Drug delivery systems and liver targeting for the improved pharmacotherapy of the hepatitis B virus (HBV) infection

Advances in Nanoparticle Drug Delivery Systems for Anti-Hepatitis B Virus Therapy: A Narrative Review

Chronic hepatitis B (CHB) is an infectious viral disease that is prevalent worldwide. Traditional nucleoside analogues, as well as the novel drug targets against hepatitis B virus (HBV), are associated with certain critical factors that influence the curative effect, such as biological stability and safety, effective drug delivery, and controlled release. Nanoparticle drug delivery systems have significant advantages and have provided a basis for the development of anti-HBV strategies. In this review, we aim to review the advances in nanoparticle drug delivery systems for anti-hepatitis B virus therapy by summarizing the relevant literature. First, we focus on the characteristics of nanoparticle drug delivery systems for anti-HBV therapy. Second, we discuss the nanoparticle delivery systems for anti-HBV nucleoside drugs, gene-based drugs, and vaccines. Lastly, we provide an overview of the prospects for nanoparticle-based anti-HBV agents.

Design, synthesis, and biological evaluation of novel 2'-deoxy-2'-fluoro-2'-C-methyl 8-azanebularine derivatives as potent anti-HBV agents

Hepatitis B virus (HBV) is a global health problem requiring more efficient and better tolerated anti-HBV agent. In this paper, a series of novel 2'-deoxy-2'-fluoro-2'-C-methyl-β-d-arabinofuranosyl 8-azanebularine analogues (1 and 2a) and N⁴-substituted 8-azaadenosine derivatives (2b-g) were designed, synthesized and screened for in vitro anti-HBV activity. Two concise and practical synthetic routes were developed toward the structural motif construction of 2'-deoxy-2'-fluoro-2'-C-methyl-β-d-arabinofuranosyl 8-azainosine from the ribonolactone 3 under mild conditions. The in vitro anti-HBV screening results showed that these 8-azanebularine analogues had a significant inhibitory effect on the expression of HBV antigens and HBV DNA at a concentration of 20 μM. Among them, halogen-substituted 8-azaadenosine derivative 2g displayed activities comparable to that of 3TC. In particular, 2g retained excellent activity against lamivudine-resistant HBV mutants.

Liver-Targeted Co-delivery of Entecavir and Glycyrrhetinic Acid Based on Albumin Nanoparticle To Enhance the Accumulation of Entecavir

Hepatitis B, one of the most common contagious viral hepatitis with high infection rate, is challenging to treat. Although the treatment for hepatitis B has been improved over the years, many therapeutic drugs still have either severe adverse effects or insufficient effectiveness via systemic administration. In this study, we confirmed that glycyrrhetinic acid can enhance the accumulation of entecavir in HepaRG cell and liver. Then we constructed a novel albumin nanoparticle co-loading entecavir and glycyrrhetinic acid (ETV-GA-AN) to improve liver accumulation of entecavir and investigated its ability to deliver both drugs to liver. In vitro cellular uptake study and in vivo tissue distribution experiment showed that these negatively charged ETV-GA-AN (112 ± 2 nm in diameter) can increase the accumulation of entecavir in hepatic HepaRG cells and improve entecavir distribution in liver. We also revealed the mechanism that glycyrrhetinic acid enhances intracellular accumulation of entecavir by inhibiting the activity of specific efflux transporters. Our delivery system is the first liver-targeted albumin nanoparticle that utilizes the site-specific co-delivery strategy to delivery entecavir and glycyrrhetinic acid. As it combines high efficiency and low toxicity, it possess great potential for treating hepatitis B.

