Pharmacokinetic interactions of maraviroc with darunavir-ritonavir, etravirine, and etravirine-darunavir-ritonavir in healthy volunteers: results of two drug interaction trials.

The effects of darunavir-ritonavir at 600 and 100 mg twice daily (b.i.d.) alone, 200 mg of etravirine b.i.d. alone, or 600 and 100 mg of darunavir-ritonavir b.i.d. with 200 mg etravirine b.i.d. at steady state on the steady-state pharmacokinetics of maraviroc, and vice versa, in healthy volunteers were investigated in two phase I, randomized, two-period crossover studies. Safety and tolerability were also assessed. Coadministration of 150 mg maraviroc b.i.d. with darunavir-ritonavir increased the area under the plasma concentration-time curve from 0 to 12 h (AUC12) for maraviroc 4.05-fold relative to 150 mg of maraviroc b.i.d. alone. Coadministration of 300 mg maraviroc b.i.d. with etravirine decreased the maraviroc AUC12 by 53% relative to 300 mg maraviroc b.i.d. alone. Coadministration of 150 mg maraviroc b.i.d. with etravirine-darunavir-ritonavir increased the maraviroc AUC12 3.10-fold relative to 150 mg maraviroc b.i.d. alone. Maraviroc did not significantly affect the pharmacokinetics of etravirine, darunavir, or ritonavir. Short-term coadministration of maraviroc with darunavir-ritonavir, etravirine, or both was generally well tolerated, with no safety issues reported in either trial. Maraviroc can be coadministered with darunavir-ritonavir, etravirine, or etravirine-darunavir-ritonavir. Maraviroc should be dosed at 600 mg b.i.d. with etravirine in the absence of a potent inhibitor of cytochrome P450 3A (CYP3A) (i.e., a boosted protease inhibitor) or at 150 mg b.i.d. when coadministered with darunavir-ritonavir with or without etravirine.

Safety, tolerability, and preliminary efficacy of 48 weeks of etravirine therapy in a phase IIb dose-ranging study involving treatment-experienced patients with HIV-1 infection.

BACKGROUND: Etravirine (ETR; also known as TMC125) is a new nonnucleoside reverse-transcriptase inhibitor with activity against wild-type and nonnucleoside reverse-transcriptase inhibitor-resistant human immunodeficiency virus type 1 (HIV-1). METHODS: This randomized, phase IIb, placebo-controlled, 2-stage, dose-escalating trial evaluated the safety, tolerability, and preliminary efficacy of 3 twice-daily doses of ETR (experimental formulation TF035; compared with placebo), administered with an individually optimized background regimen, in treatment-experienced HIV-1-infected patients. In stage 1 of the trial, 166 patients received ETR (400 mg or 800 mg twice daily) or placebo. In stage 2 of the trial, 74 patients received ETR (800 mg or 1200 mg twice daily) or placebo. The primary objective was to assess the safety and tolerability of the regimens over 48 weeks. RESULTS: Neuropsychiatric adverse events (AEs) of interest occurred in 46.6% of patients in the combined ETR group and in 45.5% of patients in the combined placebo group (P=.89). Clinically relevant hepatic AEs occurred in 3.4% of patients who received ETR and in 6.1% of patients who received placebo (P=.47), and rash occurred in 19.5% and 12.1%, respectively (P=.25). In general, there was no evidence of a relationship between ETR dose and specific AEs. Most AEs were severity grade 1 or 2; the incidence of grade 3 or 4 AEs was comparable between groups (27.0% in the combined ETR group vs. 27.3% in the placebo group). Plasma preparation tubes were used for viral load measurement. In stage 1, there was no statistically significant difference in efficacy between ETR and placebo. In stage 2, the decrease in log10 plasma viral load between baseline and week 24 was statistically significantly greater in patients who received ETR, compared with patients who received placebo; a trend in favor of ETR persisted until week 48. CONCLUSIONS: ETR was generally safe and well tolerated during long-term administration in treatment-experienced, HIV-1-infected patients, and it had a safety profile comparable to that of placebo.

Single- and multiple-dose pharmacokinetics of etravirine administered as two different formulations in HIV-1-infected patients.

