Incidence of atazanavir-associated hyperbilirubinemia in Korean HIV patients: 30 months follow-up results in a population with low UDP-glucuronosyltransferase1A1*28 allele frequency

The Functionality of UDP-Glucuronosyltransferase Genetic Variants and their Association with Drug Responses and Human Diseases

UDP-glucuronosyltransferases (UGTs) are phase II drug-metabolizing enzymes that metabolize endogenous fatty acids such as arachidonic acid metabolites, as well as many prescription drugs, such as opioids, antiepileptics, and antiviral drugs. The UGT1A and 2B genes are highly polymorphic, and their genetic variants may affect the pharmacokinetics and hence the responses of many drugs and fatty acids. This study collected data and updated the current view of the molecular functionality of genetic variants on UGT genes that impact drug responses and the susceptibility to human diseases. The functional information of UGT genetic variants with clinical associations are essential to understand the inter-individual variation in drug responses and susceptibility to toxicity.

The Changing Face of Human Immunodeficiency Virus-Mediated Kidney Disease

In nearly 40 years since human immunodeficiency virus (HIV) first emerged, much has changed. Our understanding of the pathogenesis of HIV infection and its effect on the cells within each kidney compartment has progressed, and the natural history of the disease has been transformed. What was once an acutely fatal illness is now a chronic disease managed with oral medications. This change is largely due to the advent of antiretroviral drugs, which have dramatically altered the prognosis and progression of HIV infection. However, the success of antiretroviral therapy has brought with it new challenges for the nephrologist caring for patients with HIV/acquired immune deficiency syndrome, including antiretroviral therapy-induced nephrotoxicity, development of non-HIV chronic kidney disease, and rising incidence of immune-mediated kidney injury. In this review, we discuss the pathogenesis of HIV infection and how it causes pathologic changes in the kidney, review the nephrotoxic effects of select antiretroviral medications, and touch upon other causes of kidney injury in HIV cases, including mechanisms of acute kidney injury, HIV-related immune complex glomerular disease, and thrombotic microangiopathy.

Uridine 5'-diphospho-glucronosyltrasferase: Its role in pharmacogenomics and human disease

Biotransformation is an enzyme-catalyzed process in which the body converts endogenous compounds, xenobiotics and toxic substances into harmless or easily excreted metabolites. The biotransformation reactions are classified as phase I and II reactions. Uridine 5'-diphospho (UDP)-glucuronosyltransferases (UGTs) are a superfamily of phase II enzymes which have roles in the conjugation of xenobiotics or endogenous compounds, including drugs and bilirubin, with glucuronic acid to make them easier to excrete. The method the human body uses to achieve glucuronidation may be affected by a large interindividual variation due to changes in the sequences of the genes encoding these enzymes. In the last five years, the study of the genetic variants of the UGTs at a molecular level has become important due to its association with several diseases and the ability to predict adverse events due to drug metabolism. In the present review, the structure and the prominent genetic variants of the UGT1A subfamily and their metabolic and clinical implications are described.

Incidence of atazanavir- associated adverse drug reactions in second -line drugs treated south Indian HIV-1 infected patients

Background:

Ritonavir-boosted atazanavir (ATV/r) is the preferred second-line protease inhibitor (PI) option for HIV patients in resource-limited settings; its pattern of adverse drug reactions (ADRs) has not been much reported from India; hence, in this study, we have analyzed the incidence of ATV/r-associated ADRs in Southern Indian HIV-1-infected patients.

Methods:

In this prospective study, 111 HIV patients treated with ATV/r were included with at least 2 years follow-up visits for the emergence of hyperbilirubinemia, hypertransaminasemia, and serum creatinine elevation. The causality assessment was done based on the WHO scale for the causality assessment of suspected ADR.

Results:

The incidence of severe hyperbilirubinemia, hypertransaminasemia, and creatinine elevation was 28.6, 0.76, and 1.62 cases/100 person years, respectively. 3TC/FTC + TDF (odds ratio [OR]: 6.07, confidence interval [CI]: 1.31–27.98, P = 0.015) nucleos (t) ide reverse transcriptase inhibitor backbone and male sex (OR: 18.64, CI: 2.13–162.93, P = 0.0082) were found to be significantly associated with hypertransaminasemia and creatinine elevation, respectively. The causality assessment of ADR was “possible” for all the participants. Kaplan–Meier analysis showed hyperbilirubinemia to emerge earlier (mean duration: 32.18 months, CI: 24.9–39.4 months) followed by hypertransaminasemia and creatinine elevation. Hyperbilirubinemia is an expected side effect associated with ATV/r which is benign, transient, and does not predispose to hypertransaminasemia.

Conclusion:

Our study results show that patients starting ATV/r should be counseled for a good adherence in spite of the emergence of hyperbilirubinemia which generally reverts to normal range.

Individualization of antiretroviral therapy--pharmacogenomic aspect

Combination therapy with three drug regimens for human immunodeficiency virus (HIV) infection significantly suppresses the viral replication. However, this therapeutic impact is restricted by adverse drug events and response in terms of short and long term efficacy. There are multiple factors involved in different responses to antiretrovirals (ARVs) such as age, body weight, disease status, diet and heredity. Pharmacogenomics deals with individual genetic make-up and its role in drug efficacy and toxicity. In depth genetic research has provided evidence to predict the risk of developing certain toxicities for which personalized screening and surveillance protocols may be developed to prevent side effects. Here we describe the use of pharmacogenomics for optimal use of HAART (highly active antiretroviral therapy).