Drug Delivery Strategies for Antivirals against Hepatitis B Virus

Chronic hepatitis B virus (HBV) infection poses a significant health challenge due to associated morbidity and mortality from cirrhosis and hepatocellular cancer that eventually results in the breakdown of liver functionality. Nanotechnology has the potential to play a pivotal role in reducing viral load levels and drug-resistant HBV through drug targeting, thus reducing the rate of evolution of the disease. Apart from tissue targeting, intracellular delivery of a wide range of drugs is necessary to exert a therapeutic action in the affected organelles. This review encompasses the strategies and techniques that have been utilized to target the HBV-infected nuclei in liver hepatocytes, with a significant look at the new insights and most recent advances in drug carriers and their role in anti-HBV therapy.

Targeting hepatitis B virus cccDNA by CRISPR/Cas9 nuclease efficiently inhibits viral replication

Chronic hepatitis B virus (HBV) infection causes liver cirrhosis and hepatocellular carcinoma and remains a serious health problem worldwide. Covalently closed circular DNA (cccDNA) in the liver cell nucleus sustains HBV infection. Major treatments for HBV infection include the use of interferon-α and nucleotide analogs, but they cannot eradicate cccDNA. As a novel tool for genome editing, clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system developed from bacteria can be used to accurately and efficiently engineer and modify genomic DNA. In this study, the CRISPR/Cas9 system was used to target the HBV genome and efficiently inhibit HBV infection. We synthesized four single-guide RNAs (sgRNAs) targeting the conserved regions of HBV. The expression of these sgRNAS with Cas9 reduced the viral production in Huh7 cells as well as in HBV-replication cell HepG2.2.15. We further demonstrated that CRISPR/Cas9 direct cleavage and cleavage-mediated mutagenesis occurred in HBV cccDNA of transfected cells. In the new mouse model carrying HBV cccDNA, injection of sgRNA-Cas9 plasmids via rapid tail vein resulted in the low level of cccDNA and HBV protein. In conclusion, the designed CRISPR/Cas9 system can accurately and efficiently target HBV cccDNA and inhibit HBV replication. This system may be used as a novel therapeutic strategy against chronic HBV infection.

Hepatocellular carcinoma and multidrug resistance: Past, present and new challenges for therapy improvement

Hepatocellular carcinoma (HCC) is the most frequent form of liver cancer and the third most common cause of cancer-related death in the world. The main risk factor worldwide for this type of malignancy is chronic hepatitis caused by hepatitis B virus and hepatitis C virus infections. Advances in early detection and treatment have improved life expectancy of patients with HCC. However, this disorder remains as a disease with poor prognosis. In fact, epidemiological studies have revealed that there is an 8-mo median survival rate in patients, approximately 20% of whom survive one year while only 5% remain alive after three years. Additionally, HCC is particularly difficult to treat because of its high recurrence rate, and its resistance to conventional chemotherapy is due, among other mechanisms, to several members of the ATP-Binding Cassette protein family involved in drug transport being overexpressed. Fortunately, there is evidence that these patients may benefit from alternative molecular-targeted therapies. This manuscript intends to provide further insight into the etiology and molecular mechanisms related to HCC development and the latest therapeutic approaches to treat this malignancy. The development of effective delivery systems of antitumor drugs able to target the liver parenchyma is also assessed. Finally, the prospects in the development of more efficient drug therapies to overcome multidrug resistance are also examined.

Reversal of multidrug resistance by the inhibition of ATP-binding cassette pumps employing "Generally Recognized As Safe" (GRAS) nanopharmaceuticals: A review

Pumps of the ATP-binding cassette superfamily (ABCs) regulate the access of drugs to the intracellular space. In this context, the overexpression of ABCs is a well-known mechanism of multidrug resistance (MDR) in cancer and infectious diseases (e.g., viral hepatitis and the human immunodeficiency virus) and is associated with therapeutic failure. Since their discovery, ABCs have emerged as attractive therapeutic targets and the search of compounds that inhibit their genetic expression and/or their functional activity has gained growing interest. Different generations of pharmacological ABC inhibitors have been explored over the last four decades to address resistance in cancer, though clinical results have been somehow disappointing. "Generally Recognized As Safe" (GRAS) is a U.S. Food and Drug Administration designation for substances that are accepted as safe for addition in food. Far from being "inert", some amphiphilic excipients used in the production of pharmaceutical products have been shown to inhibit the activity of ABCs in MDR tumors, emerging as a clinically translatable approach to overcome resistance. The present article initially overviews the classification, structure and function of the different ABCs, with emphasis on those pumps related to drug resistance. Then, the different attempts to capitalize on the activity of GRAS nanopharmaceuticals as ABC inhibitors are discussed.

