Addressing the global burden of hepatitis B virus while developing long-acting injectables for the prevention and treatment of HIV

Prospects for Controlling Hepatitis B Globally

Infection with the hepatitis B virus (HBV) is highly prevalent globally. Over 250 million people suffer from chronic hepatitis B, and more than 800,000 patients die each year due to hepatitis B complications, including liver cancer. Although protective HBV vaccines are recommended for all newborns, global coverage is suboptimal. In adults, sexual transmission is by far the most frequent route of contagion. The WHO estimates that 1.5 million new HBV infections occur annually. Oral nucleos(t)ide analogues entecavir and tenofovir are the most frequent antivirals prescribed as HBV therapy. Almost all patients adherent to the medication achieve undetectable plasma viremia beyond 6 months of monotherapy. However, less than 5% achieve anti-HBs seroconversion, and viral rebound occurs following drug discontinuation. Therefore, nucleos(t)ide analogues need to be lifelong. New long-acting formulations of tenofovir and entecavir are being developed that will maximize treatment benefit and overcome adherence barriers. Furthermore, new antiviral agents are in development, including entry inhibitors, capside assembly modulators, and RNA interference molecules. The use of combination therapy pursues a functional HBV cure, meaning it is negative for both circulating HBV-DNA and HBsAg. Even when this goal is achieved, the cccDNA reservoir within infected hepatocytes remains a signal of past infection, and HBV can reactivate under immune suppression. Therefore, new gene therapies, including gene editing, are eagerly being pursued to silence or definitively disrupt HBV genomes within infected hepatocytes and, in this way, ultimately cure hepatitis B. At this time, three actions can be taken to push HBV eradication globally: (1) expand universal newborn HBV vaccination; (2) perform once-in-life testing of all adults to identify susceptible HBV persons that could be vaccinated (or re-vaccinated) and unveil asymptomatic carriers that could benefit from treatment; and (3) provide earlier antiviral therapy to chronic HBV carriers, as being aviremic reduces the risk of both clinical progression and transmission.

What does the scale-up of long-acting HIV pre-exposure prophylaxis mean for the global hepatitis B epidemic?

INTRODUCTION

The HIV and hepatitis B virus (HBV) epidemics are interconnected with shared routes of transmission and specific antiviral drugs that are effective against both viruses. Nearly, 300 million people around the world live with chronic HBV, many of whom are from priority populations who could benefit from HIV prevention services. Oral pre-exposure prophylaxis (PrEP) for HIV has implications in the prevention and treatment of HBV infection, but many people at increased risk of HIV acquisition may instead prefer long-acting formulations of PrEP, which are currently not active against HBV.

DISCUSSION

People at increased risk for HIV acquisition may also be at risk for or already be living with HBV infection. Oral PrEP with tenofovir is effective in preventing both HIV and HBV, and tenofovir is also the recommended treatment for chronic HBV infection. Although implementation of oral PrEP has been challenging in sub-Saharan Africa, investments in its scale-up could secondarily reduce the clinical impact of HBV. Long-acting PrEP, including injectable medicines and implantable rings, may overcome some of the implementation challenges associated with oral PrEP, such as daily pill burden, adherence challenges and stigma; however, current formulations of long-acting PrEP do not have activity against HBV replication. Ideally, PrEP programmes would offer both oral and long-acting formulations with HBV screening to optimize HIV prevention services and HBV prevention and care, when appropriate. People who are not immune to HBV would benefit from being vaccinated against HBV before initiating long-acting PrEP. People who remain non-immune to HBV despite vaccination may benefit from being offered oral, tenofovir-based PrEP given its potential for HBV PrEP. People using PrEP and living with HBV who are not linked to dedicated HBV care would also benefit from laboratory monitoring at PrEP sites to ensure safety when using and after stopping tenofovir. PrEP programmes are ideal venues to offer HBV screening, HBV vaccination for people who are non-immune and treatment with tenofovir-based PrEP for people with indications for HBV therapy.

CONCLUSIONS

Long-acting PrEP holds promise for reducing HIV incidence, but its implications for the HBV epidemic, particularly in sub-Saharan Africa, should not be overlooked.

