Gene Therapy in Patients with the Crigler-Najjar Syndrome

Immune remodulation in pediatric inherited metabolic liver diseases

Inherited metabolic liver diseases arise from genetic mutations that lead to disruptions in liver metabolic pathways and are predominantly observed in pediatric populations. The spectrum of genetic metabolic liver disorders is diverse, encompassing a range of conditions associated with aberrations in iron, copper, carbohydrate, lipid, protein, and amino acid metabolism. Historically, research in the domain of genetic metabolic liver diseases has predominantly concentrated on hepatic parenchymal cell alterations. Nevertheless, emerging studies suggest that inherited metabolic liver diseases exert significant influences on the immune microenvironment, both within the liver and systemically. This review endeavors to encapsulate the immunological features of genetic metabolic liver diseases, aiming to expand the horizons of researchers in this discipline, and to elucidate the underlying pathophysiological mechanisms pertinent to hereditary metabolic liver diseases and to propose innovative therapeutic approaches.

Drug-induced liver injury related to gene therapy: A new challenge to be managed

Gene therapy is being successfully developed for the treatment of several genetic disorders. Various methods of gene transfer have been developed to enable the production of the deficient enzyme or protein. One of the most important is adeno-associated virus vectors, which have been shown to be viable for use in in vivo gene therapy. Several gene therapies have already been approved. They are also promising for acquired diseases. Important examples include gene therapy for haemophilia A and B, X-linked myotubular myopathy, spinal muscular atrophy and several liver diseases such as Criggler-Najjar disease, alpha-1 antitrypsin deficiency and Fabry disease. However, the introduction of a foreign compound into hepatocytes leads to hepatic reactions with heterogeneous phenotypic expression and a wide spectrum of severity, ranging from mild transaminase elevation to acute liver failure. Several mechanisms appear to be involved in liver injury, including an immune response, but also direct toxicity depending on the method of gene transfer. As a result, the incidence, expression and severity of liver injury vary from indication to indication and from patient to patient. Patients treated for haemophilia A are more prone to transaminase elevation than those treated for haemophilia B. Corticosteroids are successfully used to correct liver reactions but also to prevent degradation of the transferred gene and loss of therapeutic activity. The aim of this review is to describe the risk of liver injury according to the indication for gene therapy and the short- and long-term management currently proposed to prevent or correct liver reactions in clinical practice.

The menace of severe adverse events and deaths associated with viral gene therapy and its potential solution

Over the past decade, in vivo gene replacement therapy has significantly advanced, resulting in market approval of numerous therapeutics predominantly relying on adeno-associated viral vectors (AAV). While viral vectors have undeniably addressed several critical healthcare challenges, their clinical application has unveiled a range of limitations and safety concerns. This review highlights the emerging challenges in the field of gene therapy. At first, we discuss both the role of biological barriers in viral gene therapy with a focus on AAVs, and review current landscape of in vivo human gene therapy. We delineate advantages and disadvantages of AAVs as gene delivery vehicles, mostly from the safety perspective (hepatotoxicity, cardiotoxicity, neurotoxicity, inflammatory responses etc.), and outline the mechanisms of adverse events in response to AAV. Contribution of every aspect of AAV vectors (genomic structure, capsid proteins) and host responses to injected AAV is considered and substantiated by basic, translational and clinical studies. The updated evaluation of recent AAV clinical trials and current medical experience clearly shows the risks of AAVs that sometimes overshadow the hopes for curing a hereditary disease. At last, a set of established and new molecular and nanotechnology tools and approaches are provided as potential solutions for mitigating or eliminating side effects. The increasing number of severe adverse reactions and, sadly deaths, demands decisive actions to resolve the issue of immune responses and extremely high doses of viral vectors used for gene therapy. In response to these challenges, various strategies are under development, including approaches aimed at augmenting characteristics of viral vectors and others focused on creating secure and efficacious non-viral vectors. This comprehensive review offers an overarching perspective on the present state of gene therapy utilizing both viral and non-viral vectors.

Adeno-associated viral vector gene therapy: Challenges for the paediatric hepatologist

Hepatoxicity associated with recombinant adeno-associated virus gene therapy is being increasingly encountered by hepatologists in tertiary and quaternary referral units due to the recent increase of these therapies for neuromuscular and haematological disorders. The challenges in managing the condition stem from a lack of good-quality evidence on the appropriate protocols for immunosuppressants due to lack of representative animal models. There is a need for protocols for diagnosing and treating hepatotoxicity and this possible with further research to understand the problem and its management. The review also highlights the importance of a multidisciplinary team in managing hepatotoxicity and recommends further research to better identify at-risk individuals, define the extent of the problem and assess the long-term effects of liver injury and immunosuppressants.

rAAV expressing a COBRA-designed influenza hemagglutinin generates a protective and durable adaptive immune response with a single dose

