Oral Selective TLR8 Agonist Selgantolimod Induces Multiple Immune Cell Responses in Humans

Advances in discovery of novel investigational agents for functional cure of chronic hepatitis B: A comprehensive review of phases II and III therapeutic agents

Chronic hepatitis B virus (HBV) infection affects over 295 million people globally and an estimated 1.6 million people in the United States. It is associated with significant morbidity and mortality due to cirrhosis, liver failure, and liver cancer. Antiviral therapy with oral nucleos(t)ide analogues is associated with high rates of virologic suppression, which in turn has been associated with a decreased risk of liver complications. However, current antiviral regimens are limited by concerns with adverse effects, adherence, resistance, long-term treatment, and ongoing risk for liver events. Novel investigational agents are currently in development and are targeted at achieving functional cure with sustained hepatitis B surface antigen (HBsAg) loss and suppression of HBV DNA. Herein we review key evidence from phases II and III trials defining the efficacy and safety profiles for key investigational agents for functional cure of chronic hepatitis B, including core/capsid inhibitors, entry inhibitors, RNA interference (siRNA/ASO), HBsAg inhibitors, Toll-like receptor agonists, checkpoint inhibitors, and therapeutic vaccines.

A genetic variant in the CD40 gene is related to HBV infection in the Chinese Han population

BACKGROUND

CD40 is an important immune costimulatory molecule that has recently been found to be associated with chronic hepatitis B. This study aims to explore the association between CD40 polymorphisms and HBV infection, as well as to investigate the impact of different rs1883832 genotypes on CD40 expression and its effect on the progression of chronic HBV infection.

METHODS

We genotyped rs1883832 in 3433 individuals using MassARRAY, and quantified the CD40 expression, including CD40 mRNA, sCD40, and mCD40. The CD40 and HBV infection indicators were assessed to investigate the potential function of rs1883832 in suppressing HBV replication in HepG2.2.15 and HepAD38, CD40L in cytotoxic t lymphocytes (CTLs) and interferon-γ, TNF-α, granzyme B, and perforin were measured to elucidate the mechanism by which CD40 inhibits HBV replication.

RESULTS

Our study revealed that the frequencies of CC genotype and C allele of rs1883832 were significantly higher in immune recovery compared to chronic hepatitis B. Individuals with CC genotype exhibited significantly elevated CD40 in serum and B cells compared to TT genotypes in chronic hepatitis B. Additionally, CD40 is capable of inhibiting HBV replication and transcription in hepatocytes by means of interaction with CD40L. A significant negative correlation was found between HBV DNA, HBeAg, and mCD40. Conversely, the expressions of ALT and mCD40 showed a positive correlation, which aligns with the trend of CD40L.

CONCLUSIONS

rs1883832 C allele may have a protective role in HBV immune recovery. This protective effect could potentially be attributed to the regulation of CD40 expression. The activation of the anti-HBV immune response, which occurs through binding CD40L on CTL, can suppress HBV DNA replication and potentially facilitate immune recovery in HBV infection.

Toll-Like Receptors 7/8: A Paradigm for the Manipulation of Immunologic Reactions for Immunotherapy

The innate immune system recognizes conserved features of viral and microbial pathogens through pattern recognition receptors (PRRs). Toll-like receptors (TLRs) are one type of PRR used by the innate immune system to mediate the secretion of proinflammatory cytokines and promote innate and adaptive immune responses. TLR family members TLR7 and TLR8 (referred to as TLR7/8 from herein) are endosomal transmembrane receptors that recognize purine-rich single-stranded RNA (ssRNA) and bacterial DNA, eliciting an immunologic reaction to pathogens. TLR7/8 were discovered to mediate the secretion of proinflammatory cytokines by activating immune cells. In addition, accumulating evidence has indicated that TLR7/8 may be closely related to numerous immune-mediated disorders, specifically several types of cancer, autoimmune disease, and viral disease. TLR7/8 agonists and antagonists, which are used as drugs or adjuvants, have been identified in preclinical studies and clinical trials as promising immune stimulators for the immunotherapy of these immune-mediated disorders. These results provided reasoning to further explore immunotherapy for the treatment of immune-mediated disorders. Nevertheless, numerous needs remain unmet, and the therapeutic effects of TLR7/8 agonists and antagonists are poor and exert strong immune-related toxicities. The present review aimed to provide an overview of the TLR family members, particularly TLR7/8, and address the underlying molecular mechanisms and clinical implications of TLR7/8 in immune-mediated disorders. The aim of the work is to discuss the underlying molecular mechanisms and clinical implications of TLR7/8 in immune-mediated disorders.

