Capsid Assembly Modulators Have a Dual Mechanism of Action in Primary Human Hepatocytes Infected with Hepatitis B Virus

Abstract

Hepatitis B virus (HBV) capsid assembly is a critical step in the propagation of the virus and is mediated by the core protein. Due to its multiple functions in the viral life cycle, core became an attractive target for new antiviral therapies. Capsid assembly modulators (CAMs) accelerate the kinetics of capsid assembly and prevent encapsidation of the polymerase-pregenomic RNA (Pol-pgRNA) complex, thereby blocking viral replication. CAM JNJ-632 is a novel and potent inhibitor of HBV replication in vitro across genotypes A to D. It induces the formation of morphologically intact viral capsids, as demonstrated by size exclusion chromatography and electron microscopy studies. Antiviral profiling in primary human hepatocytes revealed that CAMs prevented formation of covalently closed circular DNA in a dosedependent fashion when the compound was added together with the viral inoculum, whereas nucleos(t)ide analogues (NAs) did not. This protective effect translated into a dose-dependent reduction of intracellular HBV RNA levels as well as reduced HBe/cAg and HBsAg levels in the cell culture supernatant. The same observation was made with another CAM (BAY41-4109), suggesting that mechanistic rather than compound-specific effects play a role. Our data show that CAMs have a dual mechanism of action, inhibiting early and late steps of the viral life cycle. These effects clearly differentiate CAMs from NAs and may translate into higher functional cure rates in a clinical setting when given alone or in combination with the current standard of care.

Meeting report: 31st International Conference on Antiviral Research

“…David also reported a secondary mode of action of CAMs: they efficiently (at concentrations 10× the EC 50 ) inhibit the formation of cccDNA when they are administered with the virus in animal models (Berke et al, 2017). Some CAMs inhibit the accumulation of intracellular vRNA and prevent HBeAg secretion.…”

Towards HBV curative therapies

“…Evaluation of NVR 3‐788 with PEG‐IFN in mice with humanized liver confirmed inhibition of both HBV DNA replication and HBV RNA production . Recent in vitro studies with JNJ‐632 (SBA) or Bay41‐409 (HAP) compounds in human primary hepatocytes showed that both compounds inhibited early and late steps of viral replication by (a) preventing formation of cccDNA, and (b) reducing intracellular HBV RNA levels and HBe and HBs antigens production when these compounds were added at the time of infection . Clinical studies are being conducted with 3 other potent core assembly modulators, including morphothiadine mesilate GLS4 (HAP) in phase II (HEC Pharm/Sunshie, Guangdong, China‐CFDA), JNJ56136379 in phase I (JnJ Janssen, New Brunswick, NJ, USA ‐ NCT02662712), and the first‐generation Core protein Allosteric Modifier (CpAM) in phase I Assembly Biosciences (NCT02662712).…”

Innovation and trends in the development and approval of antiviral medicines: 1987–2017 and beyond

“…The viral capsid is formed by the core protein that has multiple functions in HBV replication. CAMs accelerate the kinetics of core oligomerization and prevent encapsidation of the polymerase-pregenomic RNA, resulting in a genome-free capsid and reduction of covalently closed circular DNA (cccDNA) (Berke et al, 2017). This dual mode of action is believed to differentiate from previously approved nucleoside analogs and may be key to achieving higher functional cure rates when given alone or in combination with current standard of care.…”