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CLINICAL PHARMACOLOGY

Mechanism of Action

Efavirenz is an antiviral drug.

Pharmacokinetics

Absorption

Peak efavirenz plasma concentrations of 1.6-9.1 µM were attained by 5 hours following single oral doses of 100 mg to 1600 mg administered to uninfected volunteers. Dose-related increases in Cmax and AUC were seen for doses up to 1600 mg; the increases were less than proportional suggesting diminished absorption at higher doses.

In HIV-l-infected patients at steady state, mean Cmax, mean Cmin, and mean AUC were dose proportional following 200-mg, 400-mg, and 600-mg daily doses. Time-to-peak plasma concentrations were approximately 3-5 hours and steady-state plasma concentrations were reached in 6-10 days. In 35 patients receiving SUSTIVA600 mg once daily, steady-state Cmax was 12.9 ± 3.7 µM (mean + SD), steady-state Cmin was 5.6 ± 3.2 µM, and AUC was 184 ± 73 µM•h.

Effect of Food on Oral Absorption

Capsules: Administration of a single 600-mg dose of efavirenz capsules with a high-fat/high-caloric meal (894 kcal, 54 g fat, 54% calories from fat) or a reduced-fat/normal-caloric meal (440 kcal, 2 g fat, 4% calories from fat) was associated with a mean increase of 22% and 17% in efavirenz AUC∞ and a mean increase of 39% and 51% in efavirenz Cmax, respectively, relative to the exposures achieved when given under fasted conditions. See DOSAGE AND ADMINISTRATION and PATIENT INFORMATION.

Tablets: Administration of a single 600-mg efavirenz tablet with a high-fat/high-caloric meal (approximately 1000 kcal, 500-600 kcal from fat) was associated with a 28% increase in mean AUC∞ of efavirenz and a 79% increase in mean Cmax of efavirenz relative to the exposures achieved under fasted conditions. See DOSAGE AND ADMINISTRATION and PATIENT INFORMATION.

Distribution

Efavirenz is highly bound (approximately 99.5-99.75%) to human plasma proteins, predominantly albumin. In HIV-1 infected patients (n=9) who received SUSTIVA 200 to 600 mg once daily for at least one month, cerebrospinal fluid concentrations ranged from 0.26 to 1.19% (mean 0.69%) of the corresponding plasma concentration. This proportion is approximately 3-fold higher than the non-protein-bound (free) fraction of efavirenz in plasma.

Metabolism

Studies in humans and in vitro studies using human liver microsomes have demonstrated that efavirenz is principally metabolized by the cytochrome P450 system to hydroxylated metabolites with subsequent glucuronidation of these hydroxylated metabolites. These metabolites are essentially inactive against HIV-1. The in vitro studies suggest that CYP3A and CYP2B6 are the major isozymes responsible for efavirenz metabolism.

Efavirenz has been shown to induce CYP enzymes, resulting in the induction of its own metabolism. Multiple doses of 200-400 mg per day for 10 days resulted in a lower than predicted extent of accumulation (22-42% lower) and a shorter terminal half-life of 40-55 hours (single dose half-life 52-76 hours).

Elimination

Efavirenz has a terminal half-life of 52-76 hours after single doses and 40-55 hours after multiple doses. A one-month mass balance/excretion study was conducted using 400 mg per day with a 14C-labeled dose administered on Day 8. Approximately 14-34% of the radiolabel was recovered in the urine and 16-61% was recovered in the feces. Nearly all of the urinary excretion of the radiolabeled drug was in the form of metabolites. Efavirenz accounted for the majority of the total radioactivity measured in feces.

Special Populations

Gender and race: The pharmacokinetics of efavirenz in patients appear to be similar between men and women and among the racial groups studied.

Renal impairment: The pharmacokinetics of efavirenz have not been studied in patients with renal insufficiency; however, less than 1% of efavirenz is excreted unchanged in the urine, so the impact of renal impairment on efavirenz elimination should be minimal.

