Pharmacokinetic evaluation of the interaction between etravirine and rifabutin or clarithromycin in HIV-negative, healthy volunteers: results from two Phase 1 studies.

OBJECTIVES: Drug-drug interactions between etravirine and rifabutin or clarithromycin were examined in two separate open-label, randomized, two-period, crossover trials in HIV-negative, healthy volunteers. METHODS: Rifabutin study: 16 participants received 300 mg of rifabutin once daily (14 days) and then 800 mg of etravirine twice daily (Phase 2 formulation; 21 days) plus 300 mg of rifabutin once daily (days 8-21). Clarithromycin study: 16 participants received 200 mg of etravirine twice daily (commercial formulation; 8 days) and then 500 mg of clarithromycin twice daily (13 days) plus 200 mg of etravirine twice daily (days 6-13). A 14 day washout period between treatments was mandatory in both studies. Full pharmacokinetic profiles of each drug and safety/tolerability were assessed. RESULTS: Rifabutin decreased etravirine exposure by 37%; etravirine decreased rifabutin and 25-O-desacetyl rifabutin exposure by 17%. Clarithromycin increased etravirine exposure by 42%, whereas etravirine decreased clarithromycin exposure by 39% and increased 14-OH clarithromycin exposure by 21%. No serious adverse events were reported in either trial. CONCLUSIONS: Short-term etravirine coadministration with rifabutin or clarithromycin was well tolerated. Etravirine can be coadministered with 300 mg of rifabutin once daily in the absence of an additional potent cytochrome P450 inducer. No dose adjustments are required upon etravirine/clarithromycin coadministration, but alternatives to clarithromycin are recommended when used for Mycobacterium avium complex prophylaxis or treatment.

Rapid HCV-RNA decline with once daily TMC435: a phase I study in healthy volunteers and hepatitis C patients.

BACKGROUND & AIMS: The search for targeted anti-hepatitis C virus (HCV) drugs is driven by the adverse effect profile and limited efficacy of the current standard of care (pegylated interferon-alpha/ribavirin). In a first-in-human trial, we tested the safety, tolerability, and pharmacokinetics of the macrocyclic HCV NS3/4A protease inhibitor TMC435 in healthy volunteers, followed by HCV genotype 1-infected patients to assess antiviral activity. METHODS: The TMC435350-C101 study was a phase I, randomized, double-blind, placebo-controlled trial in 49 healthy volunteers, followed by an open-label, nonplacebo-controlled panel in 6 genotype 1 hepatitis C patients. Healthy volunteers received oral, single, ascending doses (up to 600 mg) or 5-day multiple ascending doses (200 mg twice daily or 100, 200, or 400 mg once daily). Patients received 200 mg once daily for 5 days. Pharmacokinetics and safety were evaluated for all panels, and plasma HCV-RNA levels were determined in patients. RESULTS: There were no serious adverse events, no grade 3 reactions, and no treatment-related discontinuations; pharmacokinetics supported a once daily dosing regimen. Plasma HCV-RNA levels dropped rapidly in all patients, with a median maximal reduction of 3.9-log(10) IU/mL and a median of 6 days to maximal reduction. The initial steep reduction of HCV-RNA (median 3.5-log(10) IU/mL at day 3) was followed by a more gradual decline that was maintained over the dosing period. No viral breakthroughs (>1-log(10) IU/mL HCV-RNA increase from nadir) were observed during treatment nor in the 3 days posttreatment; HCV-RNA returned to pretreatment levels by week 4. CONCLUSIONS: Once daily TMC435 given orally was generally safe and well tolerated and demonstrated potent antiviral activity.

The effect of single- and multiple-dose etravirine on a drug cocktail of representative cytochrome P450 probes and digoxin in healthy subjects.

The effect of etravirine on cytochrome P450 (CYP) enzymes and P-glycoprotein were evaluated in two randomized, crossover trials in healthy subjects. A modified Cooperstown 5 + 1 cocktail was utilized to determine the effects of etravirine on single-dose pharmacokinetics of model CYP probes. The cocktail was administered alone, then, after a 14-day washout, etravirine 200 mg twice daily (bid) was given for 14 days with cocktail on days 1 and 14. In a separate study, digoxin (0.5 mg) was administered alone, then, after a 14-day washout, etravirine 200 mg bid was administered for 12 days with digoxin on day 8. In the cocktail study, the AUClast least squares mean (LSM) ratios (90% confidence intervals [CIs]) for cocktail + etravirine versus cocktail were 0.93 (0.88, 0.99; paraxanthine), 0.58 (0.44, 0.75; 7-OH-S-warfarin), 0.43 (0.20, 0.96; 5-OH-omeprazole), 0.85 (0.78, 0.94; dextrorphan), and 0.69 (0.64, 0.74; midazolam). Digoxin AUC0-8h was slightly increased with etravirine coadministration (LSM ratio 1.18 [0.90, 1.56]). These data suggest that etravirine is a weak CYP3A isozyme inducer and minimally inhibits CYP2C9, 2C19, and P-glycoprotein activity.

Pharmacokinetics and short-term safety of etravirine in combination with fluconazole or voriconazole in HIV-negative volunteers.

The nonnucleoside reverse transcriptase inhibitor etravirine, approved for use in treatment-experienced, HIV-1-infected patients, is a substrate and inducer of cytochrome P450 (CYP) 3A4 and a substrate and inhibitor of CYP2C9/CYP2C19. Pharmacokinetic interactions and safety of etravirine 200 mg twice daily coadministered with fluconazole 200 mg daily or voriconazole 200 mg twice daily, both inhibitors of CYP3A4, CYP2C9, and CYP2C19, were evaluated in an open-label, randomized, 3-period crossover trial in 18 HIV-negative volunteers. Based on least squares means (LSM) ratios, coadministration of etravirine with fluconazole or voriconazole resulted in higher etravirine exposures (area under plasma concentration-time curve from 0-12 hours [AUC(12) (h) ] 1.86- and 1.36-fold, respectively). Fluconazole pharmacokinetics were unchanged with etravirine coadministration (AUC(12) (h) LSM ratio: 0.94), and voriconazole plasma concentrations were slightly raised (AUC(12) (h) LSM ratio: 1.14). All treatments and combinations were well tolerated, with no grade 3 or 4 adverse events observed during treatment. There was 1 adverse event-related trial withdrawal during treatment with fluconazole alone (leukocyturia). The most frequent adverse events were headache and blurred vision (11 and 8 volunteers, respectively), with blurred vision occurring exclusively during voriconazole-alone treatment. Pharmacokinetic interactions between etravirine and fluconazole or voriconazole are not expected to be clinically relevant; no dose adjustments are required during coadministration.

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.