Treatment of hepatitis delta and HIV infection

Hepatitis delta virus (HDV) is a defective agent that only infects individuals with hepatitis B virus (HBV). Around 5-10% of chronic hepatitis B patients worldwide are superinfected with HDV, which means 15-25 million people. Hepatitis delta is the most severe of all chronic viral hepatitis, leading to cirrhosis, liver cancer and/or transplantation in most patients. Despite it, many HDV patients remain undiagnosed. The only treatment available until recently was peginterferon alfa, with poor results and significant side effects. The recent approval of bulevirtide, a lipopeptide that blocks HBV/HDV entry, has revolutionized the field. Another drug, lonafarnib, already approved to treat progeria, is expected to be available soon as HDV therapy. Since there is no cell reservoir for the HDV RNA genome, hypothetically viral clearance could be achieved if complete blocking of viral replication occurs for a minimum time frame. This is what happens in hepatitis C using direct-acting antivirals, with the achievement of cure in nearly all treated patients. We envision the cure of hepatitis delta using combination antiviral therapy. Given that sexual and parenteral transmission routes are the most frequent for the acquisition of HBV and HDV, shared with HIV infection and HBV/HDV and HIV coinfection. The clinical outcome of hepatitis delta is worst in the HIV setting, with more frequent liver complications. Since most persons infected with HIV are on regular health care follow-up, we propose that HIV-HDV patients should be prioritized for moving forward new and potentially curative treatments for hepatitis delta.

Immune Responses to HBV Vaccine in People Living with HIV (PLWHs) Who Achieved Successful Treatment: A Prospective Cohort Study

BACKGROUND

Understanding immune responses after HBV vaccination is important to prevent HBV infection in PLWH and to achieve successful treatment.

METHODS

Thirty-two PLWHs with CD4⁺ cell count > 350 cells/µL and HIV RNA < 200 copies/mL were vaccinated with 20 µg of HBV vaccine at weeks 0, 4, and 24 in this prospective study. We measured total HIV DNA levels, HBsAb titers and HBsAg-specific T-cell responses during follow-up time.

RESULTS

All patients achieved protective HBsAb titer after immunization. The magnitude of the IFN-r and TNF-a response to HBsAg was 22.0 (IQR: 6.5-65.0) and 106.50 (IQR: 58.5-203.0) spot-forming cells (SFC)/10⁵ PBMC, respectively at week 0. The level of IFN-r secreted at weeks 12 and weeks 36 to 48 was comparable with that at week 0. However, IFN-r response was higher at weeks 12 than that at weeks 36 to 48 (p = 0.02). The level of TNF-a secreted at weeks 12 was higher than that at week 0 (p < 0.001). Total HIV DNA levels were 2.76 (IQR: 2.47-3.07), 2.77 (IQR: 2.50-3.09), 2.77 (IQR: 2.41-2.89) log₁₀ copies/10⁶ PBMCs at weeks 0, 12, 36 to 48, respectively. No correlation was observed between IFN-r and TNF-a levels and HBsAb titer as well as total HIV DNA levels after immunization.

CONCLUSION

Humoral immunity was satisfactory, but cellular immunity and decline in HIV reservoir were not optimal after HBV vaccine immunization in these patients.

Antiviral supramolecular polymeric hydrogels by self-assembly of tenofovir-bearing peptide amphiphiles

The development of long-acting antiviral therapeutic delivery systems is crucial to improve the current treatment and prevention of HIV and chronic HBV. We report here on the conjugation of tenofovir (TFV), an FDA approved nucleotide reverse transcriptase inhibitor (NRTI), to rationally designed peptide amphiphiles (PAs), to construct antiviral prodrug hydrogelators (TFV-PAs). The resultant conjugates can self-assemble into one-dimensional nanostructures in aqueous environments and consequently undergo rapid gelation upon injection into 1× PBS solution to create a drug depot. The TFV-PA designs containing two or three valines could attain instantaneous gelation, with one displaying sustained release for more than 28 days in vitro. Our studies suggest that minor changes in peptide design can result in differences in supramolecular morphology and structural stability, which impacted in vitro gelation and release. We envision the use of this system as an important delivery platform for the sustained, linear release of TFV at rates that can be precisely tuned to attain therapeutically relevant TFV plasma concentrations.

