Efavirenz 600 mg Tablet, Film Coated, 250-count — NDC 72865-172-25 (Billing 72865-0172-25)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Efavirenz is an antiviral drug [see Microbiology ( 12.4 )] .

12.2Pharmacodynamics Cardiac Electrophysiology The effect of efavirenz on the QTc interval was evaluated in an open-label, positive and placebo controlled, fixed single sequence 3-period, 3-treatment crossover QT study in 58 healthy subjects enriched for CYP2B6 polymorphisms. The mean C max of efavirenz in subjects with CYP2B6 *6/*6 genotype following the administration of 600 mg daily dose for 14 days was 2.25-fold the mean C max observed in subjects with CYP2B6 *1/*1 genotype. A positive relationship between efavirenz concentration and QTc prolongation was observed.

Based on the concentration-QTc relationship, the mean QTc prolongation and its upper bound 90% confidence interval are 8.7 ms and 11.3 ms in subjects with CYP2B6*6/*6 genotype following the administration of 600 mg daily dose for 14 days [see Warnings and Precautions ( 5.2 )] .

12.3Pharmacokinetics Absorption Peak efavirenz plasma concentrations of 1.6 to 9.1 μM were attained by 5 hours following single oral doses of 100 mg to 1,600 mg administered to uninfected volunteers. Dose-related increases in C max and AUC were seen for doses up to 1,600 mg; the increases were less than proportional suggesting diminished absorption at higher doses. In HIV-1-infected patients at steady state, mean C max , mean C min , and mean AUC were dose proportional following 200 mg, 400 mg, and 600 mg daily doses.

Time-to-peak plasma concentrations were approximately 3 to 5 hours and steady-state plasma concentrations were reached in 6 to 10 days. In 35 patients receiving efavirenz tablets 600 mg once daily, steady-state C max was 12.9 ± 3.7 μM (mean ± SD), steady-state C min was 5.6 ± 3.2 μM, and AUC was 184 ± 73 μM•h. Effect of Food on Oral Absorption: Tablets: Administration of a single 600 mg efavirenz tablet with a high-fat/high-caloric meal (approximately 1,000 kcal, 500 to 600 kcal from fat) was associated with a 28% increase in mean AUC ∞ of efavirenz and a 79% increase in mean C max of efavirenz relative to the exposures achieved under fasted conditions. [See Dosage and Administration ( 2 ) and Patient Counseling Information ( 17 ).] Distribution Efavirenz is highly bound (approximately 99.5 to 99.75%) to human plasma proteins, predominantly albumin.

In HIV-1 infected patients (n=9) who received efavirenz tablets 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 to 400 mg per day for 10 days resulted in a lower than predicted extent of accumulation (22 to 42% lower) and a shorter terminal half-life of 40 to 55 hours (single dose half-life 52 to 76 hours). Elimination Efavirenz has a terminal half-life of 52 to 76 hours after single doses and 40 to 55 hours after multiple doses. A one-month mass balance/excretion study was conducted using 400 mg per day with a 14 C-labeled dose administered on Day 8.

Approximately 14 to 34% of the radiolabel was recovered in the urine and 16 to 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 Populati… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Efavirenz is an antiviral drug [see Microbiology ( 12.4 )] .

12.3Pharmacokinetics Absorption Peak efavirenz plasma concentrations of 1.6 to 9.1 μM were attained by 5 hours following single oral doses of 100 mg to 1,600 mg administered to uninfected volunteers. Dose-related increases in C max and AUC were seen for doses up to 1,600 mg; the increases were less than proportional suggesting diminished absorption at higher doses. In HIV-1-infected patients at steady state, mean C max , mean C min , and mean AUC were dose proportional following 200 mg, 400 mg, and 600 mg daily doses.

Time-to-peak plasma concentrations were approximately 3 to 5 hours and steady-state plasma concentrations were reached in 6 to 10 days. In 35 patients receiving efavirenz tablets 600 mg once daily, steady-state C max was 12.9 ± 3.7 μM (mean ± SD), steady-state C min was 5.6 ± 3.2 μM, and AUC was 184 ± 73 μM•h. Effect of Food on Oral Absorption: Tablets: Administration of a single 600 mg efavirenz tablet with a high-fat/high-caloric meal (approximately 1,000 kcal, 500 to 600 kcal from fat) was associated with a 28% increase in mean AUC ∞ of efavirenz and a 79% increase in mean C max of efavirenz relative to the exposures achieved under fasted conditions. [See Dosage and Administration ( 2 ) and Patient Counseling Information ( 17 ).] Distribution Efavirenz is highly bound (approximately 99.5 to 99.75%) to human plasma proteins, predominantly albumin.

In HIV-1 infected patients (n=9) who received efavirenz tablets 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 to 400 mg per day for 10 days resulted in a lower than predicted extent of accumulation (22 to 42% lower) and a shorter terminal half-life of 40 to 55 hours (single dose half-life 52 to 76 hours). Elimination Efavirenz has a terminal half-life of 52 to 76 hours after single doses and 40 to 55 hours after multiple doses. A one-month mass balance/excretion study was conducted using 400 mg per day with a 14 C-labeled dose administered on Day 8.

