The HIV/HCV-coinfected patient and new treatment options

Clinical use of cobicistat as a pharmacoenhancer of human immunodeficiency virus therapy

The pharmacoenhancement of plasma concentrations of protease inhibitors by coadministration of so-called boosters has been an integral part of antiretroviral therapy for human immunodeficiency virus (HIV) for 1.5 decades. Nearly all HIV protease inhibitors are combined with low-dose ritonavir or cobicistat, which are able to effectively inhibit the cytochrome-mediated metabolism of HIV protease inhibitors in the liver and thus enhance the plasma concentration and prolong the dosing interval of the antiretrovirally active combination partners. Therapies created in this way are clinically effective regimens, being convenient for patients and showing a high genetic barrier to viral resistance. In addition to ritonavir, which has been in use since 1996, cobicistat, a new pharmacoenhancer, has been approved and is widely used now. The outstanding property of cobicistat is its cytochrome P450 3A-selective inhibition of hepatic metabolism of antiretroviral drugs, in contrast with ritonavir, which not only inhibits but also induces a number of cytochrome P450 enzymes, UDP-glucuronosyltransferase, P-glycoprotein, and other cellular transporters. This article reviews the current literature, and compares the pharmacokinetics, pharmacodynamics, and safety of both pharmacoenhancers and discusses the clinical utility of cobicistat in up-to-date and future HIV therapy.

The IL28B effect on hepatitis C virus kinetics among HIV patients after the first weeks of pegylated-interferon/ribavirin treatment varies according to hepatitis C virus-1 subtype

OBJECTIVE

To evaluate the IL28B effect on hepatitis C virus (HCV) decline during first weeks of treatment according to HCV-1 subtypes.

METHODS

Patients coinfected with HIV/HCV genotype 1 and naive to peginterferon-alpha-2a and ribavirin (Peg-IFN-alpha-2a/RBV) were included. Plasma HCV-RNA was measured at baseline, and then at weeks 1, 2, and 4. HCV-1 subtype (1a or 1b) was determined. HCV viral decline was analyzed according to HCV-1 subtype between baseline and week 1, week 2 and week 4 of treatment. Additionally, we analyzed the effect of the IL28B (rs12979860) genotype on HCV viral decline with HCV-1a and HCV-1b genotype patients (CC versus non-CC).

RESULTS

Two hundred and six patients were included in the study, of whom 113 (54.8%) and 93 (45.2%) were infected by HCV-1a and 1b genotypes, respectively. No differences were found between HCV-1 subtypes in terms of HCV viral decline or rapid virological response rate. The effect of the IL28B-CC genotype on HCV viral decline was observed only among patients infected with HCV-1b at all time points analyzed (week 1: CC 1.53 ± 0.33, non-CC 0.27 ± 0.24, P <0.001; week 2: CC 1.81 ± 0.39, non-CC 0.74 ± 0.39, P = 0.002; week 4: CC 2.97 ± 0.53, non-CC 1.2 ± 0.61, P < 0.001).

CONCLUSION

Our study suggests that the effect associated with the impact of the IL28B-CC genotype on HCV decline during the first weeks of treatment with Peg-IFN-alpha-2a/RBV differs according to HCV-1 subtype and may be limited to HCV-1b patients.

Boceprevir: a protease inhibitor for the treatment of hepatitis C

BACKGROUND

Boceprevir is a protease inhibitor indicated for the treatment of chronic hepatitis C virus (HCV) genotype 1 infection in combination with peginterferon and ribavirin for treatment-naive patients and those who previously failed to improve with interferon and ribavirin treatment.

OBJECTIVE

This article provides an overview of the mechanism of action, pharmacologic and pharmacokinetic properties, clinical efficacy, and tolerability of boceprevir.

METHODS

Relevant information was identified through a search of PubMed (1990-July 2012), EMBASE (1990-July 2012), International Pharmaceutical Abstracts (1970-July 2012), and Google Scholar using the key words boceprevir, SCH 503034, non-structural protein 3 (NS3) serine protease inhibitor, and direct-acting antiviral agent (DAA). Additional information was obtained from the US Food and Drug Administration's Web site, review of the reference lists of identified articles, and posters and abstracts from scientific meetings.

RESULTS

Clinical efficacy of boceprevir was assessed in 2 Phase III trials, Serine Protease Inhibitor Therapy-2 (SPRINT-2) for treatment-naive patients and Retreatment with HCV Serine Protease Inhibitor Boceprevir and PegIntron/Rebetol 2 (RESPOND-2) for treatment-experienced patients. In SPRINT-2, patients were randomized to receive peginterferon + ribavirin (PR) or peginterferon + ribavirin + boceprevir (PRB); duration of boceprevir therapy varied from 24, 32, to 44 weeks on the basis of HCV RNA results. The primary endpoint was achievement of sustained virologic response (SVR; lower limit of detection, 9.3 IU/mL). The addition of boceprevir was shown to be superior, with overall SVR rates ranging from 63% to 66% compared with 38% with PR (P < 0.001). Results of SVR in SPRINT-2 were also reorganized to monitor SVRs in black and non-black patients. Treatment-experienced patients were assessed in RESPOND-2; however, null responders were excluded. Patients were again randomized to PR or PRB; duration of boceprevir therapy varied from 32 to 44 weeks on the basis of HCV RNA results. SVR was significantly higher in patients receiving boceprevir (59%-66% vs 21% with PR; P < 0.001). This benefit was seen in both previous nonresponders (SVR, 40%-52% vs 7% with PR), as well as previous relapsers (SVR, 69%-75% vs 29% with PR). Importantly, SVR could be attained with a shortened course of therapy in almost one half of all treated patients in SPRINT-2 (44%) and RESPOND-2 (46%).

CONCLUSIONS

Boceprevir was well tolerated in clinical trials and a welcomed addition to our HCV armamentarium.

Glances in Immunology of HIV and HCV Infection

Since the identification of HIV and HCV much progress has been made in the understanding of their life cycle and interaction with the host immune system. Despite these viruses markedly differ in their virological properties and in their pathogenesis, they share many common features in their immune escape and survival strategy. Both viruses have developed sophisticated ways to subvert and antagonize host innate and adaptive immune responses. In the last years, much effort has been done in the study of the AIDS pathogenesis and in the development of efficient treatment strategies, and a fatal infection has been transformed in a potentially chronic pathology. Much of this knowledge is now being transferred in the HCV research field, especially in the development of new drugs, although a big difference still remains between the outcome of the two infections, being HCV eradicable after treatment, whereas HIV eradication remains at present unachievable due to the establishment of reservoirs. In this review, we present current knowledge on innate and adaptive immune recognition and activation during HIV and HCV mono-infections and evasion strategies. We also discuss the genetic associations between components of the immune system, the course of infection, and the outcome of the therapies.