An efficient antiviral strategy for targeting hepatitis B virus genome using transcription activator-like effector nucleases

The hepatitis B virus (HBV) is a DNA virus that can cause chronic hepatitis B (CHB) in humans. Current therapies for CHB infection are limited in efficacy and do not target the pre-existing viral genomic DNA, which are present in the nucleus as a covalently closed circular DNA (cccDNA) form. The transcription activator-like (TAL) effector nucleases (TALENs) are newly developed enzymes that can cleave sequence-specific DNA targets. Here, TALENs targeting the conserved regions of the viral genomic DNA among different HBV genotypes were constructed. The expression of TALENs in Huh7 cells transfected with monomeric linear full-length HBV DNA significantly reduced the viral production of HBeAg, HBsAg, HBcAg, and pgRNA, resulted in a decreased cccDNA level and misrepaired cccDNAs without apparent cytotoxic effects. The anti-HBV effect of TALENs was further demonstrated in a hydrodynamic injection-based mouse model. In addition, an enhanced antiviral effect with combinations of TALENs and interferon-α (IFN-α) treatment was observed and expression of TALENs restored HBV suppressed IFN-stimulated response element-directed transcription. Taken together, these data indicate that TALENs can specifically target and successfully inactivate the HBV genome and are potently synergistic with IFN-α, thus providing a potential therapeutic strategy for treating CHB infection.

Medical management of chronic liver diseases in children (part I): focus on curable or potentially curable diseases

The management of children with chronic liver disease (CLD) mandates a multidisciplinary approach. CLDs can be classified into 'potentially' curable, treatable non-curable, and end-stage diseases. Goals pertaining to the management of CLDs can be divided into prevention or minimization of progressive liver damage in curable CLD by treating the primary cause; prevention or control of complications in treatable CLD; and prediction of the outcome in end-stage CLD in order to deliver definitive therapy by surgical procedures, including liver transplantation. Curative, specific therapies aimed at the primary causes of CLDs are, if possible, best considered by a pediatric hepatologist. Medical management of CLDs in children will be reviewed in two parts, with part I (this article) specifically focusing on 'potentially' curable CLDs. Dietary modification is the cornerstone of management for galactosemia, hereditary fructose intolerance, and certain glycogen storage diseases, as well as non-alcoholic steatohepatitis. It is also essential in tyrosinemia, in addition to nitisinone [2-(nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione] therapy, as well as in Wilson disease along with copper-chelating agents such as D-penicillamine, triethylenetetramine dihydrochloride, and ammonium tetrathiomolybdate. Zinc and antioxidants are adjuvant drugs in Wilson disease. New advances in chronic viral hepatitis have been made with the advent of oral antivirals. In children, currently available drugs for the treatment of chronic hepatitis B virus infection are standard interferon (IFN)-α-2, pegylated IFN-α-2 (PG-IFN), and lamivudine. In adults, adefovir and entecavir have also been licensed, whereas telbivudine, emtricitabine, tenofovir disoproxil fumarate, clevudine, and thymosin α-1 are currently undergoing clinical testing. For chronic hepatitis C virus infection, the most accepted treatment is PG-IFN plus ribavirin. Corticosteroids, with or without azathioprine, remain the basic strategy for inducing remission in autoimmune hepatitis. Ciclosporin (cyclosporine) and other immune suppressants may be used for patients who do not achieve remission, or who have significant side effects, with corticosteroid/azathioprine therapy. The above therapies can prevent, or at least minimize, progression of liver damage, particularly if started early, leading to an almost normal quality of life in affected children.

