Charles la Porte

Haplotype structure of CYP2B6 and association with plasma efavirenz concentrations in a Chilean HIV cohort

OBJECTIVES Efavirenz is extensively metabolized by CYP2B6, and associations between CYP2B6 polymorphisms and plasma efavirenz exposure have been reported. The objective of this study was to investigate CYP2B6 haplotype structure and functional consequences in a Latin American population. PATIENTS AND METHODS Two hundred and nineteen patients were recruited at Fundación Arriarán, Chile, between September and December 2008. Plasma efavirenz concentrations were determined using liquid chromatography with mass spectrometry. Genotyping for 30 single nucleotide polymorphisms (SNPs) with a minor allele frequency of >0.05 in the HapMap CEU population at intervals of approximately 1 kb across the CYP2B6 locus was conducted using Sequenom iPLEX MALDI-TOF. RESULTS Thirteen SNPs passed quality control and, of these, statistically significant associations (P < 0.001) with plasma efavirenz concentrations were observed for 11. Pairwise tagging SNP analysis (R(2) > 0.8) identified 3 SNPs (rs10403955, rs2279345 and rs8192719) representative of the 11 associated SNPs. A composite genetic model of these three alleles was constructed, and an association between carriers of four to six of these alleles and the risk of efavirenz plasma concentrations >4 microg/mL was identified with an odds ratio of 48.1 (95% confidence interval: 13.5-207.7). This represents a positive predictive value of 80.9% and a negative predictive value of 91.8%, with sensitivity of 57.9% and specificity of 97.2%. CONCLUSIONS A composite genetic model of CYP2B6 SNPs in a Chilean HIV-positive cohort may have value in predicting concentrations of efavirenz associated with a higher likelihood of CNS toxicity. Further investigation of the functional basis of these associations is now required.

Role of P-Glycoprotein in the Distribution of the HIV Protease Inhibitor Atazanavir in the Brain and Male Genital Tract

ABSTRACT The blood-testis barrier and blood-brain barrier are responsible for protecting the male genital tract and central nervous system from xenobiotic exposure. In HIV-infected patients, low concentrations of antiretroviral drugs in cerebrospinal fluid and seminal fluid have been reported. One mechanism that may contribute to reduced concentrations is the expression of ATP-binding cassette drug efflux transporters, such as P-glycoprotein (P-gp). The objective of this study was to investigate in vivo the tissue distribution of the HIV protease inhibitor atazanavir in wild-type (WT) mice, P-gp/breast cancer resistance protein (Bcrp)-knockout (Mdr1a−/−, Mdr1b−/−, and Abcg2−/− triple-knockout [TKO]) mice, and Cyp3a−/− (Cyp) mice. WT mice and Cyp mice were pretreated with a P-gp/Bcrp inhibitor, elacridar (5 mg/kg of body weight), and the HIV protease inhibitor and boosting agent ritonavir (2 mg/kg intravenously [i.v.]), respectively. Atazanavir (10 mg/kg) was administered i.v. Atazanavir concentrations in plasma (Cplasma), brain (Cbrain), and testes (Ctestes) were quantified at various times by liquid chromatography-tandem mass spectrometry. In TKO mice, we demonstrated a significant increase in atazanavir Cbrain/Cplasma (5.4-fold) and Ctestes/Cplasma (4.6-fold) ratios compared to those in WT mice (P < 0.05). Elacridar-treated WT mice showed a significant increase in atazanavir Cbrain/Cplasma (12.3-fold) and Ctestes/Cplasma (13.5-fold) ratios compared to those in vehicle-treated WT mice. In Cyp mice pretreated with ritonavir, significant (P < 0.05) increases in atazanavir Cbrain/Cplasma (1.8-fold) and Ctestes/Cplasma (9.5-fold) ratios compared to those in vehicle-treated WT mice were observed. These data suggest that drug efflux transporters, i.e., P-gp, are involved in limiting the ability of atazanavir to permeate the rodent brain and genital tract. Since these transporters are known to be expressed in humans, they could contribute to the low cerebrospinal and seminal fluid antiretroviral concentrations reported in the clinic.