Safety considerations in the management of hepatitis C and HIV co-infection

INTRODUCTION

Both HCV and HIV are highly prevalent infections with current estimates of 57 and 38 million people infected worldwide, respectively. Oral antivirals can be curative for HCV and rescue HIV patients from disease progression. Dual therapy in coinfected patients requires expertise.

AREAS COVERED

Four major issues challenge dual HCV and HIV treatment, including overlapping drug-related side effects, hepatitis B reactivation, immune reconstitution inflammatory syndromes (IRIS), and drug-drug interactions (DDI). A search was conducted in PubMed from January 2010 to March 2023.

EXPERT OPINION

The advent of second-generation direct-acting antivirals (DDA) that depict higher antiviral potency, fewer side effects, pangenotypic activity and are co-formulated has expanded the indication of HCV therapy and particularly in HIV-coinfected individuals. Sequential initiation of antiretrovirals (ARV) followed by DAA is generally preferred to start dual treatment concomitantly. Close monitoring of rare episodes of HBV reactivation and IRIS is warranted. The most frequent DDI between DAA and ARV affect drug metabolism by CYP450 induction/inhibition, leading to abnormal drug exposures. Throughout this mechanism interact most HCV and HIV protease inhibitors and non-nucleoside polymerase inhibitors. Exposure to some HIV and HCV nucleos(t)ide analogues (e.g. tenofovir and sofosbuvir, respectively) is subject to induction/inhibition of drug transporters and requires special attention in patients with renal insufficiency.

A Systemic Inflammation Response Score for Prognostic Prediction in Hepatocellular Carcinoma Patients After Hepatectomy

Purpose

To investigate the value of preoperative systemic inflammation response (SIRS) score in predicting the prognosis of hepatocellular carcinoma (HCC) after hepatectomy.

Patients and Methods

The study analyzed 1001 patients with pathologically proven HCC who received curative resection at Sun Yat-sen University Cancer Center between March 2016 and May 2020. Patients were randomly divided into a training cohort (n = 751) and a validation cohort (n = 250). Clinicopathological characteristics were collected retrospectively. The SIRS score formula was based on the results of a multivariate cox analysis of hematological inflammation indexes in the training cohort. Then, a nomogram consisting of the SIRS score was constructed and the calibration plot, areas under the receiver operating characteristic (AUC) curve, and decision curve analysis (DCA) showed good predictive ability.

Results

Univariate and multivariate cox analysis revealed that the SIRS score is an independent prognostic factor for OS in HCC patients. A higher SIRS score was associated with a larger maximum lesion diameter, poor tumor differentiation, a greater possibility of vascular invasion, and a more advanced cancer stage. When the nomogram was used to predict 1-year, 3-year, and 5-year survival rates, the AUC in the training cohort was 0.763, 0.712, and 0.687, respectively; In the validation cohort, it was 0.715, 0.648, and 0.614, respectively. The AUC of this nomogram showed significantly better predictive performance than those of commonly used staging systems.

Conclusion

The preoperative SIRS score has good efficacy in predicting the prognosis of HCC patients undergoing hepatectomy, and nomograms based on the SIRS score can potentially guide individualized follow-up and adjuvant therapy.

An ultralong-acting tenofovir ProTide nanoformulation achieves monthslong HBV suppression

Treatment of chronic hepatitis B virus (HBV) requires lifelong daily therapy. However, suboptimal adherence to the existing daily therapy has led to the need for ultralong-acting antivirals. A lipophilic and hydrophobic ProTide was made by replacing the alanyl isopropyl ester present in tenofovir alafenamide (TAF) with a docosyl phenyl alanyl ester, now referred to as M1TFV. NM1TFV and nanoformulated TAF (NTAF) nanocrystals were formulated by high-pressure homogenization. A single intramuscular injection of NM1TFV, but not NTAF, delivered at a dose of TFV equivalents (168 milligrams per kilogram) demonstrated monthslong antiviral activities in both HBV-transgenic and human hepatocyte transplanted TK-NOG mice. The suppression of HBV DNA in blood was maintained for 3 months. Laboratory experiments on HBV-transfected HepG2.2.15 cells affirmed the animal results and the critical role of docosanol in the sustained NM1TFV antiviral responses. These results provide clear "proof of concept" toward an emerging therapeutic paradigm for the treatment and prevention of HBV infection.

