Objective To investigate the concentration of the integrase strand inhibitor raltegravir (RAL) throughout gastrointestinal (GI) tissue, especially gutassociated lymphoid tissue (GALT), as an adjunct to current prevention and cure strategies. Design Open-label pharmacokinetic study Methods HIV-negative men received RAL 400 mg twice daily for 7 days. Seven blood plasma (BP) specimens were collected over 12-hr intervals; timed tissue specimens from terminal ileum, splenic flexure, and rectum were also obtained by colonoscopy following the first dose (FD) and on Day 7 [Multiple Dose (MD)]. RAL concentrations were measured by validated LC-MS assay with 1 ng/mL lower limit of detection. Data were analyzed by noncompartmental methods (WinNonlin 6). Tissue exposures are reported as composite medians and tissue density of 1.04 g/mL is assumed for comparisons. Results Fourteen men completed evaluations. Median (range) age was 24 (19–49) yrs and BMI 25 (19–31) kg/m2. After the FD, AUC-0-12h was highest in the terminal ileum (594 μg*h/mL). Exposures were 160, 68 and 39-fold greater than BP at the terminal ileum, splenic flexure and rectum, respectively. After multiple doses, exposure was highest at the splenic flexure (2240 μg*h/mL); exposure at the terminal ileum and rectum were equivalent (both 788 μg*h/mL). Following multiple doses, exposures were 160–650-fold greater than BP throughout the colon. Conclusions RAL rapidly disseminates into GI tissue and concentrations remain significantly higher than BP. RAL exposure in GI tissue remains higher than any ARV investigated to date. These data suggest that RAL should result in full suppression of viral replication in GI tissue and GALT.

The effects of tipranavir/ritonavir (TPV/r) on hepatic and intestinal P-glycoprotein (P-gp) and cytochrome P450 (CYP) enzyme activity were evaluated in 23 volunteers. The subjects received oral (p.o.) caffeine, warfarin + vitamin K, omeprazole, dextromethorphan, and midazolam and digoxin (p.o. and intravenous (i.v.)) at baseline, during the first three doses of TPV/r (500 mg/200 mg b.i.d.), and at steady state. Plasma area under the curve (AUC) 0-∞ and urinary metabolite ratios were used for quantification of protein activities. A single dose of TPV/r had no effect on the activity of CYP1A2 and CYP2C9; it weakly inhibited CYP2C19 and P-gp; and it potently inhibited CYP2D6 and CYP3A. Multiple dosing produced weak induction of CYP1A2, moderate induction of CYP2C19, potent induction of intestinal P-gp, and potent inhibition of CYP2D6 and CYP3A, with no significant effects on CYP2C9 and hepatic P-gp. Several P450/transporter single-nucleotide polymorphisms correlated with the baseline phenotype but not with the extent of inhibition or induction. Although mixed induction and inhibition are present, this approach offers an understanding of drug interaction mechanisms and ultimately assists in optimizing the clinical use of TPV/r.Cocktail phenotyping involves simultaneous, single-dose administration of marketed drugs (also known as probes) to measure the activity (or phenotype) of multiple hepatic and intestinal drug-metabolizing enzymes and transporters for rapid and efficient assessment of the drug interaction potential of a new compound. [1][2][3][4][5] The "Cooperstown 5 + 1 cocktail" consists of caffeine, warfarin, omeprazole, dextromethorphan, intravenous (i.v.) midazolam, and vitamin K (to negate warfarin's anticoagulant effect). 6 We have modified this approach to elucidate the specific influences of drugs on hepatic and intestinal proteins by evaluating enzyme activity NIH Public Access Author ManuscriptClin Pharmacol Ther. Author manuscript; available in PMC 2011 June 1. Published in final edited form as:Clin Pharmacol Ther. 2010 June ; 87(6): 735-742. doi:10.1038/clpt.2009.253. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript under baseline conditions in addition to conditions of both acute and chronic drug exposure. Oral (p.o.) midazolam and i.v. and p.o. digoxin were also added as probe substrates in order to measure hepatic + intestinal CYP3A activity, hepatic P-glycoprotein (P-gp) activity, and hepatic + intestinal P-gp activity, respectively. 7,8 The genotyping of cytochrome P450 (CYP) genes corresponding to enzymes investigated with phenotype probes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5/7/43) and P-gp (ABCB1) also allows for investigating genotype-phenotype correlations and determining genetic influences on drug interactions.We used this modified cocktail approach to investigate the drug interaction potential of tipranavir (TPV) administered along with low-dose ritonavir (RTV). TPV is a nonpeptidic protease inhibitor (PI) with potent activity against HIV-1-res...