Hepatic impairment: A multiple-dose study showed no significant effect on efavirenz pharmacokinetics in patients with mild hepatic impairment (Child-Pugh Class A) compared with controls. There were insufficient data to determine whether moderate or severe hepatic impairment (Child-Pugh Class B or C) affects efavirenz pharmacokinetics.

Drug Interaction Studies

Efavirenz has been shown in vivo to cause hepatic enzyme induction, thus increasing the biotransformation of some drugs metabolized by CYP3A and CYP2B6. In vitro studies have shown that efavirenz inhibited CYP isozymes 2C9, 2C19, and 3A4 with Ki values (8.5-17 µM) in the range of observed efavirenz plasma concentrations. In in vitro studies, efavirenz did not inhibit CYP2E1 and inhibited CYP2D6 and CYP1A2 (Ki values 82-160 µM) only at concentrations well above those achieved clinically. The inhibitory effect on CYP3A is expected to be similar between 200-mg, 400-mg, and 600-mg doses of efavirenz. Coadministration of efavirenz with drugs primarily metabolized by 2C9, 2C19, and 3 A isozymes may result in altered plasma concentrations of the coadministered drug. Drugs which induce CYP3A activity would be expected to increase the clearance of efavirenz resulting in lowered plasma concentrations.

Drug interaction studies were performed with efavirenz and other drugs likely to be coadministered or drugs commonly used as probes for pharmacokinetic interaction. The effects of Coadministration of efavirenz on the Cmax, AUC, and Cmin are summarized in Table 8 (effect of efavirenz on other drugs) and Table 9 (effect of other drugs on efavirenz). For information regarding clinical recommendations see CONTRAINDICATIONS and DRUG INTERACTIONS.

