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

Validation of a Genotype-Independent Hepatitis C Virus Near-Whole Genome Sequencing Assay

Despite the effectiveness of direct-acting antiviral agents in treating hepatitis C virus (HCV), cases of treatment failure have been associated with the emergence of resistance-associated substitutions. To better guide clinical decision-making, we developed and validated a near-whole-genome HCV genotype-independent next-generation sequencing strategy. HCV genotype 1-6 samples from direct-acting antiviral agent treatment-naïve and -treated HCV-infected individuals were included. Viral RNA was extracted using a NucliSens easyMAG and amplified using nested reverse transcription-polymerase chain reaction. Libraries were prepared using Nextera XT and sequenced on the Illumina MiSeq sequencing platform. Data were processed by an in-house pipeline (MiCall). Nucleotide consensus sequences were aligned to reference strain sequences for resistance-associated substitution identification and compared to NS3, NS5a, and NS5b sequence data obtained from a validated in-house assay optimized for HCV genotype 1. Sequencing success rates (defined as achieving >100-fold read coverage) approaching 90% were observed for most genotypes in samples with a viral load >5 log₁₀ IU/mL. This genotype-independent sequencing method resulted in >99.8% nucleotide concordance with the genotype 1-optimized method, and 100% agreement in genotype assignment with paired line probe assay-based genotypes. The assay demonstrated high intra-run repeatability and inter-run reproducibility at detecting substitutions above 2% prevalence. This study highlights the performance of a freely available laboratory and bioinformatic approach for reliable HCV genotyping and resistance-associated substitution detection regardless of genotype.

Scintigraphic evaluation of the in vivo performance of dry-coated delayed-release tablets in humans

We characterized the gastrointestinal (GI) transit and drug release characteristics of dry-coated delayed-release tablets under both prandial states in humans using a gamma scintigraphy approach. We also estimated the onset time of drug release from the dry-coated tablets after dissolution of the outer layer in a clinical study, and compared findings with those of in vitro release testing. The dry-coated tablets used in this study were composed of a core containing radiolabeled resin (111-Indium) and a gel forming outer layer made of polyethylene oxide and polyethylene glycol. The dry-coated tablets were administered to human subjects in the fasted and fed state (30 min after ingestion of a standard breakfast radiolabeled with 99m-Technetium). Gastric emptying time, small intestinal transit time, and onset of radioactivity release in the GI tract were estimated from scintigraphic imaging. Release characteristics of the radiolabel from the dry-coated tablets were also assessed in in vitro dissolution testing using a USP apparatus 2 (paddle). Ingestion of food affected the gastric emptying time of the dry-coated tablets but not small intestinal transit. Onset timing of the release of radioactivity from the core of two different formulas of dry-coated tablets was characterized. The onset timing of drug release in the fasted subjects was markedly similar to that in the in vitro dissolution testing at a paddle rate of 200 rpm.

Drug-Drug Interactions in Prostate Cancer Treatment

Polypharmacy is associated with an increased risk of drug-drug interactions (DDIs), which can cause serious and debilitating drug-induced adverse events. With a steadily aging population and associated increasing multimorbidity and polypharmacy, the potential for DDIs becomes considerably important. Prostate cancer (PCa) is the most common cancer in men and occurs mostly in elderly men in the Western world. Therefore, the aim of this review is to give an overview of DDIs in PCa therapy to better understand pharmacodynamic and pharm kinetic side effects as well as their interactions with other medications. Last, we explore potential future strategies, which might help to optimize treatment and reduce adverse events patients with polypharmacy and PCa.