Crosstalk between TLR8 and RIG-I-like receptors enhances antiviral immune responses

Background

Toll-like receptor (TLR) agonists have been investigated due to their potential dual effects as latency reverting agents and immune modulatory compounds in people living with HIV (PLWH). Here, we investigated whether co-stimulation of TLR7/8 agonists with RIG-I-like receptor (RLR) agonists enhances antiviral immunity.

Methods

Peripheral blood mononuclear cells (PBMCs) and monocyte-derived dendritic cells (DCs) were incubated with TLR and RLR-agonists for 24 h and innate and adaptive immune responses were determined (maturation markers, cytokines in supernatant, ISG expression).

Results

Both TLR7 and TLR8 agonists induced pro-inflammatory cytokines in DCs as well as PBMCs. TLR8 agonists were more potent in inducing cytokine responses and had a stronger effect on DC-induced immunity. Notably, while all compounds induced IL-12p70, co-stimulation with TLR8 agonists and RLR agonist polyI: C induced significantly higher levels of IL-12p70 in PBMCs. Moreover, crosstalk between TLR8 and RLR agonists induced a strong type I Interferon (IFN) response as different antiviral IFN-stimulated genes were upregulated by the combination compared to the agonists alone.

Conclusion

Our data strongly suggest that TLR crosstalk with RLRs leads to strong antiviral immunity as shown by induction of IL-12 and type I IFN responses in contrast to TLRs alone. Thus, co-stimulation of TLRs and RLRs might be a powerful strategy to induce reactivation of latent reservoir as well as antiviral immunity that eliminates the reactivated cells.

Developments in pharmacotherapeutic agents for hepatitis B - how close are we to a functional cure?

INTRODUCTION

Hepatitis B virus (HBV) remains a public health concern given its global prevalence and potential complications including hepatocellular carcinoma (HCC). Current therapies, including nucleos(t)ide analogs (NA) and interferons (IFN), are effective in chronic treatment of HBV but rarely provide a functional cure due to inadequate host response and the presence of viral DNA. Therefore, novel therapies that enhance the innate immune response while suppressing DNA transcription may provide definitive treatment of HBV.

AREAS COVERED

In this review, the authors provide a brief overview of commonly used agents and their efficacy in treatment of HBV. Newer therapies with direct antiviral agents such as bepirovirsen (antisense oligonucleotide (ASO)) and entry inhibitors such as bulevirtide have shown efficacy in reducing viral load but demonstrate further reductions in conjunction with immune modulators such as therapeutic vaccines.

EXPERT OPINION

Combination therapy is far superior to monotherapy alone, necessitating the need for both immunomodulators and direct antiviral agents in chronic treatment of HBV. Therapies that target covalently closed circular (cccDNA) with immunomodulators like therapeutic vaccines have shown promising results and may ultimately achieve functional cure. However, therapies need to be evaluated in the context of the patient, considering both financial and socioeconomic factors.

Blockade of CCR4 breaks immune tolerance in chronic hepatitis B patients by modulating regulatory pathways

BACKGROUND

Immunotargets including checkpoint inhibitors and toll-like receptor 8 agonists have recently gained attention for the recovery of hepatitis B virus (HBV)-specific T cell exhaustion in chronic hepatitis B(CHB). Chemokine receptors have a similar significant role during viral infections; however, their role in CHB remains poorly understood. Therefore, in this study we evaluated the role of chemokine receptor 4 (CCR4) in deriving immunosuppression during CHB.

METHODS

We characterized CCR4+CD8+ T cells in CHB and identified their involvement in immunosuppression. Further, we examined if CCR4 blockade with mogamulizumab antibody can recover the functional exhaustion in HBsAg-specific T cells.