Table 8: Effect of Efavirenz on Coadministered Drug Plasma Cmax, AUC, and Cmin

Coadministered Drug Dose Efavirenz Dose Number of Subjects Coadministered Drug
(mean % change)
Cmax
(90% CI)		 AUC
(90% CI)		 Cmin
(90% CI)
Atazanavir 400 mg qd with a light meal d 1-20 600 mg qd with a light meal d 7-20 27 ↓59%
(49-67%)		 ↓74%
(68-78%)		 ↓93%
(90-95%)
400 mg qd d 1-6, then 300 mg qd d 7-20 with ritonavir 100 mg qd and a light meal 600 mg qd 2 h after atazanavir and ritonavir d 7-20 13 ↑14%a
(↓17-↑58%)		 ↑39%a
(2-88%)		 ↑48%a
(24-76%)
300 mg qd/ritonavir 100 mg qd d 1-10 (pm), then 400 mg qd/ritonavir 100 mg qd d 11-24 (pm) (simultaneous with efavirenz) 600 mg qd with a light snack d 11-24 (pm) 14 ↑ 17%
(8-27%)		 ↔ ↓42%
(31-51%)
Indinavir 1000 mg q8h x 10 days 600 mg qd x 10 days 20      
After morning dose     ↔b ↓ 33%b
(26-39%)		 ↓ 39%b
(24-51%)
After afternoon dose     ↔b ↓ 37%b
(26-46%)		 ↓ 52%b
(47-57%)
After evening dose     ↓29%b
(11-43%)		 ↓46%b
(37-54%)		 ↓ 57%b
(50-63%)
Lopinavir/ritonavir 400/100 mg capsule q12h x 9 days 600 mg qd x 9 days 11,7c ↔d ↓19%d
(↓36-↑3%)		 ↓ 39%d
(3-62%)
600/150 mg tablet q12h x 10 days with efavirenz compared to 400/100 mg q12h alone 600 mg qd x 9 days 23 ↑36%d
(28-44%)		 ↑ 36%d
(28-44%)		 ↑ 32%d
(21-44%)
Nelfinavir 750 mg q8h x 7 days 600 mg qd x 7 days 10 ↑21%
(10-33%)		 ↑ 20%
(8-34%)		 ↔
Metabolite AG-1402       ↓ 40%
(30-48%)		 ↓ 37%
(25-48%)		 ↓ 43%
(21-59%)
Ritonavir 500 mg q12h x 8 days 600 mg qd x 10 days 11      
After AM dose     ↑24%
(12-38%)		 ↑18%
(6-33%)		 ↑42%
(9-86%)e
After PM dose     ↔ ↔ ↑ 24%
(3-50%)e
Saquinavir SGCf 1200 mg q8h x 10 days 600 mg qd x 10 days 12 ↓50%
(28-66%)		 ↓62%
(45-74%)		 ↓ 56%
(16-77%)e
Lamivudine 150 mg q12h x 14 days 600 mg qd x 14 days 9 ↔ ↔ ↑ 265%
(37-873%)
Tenofovirg 300 mg qd 600 mg qd x 14 days 29 ↔ ↔ ↔
Zidovudine 300 mg q12h x 14 days 600 mg qd x 14 days 9 ↔ ↔ ↑ 225%
(43-640%)
Maraviroc 100 mg bid 600 mg qd 12 ↓51%
(37-62%)		 ↓ 45%
(38-51%)		 ↓ 45%
(28-57%)
Azithromycin 600 mg single dose 400 mg qd x 7 days 14 ↑22%
(4-42%)		 ↔ NA
Clarithromycin 500 mg q12h x 7 days 400 mg qd x 7 days 11 ↓ 26%
(15-35%)		 ↓ 39%
(30-46%)		 ↓ 53%
(42-63%)
14-OH metabolite       ↑49%
(32-69%)		 ↑34%
(18-53%)		 ↑ 26%
(9-45%)
Fluconazole 200 mg x 7 days 400 mg qd x 7 days 10 ↔ ↔ ↔
Itraconazole 200 mg q12h x 28 days 600 mg qd x 14 days 18 ↓37%
(20-51%)		 ↓ 39%
(21-53%)		 ↓ 44%
(27-58%)
Hydroxy-itraconazole       ↓35%
(12-52%)		 ↓ 37%
(14-55%)		 ↓ 43%
(18-60%)
Posaconazole 400 mg (oral suspension) bid x 10 and 20 days 400 mg qd x 10 and 20 days 11 ↓45%
(34-53%)		 ↓ 50%
(40-57%)		 NA
Rifabutin 300 mg qd x 14 days 600 mg qd x 14 days 9 ↓ 32%
(15-46%)		 ↓ 38%
(28-47%)		 ↓ 45%
(31-56%)