Effect of D168V mutation in NS3/4A HCV protease on susceptibilities of faldaprevir and danoprevir

Hepatitis C virus (HCV) is a serious cause of liver inflammation, cirrhosis and the development of hepatocellular carcinoma. Its NS3/4A serine protease functions to cleave a specific peptide bond, which is an important step in HCV replication. Thus the NS3/4A protease has become one of the main drug-targets in the design and development of anti-HCV agents. Unfortunately, high mutation rates in HCV have been reported due to the lack of RNA proofreading activity resulting in drug resistance. Herein, all-atom molecular dynamics simulations were employed to understand and illustrate the effects of the NS3/4A D168V mutation on faldaprevir (FDV) and danoprevir (DNV) binding efficiency. The D168V mutation was shown to interrupt the hydrogen bonding network of Q80R155D168R123 embedded in the extended S2 and partial S4 subsites of the NS3 protein and as a result the R123 side chain was displaced and moved out from the binding pocket. By means of MM/PBSA and MM/GBSA binding free energy calculations, the FDV and DNV binding affinities were shown to be significantly reduced by ∼10-15 kcal mol^-1 and ∼4-9 kcal mol^-1 relative to the wild-type complexes, respectively, which somewhat agrees with the experimental resistance folds.

Direct Acting Anti-hepatitis C Virus Drugs: Clinical Pharmacology and Future Direction

Chronic hepatitis C virus (HCV) infection is a leading cause of chronic liver disease. The introduction of direct acting antiviral agents (DAAs) for its treatment represents a major advance in terms of sustained virologic response (SVR) rates and adverse effect profiles. Mechanistically, DAAs inhibit specific HCV non-structural proteins (NS) that are vital for its replication. Boceprevir, telaprevir, simeprevir, asunaprevir, grazoprevir and paritaprevir are NS3/4A inhibitors. Ombitasvir, ledipasvir, daclatasvir, elbasvir and velpatasvir are NS5A inhibitors. Sofosbuvir and dasabuvir are NS5B inhibitors. Currently, a combination of two or more DAAs is the corner stone for the treatment of HCV infection. However, the success of DAA therapy is facing several challenges, including the potential of drug-drug interactions and resistant variance. Moreover, the shortage of relevant clinical pharmacological data and drug interaction regarding DAA is a clinical concern. The present review discusses the clinical pharmacology of DAAs with special emphasis on drug-drug interaction.

Managing drug-drug interactions with new direct-acting antiviral agents in chronic hepatitis C

Several direct-acting antiviral agents (DAAs) have marketing authorization in Europe and in the USA and have changed the landscape of hepatitis C treatment: each DAA has its own metabolism and drug-drug interactions (DDIs), and managing them is a challenge. To compile the pharmacokinetics and DDI data of the new DAA and to provide a guide for management of DDI. An indexed MEDLINE search was conducted using the keywords: DAA, hepatitis C, simeprevir, daclatasvir, ledipasvir, sofosbuvir, 3D regimen (paritaprevir/ritonavir, ombitasvir, dasabuvir), DDI and pharmacokinetics. Data were also collected from hepatology, and infectious disease and clinical pharmacology conferences abstracts. Food can play a role in the absorption of DAAs. Most of the interactions are linked to metabolism (cytochrome P450-3 A4 [CYP3A4]) or hepatic and/or intestinal transporters (organic anion-transporting polypeptide and P-glycoprotein [P-gp]). To a lesser extent other pathways can be involved such as breast cancer resistance protein transporter or UDP-glucuronosyltransferase metabolism. DDI are more likely to occur with 3D regimen, daclatasvir, simeprevir and ledipasvir, as they are all both substrates and inhibitors of P-gp and/or CYP3A4, than with sofosbuvir. They can increase concentrations of coadministered drugs and their concentrations may be influenced by P-gp or CYP3A4 inducers or inhibitors. Overdosage or low dosage can be encountered with potent inducers or inhibitors of CYP3A4 or drugs with a narrow therapeutic range. The key to interpret DDI data is a good understanding of the pharmacokinetic profiles of the drugs involved. Their ability to inhibit CYP450-3A4 and transporters (hepatic and/or intestinal) can have significant clinical consequences.