Lack of a clinically significant drug-drug interaction in healthy volunteers between the HCV protease inhibitor boceprevir and the proton pump inhibitor omeprazole

Clinical pharmacology profile of boceprevir, a hepatitis C virus NS3 protease inhibitor: focus on drug-drug interactions

Boceprevir is a potent, orally administered ketoamide inhibitor that targets the active site of the hepatitis C virus (HCV) non-structural (NS) 3 protease. The addition of boceprevir to peginterferon plus ribavirin resulted in higher rates of sustained virologic response (SVR) than for peginterferon plus ribavirin alone in phase III studies in both previously treated and untreated patients with HCV infection. Because boceprevir is metabolized by metabolic routes common to many other drugs, and is an inhibitor of cytochrome P450 (CYP) 3A4/5, there is a high potential for drug-drug interactions when boceprevir is administered with other therapies, particularly when treating patients with chronic HCV infection who are often receiving other medications concomitantly. Boceprevir is no longer widely used in the US or EU due to the introduction of second-generation treatments for HCV infection. However, in many other geographic regions, first-generation protease inhibitors such as boceprevir continue to form an important treatment option for patients with HCV infection. This review summarizes the interactions between boceprevir and other therapeutic agents commonly used in this patient population, indicating dose adjustment requirements where needed. Most drug interactions do not affect boceprevir plasma concentrations to a clinically meaningful extent, and thus efficacy is likely to be maintained when boceprevir is coadministered with the majority of other therapeutics. Overall, the drug-drug interaction profile of boceprevir suggests that this agent is suitable for use in a wide range of HCV-infected patients receiving concomitant therapies.

Drug interactions and protease inhibitors used in the treatment of hepatitis C: how to manage?

PURPOSE

The first-generation protease inhibitors (PI) boceprevir and telaprevir combined with pegylated interferon have revolutionized the treatment of type-1 hepatitis C by increasing the rates of sustained virologic response. However, they induce drug interactions, and their clinical relevance is difficult to predict. This review compiles available data on drug-drug interactions (DDI) based on their pharmacokinetic and pharmacodynamic properties with the aim of assisting clinicians in managing DDI METHODS: PubMed, drug interaction databases and hepatology and infectious disease conference abstracts were systematically searched using the key search terms "interaction", "hepatitis C", "telaprevir" and "boceprevir". All known interactions were compiled and reclassified according to their pharmacokinetic and pharmacodynamic mechanisms. The state of knowledge of interaction mechanisms are reported and a therapeutic approach is proposed.

RESULTS

Boceprevir and telaprevir are both substrates and potent inhibitors of cytochrome P450 3A4 and the drug transporter P-glycoprotein. They induce overdosage but can sometimes decrease the effect of other drugs by inducing other cytochromes. Overdosage or low dosage mainly affects drugs with a narrow therapeutic range, such as immunosuppressants or antiretrovirals. The distribution and elimination of PI are unaffected by interactions. In terms of pharmacodynamic interactions, PI can trigger drug-induced QT interval prolongation, which means that clinicians should manage such risk factors as potassium/magnesium levels or avoid other QT-prolonging drugs.

CONCLUSIONS

Management of hepatitis C therapy is complex. The key to interpreting DDI data is a solid understanding of the pharmacokinetic and pharmacodynamic profiles of the drugs involved. Their ability to inhibit cytochrome P450 3A4 and prolong the QT interval can have significant clinical consequences. This review provides a practical guide to the safe and effective management of therapy with boceprevir and telaprevir.

Priapism induced by boceprevir-CYP3A4 inhibition and α-adrenergic blockade: case report

A 44-year-old white man presented to the emergency department with a 3-day history of priapism requiring a surgically performed distal penile shunt. A drug-drug interaction is the suspected cause whereby CYP3A4 inhibition by boceprevir led to increased exposures of doxazosin, tamsulosin, and/or quetiapine, resulting in additional α-adrenergic blockade.

Drug-drug interactions during antiviral therapy for chronic hepatitis C

The emergence of direct-acting antiviral agents (DAAs) for HCV infection represents a major advance in treatment. The NS3 protease inhibitors, boceprevir and telaprevir, were the first DAAs to receive regulatory approval. When combined with PEG-IFN and ribavirin, these agents increase rates of sustained virologic response in HCV genotype 1 to ∼70%. However, this treatment regimen is associated with several toxicities. In addition, both boceprevir and telaprevir are substrates for and inhibitors of the drug transporter P-glycoprotein and the cytochrome P450 enzyme 3A4 and are, therefore, prone to clinically relevant drug interactions. Several new DAAs for HCV are in late stages of clinical development and are likely to be approved in the near future. These include the protease inhibitors, simeprevir and faldaprevir, the NS5A inhibitor, daclatasvir, and the nucleotide polymerase inhibitor, sofosbuvir. Herein, we review the clinical pharmacology and drug interactions of boceprevir, telaprevir and these investigational DAAs. Although boceprevir and telaprevir are involved in many interactions, these interactions are manageable if health-care providers proactively identify and adjust treatments. Emerging DAAs seem to have a reduced potential for drug interactions, which will facilitate their use in the treatment of HCV.