ANTI CAPSID DRUGS HAP12 AND AT130 TARGET HBV CORE PROTEIN NUCLEAR FUNCTIONS

Introduction and aim: HBV core protein (Cp) represents an attractive new therapeutic target for HBV chronic infection. Cp has been shown to bind the nuclear cccDNA mini-chromosome as well as a number of cellular genes promoters. Several compounds that target Cp and HBV capsids assembly, including the hetero- aryl-dihydropyrimidines (HAPs) and the phenyl-propenamide derivatives AT61 and AT130, have been shown to inhibit HBV repli- cation in vitro and in vivo. HAPs and AT130 enhance the rate of Cp assembly and stabilize preferentially non-capsid polymers of Cp. Here we investigated the ability of the Core protein Assembly Mod- ulators (CaMPs) HAP12 and AT130 to affect both nuclear cccDNA transcription and cytoplasmic capsid assembly Cp functions. Methods: HAP12 and AT130 effects on capsid-associated HBV- DNA, cccDNA and pgRNA levels (quantitative real-time PCR with specific primers) were assessed in: (a) HBV-infected NTCP-HepG2 cells; (b) AD38 inducible HBV stable cell line. Recruitment of HBc and histone modifications on the viral minichromosome were assessed using the cccDNA ChIP assay in AD38 cells. Results: CaMPs treatments resulted in a very strong inhibition of HBV replication (>95%) and a significant but incomplete reduction of the stable cccDNA pool. A strong effect on cccDNA-dependent HBeAg production (AD38 tet-off) and pgRNA transcription (AD38 tet-off/tet-on and NTCP-HepG2 infected cells) was also demon- strated. The ability of HAP12 to target cccDNA transcription was confirmed by the reduced cccDNA-bound H3 histone acetylation and the decreased HBc occupancy on the cccDNA in induced AD38 cells. Importantly, when CaMPs treatment was started during infec- tion, cccDNA formation/accumulation was completely inhibited (>95%) and viral replication was blunted. Conclusions: Anti-capsid compounds (CpAMs) have an impact on Cp nuclear functions at multiple levels: block of new cccDNA formation/accumulation, reduction of an established cccDNA pool and inhibition of HBc occupancy and histone acetylation on the cccDNA that translate into a reduced pgRNA transcription.