The new potent combination of antiretrovirals etravirine, darunavir, and ritonavir requires a new bioanalytical method for clinical pharmacology investigations and potential therapeutic drug monitoring. The development and validation of a novel LC-MS method for the simultaneous quantification of the most recently FDA-approved protease inhibitor and non-nucleoside reverse transcriptase inhibitor is described. This novel method was developed and validated using a sub-2 μm particle column, and provides excellent chromatographic separation and peak shape for all three analytes and internal standard. The method was validated over the range of 0.002-2.0 μg/mL. Intraand inter-day accuracy of all analytes ranged from 88 to 106%, and intra-and inter-day precision was <7%. Dilution of samples 2-, 5-, and 10-fold maintained accuracy and precision, using a sample volume as low as 10 μL. Finally, the applicability of the method was investigated with clinical samples and external quality assurance proficiency testing samples.

Background Antiretroviral therapy (ART) has become a central component of combination HIV prevention efforts. Defining the individual exposure of commercially available ART in genital secretions and vulnerable mucosal tissues is paramount to designing future prevention interventions. Methods A pharmacokinetic study was performed in 12 HIV-negative men receiving darunavir 600mg, ritonavir 100mg, and etravirine 200mg orally twice daily for 8 days. Seven blood plasma (BP) samples were collected over 12 hours on Day 1 (PK1) and Days 7 and 8 (PK2). One rectal tissue (RT)sample from each subject was collected during PK1 and PK2. During PK1, two seminal plasma (SP)samples were collected from each subject. During PK2, six SP samples were collected from each subject over 2 days. Results Antiretrovirals were detected in SP and RT within 1 hour after a single dose. Over PK1 and PK2, SP exposures were lower than BP by 80–92% (DRV), 89–95% (RTV), 83–88% (ETR). However, protein binding in SP (14% for darunavir, 70% for ritonavir, and 97% for etravirine) was lower than in BP. RT AUCs were higher than BP by 39 to 155-fold for darunavir, 12 to 61-fold for ritonavir, and 20 to 40-fold for etravirine. Conclusions Lower SP protein binding resulted in higher pharmacologically active darunavir and etravirine concentrations compared to BP. High RT concentrations may also be favorable for suppressing viral replication in the gastrointestinal mucosa. The high protein-unbound exposures in SP and total exposures in RT support further investigations of darunavir+ritonavir and etravirine in secondary prevention.

Background The pharmacokinetics (PK) of antiretrovirals (ARVs) in older HIV-infected patients are poorly described. Here, the steady-state PK of 2 common ARV regimens (tenofovir [TFV]/emtricitabine [FTC]/efavirenz [EFV]; TFV/FTC/atazanavir [ATV]/ritonavir [RTV]) in older non-frail HIV-infected patients are presented. Methods HIV-infected subjects ≥ 55 years old not demonstrating the frailty phenotype were enrolled in an unblinded, intensive-sampling PK study. Blood plasma (for TFV, FTC, EFV, ATV, and RTV concentrations) and peripheral blood mononuclear cells (PBMCs; for tenofovir diphosphate [TFV-DP] and emtricitabine triphosphate [FTC-TP] concentrations) were collected at 11 time points over a 24-hour dosing interval. Drug concentrations were analyzed using validated LC-UV or LC-MS/MS methods. Noncompartmental pharmacokinetic analysis was used to estimate PK parameters (AUC0–24hr, Cmax). These parameters were compared to historical values from the general HIV-infected population. Results Six subjects on each regimen completed the study. Compared to the general population, these elderly subjects had 8–13% decreased TFV AUC0–24hr and Cmax, and 19–78% increased FTC and RTV AUC0–24hr and Cmax. Decreased ATV AUC0–24hr (12%) and increased Cmax (9%) were noted, while EFV exposure was unchanged (5%) with a 16% decrease in Cmax. Intracellular nucleoside/tide metabolite concentrations and AUC are also reported for these subjects. Conclusions This study demonstrates that the PK of these ARVs are altered by 5–78% in an older HIV-infected population. Implications of PK differences on clinical outcomes, particularly with the active nucleoside metabolites, remain to be explored. This study forms the basis for further study of ARV PK, efficacy, and toxicity in older HIV-infected patients.