Voriconazole 400 mg po q12h x 1 day, then 200 mg po q12h x 8 days 400 mg qd x 9 days NA ↓61%h ↓77%h NA
300 mg po q12h days 2-7 300 mg qd x 7 days NA ↓36%i
(21-49%)		 ↓ 55%i
(45-62%)		 NA
400 mg po q12h days 2-7 300 mg qd x 7 days NA ↑ 23%i
(↓ 1-↑ 53%)		 ↓7%i
(↓ 23-↑ 13%)		 NA
Atorvastatin 10 mg qd x 4 days 600 mg qd x 15 days 14 ↓14%
(1-26%)		 ↓43%
(34-50%)		 ↓ 69%
(49-81%)
Total active (including metabolites)       ↓15%
(2-26%)		 ↓ 32% (21-41%) ↓48%
(23-64%)
Pravastatin 40 mg qd x 4 days 600 mg qd x 15 days 13 ↓32%
(↓59-↑12%)		 ↓ 44% (26-57%) ↓19%
(0-35%)
Simvastatin 40 mg qd x 4 days 600 mg qd x 15 days 14 ↓72%
(63-79%)		 ↓68% (62-73%) ↓45%
(20-62%)
Total active (including metabolites)       ↓ 68%
(55-78%)		 ↓60%
(52-68%)		 NAj
Carbamazepine 200 mg qd x 3 days, 200 mg bid x 3 days, then 400 mg qd x 29 days 600 mg qd x 14 days 12 ↓ 20%
(15-24%)		 ↓27%
(20-33%)		 ↓ 35%
(24-44%)
Epoxide metabolite       ↔ ↔ ↓13%
(↓30-↑7%)
Cetirizine 10 mg single dose 600 mg qd x 10 days 11 ↓24%
(18-30%)		 ↔ NA
Diltiazem 240mgx21 days 600 mg qd x 14 days 13 ↓60%
(50-68%)		 ↓ 69%
(55-79%)		 ↓63%
(44-75%)
Desacetyl diltiazem       ↓ 64%
(57-69%)		 ↓75%
(59-84%)		 ↓ 62%
(44-75%)
N-monodes-methyl diltiazem       ↓28%
(7-44%)		 ↓ 37%
(17-52%)		 ↓ 37%
(17-52%)
Ethinyl estradiol/ Norgestimate 0.035 mg/0.25 mg x 14 days 600 mg qd x 14 days        
Ethinyl estradiol     21 ↔ ↔ ↔
Norelgestromin     21 ↓46%
(39-52%)		 ↓64%
(62-67%)		 ↓82%
(79-85%)
Levonorgestrel     6 ↓80%
(77-83%)		 ↓ 83%
(79-87%)		 ↓86%
(80-90%)
Lorazepam 2 mg single dose 600 mg qd x 10 days 12 ↑ 16%
(2-32%)		 ↔ NA
Methadone Stable maintenance 35-100 mg daily 600 mg qd x 14-21 days 11 ↓45%
(25-59%)		 ↓ 52%
(33-66%)		 NA
Bupropion 1 50 mg single dose (sustained-release) 600 mg qd x!4 days 13 ↓ 34%
(21-47%)		 ↓ 55%
(48-62%)		 NA
Hydroxy-bupropion       ↑ 50%
(20-80%)		 ↔ NA
Paroxetine 20 mg qd x 14 days 600 mg qd x 14 days 16 ↔ ↔ ↔
Sertraline 50 mg qd x 14 days 600 mg qd x 14 days 13 ↓29%
(15-40%)		 ↓39%
(27-50%)		 ↓46%
(31-58%)
↑ Indicates increase ↓ Indicates decrease ↔ Indicates no change or a mean increase or decrease of < 10%.
aCompared with atazanavir 400 mg qd alone.
bComparator dose of indinavir was 800 mg q8h x 10 days.
c Parallel-group design; n for efavirenz + lopinavir/ritonavir, n for lopinavir/ritonavir alone.
d Values are for lopinavir; the pharmacokinetics of ritonavir in this study were unaffected by concurrent efavirenz.
e 95% CI.
f Soft Gelatin Capsule.
g Tenofovir disoproxil fumarate.
h 90% CI not available.
i Relative to steady-state administration of voriconazole (400 mg for 1 day, then 200 mg po q12h for 2 days).
j Not available because of insufficient data.
NA = not available.