Tenofovir use is associated with a decreased risk of hepatocellular carcinoma among men with HIV irrespective of coinfection status

Background & Aims

Tenofovir is recommended as part of the first-line antiretroviral therapy (ART) to treat people living with HIV (PLWH) with HBV coinfection. However, the effects of tenofovir-containing ART on hepatocellular carcinoma (HCC) risk among PLWH with/without chronic hepatitis virus infections remain unclear.

Methods

This study included 23,838 PLWH. All of them were males aged ≥20 years and followed prospectively during 2000-2017. Four major nationwide registries - the Human Immunodeficiency Virus surveillance database, Taiwan Cancer Registry, Death Certification System, and National Health Insurance Database - were applied to define ART and comorbidities and ascertain newly diagnosed HCC. Tenofovir-containing ART was identified through prescription records. Cox proportional hazards models were used to determine the association of tenofovir use with HCC incidence.

Results

HCC incidence was lower among ever users of tenofovir than among never users (24.2 and 85.7 per 100,000 person-years, respectively). Ever users had significantly reduced HCC risk (adjusted hazard ratio 0.20, 95% CI 0.13-0.31). The effect of tenofovir use on reduced risk for HCC consistently favored never users across many prespecified subgroups, including HBV or HCV coinfection (p <0.05). The findings were consistent in subgroups of PLWH diagnosed with HIV before tenofovir's approval and in those born before the nationwide roll-out of neonatal HBV vaccination.

Conclusions

Our findings underscore the need for randomized controlled trials of tenofovir in combination with long-acting injectable ART regimens to assess its safety and efficacy in PLWH, particularly in those with HBV or HCV coinfection.

Impact and implications

Tenofovir's effect on the risk of hepatocellular carcinoma (HCC) among people living with HIV with hepatitis B or C coinfection remains under investigated. This nationwide prospective cohort study, comprising 23,838 men living with HIV, showed that tenofovir-containing antiretroviral therapy was associated with reduced risk of HCC (adjusted relative risk: 0.20, 95% CI 0.13-0.31), which was consistently observed across many prespecified subgroups. The effect of tenofovir use on HCC risk should be further investigated in PLWH, particularly following the development of long-acting injectable ART regimens.

The LEAP Process: Streamlining the Development of Long-Acting Products and Formulations for Infectious Diseases

Developing long-acting products and formulations for infectious diseases is a nontrivial undertaking that is frequently classified as high risk and low reward by the pharmaceutical industry. The Long-Acting/Extended Release Antiretroviral Research Resource Program (LEAP) was founded in 2015 with the support of the National Institutes of Health to encourage, promote, and accelerate the development of such products. Assessment methodology for any new proposal brought to this group is part of a framework-the LEAP Process-that includes a landscape analysis of what is currently available in the public domain. This is followed by in silico modeling and simulation offered as a service to the relevant scientific community. A variety of preclinical and clinical outcome metrics are applied to each new agent as part of a continuous feedback loop to improve product characteristics. This allows us to catalog knowledge gaps and barriers that can be addressed by engaged stakeholders. Results are communicated in scientific articles, reviews, and position papers. This undertaking serves to de-risk discovery, development, and implementation by bridging the gaps between academic, regulatory, and industrial investigators, and by engaging those in the community who will be the eventual users of these medicines. The LEAP Process has supported formulations now approved for human immunodeficiency virus, as well as products in clinical and preclinical development for tuberculosis and hepatitis viruses B and C.