Approximately 14 to 34% of the radiolabel was recovered in the urine and 16 to 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 Pediatric: The pharmacokinetic parameters for efavirenz at steady state in pediatric patients were predicted by a population pharmacokinetic model. 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 hepati… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics Cardiac Electrophysiology The effect of efavirenz on the QTc interval was evaluated in an open-label, positive and placebo controlled, fixed single sequence 3-period, 3-treatment crossover QT study in 58 healthy subjects enriched for CYP2B6 polymorphisms. The mean C max of efavirenz in subjects with CYP2B6 *6/*6 genotype following the administration of 600 mg daily dose for 14 days was 2.25-fold the mean C max observed in subjects with CYP2B6 *1/*1 genotype. A positive relationship between efavirenz concentration and QTc prolongation was observed.

Based on the concentration-QTc relationship, the mean QTc prolongation and its upper bound 90% confidence interval are 8.7 ms and 11.3 ms in subjects with CYP2B6*6/*6 genotype following the administration of 600 mg daily dose for 14 days [see Warnings and Precautions ( 5.2 )] .

14 CLINICAL STUDIES

14.1Adults Study 006 , a randomized, open-label trial, compared efavirenz tablets (600 mg once daily) + zidovudine (ZDV, 300 mg q12h) + lamivudine (LAM, 150 mg q12h) or efavirenz tablets (600 mg once daily) + indinavir (IDV, 1,000 mg q8h) with indinavir (800 mg q8h) + zidovudine (300 mg q12h) + lamivudine (150 mg q12h). Twelve hundred sixty-six patients (mean age 36.5 years [range 18 to 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/mm 3 and the median baseline HIV-1 RNA level was 4.8 log 10 copies/mL. Treatment outcomes with standard assay (assay limit 400 copies/mL) through 48 and 168 weeks are shown in Table 9. 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 9: Outcomes of Randomized Treatment Through 48 and 168 Weeks, Study 006 Outcome Efaverinz tablets + ZDV + LAM (n=422) Efavirenz tablets + IDV (n=429) IDV + ZDV + LAM (n=415) Week 48 Week 168 Week 48 Week 168 Week 48 Week 168 Responder a 69% 48% 57% 40% 50% 29% Virologic failure b 6% 12% 15% 20% 13% 19% Discontinued for adverse events 7% 8% 6% 8% 16% 20% Discontinued for other reasons c 17% 31% 22% 32% 21% 32% CD4+ cell count (cells/mm 3 ) 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 efavirenz tablets + zidovudine + lamivudine, efavirenz tablets + 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 to 76], 74% Caucasian, 88% male) received NRTIs in combination with efavirenz tablets (600 mg once daily), or nelfinavir (NFV, 750 mg three times daily), or efavirenz tablets (600 mg once daily) + nelfinavir in a randomized, double-blinded manner. The mean baseline CD4+ cell count was 389 cells/mm3 and mean baseline HIV-1 RNA level was 8,130 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 10.

Plasma HIV RNA levels were quantified with the AMPLICOR HIV-1 MONITOR assay using a lower limit of quantification of 500 copies/mL. Table 10: Outcomes of Randomized Treatment Through 48 Weeks, Study ACTG 364* Outcome Efavirenz tablets + NFV + NRTIs (n=65) Efavirenz tablets + NRTIs (n=65) NFV + NRTIs (n=… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis Long-term carcinogenicity studies in mice and rats were carried out with efavirenz. Mice were dosed with 0, 25, 75, 150, or 300 mg/kg/day for 2 years. Incidences of hepatocellular adenomas and carcinomas and pulmonary alveolar/bronchiolar adenomas were increased above background in females.

No increases in tumor incidence above background were seen in males. There was no NOAEL in females established for this study because tumor findings occurred at all doses. AUC at the NOAEL (150 mg/kg) in the males was approximately 0.9 times that in humans at the recommended clinical dose.

In the rat study, no increases in tumor incidence were observed at doses up to 100 mg/kg/day, for which AUCs were 0.1 (males) or 0.2 (females) times those in humans at the recommended clinical dose. Mutagenesis Efavirenz tested negative in a battery of in vitro and in vivo genotoxicity assays. These included bacterial mutation assays in S. typhimurium and E. coli , mammalian mutation assays in Chinese hamster ovary cells, chromosome aberration assays in human peripheral blood lymphocytes or Chinese hamster ovary cells, and an in vivo mouse bone marrow micronucleus assay.

Impairment of Fertility Efavirenz did not impair mating or fertility of male or female rats, and did not affect sperm of treated male rats. The reproductive performance of offspring born to female rats given efavirenz was not affected. The AUCs at the NOAEL values in male (200 mg/kg) and female (100 mg/kg) rats were approximately ≤0.15 times that in humans at the recommended clinical dose.

13.2Animal 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 ( 5.10 )] .