Table 9: Effect of Coadministered Drug on Efavirenz Plasma Cmax, AUC, and Cmin

Coadministered Drug Dose Efavirenz Dose Number of Subjects Efavirenz
(mean % change)
Cmax
(90% CI)		 AUC
(90% CI)		 Cmin
(90% CI)
Indinavir 800 mg q8h x 14 days 200 mg qd x 14 days 11 ↔ ↔ ↔
Lopinavir/ritonavir 400/100 mg q12h x 9 days 600 mg qd x 9 days 11,12a ↔ ↓16%
(↓38-↓15%)		 ↓16%
(↓42-↑ 20%)
Nelfinavir 750 mg q8h x 7 days 600 mg qd x 7 days 10 ↓ 12%
(↓32-↑13%)b		 ↓ 12%
(↓35-↑18%)b		 ↓21%
(↓53-↑33%)
Ritonavir 500 mg q12h x 8 days 600 mg qd x 10 days 9 ↑14%
(4-26%)		 ↑ 21%
(10-34%)		 ↑ 25%
(7-46%)b
Saquinavir C SGc 1200 mg q8h x 10 days 600 mg qd x 10 days 13 ↓13%
(5-20%)		 ↓12%
(4-19%)		 ↓14%
(2-24%)b
Tenofovird 300 mg qd 600 mg qd x 14 days 30 ↔ ↔ ↔
Azithromycin 600 mg single dose 400 mg qd x 7 days 14 ↔ ↔ ↔
Clarithromycin 500 mg q12h x 7 days 400 mg qd x 7 days 12 ↑11%
(3-19%)		 ↔ ↔
Fluconazole 200 mg x 7 days 400 mg qd x 7 days 10 ↔ ↑16%
(6-26%)		 ↑22%
(5-41%)
Itraconazole 200 mg q12h x 14 days 600 mg qd x 28 days 16 ↔ ↔ ↔
Rifabutin 300 mg qd x 14 days 600 mg qd x 14 days 11 ↔ ↔ ↓ 12%
(↓24-↑1%)
Rifampin 600 mg x 7 days 600 mg qd x 7 days 12 ↓ 20%
(11-28%)		 ↓ 26%
(15-36%)		 ↓ 32%
(15-46%)
Voriconazole 400 mg po q12h x 1 day, then 200 mg po q12h x 8 days 400 mg qd x 9 days NA ↑38%e ↑ 44%e NA
300 mg po q12h days 2-7 300 mg qd x 7 days NA ↓14%f
(7-21%)		 ↔f NA
400 mg po q12h days 2-7 300 mg qd x 7 days NA ↔f ↑17%f
(6-29%)		 NA
Atorvastatin 10 mg qd x 4 days 600 mg qd x 15 days 14 ↔ ↔ ↔
Pravastatin 40 mg qd x 4 days 600 mg qd x 15 days 11 ↔ ↔ ↔
Simvastatin 40 mg qd x 4 days 600 mg qd x 15 days 14 ↓12%
(↓28-↑8%)		 ↔ ↓12%
(↓25-↑3%)
Aluminum hydroxide
400 mg, magnesium hydroxide 400 mg, plus simethicone 40 mg		 30 mL single dose 400 mg single dose 17 ↔ ↔ NA
Carbamazepine 200 mg qd x 3 days, 200 mg bid x 3 days, then 400 mg qd x 15 days 600 mg qd x 35 days 14 ↓21%
(15-26%)		 ↓ 36%
(32-40%)		 ↓ 47%
(41-53%)
Cetirizine 10 mg single dose 600 mg qd x 10 days 11 ↔ ↔ ↔
Diltiazem 240 mg x 14 days 600 mg qd x 28 days 12 ↑16%
(6-26%)		 ↑11%
(5-18%)		 ↑13%
(1-26%)
Famotidine 40 mg single dose 400 mg single dose 17 ↔ ↔ NA
Paroxetine 20 mg qd x 14 days 600 mg qd x 14 days 12 ↔ ↔ ↔
Sertraline 50 mg qd x 14 days 600 mg qd x 14 days 13 ↑ 11%
(6-16%)		 ↔ ↔
↑ Indicates increase ↓ Indicates decrease ↔ Indicates no change or a mean increase or decrease of < 10%.
a Parallel-group design; n for efavirenz + lopinavir/ritonavir, n for efavirenz alone.
b 95% CI.
c Soft Gelatin Capsule.
d Tenofovir disoproxil fumarate.
e 90% CI not available.
f Relative to steady-state administration of efavirenz (600 mg once daily for 9 days).
NA = not available.

Microbiology

Mechanism of Action

Efavirenz (EFV) is an NNRTI of HIV-1. EFV activity is mediated predominantly by noncompetitive inhibition of HIV-1 reverse transcriptase (RT). HIV-2 RT and human cellular DNA polymerases α, β, γ, and 8 are not inhibited by EFV.

Antiviral Activity in Cell Culture

The concentration of EFV inhibiting replication of wild-type laboratory adapted strains and clinical isolates in cell culture by 90-95% (EC90-95) ranged from 1.7 to 25 nM in lymphoblastoid cell lines, peripheral blood mononuclear cells (PBMCs), and macrophage/monocyte cultures. EFV demonstrated antiviral activity against clade B and most non-clade B isolates (subtypes A, AE, AG, C, D, F, G, J, N), but had reduced antiviral activity against group O viruses. EFV demonstrated additive antiviral activity without cytotoxicity against HIV-1 in cell culture when combined with the NNRTIs delavirdine (DLV) and nevirapine (NVP), NRTIs (abacavir, didanosine, emtricitabine, lamivudine [LAM], stavudine, tenofovir, zalcitabine, zidovudine [ZDV]), Pis (amprenavir, indinavir [IDV], lopinavir, nelfmavir, ritonavir, saquinavir), and the fusion inhibitor enfuvirtide. EFV demonstrated additive to antagonistic antiviral activity in cell culture with atazanavir. EFV was not antagonistic with adefovir, used for the treatment of hepatitis B virus infection, or ribavirin, used in combination with interferon for the treatment of hepatitis C virus infection.

