Novel non-HAP class A HBV capsid assembly modulators have distinct in vitro and in vivo profiles.

IMPORTANCE: Chronic hepatitis B is the most important cause of liver cancer worldwide and affects more than 290 million people. Current treatments are mostly suppressive and rarely lead to a cure. Therefore, there is a need for novel and curative drugs that target the host or the causative agent, hepatitis B virus itself. Capsid assembly modulators are an interesting class of antiviral molecules that may one day become part of curative treatment regimens for chronic hepatitis B. Here we explore the characteristics of a particularly interesting subclass of capsid assembly modulators. These so-called non-HAP CAM-As have intriguing properties in cell culture but also clear virus-infected cells from the mouse liver in a gradual and sustained way. We believe they represent a considerable improvement over previously reported molecules and may one day be part of curative treatment combinations for chronic hepatitis B.

Class A capsid assembly modulator RG7907 clears HBV-infected hepatocytes through core-dependent hepatocyte death and proliferation.

BACKGROUND AND AIMS: Effective therapies leading to a functional cure for chronic hepatitis B are still lacking. Class A capsid assembly modulators (CAM-As) are an attractive modality to address this unmet medical need. CAM-As induce aggregation of the HBV core protein (HBc) and lead to sustained HBsAg reductions in a chronic hepatitis B mouse model. Here, we investigate the underlying mechanism of action for CAM-A compound RG7907. APPROACH AND RESULTS: RG7907 induced extensive HBc aggregation in vitro , in hepatoma cells, and in primary hepatocytes. In the adeno-associated virus (AAV)-HBV mouse model, the RG7907 treatment led to a pronounced reduction in serum HBsAg and HBeAg, concomitant with clearance of HBsAg, HBc, and AAV-HBV episome from the liver. Transient increases in alanine transaminase, hepatocyte apoptosis, and proliferation markers were observed. These processes were confirmed by RNA sequencing, which also uncovered a role for interferon alpha and gamma signaling, including the interferon-stimulated gene 15 (ISG15) pathway. Finally, the in vitro observation of CAM-A-induced HBc-dependent cell death through apoptosis established the link of HBc aggregation to in vivo loss of infected hepatocytes. CONCLUSIONS: Our study unravels a previously unknown mechanism of action for CAM-As such as RG7907 in which HBc aggregation induces cell death, resulting in hepatocyte proliferation and loss of covalently closed circular DNA or its equivalent, possibly assisted by an induced innate immune response. This represents a promising approach to attain a functional cure for chronic hepatitis B.

Aggregated Tau activates NLRP3-ASC inflammasome exacerbating exogenously seeded and non-exogenously seeded Tau pathology in vivo.

Brains of Alzheimer's disease patients are characterized by the presence of amyloid plaques and neurofibrillary tangles, both invariably associated with neuroinflammation. A crucial role for NLRP3-ASC inflammasome [NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-Apoptosis-associated speck-like protein containing a CARD (ASC)] in amyloid-beta (Aß)-induced microgliosis and Aß pathology has been unequivocally identified. Aß aggregates activate NLRP3-ASC inflammasome (Halle et al. in Nat Immunol 9:857-865, 2008) and conversely NLRP3-ASC inflammasome activation exacerbates amyloid pathology in vivo (Heneka et al. in Nature 493:674-678, 2013), including by prion-like ASC-speck cross-seeding (Venegas et al. in Nature 552:355-361, 2017). However, the link between inflammasome activation, as crucial sensor of innate immunity, and Tau remains unexplored. Here, we analyzed whether Tau aggregates acting as prion-like Tau seeds can activate NLRP3-ASC inflammasome. We demonstrate that Tau seeds activate NLRP3-ASC-dependent inflammasome in primary microglia, following microglial uptake and lysosomal sorting of Tau seeds. Next, we analyzed the role of inflammasome activation in prion-like or templated seeding of Tau pathology and found significant inhibition of exogenously seeded Tau pathology by ASC deficiency in Tau transgenic mice. We furthermore demonstrate that chronic intracerebral administration of the NLRP3 inhibitor, MCC950, inhibits exogenously seeded Tau pathology. Finally, ASC deficiency also decreased non-exogenously seeded Tau pathology in Tau transgenic mice. Overall our findings demonstrate that Tau-seeding competent, aggregated Tau activates the ASC inflammasome through the NLRP3-ASC axis, and we demonstrate an exacerbating role of the NLRP3-ASC axis on exogenously and non-exogenously seeded Tau pathology in Tau mice in vivo. The NLRP3-ASC inflammasome, which is an important sensor of innate immunity and intensively explored for its role in health and disease, hence presents as an interesting therapeutic approach to target three crucial pathogenetic processes in AD, including prion-like seeding of Tau pathology, Aß pathology and neuroinflammation.