Pre-Exposure Prophylaxis for viral infections other than HIV

The battle against human viral infections has historically relied on two medical strategies, namely vaccines to protect from contagion and antivirals to treat infected patients. In the absence of vaccines, antivirals have occasionally been used as peri-exposure prophylaxis, given either before (pre-exposure prophylaxis) or right after (post-exposure prophylaxis). In an unprecedented way, the use of antiretrovirals as chemoprophylaxis has triumphed in the HIV field. Indeed, oral antiretrovirals given either daily or at demand to HIV-uninfected individuals engaged in high-risk behaviors protect from contagion. More recently, the advent of long-acting formulations has allowed HIV protection following intramuscular injections every three months. Can we envision a similar prophylactic strategy for other human viral infections? The advent of such 'chemical vaccines' would fill an unmet need when classical vaccines do not exist, cannot be recommended, immune responses are suboptimal, escape mutants emerge or immunity wanes. In this review, we discuss the opportunities for antiviral chemoprophylaxis for viral hepatitis B and C, retroviruses HTLV-1 and HIV-2, and respiratory viruses influenza and SARS-CoV-2, among others.

Physiologically Based Pharmacokinetic Modeling of 3 HIV Drugs in Combination and the Role of Lymphatic System after Subcutaneous Dosing. Part 2: Model for the Drug-combination Nanoparticles

We previously developed a mechanism-based pharmacokinetic (MBPK) model to characterize the PK of a lymphocyte-targeted, long-acting 3 HIV drug-combination nanoparticle (DcNP) formulation of lopinavir, ritonavir, and tenofovir. MBPK describes time-courses of plasma drug concentration and has provided an initial hypothesis for the lymphatic PK of DcNP. Because anatomical and physiological interpretation of MBPK is limited, in this Part 2, we report the development of a Physiologically Based Pharmacokinetic (PBPK) model for a detailed evaluation of the systemic and lymphatic PK of drugs associated with DcNP. The DcNP model is linked to the PBPK model presented earlier in Part 1 to account for the disposition of released free drugs. A key feature of the DcNP model is the uptake of the injected dose from the subcutaneous site to the adjacent lymphoid depot, routing through the nodes within and throughout the lymphatic network, and its subsequent passage into the blood circulation. Furthermore, the model accounts for DcNP transport to the lymph by lymphatic recirculation and mononuclear cell migration. The present PBPK model can be extended to other nano-drug combinations that target or transit through the lymphatic system. The PBPK model may allow scaling and prediction of DcNP PK in humans.

Impact of long-acting therapies on the global HIV epidemic

Long-acting antiretroviral drugs have emerged as exciting treatment and preexposure prophylaxis (PrEP) options for people with HIV and at risk of HIV. Long-acting regimens may improve dosing convenience, tolerability and cost compared with current daily-based oral therapy. They can also circumvent stigma associated with oral therapy for both treatment and PrEP, thereby improving adherence and outcomes. Yet, multiple challenges remain, many specific to low-income and middle-income countries (LMICs), where the epidemic is most concentrated and HIV prevention and treatment options are limited. To optimize the use of long-acting formulations, key outstanding questions must be addressed. Uncertain costing, scale-up manufacturing, complex delivery systems and implementation challenges are potential barriers when considering the scalability of long-acting ARVs for global use.

Evolution of hepatitis B virus (HBV) serologic markers among antiretroviral-naïve, young people living with HIV who had undergone neonatal HBV vaccination and initiated antiretroviral therapy

BACKGROUND

With initiation of antiretroviral therapy (ART) containing nucleos(t)ide reverse-transcriptase inhibitors (NRTIs) with anti-hepatitis B virus (HBV) activity, the evolution of HBV serologic markers among people living with HIV (PLWH) who were born in the era of nationwide neonatal HBV vaccination is rarely investigated.

METHODS

This retrospective cohort study evaluated the changes of HBV serologic markers (HBsAg, anti-HBs, and anti-HBc) of PLWH who had undergone neonatal HBV vaccination. Clinical characteristics were analyzed and the incidences of evolution of HBV serologic markers were estimated.