Resistance

In cell culture

In cell culture, HFV-1 isolates with reduced susceptibility to EFV ( > 380-fold increase in £€90 value) emerged rapidly in the presence of drug. Genotypic characterization of these viruses identified single amino acid substitutions L100I or V179D, double substitutions L100I/V108I, and triple substitutions L100I/V179D/Y181C in RT.

Clinical studies

Clinical isolates with reduced susceptibility in cell culture to EFV have been obtained. One or more RT substitutions at amino acid positions 98, 100, 101, 103, 106, 108, 188, 190, 225, and 227 were observed in patients failing treatment with EFV in combination with IDV, or with ZDV plus LAM. The mutation K103N was the most frequently observed. Long-term resistance surveillance (average 52 weeks, range 4-106 weeks) analyzed 28 matching baseline and virologic failure isolates. Sixty-one percent (17/28) of these failure isolates had decreased EFV susceptibility in cell culture with a median 88-fold change in EFV susceptibility (EC50 value) from reference. The most frequent NNRTI substitution to develop in these patient isolates was K103N (54%). Other NNRTI substitutions that developed included L100I (7%), K101E/Q/R (14%), V108I (11%), G190S/T/A (7%), P225H (18%), and M230I/L (11%).

Cross-Resistance

Cross-resistance among NNRTIs has been observed. Clinical isolates previously characterized as EFV-resistant were also phenotypically resistant in cell culture to DLV and NVP compared to baseline. DLV- and/or NVP-resistant clinical viral isolates with NNRTI resistance-associated substitutions (A98G, L100I, K101E/P, K103N/S, V106A, Y181X, Y188X, G190X, P225H, F227L, or M230L) showed reduced susceptibility to EFV in cell culture. Greater than 90% of NRTI-resistant clinical isolates tested in cell culture retained susceptibility to EFV.

Animal Toxicology

Nonsustained convulsions were observed in 6 of 20 monkeys receiving efavirenz at doses yielding plasma AUC values 4- to 13-fold greater than those in humans given the recommended dose [see WARNINGS AND PRECAUTIONS].

Clinical Studies

Study 006, a randomized, open-label trial, compared SUSTIVA (600 mg once daily) + zidovudine (ZDV, 300 mg q!2h) + lamivudine (LAM, 150 mg q!2h) or SUSTIVA (600 mg once daily) + indinavir (IDV, 1000 mg q8h) with indinavir (800 mg q8h) + zidovudine (300 mg q!2h) + lamivudine (150 mg q!2h). Twelve hundred sixty-six patients (mean age 36.5 years [range 18-81], 60% Caucasian, 83% male) were enrolled. All patients were efavirenz-, lamivudine-, NNRTI-, and Pi-naive at study entry. The median baseline CD4+ cell count was 320 cells/mm3 and the median baseline HIV-1 RNA level was 4.8 logio copies/mL. Treatment outcomes with standard assay (assay limit 400 copies/mL) through 48 and 168 weeks are shown in Table 10. Plasma HIV RNA levels were quantified with standard (assay limit 400 copies/mL) and ultrasensitive (assay limit 50 copies/mL) versions of the AMPLICOR HIV-1 MONITOR assay. During the study, version 1.5 of the assay was introduced in Europe to enhance detection of non-clade B virus.