A systematic review of the use of atazanavir in women infected with HIV-1

BACKGROUND

Despite increasing numbers of women with HIV worldwide, females are under-represented in clinical trials of antiretrovirals and literature addressing gender differences in clinical outcomes, treatment discontinuation, adverse events and adherence are limited. Most recommendations specific to women in current guidelines relate to pregnant women or women wishing to become pregnant. The purpose of this systematic review is to provide clinicians with an overview of available literature regarding the use of ritonavir-boosted atazanavir (ATV/r) in women.

METHODS

The online databases PubMed and EMBASE, HIV-related conference abstracts and reference lists of relevant articles were searched according to predefined terms and limited to items published from 1 October 2007 to 1 October 2012. Updates to conference presentations were checked for substantive journal publication up to 28 November 2013.

RESULTS

Of the 294 initial citations retrieved, manual selection identified 19 relevant publications describing gender-based analyses of ATV/r. Publications describing gender-based differences in efficacy, safety, tolerability, pharmacokinetics, drug-drug interactions and adherence are critically evaluated.

CONCLUSIONS

As part of a combination antiretroviral therapy regimen, ATV/r appears to be a safe, effective and durable option for treatment-naive and early treatment-experienced patients with HIV-1 infection, including non-pregnant and pregnant women.

In vitro OATP1B1 and OATP1B3 inhibition is associated with observations of benign clinical unconjugated hyperbilirubinemia

1.  Transient benign unconjugated hyperbilirubinemia has been observed clinically with several drugs including indinavir, cyclosporine, and rifamycin SV. Genome-wide association studies have shown significant association of OATP1B1 and UGT1A1 with elevations of unconjugated bilirubin, and OATP1B1 inhibition data correlated with clinical unconjugated hyperbilirubinemia for several compounds. 2.  In this study, inhibition of OATP1B3 and UGT1A1, in addition to OATP1B1, was explored to determine whether one measure offers value over the other as a potential prospective tool to predict unconjugated hyperbilirubinemia. OATP1B1 and OATP1B3-mediated transport of bilirubin was confirmed and inhibition was determined for atazanavir, rifampicin, indinavir, amprenavir, cyclosporine, rifamycin SV and saquinavir. To investigate the intrinsic inhibition by the drugs, both in vivo Fi (fraction of intrinsic inhibition) and R-value (estimated maximum in vivo inhibition) for OATP1B1, OATP1B3 and UGT1A1 were calculated. 3.  The results indicated that in vivo Fi values >0.2 or R-values >1.5 for OATP1B1 or OATP1B3, but not UGT1A1, are associated with previously reported clinical cases of drug-induced unconjugated hyperbilirubinemia. 4.  In conclusion, inhibition of OATP1B1 and/or OATP1B3 along with predicted human pharmacokinetic data could be used pre-clinically to predict potential drug-induced benign unconjugated hyperbilirubinemia in the clinic.

Effect of the UGT1A1*28 Allele on Unconjugated Hyperbilirubinemia in HIV-Positive Patients Receiving Atazanavir: A Systematic Review

OBJECTIVE

To systematically examine the literature assessing the effect of uridine 5′-diphospho-glucuronosyltransferase (UGT) 1A1*28 genetic polymorphisms on atazanavir-associated hyperbilirubinemia.

DATA SOURCES

MEDLINE (1948–November 2012), EMBASE (1980–November 2012), International Pharmaceutical Abstracts (1970–November 2012), Google, and Google Scholar were searched using combinations of the following terms: glucuronosyltransferase, glucuronosyltransferase 1A1, atazanavir, atazanavir plus ritonavir, or polymorph$. The reference lists of all identified articles were manually searched.

STUDY SELECTION AND DATA EXTRACTION

Studies were included if at least 1 group of patients received atazanavir therapy and assessed the effect of UGT1A1*28 variants on bilirubin concentrations or atazanavir discontinuation rates. The quality of each study was ranked according to the US Preventive Services Task Force 1996 classification system. Information extracted included study design, baseline characteristics, treatment regimens, UGT1A1*28 genotype frequencies, bilirubin concentrations, incidence of hyperbilirubinemia, and atazanavir discontinuation rates.

DATA SYNTHESIS

Our search produced 12 studies, of which 9 were included (6 full manuscripts [level II-2], 2 abstracts, and 1 letter to the editor [level III]). Reported UGT1A1*28 homozygote genotype frequencies (0.8–23.8%) were in general agreement with the literature for the diverse ethnic population captured in the 9 studies. An association between the incidence of hyperbilirubinemia and UGT1A1*28 genotype (homozygotes > heterozygotes > wild-type) was demonstrated in all studies that reported such data (6 of 9 studies). However, the calculated positive predictive value for homozygosity and hyperbilirubinemia from pooled data was low (40.3%). Only 2 studies (levels II-2 and III) reported rates of atazanavir discontinuation due to hyperbilirubinemia and showed some positive correlation with presence of the UGT1A1*28 allele.

CONCLUSIONS

Based on the available evidence, homozygosity of the UGT1A1*28 allele does not strongly predict the incidence of severe hyperbilirubinemia. Thus, until large, prospective trials demonstrate otherwise, UGT1A1*28 testing does not appear to provide additional information to aid clinical decision-making when initiating atazanavir treatment in HIV-infected patients.