RESULTS

Between 2004 and 2020, 608 PLWH (mean age, 24 years) were included and 62.0% initiated tenofovir-containing ART: 13 (2.1%) were HBsAg-positive; 312 (51.3%) tested triple-negative; 209 (34.4%) had vaccine-induced seroprotection against HBV; and 74 (12.2%) tested positive for anti-HBc with or without anti-HBs. Among 492 PLWH who received a median follow-up of 2.8 years, 4 cases of incident HBV infection occurred (0.59 per 100 PYFU) in PLWH testing triple-negative at baseline despite ART containing NRTIs with anti-HBV activity. Of PLWH with seroprotection against HBV at baseline, 38 subsequently lost anti-HBs (4.46 per 100 PYFU) and 4 cases of incident HBV infection occurred (0.47 per 100 PYFU). PLWH with an anti-HBs antibody titer ≥100 mIU/ml at baseline (adjusted hazard ratio [aHR], 0.10; 95%CI, 0.02-0.42) and CD4 ≥500 cells/mm 3 during follow-up (aHR, 0.51; 95%CI, 0.30-1.00) were less likely to lose HBV seroprotection.

CONCLUSIONS

Among young PLWH who had undergone neonatal HBV vaccination, evolution of HBV serologic markers and incident infections occurred despite ART containing NRTIs with anti-HBV activity.

HBV/HIV Coinfection: Impact on the Development and Clinical Treatment of Liver Diseases

Hepatitis B virus (HBV) infection is a common contributor to chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Approximately 10% of people with human immunodeficiency virus (HIV) also have chronic HBV co-infection, owing to shared transmission routes. HIV/HBV coinfection accelerates the progression of chronic HBV to cirrhosis, end-stage liver disease, or hepatocellular carcinoma compared to chronic HBV mono-infection. HBV/HIV coinfection alters the natural history of hepatitis B and renders the antiviral treatment more complex. In this report, we conducted a critical review on the epidemiology, natural history, and pathogenesis of liver diseases related to HBV/HIV coinfection. We summarized the novel therapeutic options for these coinfected patients.

Nanoparticle-Based Lateral Flow Biosensors Integrated With Loop-Mediated Isothermal Amplification for the Rapid and Visual Diagnosis of Hepatitis B Virus in Clinical Application

Hepatitis B virus (HBV) infection remains one of the major public health issues worldwide. Developing a rapid, sensitive, specific, easy-to-operate, and cost-saving approach for the diagnosis of HBV is essential for its therapy and prevention. Here, we first devised a novel approach, termed “loop-mediated isothermal amplification integrated with a nanoparticle-based lateral flow biosensor (LAMP-LFB),” for the detection of HBV in clinical application. The results indicated that a set of LAMP primers based on the S gene were valid for the establishment of HBV-LAMP-LFB. The optimal HBV-LAMP can be carried out at a constant temperature of 65°C for 40 min. The whole detection process, including HBV genomic DNA preparation (∼10 min), LAMP (40 min), and LFB reading (within 2 min), can be accomplished within 60 min. The limit of detection of the HBV-LAMP-LFB assay was 7.5 IU per test. The specificity of this assay was one hundred percent, and there was no cross-reactivity with other pathogens. Hence, these results indicated that the HBV-LAMP-LFB assay established in the current study is a sensitive, rapid, specific, visual, simple, and cost-saving method for the screening of HBV agents. More importantly, the HBV-LAMP-LFB has remarkable potential to develop a point-of-care testing in clinical application, especially in resource-scarce regions.

Transformation of tenofovir into stable ProTide nanocrystals with long-acting pharmacokinetic profiles

Treatment and prevention of human immunodeficiency virus type one (HIV-1) infection was transformed through widespread use of antiretroviral therapy (ART). However, ART has limitations in requiring life-long daily adherence. Such limitations have led to the creation of long-acting (LA) ART. While nucleoside reverse transcriptase inhibitors (NRTI) remain the ART backbone, to the best of our knowledge, none have been converted into LA agents. To these ends, we transformed tenofovir (TFV) into LA surfactant stabilized aqueous prodrug nanocrystals (referred to as NM1TFV and NM2TFV), enhancing intracellular drug uptake and retention. A single intramuscular injection of NM1TFV, NM2TFV, or a nanoformulated tenofovir alafenamide (NTAF) at 75 mg/kg TFV equivalents to Sprague Dawley rats sustains active TFV-diphosphate (TFV-DP) levels ≥ four times the 90% effective dose for two months. NM1TFV, NM2TFV and NTAF elicit TFV-DP levels of 11,276, 1,651, and 397 fmol/g in rectal tissue, respectively. These results are a significant step towards a LA TFV ProTide.