BACKGROUND: An open-label, randomized, crossover study to evaluate the pharmacokinetics of two different formulations of etravirine after single and multiple dosing. METHODS: Treatment-experienced HIV-1-infected patients with viral load <50 copies/ml continued their current antiretroviral regimen and added etravirine twice daily for 7 days with a morning intake on day 8. Etravirine was administered following food as either 800 mg twice daily of the Phase II formulation or 100 mg or 200 mg twice daily of the Phase III formulation. A 12 h pharmacokinetic assessment was performed on days 1 and 8. RESULTS: After single- and multiple-dose administration, the exposure to etravirine was lower with 100 mg twice daily and higher with 200 mg twice daily compared with 800 mg twice daily. On day 8, the mean (+/-SD) area under the plasma concentration-time curve over 12 h (AUC0-12 h) was 1,284 (+/-958) ng x h/ml when etravirine was administered as 100 mg twice daily (n=33), 3,713 (+/-2,069) ng x h/ml when administered as 200 mg twice daily (n=27) and 2,607 (+/-2,135) ng x h/ml when administered as 800 mg twice daily (n=32). Both formulations and all doses of etravirine tested were generally safe and well tolerated. CONCLUSIONS: The range of exposure to etravirine was comparable between 200 mg twice daily dose and 800 mg twice daily. The Phase III formulation of etravirine significantly improves the bioavailability of etravirine over the Phase II formulation with reduced interpatient variability in etravirine pharmacokinetics.

Pharmacokinetic and pharmacodynamic study of the concomitant administration of methadone and TMC125 in HIV-negative volunteers.

TMC125 is a nonnucleoside reverse transcriptase inhibitor (NNRTI) with potent in vitro activity against wild-type and NNRTI-resistant HIV-1. TMC125 is an inducer of CYP3A and an inhibitor of CYP2C. This trial evaluated the effect of TMC125 on the pharmacokinetics and pharmacodynamics of methadone. In an open-label, add-on, 1-way interaction trial, 16 male HIV-negative volunteers on stable methadone maintenance therapy received 100 mg TMC125 bid for 14 days. Plasma concentrations and pharmacokinetic parameters of R- and S-methadone isomers were determined on days -1, 7, and 14 and of TMC125 on days 7 and 14. Safety and tolerability were assessed. The LSmeans ratios (90% confidence interval) for AUC(24h), C(max), and C(min) of the pharmacologically active R-methadone were 1.08 (1.02-1.13), 1.03 (0.97-1.09), and 1.12 (1.05-1.19), respectively, on day 7 and 1.06 (0.99-1.13), 1.02 (0.96-1.09), and 1.10 (1.02-1.19), respectively, on day 14 compared with methadone alone. No withdrawal symptoms were observed; dose adjustment of methadone was not required. The concomitant administration of TMC125 and methadone was generally safe and well tolerated. TMC125 has no clinically relevant effect on the pharmacokinetics or pharmacodynamics of methadone. No dose adjustment for methadone is anticipated when coadministered with TMC125.

A pharmacokinetic study of etravirine (TMC125) co-administered with ranitidine and omeprazole in HIV-negative volunteers.

AIMS: Etravirine is a next-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) with activity against wild-type and NNRTI-resistant HIV. Proton pump inhibitors and H(2)-antagonists are frequently used in the HIV-negative-infected population, and drug-drug interactions have been described with other antiretrovirals. This study evaluated the effect of steady-state omeprazole and ranitidine on the pharmacokinetics of a single dose of etravirine. METHODS: In an open-label, randomized, one-way, three-period crossover trial, HIV-negative volunteers randomly received a single dose of 100 mg etravirine alone (treatment A); 11 days of 150 mg ranitidine b.i.d. (treatment B); and 11 days of 40 mg omeprazole q.d. (treatment C). A single dose of 100 mg etravirine was co-administered on day 8 of sessions 2 and 3. Each session was separated by a 14-day wash-out. RESULTS: Nineteen volunteers (seven female) participated. When a single dose of etravirine was administered in the presence of steady-state ranitidine, etravirine least squares means ratios (90% confidence interval) for AUC(last) and C(max) were 0.86 (0.76, 0.97) and 0.94 (0.75, 1.17), respectively, compared with administration of etravirine alone. When administered with steady-state omeprazole, these values were 1.41 (1.22, 1.62) and 1.17 (0.96, 1.43), respectively. Co-administration of a single dose of etravirine and ranitidine or omeprazole was generally safe and well tolerated. CONCLUSIONS: Ranitidine slightly decreased etravirine exposure, whereas omeprazole increased it by approximately 41%. The increased exposure of etravirine when co-administered with omeprazole is attributed to CYP2C19 inhibition. Considering the favourable safety profile of etravirine, these changes are not clinically relevant. Etravirine can be co-administered with proton pump inhibitors and H(2) antagonists without dose adjustments.