Poloxamines display a multiple inhibitory activity of ATP-binding cassette (ABC) transporters in cancer cell lines

Primary hepatocellular carcinoma is the third most common fatal cancer worldwide with more than 500,000 annual deaths. Approximately 40% of the patients with HCC showed tumoral overexpression of transmembrane proteins belonging to the ATP-binding cassette protein superfamily (ABC) which pump drugs out of cells. The overexpression of these efflux transporters confers on the cells a multiple drug resistance phenotype, which is considered a crucial cause of treatment refractoriness in patients with cancer. The aim of this study was to investigate the inhibitory effect of different concentrations of pH- and temperature-responsive X-shaped poly(ethylene oxide)-poly(propylene oxide) block copolymers (poloxamines, Tetronic, PEO-PPO) showing a wide range of molecular weights and EO/PO ratios on the functional activity of three different ABC proteins, namely P-glycoprotein (P-gp or MDR1), breast cancer resistance protein (BCRP), and multidrug resistance-associated protein MRP1, in two human hepatocarcinoma cell lines, HepG2 and Huh7. First, the cytotoxicity of the different copolymers (at different concentrations) on both liver carcinoma cell lines was thoroughly evaluated by means of apoptosis analysis using annexin V and propidium iodide (PI). Thus, viable cells (AV-/PI-), early apoptotic cells (AV+/PI-) and late apoptotic cells (V-FITC+/PI+) were identified. Results pointed out copolymers of intermediate to high hydrophobicity and intermediate molecular weight (e.g., T904) as the most cytotoxic. Then, DiOC2, rhodamine 123 and vinblastine were used as differential substrates of these pumps. HeLa, an epithelial cell line of human cervical cancer that does not express P-gp, was used exclusively as a control and enabled the discerning between P-gp and MRP1 inhibition. Moderate to highly hydrophobic poloxamines T304, T904 and T1301 showed inhibitory activity against P-gp and BCRP but not against MRP1 in both hepatic cell lines. A remarkable dependence of this effect on the copolymer concentration and hydrophobicity was found. No inhibitory effect against these ABC pumps was observed with the hydrophilic T1107. These findings further evidence the potential usefulness of these Trojan horses as both drug nanocarriers and ABC inhibitors in hepatic MDR tumors and infections that involve the activity of these efflux transporters.

Quantitative measurement of serum hepatitis B surface antigen using an immunoradiometric assay in chronic hepatitis B

PURPOSE

Measurement of serum hepatitis B virus surface antigen (HBsAg) levels is important for the management of chronic hepatitis B patients in terms of monitoring response to antiviral therapy. This study aimed to evaluate the diagnostic performance of a new diagnostic kit, which quantitatively measures serum HBsAg level using an immunoradiometric assay (IRMA)-based method. Measurements were compared with those obtained using a chemiluminescent microparticle immunoassay (CMIA)-based method.

METHODS

The blood samples of 96 patients with chronic hepatitis B were used in this study. Copy numbers of serum hepatitis B virus (HBV) DNA were determined in 23 of these samples. The correlation between and the concordance of IRMA and CMIA results were determined using Pearson's correlation coefficients. P values of 0.05 were considered to be statistically significant throughout.

RESULTS

Laboratory diagnoses based on IRMA were wholly in agreement with those based on CMIA. Furthermore, serum HBsAg levels by IRMA were found to be highly correlated with those determined by CMIA (correlation coefficient R (2) = 0.838, p < 0.001). Serum HBsAg level and serum HBV DNA copies were found to be linearly related by both methods (R (2) = 0.067, p = 0.316 by IRMA, and R (2) = 0.101, p = 0.215 by CMIA).

CONCLUSION

The diagnostic performance of the investigated IRMA method of determining HBsAg levels was found to be comparable with that of a CMIA-based method in chronic hepatitis B patients.