A review of existing strategies for designing long-acting parenteral formulations: Focus on underlying mechanisms, and future perspectives

The need for long-term treatments of chronic diseases has motivated the widespread development of long-acting parenteral formulations (LAPFs) with the aim of improving drug pharmacokinetics and therapeutic efficacy. LAPFs have been proven to extend the half-life of therapeutics, as well as to improve patient adherence; consequently, this enhances the outcome of therapy positively. Over past decades, considerable progress has been made in designing effective LAPFs in both preclinical and clinical settings. Here we review the latest advances of LAPFs in preclinical and clinical stages, focusing on the strategies and underlying mechanisms for achieving long acting. Existing strategies are classified into manipulation of in vivo clearance and manipulation of drug release from delivery systems, respectively. And the current challenges and prospects of each strategy are discussed. In addition, we also briefly discuss the design principles of LAPFs and provide future perspectives of the rational design of more effective LAPFs for their further clinical translation.

HIV/HBV coinfection: temporal trends and patient characteristics, Spain, 2002 to 2018

Background

Recent and reliable estimates on the prevalence of coinfection with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) in Europe are lacking.

Aim

Leveraged on a study designed to assess HIV/HCV coinfection prevalence, we assessed the prevalence of HIV/HBV coinfection in Spain in 2018 and compared the results with five similar studies performed since 2002.

Methods

This cross-sectional prevalence study was carried out in 43 centres, and patients were selected using simple random sampling. The reference population comprised 40,322 patients and the sample size were 1,690 patients.

Results

The prevalence of HIV/HBV coinfection in Spain at the end of 2018 was 3.2%. The prevalence in 2002, 2009, 2015, 2016 and 2017 was 4.9%, 3.4%, 3%, 3.9% and 3%, respectively. Among the HIV/HBV-coinfected patients identified in 2018, 16.7% had cirrhosis according to transient elastography and 26.3% tested positive for antibodies against hepatitis D virus. All HIV/HBV-coinfected patients were receiving drugs with activity against HBV, and 97% of those tested for HBV DNA had an HBV DNA load < 80 IU/mL.

Conclusions

The prevalence of HIV/HBV coinfection in Spain remained stable at around 3% for a decade. Our data could facilitate the design of national programmes to control HBV infection and help identify areas of patient management that need improvement.

Humanized Mice for Infectious and Neurodegenerative disorders

Humanized mice model human disease and as such are used commonly for research studies of infectious, degenerative and cancer disorders. Recent models also reflect hematopoiesis, natural immunity, neurobiology, and molecular pathways that influence disease pathobiology. A spectrum of immunodeficient mouse strains permit long-lived human progenitor cell engraftments. The presence of both innate and adaptive immunity enables high levels of human hematolymphoid reconstitution with cell susceptibility to a broad range of microbial infections. These mice also facilitate investigations of human pathobiology, natural disease processes and therapeutic efficacy in a broad spectrum of human disorders. However, a bridge between humans and mice requires a complete understanding of pathogen dose, co-morbidities, disease progression, environment, and genetics which can be mirrored in these mice. These must be considered for understanding of microbial susceptibility, prevention, and disease progression. With known common limitations for access to human tissues, evaluation of metabolic and physiological changes and limitations in large animal numbers, studies in mice prove important in planning human clinical trials. To these ends, this review serves to outline how humanized mice can be used in viral and pharmacologic research emphasizing both current and future studies of viral and neurodegenerative diseases. In all, humanized mouse provides cost-effective, high throughput studies of infection or degeneration in natural pathogen host cells, and the ability to test transmission and eradication of disease.