Effects of different meal compositions and fasted state on the oral bioavailability of etravirine.

STUDY OBJECTIVE: To determine the effects of various meal compositions and the fasted state on the pharmacokinetics of etravirine, a nonnucleoside reverse transcriptase inhibitor. DESIGN: Phase I, open-label, randomized, repeated single-dose, three-period crossover trial. SETTING: Clinical pharmacology unit. PARTICIPANTS: Two parallel panels of 12 human immunodeficiency virus (HIV)-negative, healthy, male volunteers. Twenty volunteers completed the study; three withdrew consent, and one was lost to follow-up. Intervention. Panel 1 received a single dose of etravirine 100 mg after a standard breakfast, in the fasted state, and after a light breakfast (croissant). Panel 2 received the same treatment after a standard breakfast, after an enhanced-fiber breakfast, and after a high-fat breakfast. Each treatment was separated by a washout period of at least 14 days. MEASUREMENTS AND MAIN RESULTS: For each treatment, full pharmacokinetic profiles of etravirine were determined up to 96 hours after dosing. Pharmacokinetic parameters were determined by noncompartmental methods and analyzed using a linear mixed-effects model for a crossover design. The least-squares mean ratio for the area under the plasma concentration-time curve from time of administration to the last time point with a measurable concentration after dosing (AUClast) was 0.49 (90% confidence interval [CI] 0.39-0.61) for the fasted state compared with dosing after a standard breakfast. When dosing occurred after a light or enhanced-fiber breakfast, the corresponding values were 0.80 (90% CI 0.69-0.94) and 0.75 (90% CI 0.63-0.90), respectively. When administered after a high-fat breakfast the least-squares mean ratio of AUC(last) was 1.09 (0.84-1.41), compared with dosing after a standard breakfast. Adverse events were also assessed. Under all conditions, single doses of etravirine 100 mg were generally safe and well tolerated. CONCLUSION: Administration of etravirine in a fasted state resulted in 51% lower mean exposure compared with dosing after a standard breakfast. Etravirine should be administered following a meal to improve bioavailability; however, differences in exposure after a standard breakfast versus a high-fat, enhanced-fiber, or light breakfast (croissant) were not considered clinically relevant.

Etravirine has no effect on QT and corrected QT interval in HIV-negative volunteers.

BACKGROUND: Etravirine (TMC125), a next-generation nonnucleoside reverse transcriptase inhibitor, has shown antiviral efficacy in 2 large Phase 3 trials. In vitro and in vivo studies have shown that etravirine is not associated with proarrhythmic potential. Electrocardiograms (ECGs) from healthy and HIV 1-infected volunteers showed no clinically relevant changes. OBJECTIVE: To evaluate the effect of 2 etravirine dosing regimens on QT/corrected QT interval (QTc) in HIV-negative volunteers and assess pharmacokinetic and additional safety parameters. METHODS: A double-blind, double-dummy, randomized, placebo- and active-controlled, 4-period crossover trial was conducted in 41 HIV-negative volunteers. Participants received 4 regimens: etravirine 200 mg twice daily, etravirine 400 mg once daily, moxifloxacin 400 mg once daily (positive control), and placebo in separate 8-day sessions, with each followed by a washout period of 14 or more days. On days -1, 1, and 8 of each session, ECGs were recorded at 11 time points over 12 hours. Pharmacokinetic profiles of etravirine regimens were evaluated and safety was assessed. RESULTS: Thirty-seven subjects completed the study. For etravirine, the upper limit of the 90% CIs of mean time-matched differences in QTc determined using Fridericia's formula (QTcF) was below 10 msec at all time points, the threshold for prolonged QT as defined by regulatory guidelines. The maximum mean (90% CI) difference of time-matched changes in QTcF versus placebo on day 1 was +0.1 msec (-2.6 to 2.9), -0.2 msec (-2.6 to 2.1), and +10.1 msec (7.3 to 12.8) for etravirine 200 mg twice daily, etravirine 400 mg once daily, and moxifloxacin, respectively. On day 8, these values were +0.6 msec (-2.1 to 3.3), -1.0 msec (-4.4 to 2.5), and +10.3 msec (6.8 to 13.9), respectively. Etravirine produced no clinically significant changes in other ECG parameters. No significant differences between males and females were observed. Both etravirine regimens had similar pharmacokinetic exposure and safety profiles. CONCLUSIONS: Etravirine does not prolong the QTc interval. No clinically relevant ECG changes were observed in HIV-negative volunteers. Short-term dosing of etravirine in HIV-negative volunteers was generally safe and well tolerated.

