Pharmacokinetic Interactions Between the Fixed-Dose Combinations of Elvitegravir/Cobicistat/Tenofovir Disoproxil Fumarate/Emtricitabine and Elbasvir/Grazoprevir in Healthy Adult Participants

Mechanisms and Clinical Significance of Pharmacokinetic Drug Interactions Mediated by FDA and EMA-approved Hepatitis C Direct-Acting Antiviral Agents

The treatment of patients infected with the hepatitis C virus (HCV) has been revolutionised by the development of direct-acting antiviral agents (DAAs) that target specific HCV proteins involved in viral replication. The first DAAs were associated with clinical problems such as adverse drug reactions and pharmacokinetic drug-drug interactions (DDIs). Current FDA/EMA-approved treatments are combinations of DAAs that simultaneously target the HCV N5A-protein, the HCV N5B-polymerase and the HCV NS3/4A-protease. Adverse events and DDIs are less likely with these DAA combinations but several DDIs of potential clinical significance remain. Much of the available information on the interaction of DAAs with CYP drug-metabolising enzymes and influx and efflux transporters is contained in regulatory summaries and is focused on DDIs of likely clinical importance. Important DDIs perpetrated by current DAAs include increases in the pharmacokinetic exposure to statins and dabigatran. Some mechanistic information can be deduced. Although the free concentrations of DAAs in serum are very low, a number of these DDIs are likely mediated by the inhibition of systemic influx transporters, especially OATP1B1/1B3. Other DDIs may arise by DAA-mediated inhibition of intestinal efflux transporters, which increases the systemic concentrations of some coadministered drugs. Conversely, DAAs are victims of DDIs mediated by cyclosporin, ketoconazole, omeprazole and HIV antiretroviral drug combinations, especially when boosted by ritonavir and, to a lesser extent, cobicistat. In addition, concurrent administration of inducers, such as rifampicin, carbamazepine and efavirenz, decreases exposure to some DAAs. Drug-drug interactions that increase the accumulation of HCV N3/4A-protease inhibitors like grazoprevir may exacerbate hepatic injury in HCV patients.

Comorbidities and concomitant medications in patients with chronic hepatitis C virus infection receiving second-generation direct-acting antiviral regimens in Belgium: an observational study

Objective

To describe comorbidities and concomitant medications in patients initiating treatment for hepatitis C virus (HCV) infection with direct-acting antiviral (DAA) regimens in Belgium.

Methods

This was a noninterventional, observational, multicenter study of data from patient charts. Adult patients with HCV infection receiving second-generation DAA therapy were included. Comorbidities were assessed at the time of HCV treatment initiation. Concomitant medications were recorded at the time of diagnosis and at treatment initiation. Potential clinically relevant drug-drug interactions (DDIs) were assessed based on information available at www.hep-druginteractions.org. The primary objective was to describe concomitant medication use ; secondary objectives were to describe modifications in concomitant therapies and comorbidities.

Results

405 patients were included. A total of 956 comorbidities were reported by 362 patients (median, 2 ; range, 0-15). The most common comorbidities were hypertension (27.2%) ; HIV coinfection (22.5%), and type 2 diabetes mellitus (14.3%). Overall, 1455 concomitant medications were being taken by 365 patients (90.1% ; median, 3 ; range 0-16). The most common concomitant medications were psycholeptics (28.6%), antiviral agents (24.2%), and medications for acid-related disorders (21.0%) Overall, 74/365 (20.3%) patients receiving a concomitant medication required an adaptation to their concomitant medication. The medications that most frequently required change were drugs for acid-related disorders (n = 14) and antiviral drugs (n = 5) ; those that were most frequently stopped were lipid-modifying drugs (n = 25) and drugs for acid-related disorders (n = 13).

Conclusion

Physicians are aware of the potential for DDIs with DAAs, but improved alignment between clinical practice and theoretical recommendations is required.