Correlates of Efavirenz Exposure in Chilean Patients Affected With Human Immunodeficiency Virus Reveals a Novel Association With a Polymorphism in the Constitutive Androstane Receptor

Objective:To explore the effect of demographics and single-nucleotide polymorphisms in cytochrome P450 (CYP) 2B6, 2A6, UDP-glucuronosyltransferase (UGT) 2B7, and the constitutive androstane receptor (CAR) genes on efavirenz pharmacokinetics in a Chilean cohort affected with human immunodeficiency virus. Methods:Timed plasma samples obtained throughout the dosing interval were analyzed for efavirenz concentrations with liquid chromatography/tandem mass spectrometry. DNA from whole-blood samples was used for genetic analysis. Data were analyzed using a Mann–Whitney statistical test; furthermore, a Pearson or Spearman correlation was used. A multivariate analysis was then conducted using multiple linear regression by best subset analysis. Results:Overall 219 patients were included, 208 patients had measurable efavirenz levels and available genetic samples. The overall median (interquartile range) of efavirenz concentration was 2.6 (2.1–3.7) mcg/mL. In multivariate regression analysis, CYP2B6 516G>T (P < 0.0001) and CAR rs2307424 C>T (P = 0.002) were significantly related to efavirenz plasma concentrations. Conclusion:This novel association between CAR rs2307424 and efavirenz plasma concentrations now requires validation in other cohorts.

Impact of antiretroviral therapy duration and intensification on isolated shedding of HIV-1 RNA in semen.

BACKGROUND Effective antiretroviral therapy (ART) dramatically reduces human immunodeficiency virus (HIV) transmission. However, isolated shedding of HIV type 1 (HIV-1) in semen (IHS) can occur in the absence of detectable viremia or genital infections. We hypothesized that ART intensification with medications active in semen might prevent IHS. METHODS Paired blood and semen samples were collected monthly for 6 months from HIV-infected men starting ART that was intensified (iART) with maraviroc and raltegravir in an open-label fashion. Semen parameters were compared to those of historical controls starting standard ART (sART). RESULTS Compared with 25 controls who started sART, the semen HIV-1 load in 13 subjects who started iART was more rapidly suppressed (P = .043). IHS was detected at >1 visit in 2 participants (15%) receiving iART and in 12 controls (48%) receiving sART (P = .040). Among iART recipients, IHS was associated with lower raltegravir concentrations in blood and semen, compared with complete HIV-1 suppression (P = .03). Prolonged, high-level IHS (ie, shedding of >5000 RNA copies/mL) was observed in 1 iART recipient (8%), despite rapid viremia suppression and therapeutic drug levels; for 10 months, this virus remained R5 tropic, drug susceptible, and similar in sequence to virus recovered from blood. IHS was not seen after >3 years of effective ART in a parallel, prospective cohort study. CONCLUSIONS iART transiently reduced the occurrence of IHS early after ART initiation but did not prevent high-level IHS. IHS was not seen after more prolonged sART.

Saquinavir, the pioneer antiretroviral protease inhibitor

Background: The treatment of HIV infection underwent a major change in 1995 when saquinavir was the first protease inhibitor introduced into the market. This drug made the use of combination therapy in the treatment of HIV possible and increased the success rate of treatment. Objective: This article will review recent literature on saquinavir to define its current role in HIV treatment, among the newer antiretroviral drugs. Methods: Scientific literature and conference presentations were evaluated for relevant information pertaining to saquinavir. Results/conclusions: Although underused, saquinavir has good efficacy and tolerability when compared to other protease inhibitors. The film-coated tablet formulation improved pill burden. Saquinavir still has potential in the treatment of adults, children and pregnant women.Background: The treatment of HIV infection underwent a major change in 1995 when saquinavir was the first protease inhibitor introduced into the market. This drug made the use of combination therapy in the treatment of HIV possible and increased the success rate of treatment. Objective: This article will review recent literature on saquinavir to define its current role in HIV treatment, among the newer antiretroviral drugs. Methods: Scientific literature and conference presentations were evaluated for relevant information pertaining to saquinavir. Results/conclusions: Although underused, saquinavir has good efficacy and tolerability when compared to other protease inhibitors. The film-coated tablet formulation improved pill burden. Saquinavir still has potential in the treatment of adults, children and pregnant women.