Pharmacokinetics of darunavir/ritonavir and TMC125 alone and coadministered in HIV-negative volunteers.

OBJECTIVE: To evaluate the pharmacokinetics of TMC125 (etravirine) and darunavir (DRV) with low-dose ritonavir (DRV/r). DESIGN: Open-label, randomized, two-way crossover Phase I trial. METHODS: Thirty-two HIV-negative volunteers were randomized 1:1 to two panels. All received TMC125 100 mg twice daily for 8 days and, after 14 days washout, DRV/r 600/100 mg twice daily for 16 days. During days 9-16, TMC125 100 or 200 mg twice daily was coadministered (Panel I or II, respectively). RESULTS: Twenty-three volunteers completed the trial. With DRV/r coadministration, mean exposure (area under the plasma concentration-time curve from 0 to 12 h [AUC12h) to TMC125 given as 100 mg twice daily was decreased by 37%; maximum and minimum plasma concentrations (Cmax and Cmin) were decreased by 32% and 49%, respectively. For TMC125 200 mg twice daily coadministered with DRV/r, AUC12h, Cmax and Cmin of TMC125 were 80%, 81% and 67% greater, respectively, versus TMC125 100 mg twice daily alone. DRV pharmacokinetics were unchanged except a 15% increase in AUC12h when given with TMC125 200 mg twice daily. CONCLUSIONS: No clinically relevant changes in DRV pharmacokinetics were observed when combined with TMC125; therefore DRV dose adjustment is not required. Coadministration of TMC125 100 mg twice daily with DRV/r decreased TMC125 exposure by 37%. The increase of TMC125 exposure by 80% when given as 200 mg twice daily reflects the higher dose and the interaction with DRV/r. The magnitude of this interaction is comparable to TMC125 interactions with other boosted PIs observed in Phase IIb trials in HIV-1-infected patients. As these trials demonstrated TMC125 efficacy, no dose adjustment of TMC125 is needed when combined with DRV/r.

Steady-state pharmacokinetics of etravirine and lopinavir/ritonavir melt extrusion formulation, alone and in combination, in healthy HIV-negative volunteers.

BACKGROUND: A previous study investigating coadministration of etravirine, a nonnucleoside reverse transcriptase inhibitor, and lopinavir/ritonavir soft-gel formulation resulted in nonclinically relevant changes in etravirine and lopinavir exposure. The current study evaluated the pharmacokinetic interaction between etravirine and the lopinavir/ritonavir melt extrusion formulation. METHOD: Sixteen human immunodeficiency virus (HIV)-negative volunteers were randomized to either treatment sequence A/B or B/A, with 14 days- washout between treatments (treatment A: etravirine 200 mg bid for 8 days; treatment B: lopinavir/ritonavir 400/100 mg bid for 16 days with etravirine 200 mg bid on days 9-16). Steady-state pharmacokinetics were assessed for all antiretrovirals alone and coadministered; pharmacokinetic parameters were obtained by noncompartmental analysis. Safety and tolerability were assessed. RESULTS: Coadministration of etravirine and lopinavir/ritonavir resulted in a 35% decrease in etravirine exposure. Smaller decreases (<13%) were observed in lopinavir and ritonavir exposure. Six volunteers reported headache; 1 grade 3 triglyceride increase was reported. CONCLUSION: Lopinavir/ritonavir induced etravirine metabolism to a similar extent as most other boosted HIV protease inhibitors. The short-term coadministration of etravirine and lopinavir/ritonavir was well tolerated and did not lead to increased incidences of adverse events.

