Efficacy and safety of a two-drug direct-acting antiviral agent regimen ruzasvir 180 mg and uprifosbuvir 450 mg for 12 weeks in adults with chronic hepatitis C virus genotype 1, 2, 3, 4, 5 or 6

Bemnifosbuvir (BEM, AT-527), a novel nucleotide analogue inhibitor of the hepatitis C virus NS5B polymerase

INTRODUCTION

Chronic hepatitis C virus (HCV) persists as a public health concern worldwide. Consequently, optimizing HCV therapy remains an important objective. While current therapies are generally highly effective, advanced antiviral agents are needed to maximize cure rates with potentially shorter treatment durations in a broader patient population, particularly those patients with advanced diseases who remain difficult to treat.

AREAS COVERED

This review summarizes the in vitro anti-HCV activity, preclinical pharmacological properties of bemnifosbuvir (BEM, AT-527), a novel prodrug that is metabolically converted to AT-9010, the active guanosine triphosphate analogue that potently and selectively inhibits several viral RNA polymerases, including the HCV NS5B polymerase. Results from clinical proof-of-concept and phase 2 combination studies are also discussed.

EXPERT OPINION

BEM exhibits potent pan-genotype activity against HCV, and has favorable safety, and drug interaction profiles. BEM is approximately 10-fold more potent than sofosbuvir against HCV genotypes (GT) tested in vitro. When combined with a potent NS5A inhibitor, BEM is expected to be a promising once-daily oral antiviral for chronic HCV infection of all genotypes and fibrosis stages with potentially short treatment durations.

Genotype 3-hepatitis C virus’ last line of defense

Chronic infection with hepatitis C virus (HCV) is one of the leading causes of liver disease globally, affecting approximately 71 million people. The majority of them are infected with genotype (GT) 1 but infections with GT3 are second in frequency. For many years, GT3 was considered to be less pathogenic compared to other GTs in the HCV family due to its favorable response to interferon (IFN)-based regimen. However, the growing evidence of a higher rate of steatosis, more rapid progression of liver fibrosis, and lower efficacy of antiviral treatment compared to infection with other HCV GTs has changed this conviction. This review presents the specifics of the course of GT3 infection and the development of therapeutic options for GT3-infected patients in the era of direct-acting antivirals (DAA). The way from a standard of care therapy with pegylated IFN-alpha (pegIFNα) and ribavirin (RBV) through a triple combination of pegIFNα + RBV and DAA to the highly potent IFN-free pangenotypic DAA regimens is discussed along with some treatment options which appeared to be dead ends. Although the implementation of highly effective pangenotypic regimens is the most recent stage of revolution in the treatment of GT3 infection, there is still room for improvement, especially in patients with liver cirrhosis and those who fail to respond to DAA therapies, particularly those containing inhibitors of HCV nonstructural protein 5A.

Hepatitis C genotype 4: A report on resistance-associated substitutions in NS3, NS5A, and NS5B genes

AUTHOR CONTRIBUTION

FN performed the literature review and wrote the manuscript; STZ coauthored, edited, and reviewed the manuscript.

ABSTRACT

Treatment response in Hepatitis C virus (HCV) has generated varied effects in patients. Recently, nonresponsive and relapse patients related to host and genotype variabilities have been reported in clinical trials. However, these trials included minimal sample sizes of patients with genotype 4, the most prevalent genotype in Egypt and the Middle East, compared with genotypes 1 and 2. The genetic variabilities that have been detected within the HCV genes, especially the ones associated with genotype 4, and are linked to treatment response, will be the focus of this review with emphasis on direct acting antiviral agents. In addition, the major studies and clinical trials performed globally and their inclusivity of genotype 4 are reported. This review also delineates future study areas and missing data that need further investigation when it comes to genotype 4.

Safety, pharmacokinetics and antiviral activity of AT-527, a novel purine nucleotide prodrug, in HCV-infected subjects with and without cirrhosis

AT-527 is a novel modified guanosine nucleotide prodrug inhibitor of the hepatitis C virus (HCV) NS5B polymerase, with increased in vitro antiviral activity compared to sofosbuvir and a highly differentiated favorable preclinical profile compared to other anti-HCV nucleoside/nucleotide analogs.

AT-527 is a novel modified guanosine nucleotide prodrug inhibitor of the hepatitis C virus (HCV) NS5B polymerase, with increased in vitro antiviral activity compared to sofosbuvir and a highly differentiated favorable preclinical profile compared to other anti-HCV nucleoside/nucleotide analogs. This was a multiple-part clinical study where multiple ascending doses of AT-527 up to 600 mg (expressed as AT-527 salt form; equivalent to 553 mg free base) once daily for 7 days were evaluated in a randomized, double-blind, placebo-controlled study of treatment-naive, noncirrhotic, genotype 1b, HCV-infected subjects. The highest dose of AT-527 for the same duration was then evaluated in two open-label cohorts of (i) noncirrhotic, genotype 3, HCV-infected subjects and (ii) HCV-infected subjects of any genotype with compensated (Child-Pugh A) cirrhosis. AT-527 was well tolerated for 7 days in all cohorts. At the highest dose tested, mean HCV RNA reductions of up to 2.4 log₁₀ IU/ml occurred within the first 24 h of dosing. Mean maximum reductions observed with 7 days of dosing were 4.4, 4.5, and 4.6 log₁₀ IU/ml in noncirrhotic subjects with HCV genotype 1b, noncirrhotic subjects with HCV genotype 3, and subjects with compensated cirrhosis, respectively. The systemic half-life of AT-273, the nucleoside metabolite considered a surrogate of intracellular phosphates including the active triphosphate, exceeded 20 h, supporting once-daily dosing. In summary, AT-527 demonstrated rapid, potent, dose/exposure-related, and pangenotypic antiviral activity with similar responses between subjects with and without cirrhosis. Exposure-antiviral response analysis identified 550 mg (free base equivalent) as the optimal dose of AT-527. Safety and antiviral activity data from this study warrant continued clinical development of AT-527 dosed once daily. (This study has been registered in the European Union Drug Regulating Authorities Clinical Trials Database [EudraCT] under number 2017-002148-34 and at ClinicalTrials.gov under identifier NCT03219957.)