Characterizing complex and competing drug-drug interactions between the antiviral regimen of glecaprevir and pibrentasvir with rifampin or carbamazepine

Pharmacokinetics of asundexian with combined CYP3A and P-gp inhibitors and an inducer: Target in vitro and in vivo studies

AIMS

Asundexian is an oral, direct and reversible inhibitor of activated factor XI (FXIa) in development for the treatment of thromboembolic events. This article summarizes results from preclinical and clinical studies, including identification of enzymes involved in asundexian pharmacokinetics, and evaluation of potential target drug-drug interactions.

METHODS

In vitro studies investigated the substrate characteristics of asundexian towards several cytochrome P450 (CYP) isoforms, hydrolytic enzymes and drug transporters. Inhibition of the amide hydrolysis of asundexian was investigated in vitro for several relevant drugs. Phase 1 studies in healthy male participants investigated the pharmacokinetics (PK) of asundexian upon co-administration of combined inhibitors or an inducer of P-gp and CYP3A4 (itraconazole, verapamil or carbamazepine, respectively, or the moderate CYP3A4 inhibitor fluconazole). The pharmacodynamic (PD) markers are activated partial thromboplastin time and FXIa inhibition.

RESULTS

Asundexian was predominantly metabolized via carboxylesterase 1 and, to a lesser extent, via CYP3A4 and is a substrate of P-gp. The asundexian area under the plasma concentration-time curve (AUC) increased by 103% and 75.6% upon combined inhibition of P-gp and strong or moderate inhibition of CYP3A4, respectively, but was unaffected by moderate CYP3A4 inhibition. Combined P-gp and CYP3A4 induction by carbamazepine decreased asundexian AUC by 44.4%. PD is concentration-dependent, thus no differences in maximum responses and recovery commensurate with PK effect(s) were observed. Adverse events were mild and asundexian was well tolerated.

CONCLUSIONS

The presented studies confirmed that CYP3A4 and P-gp contribute to asundexian metabolism and excretion. Observed effects were in line with data from a previous mass balance study.

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.

Hepatitis C virus treatment with glecaprevir and pibrentasvir in patients co-prescribed carbamazepine: Three case reports

BACKGROUND

Highly effective and well-tolerated direct-acting antiviral (DAA) therapies have revolutionised the management of hepatitis C virus (HCV); however, niche populations face treatment barriers. DAAs co-prescribed with several first-generation anti-epileptic drugs (AEDs) are contraindicated due to drug-drug interactions. A common example is carbamazepine whereby steady-state carbamazepine reduces the maximum concentration and area under the curve of velpatasvir, glecaprevir and pibrentasvir due to potent cytochrome P450 (CYP) 3A4 induction. Carbamazepine also induces P-glycoprotein which reduces glecaprevir and pibrentasvir’s area under curve to infinite time. Sofosbuvir-velpatasvir and glecaprevir-pibrentasvir are contraindicated in patients who are co-prescribed carbamazepine due to the risk of reduced DAA therapeutic effect and consequently, virological treatment failure. This presents a challenge for patients in whom carbamazepine substitution is medically unfeasible, impractical or unacceptable. However, the properties of current generation DAA therapies, including high-potency non-structural protein 5A inhibitory effect, may be sufficient to overcome reduced bioavailability arising from carbamazepine related CYP 3A4 and P-glycoprotein induction.

CASE SUMMARY

We present a case series of three patients with non-cirrhotic, treatment-naïve, genotype 1a, 1b, and 3a HCV who were treated with a 12 wk course of glecaprevir-pibrentasvir, while co-prescribed carbamazepine for seizure disorders. Glecaprevir-pibrentasvir combination therapy was chosen due to its potent in vitro activity and low barrier to pan-genotypic resistance associated variants. DAA therapy was dose-separated from carbamazepine to maximise time to peak concentration, and taken with meals to improve absorption. Sustained virological response at 12 wk was achieved in each patient with no adverse outcomes.

CONCLUSION

DAA therapies, including glecaprevir-pibrentasvir, warrant consideration as a therapeutic agent in people with HCV who are co-prescribed carbamazepine, particularly if AED substitution is not feasible.