Pharmacokinetic interactions between etravirine and non-antiretroviral drugs.

Etravirine (formerly TMC125) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) with activity against wild-type and NNRTI-resistant strains of HIV-1. Etravirine has been approved in several countries for use as part of highly active antiretroviral therapy in treatment-experienced patients. In vivo, etravirine is a substrate for, and weak inducer of, the hepatic cytochrome P450 (CYP) isoenzyme 3A4 and a substrate and weak inhibitor of CYP2C9 and CYP2C19. Etravirine is also a weak inhibitor of P-glycoprotein. An extensive drug-drug interaction programme in HIV-negative subjects has been carried out to assess the potential for pharmacokinetic interactions between etravirine and a variety of non-antiretroviral drugs. Effects of atorvastatin, clarithromycin, methadone, omeprazole, oral contraceptives, paroxetine, ranitidine and sildenafil on the pharmacokinetic disposition of etravirine were of no clinical relevance. Likewise, etravirine had no clinically significant effect on the pharmacokinetics of fluconazole, methadone, oral contraceptives, paroxetine or voriconazole. No clinically relevant interactions are expected between etravirine and azithromycin or ribavirin, therefore, etravirine can be combined with these agents without dose adjustment. Fluconazole and voriconazole increased etravirine exposure 1.9- and 1.4-fold, respectively, in healthy subjects, however, no increase in the incidence of adverse effects was observed in patients receiving etravirine and fluconazole during clinical trials, therefore, etravirine can be combined with these antifungals although caution is advised. Digoxin plasma exposure was slightly increased when co-administered with etravirine. No dose adjustments of digoxin are needed when used in combination with etravirine, however, it is recommended that digoxin levels should be monitored. Caution should be exercised in combining rifabutin with etravirine in the presence of certain boosted HIV protease inhibitors due to the risk of decreased exposure to etravirine. Although adjustments to the dose of clarithromycin are unnecessary for the treatment of most infections, the use of an alternative macrolide (e.g. azithromycin) is recommended for the treatment of Mycobacterium avium complex infection since the overall activity of clarithromycin against this pathogen may be altered when co-administered with etravirine. Dosage adjustments based on clinical response are recommended for clopidogrel, HMG-CoA reductase inhibitors (e.g. atorvastatin) and for phosphodiesterase type-5 inhibitors (e.g. sildenafil) because changes in the exposure of these medications in the presence of co-administered etravirine may occur. When co-administered with etravirine, a dose reduction or alternative to diazepam is recommended. When combining etravirine with warfarin, the international normalized ratio (INR) should be monitored. Systemic dexamethasone should be co-administered with caution, or an alternative to dexamethasone be found as dexamethasone induces CYP3A4. Caution is also warranted when co-administering etravirine with some antiarrhythmics, calcineurin inhibitors (e.g. ciclosporin) and antidepressants (e.g. citalopram). Co-administration of etravirine with some antiepileptics (e.g. carbamazepine and phenytoin), rifampicin (rifampin), rifapentine or preparations containing St John's wort (Hypericum perforatum) is currently not recommended as these are potent inducers of CYP3A and/or CYP2C and may potentially decrease etravirine exposure. Antiepileptics that are less likely to interact based on their known pharmacological properties include gabapentin, lamotrigine, levetiracetam and pregabalin. Overall, pharmacokinetic and clinical data show etravirine to be well tolerated and generally safe when given in combination with non-antiretroviral agents, with minimal clinically significant drug interactions and no need for dosage adjustments of etravirine in any of the cases, or of the non-antiretroviral agent in the majority of cases studied.

Clinical perspective on antiretroviral drug-drug interactions with the non-nucleoside reverse transcriptase inhibitor etravirine.