Table 10: Outcomes of Randomized Treatment Through 48 and 168 Weeks, Study 006

Outcome SUSTIVA + ZDV + LAM
(n=422)		 SUSTIVA + IDV
(n=429)		 IDV + ZDV + LAM
(n=415)
Week 48 Week 168 Week 48 Week 168 Week 48 Week 168
Respondera 69% 48% 57% 40% 50% 29%
-LVirologic failureb 6% 12% 15% 20% 13% 19%
Discontinued for adverse events 7% 8% 6% 8% 16% 20%
Discontinued for other reasonsc 17% 31% 22% 32% 21% 32%
CD4+ cell count (cells/mm3)  
  Observed subjects (n) (279) (205) (256) (158) (228) (129)
  Mean change from baseline 190 329 191 319 180 329
a Patients achieved and maintained confirmed HIV-1 RNA < 400 copies/mL through Week 48 or Week 168.
b Includes patients who rebounded, patients who were on study at Week 48 and failed to achieve confirmed HIV-1 RNA < 400 copies/mL at time of discontinuation, and patients who discontinued due to lack of efficacy.
c Includes consent withdrawn, lost to follow-up, noncompliance, never treated, missing data, protocol violation, death, and other reasons. Patients with HIV-1 RNA levels < 400 copies/mL who chose not to continue in the voluntary extension phases of the study were censored at date of last dose of study medication.

For patients treated with SUSTIVA + zidovudine + lamivudine, SUSTIVA + indinavir, or indinavir + zidovudine + lamivudine, the percentage of responders with HIV-1 RNA < 50 copies/mL was 65%, 50%, and 45%, respectively, through 48 weeks, and 43%, 31%, and 23%, respectively, through 168 weeks. A Kaplan-Meier analysis of time to loss of virologic response (HIV RNA < 400 copies/mL) suggests that both the trends of virologic response and differences in response continue through 4 years.

ACTG 364 is a randomized, double-blind, placebo-controlled, 48-week study in NRTI-experienced patients who had completed two prior ACTG studies. One-hundred ninety-six patients (mean age 41 years [range 18-76], 74% Caucasian, 88% male) received NRTIs in combination with SUSTIVA (efavirenz) (600 mg once daily), or nelfmavir (NFV, 750 mg three times daily), or SUSTIVA (600 mg once daily) + nelfmavir in a randomized, double-blinded manner. The mean baseline CD4+ cell count was 389 cells/mm3 and mean baseline HIV-1 RNA level was 8130 copies/mL. Upon entry into the study, all patients were assigned a new open-label NRTI regimen, which was dependent on their previous NRTI treatment experience. There was no significant difference in the mean CD4+ cell count among treatment groups; the overall mean increase was approximately 100 cells at 48 weeks among patients who continued on study regimens. Treatment outcomes are shown in Table 11. Plasma HIV RNA levels were quantified with the AMPLICOR HIV-1 MONITOR assay using a lower limit of quantification of 500 copies/mL.

Table 11: Outcomes of Randomized Treatment Through 48 Weeks, Study ACTG 364*

Outcome SUSTIVA + NFV + NRTIs
(n=65)		 SUSTIVA + NRTIs
(n=65)		 NFV + NRTIs
(n=66)
HIV-1 RNA ≤ 500 copies/mLa 71% 63% 41%
HIV-1 RNA ≥ 500 copies/mLb 17% 34% 54%
CDC Category C Event 2% 0% 0%
Discontinuations for adverse eventsc 3% 3% 5%
Discontinuations for other reasonsd 8% 0% 0%
*For some patients, Week 56 data were used to confirm the status at Week 48.
a Subjects achieved virologic response (two consecutive viral loads < 500 copies/mL) and maintained it through Week 48.
b Includes viral rebound and failure to achieve confirmed < 500 copies/mL by Week 48.
c See ADVERSE REACTIONS for a safety profile of these regimens.
d Includes loss to follow-up, consent withdrawn, noncompliance.

A Kaplan-Meier analysis of time to treatment failure through 72 weeks demonstrates a longer duration of virologic suppression (HIV RNA < 500 copies/mL) in the SUSTIVA-containing treatment arms.

Last reviewed on RxList: 1/12/2012
This monograph has been modified to include the generic and brand name in many instances.

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