An in vivo duck hepatitis B virus model recapitulates key aspects of nucleic acid polymer treatment outcomes in chronic hepatitis B patients.

Nucleic acid polymers (NAPs) are an attractive treatment modality for chronic hepatitis B (CHB), with REP2139 and REP2165 having shown efficacy in CHB patients. A subset of patients achieve functional cure, whereas the others exhibit a moderate response or are non-responders. NAP efficacy has been difficult to recapitulate in animal models, with the duck hepatitis B virus (DHBV) model showing some promise but remaining underexplored for NAP efficacy testing. Here we report on an optimized in vivo DHBV duck model and explore several characteristics of NAP treatment. REP2139 was efficacious in reducing DHBV DNA and DHBsAg levels in approximately half of the treated ducks, whether administered intraperitoneally or subcutaneously. Intrahepatic or serum NAP concentrations did not correlate with efficacy, nor did the appearance of anti-DHBsAg antibodies. Furthermore, NAP efficacy was only observed in experimentally infected ducks, not in endogenously infected ducks (vertical transmission). REP2139 add-on to entecavir treatment induced a deeper and more sustained virological response compared to entecavir monotherapy. Destabilized REP2165 showed a different activity profile with a more homogenous antiviral response followed by a faster rebound. In conclusion, subcutaneous administration of NAPs in the DHBV duck model provides a useful tool for in vivo evaluation of NAPs. It recapitulates many aspects of this class of compound's efficacy in CHB patients, most notably the clear division between responders and non-responders.

CSF1R inhibition rescues tau pathology and neurodegeneration in an A/T/N model with combined AD pathologies, while preserving plaque associated microglia.

Alzheimer's disease (AD) is characterized by a sequential progression of amyloid plaques (A), neurofibrillary tangles (T) and neurodegeneration (N), constituting ATN pathology. While microglia are considered key contributors to AD pathogenesis, their contribution in the combined presence of ATN pathologies remains incompletely understood. As sensors of the brain microenvironment, microglial phenotypes and contributions are importantly defined by the pathologies in the brain, indicating the need for their analysis in preclinical models that recapitulate combined ATN pathologies, besides their role in A and T models only. Here, we report a new tau-seed model in which amyloid pathology facilitates bilateral tau propagation associated with brain atrophy, thereby recapitulating robust ATN pathology. Single-cell RNA sequencing revealed that ATN pathology exacerbated microglial activation towards disease-associated microglia states, with a significant upregulation of Apoe as compared to amyloid-only models (A). Importantly, Colony-Stimulating Factor 1 Receptor inhibition preferentially eliminated non-plaque-associated versus plaque associated microglia. The preferential depletion of non-plaque-associated microglia significantly attenuated tau pathology and neuronal atrophy, indicating their detrimental role during ATN progression. Together, our data reveal the intricacies of microglial activation and their contributions to pathology in a model that recapitulates the combined ATN pathologies of AD. Our data may provide a basis for microglia-targeting therapies selectively targeting detrimental microglial populations, while conserving protective populations.