June 30, 2015
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Viracept

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Viracept




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-na´ve 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 Na´ve 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 na´ve 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

Percentage of Patients With HIV RNA Below 400 Copies/mL - Illustration

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 na´ve 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-na´ve 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.

Last reviewed on RxList: 4/27/2015
This monograph has been modified to include the generic and brand name in many instances.

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