patients with plasma HIV RNA
< 50 copies/mL at 52 weeks was 54% for the (VIRACEPT + ZDV + 3TC)-treatment
group and 13% for the (ZDV + 3TC)-treatment group.
Studies In Antiretroviral
Treatment Experienced Adult Patients
Study ACTG 364: VIRACEPT TID +
2NRTIs compared to efavirenz + 2NRTIs compared to VIRACEPT + efavirenz + 2NRTIs
Study ACTG 364 was a
randomized, double-blind study that evaluated the combination of VIRACEPT 750
mg TID and/or efavirenz 600 mg QD with 2 NRTIs (either didanosine [ddI] + d4T,
ddI + 3TC, or d4T + 3TC) in patients with prolonged prior nucleoside exposure
who had completed 2 previous ACTG studies. Patients had a mean age of 41 years
(range 18 to 75), were 88% male, and were 74% Caucasian. Mean baseline CD4 cell
count was 389 cells/mm³ and mean baseline plasma HIV RNA was 3.9 log10 copies/Ml
(7,954 copies/mL).
The percent of patients with
plasma HIV RNA < 500 copies/mL at 48 weeks was 42%, 62%, and 72% for the
VIRACEPT (n=66), EFV (n=65), and VIRACEPT + EFV (n=64) treatment groups,
respectively.
Studies In Pediatric Patients
The pharmacokinetic profile,
safety and antiviral activity of VIRACEPT in pediatric patients 2 years of age
up to 13 years were evaluated in 2 randomized studies.
Study 556 was a randomized,
double-blind, placebo-controlled trial with VIRACEPT or placebo coadministered
with ZDV and ddI in 141 HIV-positive children who had received minimal
antiretroviral therapy. The mean age of the children was 3.9 years. Ninety four
(67%) children were between 2-12 years, and 47 (33%) were < 2 years of age.
The mean baseline HIV RNA value was 5.0 log for all patients and the mean CD4
cell count was 886 cells/mm³ for all patients. The efficacy of VIRACEPT
measured by HIV RNA < 400 at 48 weeks in children ≥ 2 years of age was
26% compared to 2% of placebo patients (p=0.0008). In the children < 2 years
of age, only 1 of 27 and 2 of 20 maintained an undetectable HIV RNA level at 48
weeks for placebo and VIRACEPT patients, respectively.
PACTG 377 was an open-label
study that randomized 181 HIV treatment-experienced pediatric patients to
receive: d4T+NVP+RTV, d4T+3TC+NFV, or d4T+3TC+NVP+NFV with NFV given on a TID
schedule. The median age was 5.9 years and 46% were male. At baseline the median
HIV RNA was 4.4 log and median CD4 cell count was 690 cells/mm³. Substudy PACTG
725 evaluated d4T+3TC+NFV with NFV given on a BID schedule. The proportion of
patients with detectable viral load at baseline achieving HIV RNA < 400
copies/mL at 48 weeks was: 41% for d4T+NVP+RTV, 42% for d4T+3TC+NFV, 30% for
d4T+NVP+NFV, and 52% for d4T+3TC+NVP+NFV. No significant clinical differences
were identified between patients receiving VIRACEPT in BID or TID schedules.
VIRACEPT has been evaluated in
2 studies of young infants. The PENTA 7 study was an open-label study to
evaluate the toxicity, tolerability, pharmacokinetics, and activity of
NFV+d4T+ddI in 20 HIV-infected infants less than 12 weeks of age. PACTG 353 evaluated
the pharmacokinetics and safety of VIRACEPT in infants born to HIV-infected
women receiving NFV as part of combination therapy during pregnancy.
The following issues should be
considered when initiating VIRACEPT in pediatric patients:
- In pediatric patients ≥ 2 years of age
receiving VIRACEPT as part of triple combination antiretroviral therapy in
randomized studies, the proportion of patients achieving a HIV RNA level
< 400 copies/mL through 48 weeks ranged from 26% to 42%.
- Response rates in children
< 2 years of age appeared to be poorer than those in patients ≥ 2 years of age in
some studies.
- Highly variable drug exposure
remains a significant problem in the use of VIRACEPT in pediatric patients.
Unpredictable drug exposure may be exacerbated in pediatric patients because of
increased clearance compared to adults and difficulties with compliance and
adequate food intake with dosing. Pharmacokinetic results from the pediatric
studies are reported in Table 11 [see Pharmacokinetics].
The pharmacokinetic profile,
safety and antiviral activity of VIRACEPT in adolescent patients 13 years and
older is supported by data from the adult clinical trials where some trials
allowed enrolment of subjects 13 years and older. Thus, the data for
adolescents and adults were analyzed collectively.