Interaction Studies of Tipranavir-Ritonavir with Clarithromycin, Fluconazole, and Rifabutin in Healthy Volunteers

ABSTRACT Three separate controlled, two-period studies with healthy volunteers assessed the pharmacokinetic interactions between tipranavir-ritonavir (TPV/r) in a 500/200-mg dose and 500 mg of clarithromycin (CLR), 100 mg of fluconazole (FCZ), or 150 mg of rifabutin (RFB). The CLR study was conducted with 24 subjects. The geometric mean ratios (GMR) and 90% confidence intervals (90% CI; given in parentheses) of the areas under the concentration-time curve (AUC), the maximum concentrations of the drugs in serum (Cmax), and the concentrations in serum at 12 h postdose (Cp12h) for multiple-dose TPV/r and multiple-dose CLR, indicating the effect of TPV/r on the CLR parameters, were 1.19 (1.04-1.37), 0.95 (0.83-1.09), and 1.68 (1.42-1.98), respectively. The formation of the metabolite 14-OH-CLR was decreased by 95% in the presence of TPV, and the TPV AUC increased 66% compared to that for human immunodeficiency virus (HIV)-negative historical controls. The FCZ study was conducted with 20 subjects. The GMR (and 90% CI) of the AUC, Cmax, and Cp24h, indicating the effect of multiple-dose TPV/r on the multiple-dose FCZ parameters, were 0.92 (0.88-0.95), 0.94 (0.91-0.98), and 0.89 (0.85-0.92), respectively. The TPV AUC increased by 50% compared to that for HIV-negative historical controls. The RFB study was conducted with 24 subjects. The GMR (and 90% CI) of the AUC, Cmax, and Cp12h for multiple-dose TPV/r and single-dose RFB, indicating the effect of TPV/r on the RFB parameters, were 2.90 (2.59-3.26), 1.70 (1.49-1.94), and 2.14 (1.90-2.41), respectively. The GMR (and 90% CI) of the AUC, Cmax, and Cp12h of TPV/r and RFB with 25-O-desacetyl-RFB were 4.33 (3.86-4.86), 1.86 (1.63-2.12), and 2.76 (2.44-3.12), respectively. Coadministration of TPV with a single dose of RFB resulted in a 16% increase in the TPV Cp12h compared to that for TPV alone. In the general population, no dose adjustments are necessary for the combination of TPV/r and CLR or FCZ. Combining TPV/r with RFB should be done with caution, while toxicity and RFB drug levels should be monitored. Study medications were generally well-tolerated in these studies.

Atazanavir-Associated Choledocholithiasis Leading to Acute Hepatitis in an HIV-infected Adult

OBJECTIVE To report a case of atazanavir-associated choledocholithiasis in an HIV-infected individual. CASE SUMMARY A 47-year-old treatment-naïve HIV-positive African female presented to the emergency department with a 3-day history of right epigastric pain. Six weeks prior to this episode, she began antiretroviral therapy with a regimen consisting of atazanavir 400 mg and abacavir/lamivudine 600/300 mg once daily. Alanine aminotransferase (766 U/L), aspartate aminotransferase (876 U/L), γ-glutamyltransferase (588 U/L), alkaline phosphatase (348 U/L), and total bilirubin (3.9 mg/dL) levels were elevated. Abdominal ultrasound revealed obstructive choledocholithiasis as well as intra- and extrahepatic biliary dilatation. She underwent a laparoscopic cholecystectomy, which revealed approximately 50 small calculi present in the gallbladder. Since previous ultrasounds had also shown gallstones, an analysis of the extracted calculi was performed to determine the possible association with atazanavir use; low amounts of atazanavir were detected. DISCUSSION Atazanavir is an inhibitor of the bilirubin-conjugating enzyme UGT1A1 and has been frequently linked to the occurrence of hyperbilirubinemia without complications. This individual experienced hyperbilirubinemia that peaked at hospital presentation after she developed choledocholithiasis and secondary acute hepatitis. Analysis of the extracted gallstones revealed that smaller stones contained a higher content of atazanavir than larger stones, which suggests that atazanavir precipitation may play a role in cholelithiasis, although the mechanism remains unknown. The low yield of atazanavir may be explained by the short, 6-week duration of drug exposure as well as the lack of assay for metabolites. The Naranjo probability scale implicated choledocholithiasis as a possible atazanavir-associated adverse event. This report provides the first published evidence that even short-term use of atazanavir may lead to hyperbilirubinemia with choledocholithiasis and secondary acute hepatitis in HIV-infected adults. CONCLUSIONS Atazanavir should be considered a possible contributor in the development of cholelithiasis or choledocholithiasis, and people with HIV should receive adequate counseling in the recognition of symptoms associated with gallstones. The exact incidence and mechanism still need to be elucidated.