Etravirine is an effective and well-tolerated recently approved non-nucleoside reverse transcriptase inhibitor (NNRTI) for HIV type-1-infected patients with previous antiretroviral treatment experience. Considering the importance of combining antiretrovirals for their optimal use in treating HIV, a number of drug-drug interactions with etravirine and other antiretrovirals have been evaluated. Etravirine is a weak inducer of cytochrome P450 (CYP)3A and a weak inhibitor of CYP2C9/CYP2C19 and P-glycoprotein, and although etravirine is metabolized by the CYP enzyme system, the extent of clinically relevant interactions with other antiretrovirals is limited. Etravirine can be combined with all currently available nucleoside/nucleotide reverse transcriptase inhibitors without dose adjustments, but not with other NNRTIs. Available data indicate that etravirine can be coadministered with most of the currently available ritonavir-boosted HIV protease inhibitors. Coadministration with tipranavir/ritonavir or unboosted HIV protease inhibitors is not recommended because of clinically relevant changes in exposure to etravirine or the coadministered HIV protease inhibitor, respectively. Etravirine can be coadministered with the integrase inhibitors elvitegravir/ritonavir or raltegravir, and with the fusion inhibitor enfuvirtide, without dose adjustments. Dose adjustment of the C-C chemokine receptor type-5 antagonist maraviroc is required, with the type of adjustment depending on whether a boosted HIV protease inhibitor is included in the regimen. In conclusion, etravirine can be combined with most antiretrovirals, with no clinically meaningful effect on drug exposure or safety/tolerability profiles.

Effects of hepatic impairment on the steady-state pharmacokinetics of etravirine 200 mg BID: an open-label, multiple-dose, controlled Phase I study in adults.

BACKGROUND: Etravirine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) with activity against both wild-type HIV and viruses harboring NNRTI resistance. Etravirine is mainly eliminated via the hepatobiliary route. OBJECTIVES: This study in HIV- patients with mild or moderate hepatic impairment and healthy matched controls was conducted to explore the effects of mild and moderate hepatic impairment on the steady-state pharmacokinetics of etravirine and to provide guidance for the treatment of HIV+ patients with hepatic impairment. METHODS: This open-label, multiple-dose study enrolled HIV- patients aged 18 to 65 years with mild or moderate hepatic impairment (Child-Pugh score, 5-6 or 7-9, respectively) and healthy volunteers matched for age, sex, race, and body mass index (BMI). All subjects received etravirine 200 mg BID with food for 7 days and a morning dose on day 8. Etravirine pharmacokinetics over a period of 12 hours on days 1 and 8 were determined using noncompartmental methods and analyzed using linear mixed-effects modeling. Tolerability of etravirine was assessed based on the reported adverse events, laboratory investigations, ECG, and physical examination. RESULTS: Each group comprised 8 subjects (mild hepatic impairment patients: 5 men, 3 women; median age, 57 years [range, 41-65 years]; BMI, 26 kg/m(2) [range, 20-32 kg/m(2)]; moderate hepatic impairment patients: 6 men, 2 women; age, 54 years [range, 44-64 years]; BMI, 26 kg/m(2) [range, 22-32 kg/m(2)]). All patients were white and light smokers. On day 8, the least squares mean ratios (90% CIs) of the log transformed pharmacokinetic properties in patients with mild and moderate hepatic impairment were, respectively: C(min), 0.87 (0.65-1.17) and 0.98 (0.68-1.42) microg/mL; C(max), 0.79 (0.63-1.00) and 0.72 (0.54-0.96) ug/mL; and AUC(0-12), 0.87 (0.69-1.09) and 0.82 (0.60-1.11) microg/mL/h. All treatment-emergent adverse events were considered mild to moderate; the most common were headache (50% in healthy controls) and fatigue and nausea (both 25% in patients with mild hepatic impairment). No clinically significant changes in laboratory parameters, physical examination including vital signs, or ECG were observed. One serious adverse event was reported during the follow-up period in a patient with moderate hepatic impairment due to hepatic cirrhosis secondary to alcoholism. This patient presented at screening with dilated cardiomyopathy and cardiac arrhythmia. CONCLUSIONS: In this Phase I pharmacokinetic study, no clinically relevant differences were observed between patients with mild or moderate hepatic impairment and healthy matched subjects with regard to the pharmacokinetics of etravirine. Based on these findings in these HIV- volunteers, no dose adjustment of etravirine appears to be necessary in patients with mild or moderate hepatic impairment. Etravirine was generally well tolerated.

