Safely treating hepatitis C in patients with HIV or hepatitis B virus coinfection

INTRODUCTION

There are several clinical trials and prospective studies which support the use of direct-acting antiviral agents (DAAs) in hepatitis C virus (HCV)-coinfected patients. In this review, the safety of DAAs in HCV patients coinfected with hepatitis B virus (HBV) or HIV has been evaluated.

AREAS COVERED

All available prospective studies, clinical trials and congress abstracts in the English language that assessed the safety and efficacy of DAAs in HCV coinfections have been considered.

EXPERT OPINION

The newer DAAs in the treatment of HCV/HIV-coinfected patients resolved major limitations of the first-generation protease inhibitors including complex dosing, poor tolerability and interactions with antiretroviral drugs. There are not yet enough data regarding the safety and efficacy of DAAs in some coinfected patients with comorbidities, nor for pregnant, lactating or pediatric patients. Evaluating the safety and efficacy of these agents in these subgroups with HCV coinfection is recommended for future studies. The role of new direct-acting antiviral-based therapy for the treatment of patients with HCV/HBV coinfection remains to be evaluated.

ABCB11 and ABCB1 gene polymorphisms impact on telaprevir pharmacokinetic at one month of therapy

In 2011 direct-acting antivirals, including telaprevir, have been developed to achieve a better antiviral effect. It was reported that telaprevir is a substrate of P-glycoprotein (ABCB1) and cytochrome P450 3A4. The aim of this retrospective study was the evaluation of the influence of some single nucleotide polymorphisms (SNPs) of genes (ABCB1, SLC28A2/3, SLC29A1) involved in TLV and RBV transport and their correlation with plasma TLV drug exposure at 1 month of therapy. We also investigated the association of a SNP in ABCB11 gene, whose role in TLV transport was not yet shown. Twenty-nine HCV-1 patients treated with telaprevir, ribavirin and pegylated-interferon-α were retrospectively analyzed; allelic discrimination was performed by real-time PCR. Telaprevir Ctrough levels were influenced by Metavir score (P=0.023), ABCB1 2677 G>T (P=0.006), ABCB1 1236 C>T (P=0.015) and ABCB11 1131 T>C (P=0.033) SNPs. Regarding ABCB1 3435 C>T, a not statistically significant trend in telaprevir plasma concentration was observed. Metavir score (P=0.002, OR -336; 95% CI -535;-138), ABCB1 2677 (P=0.020, OR 497; 95% CI 86; 910), ABCB11 1131 (P=0.002, OR 641; 95% CI 259;1023) and CNT2 -146 (P=0.006, OR -426; 95% CI -721;-132) were able to predict telaprevir plasma levels in the regression analysis. Other SNPs showed no association. This study reveals BSEP implication in telaprevir transport and confirms the involvement and influence of P-glycoprotein on telaprevir plasma levels. To date, no similar data concerning pharmacogenetics and pharmacokinetics were published, but further studies in different and bigger cohorts are needed.

Seizures in patients with chronic hepatitis C treated with NS3/4A protease inhibitors: does pharmacological interaction play a role?

The addition of NS3/4A protease inhibitors boceprevir and telaprevir to pegylated interferon (Peg-IFN)-α and ribavirin for the treatment of hepatitis C virus (HCV) genotype 1-infected patients has led to higher rates of virological response and adverse events. Among the several side effects of interferon, neuropsychiatric symptoms have been described, particularly depression and anxiety, occurring in about 25% of patients. Although seizures have been reported in interferon-treated patients with multiple sclerosis and in a variety of malignancies, the epileptogenic potential of interferon-α in the treatment of HCV infection is considered minimal. In this report we present a new onset of seizures occurring in 2 patients during anti-HCV therapy in association with Peg-IFN, ribavirin and HCV protease inhibitors.

Telaprevir is a substrate and moderate inhibitor of P-glycoprotein, a strong inductor of ABCG2, but not an activator of PXR in vitro

Triple therapy combining the protease inhibitor telaprevir with interferon-α and ribavirin is a promising new option for long-term treatment of hepatitis C. The interaction potential of telaprevir has not yet been fully elucidated. The in vitro potency of telaprevir to inhibit P-glycoprotein (P-gp, ABCB1) and breast cancer resistance protein (BCRP, ABCG2) was assessed and its substrate characteristics for P-gp, BCRP and the multidrug resistance-associated proteins (MRPs, ABCCs) 1-3 were evaluated. The inducing properties of telaprevir on important drug-metabolising enzymes and transporters were also assessed and its ability to activate the pregnane X receptor (PXR) was investigated. Using growth inhibition assays, it was confirmed that telaprevir is a substrate of P-gp and it was demonstrated for the first time that it is not transported by BCRP and MRPs. Telaprevir only moderately inhibited P-gp in the calcein assay and did not inhibit BCRP in the pheophorbide A assay. In LS180 cells, telaprevir strongly induced mRNA expression of ABCG2 (4.3-fold at 30 μmol/L) and weakly induced ABCB11, CYP2C19 and UGT1A3. In contrast, telaprevir had no significant influence on mRNA expression of CYP3A4, UGT1A9, ABCB1, ABCC2 and SLCO1B1. In a reporter gene assay, telaprevir did not activate PXR. Thus, it appears unlikely that telaprevir induces CYP3A4 and P-gp in vivo in such a way as to provoke clinically relevant drug interactions. From the numerous perpetrator characteristics, telaprevir's inhibitor properties, especially of CYP3A4 and P-gp, appear to be the most relevant mechanism for drug interactions. The clinical relevance of the strong inducing effects on ABCG2 requires proper assessment.