RESULTS

CHB patients exhibit higher frequency of CCR4+CD8+ T cells that increase with higher HBsAg levels and fibrosis scores. In vitro, HBs antigen triggers CCR4 expression. These cells express multiple inhibitory receptors and exhibit immunosuppressive functions by producing excessive immunoregulatory cytokines IL-4, IL-5, IL-10 and TGF-β1. CCR4 Blockade significantly boosted HBsAg-specific antiviral-cytokine production(IFN-γ, TNF-α and IL-21) in T cells through enhancing their proliferation capacity and polarizing these cells towards T helper 1(Th1) and T follicular helper cells(T_FH) in case of CD4 cells, and cytotoxic T cell 1(TC1) and cytotoxic T follicular(T_CF) cells in case of CD8. Cytotoxic potential was improved, while no induction of immunosuppressive-cytokines was seen after anti-CCR4 treatment thereby eliminating the risk of treatment-induced immunosuppression. CCR4 blockade inhibited the development and effector function of Tregs by controlling their expansion and TGF-β1 production preventing Tregs-induced immunotolearance.

CONCLUSIONS

CCR4 blockade reconstitutes antiviral immune response in T cells and limits the immunosuppressive functions of Tregs, representing them as a promising immunotherapeutic target for functional cure of CHB.

Targeting toll-like receptor 7/8 for immunotherapy: recent advances and prospectives

Toll-like receptors (TLRs) are a large family of proteins that are expressed in immune cells and various tumor cells. TLR7/8 are located in the intracellular endosomes, participate in tumor immune surveillance and play different roles in tumor growth. Activation of TLRs 7 and 8 triggers induction of a Th1 type innate immune response in the highly sophisticated process of innate immunity signaling with the recent research advances involving the small molecule activation of TLR 7 and 8. The wide range of expression and clinical significance of TLR7/TLR8 in different kinds of cancers have been extensively explored. TLR7/TLR8 can be used as novel diagnostic biomarkers, progression and prognostic indicators, and immunotherapeutic targets for various tumors. Although the mechanism of action of TLR7/8 in cancer immunotherapy is still incomplete, TLRs on T cells are involved in the regulation of T cell function and serve as co-stimulatory molecules and activate T cell immunity. TLR agonists can activate T cell-mediated antitumor responses with both innate and adaptive immune responses to improve tumor therapy. Recently, novel drugs of TLR7 or TLR8 agonists with different scaffolds have been developed. These agonists lead to the induction of certain cytokines and chemokines that can be applied to the treatment of some diseases and can be used as good adjutants for vaccines. Furthermore, TLR7/8 agonists as potential therapeutics for tumor-targeted immunotherapy have been developed. In this review, we summarize the recent advances in the development of immunotherapy strategies targeting TLR7/8 in patients with various cancers and chronic hepatitis B.

Oligonucleotide-Based Therapies for Chronic HBV Infection: A Primer on Biochemistry, Mechanisms and Antiviral Effects

Three types of oligonucleotide-based medicines are under clinical development for the treatment of chronic HBV infection. Antisense oligonucleotides (ASOs) and synthetic interfering RNA (siRNA) are designed to degrade HBV mRNA, and nucleic acid polymers (NAPs) stop the assembly and secretion of HBV subviral particles. Extensive clinical development of ASOs and siRNA for a variety of liver diseases has established a solid understanding of their pharmacodynamics, accumulation in different tissue types in the liver, pharmacological effects, off-target effects and how chemical modifications and delivery approaches affect these parameters. These effects are highly conserved for all ASO and siRNA used in human studies to date. The clinical assessment of several ASO and siRNA compounds in chronic HBV infection in recent years is complicated by the different delivery approaches used. Moreover, these assessments have not considered the large clinical database of ASO/siRNA function in other liver diseases and known off target effects in other viral infections. The goal of this review is to summarize the current understanding of ASO/siRNA/NAP pharmacology and integrate these concepts into current clinical results for these compounds in the treatment of chronic HBV infection.