Effect of steady-state etravirine on the pharmacokinetics and pharmacodynamics of ethinylestradiol and norethindrone.

BACKGROUND: Etravirine, a non-nucleoside reverse transcriptase inhibitor (NNRTI) active against NNRTI-resistant HIV, is an inducer of CYP3A4 and an inhibitor of CYP2C9/19. STUDY DESIGN: The effect of etravirine on the pharmacokinetics and pharmacodynamics of ethinylestradiol and norethindrone was assessed in 30 HIV-negative females. Following a run-in cycle with ethinylestradiol/norethindrone, the pharmacokinetics of ethinylestradiol and norethindrone was assessed on Day 15 of Cycle 2. Etravirine 200 mg bid was coadministered on Day 1 to Day 15 of Cycle 3, with pharmacokinetic assessments of ethinylestradiol, norethindrone and etravirine on Day 15. RESULTS: When combined with etravirine, the least-squares means (LSM) ratios (90% confidence interval) for ethinylestradiol AUC(24h), C(max) and C(min) were 1.22 (1.13-1.31), 1.33 (1.21-1.46) and 1.09 (1.01-1.18), respectively, compared to administration alone. LSM ratios for norethindrone parameters were 0.95 (0.90-0.99), 1.05 (0.98-1.12) and 0.78 (0.68-0.90), respectively. CONCLUSION: These changes are not considered clinically relevant. No loss in contraceptive efficacy is expected when coadministered with etravirine.

Clinical pharmacokinetics and pharmacodynamics of etravirine.

Etravirine is a next-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) developed for the treatment of HIV-1 infection. It has a high genetic barrier to the emergence of viral resistance, and maintains its antiviral activity in the presence of common NNRTI mutations. The pharmacokinetics of etravirine in HIV-infected patients at the recommended dosage of 200 mg twice daily demonstrates moderate intersubject variability and no time dependency. Due to substantially lower exposures when taken on an empty stomach, etravirine should be administered following a meal. The drug is highly protein bound (99.9%) to albumin and alpha(1)-acid glycoprotein and shows a relatively long elimination half-life of 30-40 hours. Etravirine is metabolized by cytochrome P450 (CYP) 3A, 2C9 and 2C19; the metabolites are subsequently glucuronidated by uridine diphosphate glucuronosyltransferase. Renal elimination of etravirine is negligible. Etravirine has the potential for interactions by inducing CYP3A and inhibiting CYP2C9 and 2C19; it is a mild inhibitor of P-glycoprotein but not a substrate. The drug interaction profile of etravirine has been well characterized and is manageable. No dosage adjustments are needed in patients with renal impairment or mild to moderate hepatic impairment. Race, sex, bodyweight and age do not affect the pharmacokinetics of etravirine. In the two phase III trials DUET-1 and DUET-2, no relationship was demonstrated between the pharmacokinetics of etravirine and the primary efficacy endpoint of viral load below 50 copies/mL or the safety profile of etravirine.

Design of antiretroviral drug interaction studies.

PURPOSE OF REVIEW: Pharmacokinetic and/or pharmacodynamic drug interactions can occur as a result of treatment with antiretrovirals. Elucidating the mechanism, direction, and magnitude of an interaction, as well as its clinical impact, can be facilitated by proper study design. Two approaches may be considered: assessment based on full pharmacokinetic profiles within a conventional drug interaction trial, or a population pharmacokinetic analysis as a part of a larger trial. Consideration should be given to the population (i.e. healthy volunteer or HIV infected), dosing and administration of medications, and interpretation of findings. Dosing recommendations should be based on the clinical relevance of the interaction. RECENT FINDINGS: Guidance documents on the conduct of clinical drug interaction study designs are summarized and applied to the design of antiretroviral drug interaction trials. SUMMARY: Designing an antiretroviral drug interaction trial poses unique challenges, associated with the conditions and the drug combinations of the intended population. A rational study design can provide insights into antiretroviral pharmacology and allows the clinician to treat more effectively.