Long-acting drugs and formulations for the treatment and prevention of HIV infection

Long-acting and extended-release formulations represent one of the most important approaches to improving the treatment and prevention of chronic HIV infection. Long-acting small molecules and monoclonal antibodies have demonstrated potent anti-HIV activity in early- and late-stage clinical trials. Strategies to manage toxicity and falling drug concentrations after missed doses, as well as primary and secondary resistance to current drugs and monoclonal antibodies are important considerations. Long-acting injectable nanoformulations of the integrase inhibitor cabotegravir and the non-nucleoside reverse transcriptase inhibitor rilpivirine were safe, well tolerated and efficacious in large randomised phase 3 studies. Regulatory approval for this two-drug combination for HIV maintenance therapy was granted in Canada in 2020 and is expected in the USA during 2021. 4'-Ethynyl-2-fluoro-2'-deoxyadenosine (islatravir) is a novel nucleoside reverse transcriptase inhibitor in clinical development as a long-acting oral drug and as a long-acting subcutaneous polymer implant. GS-6207 is a novel HIV capsid inhibitor that is injected subcutaneously every 3 months. Broadly-neutralising monoclonal antibodies have potent antiviral activity in early human trials, however there is substantial baseline resistance and rapid development of resistance to these antibodies if used as monotherapy. Limitations of these antiretroviral approaches include management of toxicities and prevention of drug resistance when these drugs are discontinued and drug concentrations are slowly reduced over time. These approaches appear to be especially attractive for patients complaining of pill fatigue and for those experiencing HIV-associated stigma. As these formulations are shown to be safe, well tolerated and economical, they are likely to gain broader appeal.

A year-long extended release nanoformulated cabotegravir prodrug

Long-acting cabotegravir (CAB) extends antiretroviral drug administration from daily to monthly. However, dosing volumes, injection site reactions and health-care oversight are obstacles towards a broad usage. The creation of poloxamer-coated hydrophobic and lipophilic CAB prodrugs with controlled hydrolysis and tissue penetrance can overcome these obstacles. To such ends, fatty acid ester CAB nanocrystal prodrugs with 14, 18 and 22 added carbon chains were encased in biocompatible surfactants named NMCAB, NM2CAB and NM3CAB and tested for drug release, activation, cytotoxicity, antiretroviral activities, pharmacokinetics and biodistribution. Pharmacokinetics studies, performed in mice and rhesus macaques, with the lead 18-carbon ester chain NM2CAB, showed plasma CAB levels above the protein-adjusted 90% inhibitory concentration for up to a year. NM2CAB, compared with NMCAB and NM3CAB, demonstrated a prolonged drug release, plasma circulation time and tissue drug concentrations after a single 45 mg per kg body weight intramuscular injection. These prodrug modifications could substantially improve CAB's effectiveness.

Advances in hepatitis B therapeutics

Despite the availability of both effective preventive vaccines and oral antivirals, over 250 million people are chronically infected with the hepatitis B virus (HBV). Globally, chronic hepatitis B is the leading cause of hepatocellular carcinoma, which represents the third cause of cancer mortality, accounting for nearly 1 million annual deaths. Current oral nucleos(t)ide therapy with tenofovir or entecavir suppresses serum HBV-DNA in most treated patients, but rarely is accompanied by HBsAg loss. Thus, treatment has to be given lifelong to prevent viral rebound. A broad spectrum of antivirals that block the HBV life cycle at different steps are in clinical development, including entry inhibitors, cccDNA disrupters/silencers, translation inhibitors, capsid assembly modulators, polymerase inhibitors and secretion inhibitors. Some of them exhibit higher potency than current oral nucleos(t)ides. Drugs in more advanced stages of clinical development are bulevirtide, JNJ-6379, ABI-H0731, ARO-HBV and REP-2139. To date, only treatment with ARO-HBV and with REP-2139 have resulted in HBsAg loss in a significant proportion of patients. Combination therapies using distinct antivirals and/or immune modulators are expected to maximize treatment benefits. The current goal is to achieve a 'functional cure', with sustained serum HBsAg after drug discontinuation. Ultimately, the goal of HBV therapy will be virus eradication, an achievement that would require the elimination of the cccDNA reservoir within infected hepatocytes.