Design and methods of the MAINTAIN study: a randomized controlled clinical trial of micronutrient and antioxidant supplementation in untreated HIV infection.

Micronutrient deficiencies are common in HIV positive persons and are associated with a poorer prognosis, but the role of micronutrient supplementation in the medical management of HIV infection remains controversial, as some but not all studies show immunological and clinical benefit. Micronutrients supplementation could be a relatively low cost strategy to defer the initiation of expensive, potentially toxic and lifelong antiretroviral therapy. The MAINTAIN study is a Canadian multi-center randomized control double blind clinical trial to evaluate if micronutrient supplementation of HIV positive persons slows progression of immune deficiency and delays the need to start antiretroviral therapy and is safe, compared to standard multivitamins. Untreated asymptomatic HIV positive adults will receive a micronutrient and antioxidant preparation (n = 109) or an identical appearing recommended daily allowance multivitamin and mineral preparation (n = 109) for two years. Participants will be followed quarterly and monitored for time from baseline to CD4 T lymphocyte count <350 mm(3), or emergence of CDC-defined AIDS-defining illness, or the start of antiretroviral therapy. We will also compare safety and health related quality of life between groups. Primary analysis will compare the incidence of the composite primary outcome between study groups and will be by intention-to-treat. The study was originally expected to last three years, with accrual over one year and a minimum of two years follow up of the last enrolled participant. We discuss here the study design and methods, often used for evaluation of complementary and adjunctive treatments for health maintenance in HIV infection, which are common interventions.

Inhibitory quotient in HIV pharmacology

Results The inhibitory quotient is the ratio of drug exposure to viral susceptibility. There are a number of different ways to calculate the inhibitory quotient. The trough concentration is the most frequently used pharmacokinetic parameter to represent drug exposure in inhibitory quotient calculations. To represent resistance, both phenotypic and genotypic data can be used to calculate the inhibitory quotient. Using population averages for drug exposure and resistance it is possible to compare the inhibitory quotient of different drugs. More frequently the inhibitory quotient is used in the context of therapeutic drug monitoring. The inhibitory quotient has mainly been studied for protease inhibitors. For nonnucleoside reverse transcriptase inhibitors a single mutation can cause high level resistance, whereas for PIs, mutations have a smaller but cumulative effect. For this reason it is unlikely that the inhibitory quotient will be helpful in the therapeutic drug monitoring of nonnucleoside reverse transcriptase inhibitors. For the newer drugs in the classes of CCR5 and integrase inhibitors it is not yet clear what the role for inhibitory quotient could be. In terms of therapeutic drug monitoring cutoff values have been proposed for the genotypic inhibitory quotient as well as for the phenotypic inhibitory quotient. Discussion The inhibitory quotient has been topic of discussion for the past decade. We have moved from the initial discussions on how to compare inhibitory quotients for different drugs into the use of inhibitory quotient as a useful parameter for therapeutic drug monitoring. Further data are needed to confirm the respective roles of different forms of inhibitory quotient in daily practice.