Influenza remains a worldwide public health threat. Although seasonal influenza vaccines are currently the best means of preventing severe disease, the standard-of-care vaccines require frequent updating due to antigenic drift and can have low efficacy, particularly in vulnerable populations. Here, we demonstrate that a single administration of a recombinant adenovirus-associated virus (rAAV) vector expressing a computationally optimized broadly reactive antigen (COBRA)-derived influenza H1 hemagglutinin (HA) induces strongly neutralizing and broadly protective antibodies in naïve mice and ferrets with pre-existing influenza immunity. Following a lethal viral challenge, the rAAV-COBRA vaccine allowed for significantly reduced viral loads in the upper and lower respiratory tracts and complete protection from morbidity and mortality that lasted for at least 5 months post-vaccination. We observed no signs of antibody waning during this study. CpG motif enrichment of the antigen can act as an internal adjuvant to further enhance the immune responses to allow for lower vaccine dosages with the induction of unique interferon-producing CD4+ and CD8+ T cells specific to HA head and stem peptide sequences. Our studies highlight the utility of rAAV as an effective platform to improve seasonal influenza vaccines.

IMPORTANCE

Developing an improved seasonal influenza vaccine remains an ambitious goal of researchers and clinicians alike. With influenza routinely causing severe epidemics with the potential to rise to pandemic levels, it is critical to create an effective, broadly protective, and durable vaccine to improve public health worldwide. As a potential solution, we created a rAAV viral vector expressing a COBRA-optimized influenza hemagglutinin antigen with modestly enriched CpG motifs to evoke a robust and long-lasting immune response after a single intramuscular dose without needing boosts or adjuvants. Importantly, the rAAV vaccine boosted antibody breadth to future strains in ferrets with pre-existing influenza immunity. Together, our data support further investigation into the utility of viral vectors as a potential avenue to improve our seasonal influenza vaccines.

Gene therapy in pediatrics - Clinical studies and approved drugs (as of 2023)

Gene therapy in pediatrics represents a cutting-edge therapeutic strategy for treating a range of genetic disorders that manifest in childhood. Gene therapy involves the modification or correction of a mutated gene or the introduction of a functional gene into a patient's cells. In general, it is implemented through two main modalities namely ex vivo gene therapy and in vivo gene therapy. Currently, a noteworthy array of gene therapy products has received valid market authorization, with several others in various stages of the approval process. Additionally, a multitude of clinical trials are actively underway, underscoring the dynamic progress within this field. Pediatric genetic disorders in the fields of hematology, oncology, vision and hearing loss, immunodeficiencies, neurological, and metabolic disorders are areas for gene therapy interventions. This review provides a comprehensive overview of the evolution and current progress of gene therapy-based treatments in the clinic for pediatric patients. It navigates the historical milestones of gene therapies, currently approved gene therapy products by the U.S. Food and Drug Administration (FDA) and/or European Medicines Agency (EMA) for children, and the promising future for genetic disorders. By providing a thorough compilation of approved gene therapy drugs and published results of completed or ongoing clinical trials, this review serves as a guide for pediatric clinicians to get a quick overview of the situation of clinical studies and approved gene therapy products as of 2023.

Pre-Existing Immunity to a Nucleic Acid Contaminant-Derived Antigen Mediates Transaminitis and Resultant Diminished Transgene Expression in a Mouse Model of Hepatic Recombinant Adeno-Associated Virus-Mediated Gene Transfer

Liver injury with concomitant loss of therapeutic transgene expression can be a clinical sequela of systemic administration of recombinant adeno-associated virus (rAAV) when used for gene therapy, and a significant barrier to treatment efficacy. Despite this, it has been difficult to replicate this phenotype in preclinical models, thereby limiting the field's ability to systematically investigate underlying biological mechanisms and develop interventions. Prior animal models have focused on capsid and transgene-related immunogenicity, but the impact of concurrently present nontransgene or vector antigens on therapeutic efficacy, such as those derived from contaminating nucleic acids within rAAV preps, has yet to be investigated. In this study, using Ad5-CMV_GFP-immunized immunocompetent BALB/cJ mice, and a coagulation factor VIII expressing rAAV preparation that contains green flourescent protein (GFP) cDNA packaged as P5-associated contaminants, we establish a model to induce transaminitis and observe concomitant therapeutic efficacy reduction after rAAV administration. We observed strong epitope-specific anti-GFP responses in splenic CD8+ T cells when GFP cDNA was delivered as a P5-associated contaminant of rAAV, which coincided and correlated with alanine and aspartate aminotransferase elevations. Furthermore, we report a significant reduction in detectable circulating FVIII protein, as compared with control mice. Lastly, we observed an elevation in the detection of AAV8 capsid-specific T cells when GFP was delivered either as a contaminant or transgene to Ad5-CMV_GFP-immunized mice. We present this model as a potential tool to study the underlying biology of post-AAV hepatotoxicity and demonstrate the potential for T cell responses against proteins produced from AAV encapsidated nontherapeutic nucleic acids, to interfere with efficacious gene transfer.

Thrombotic Microangiopathy as an Emerging Complication of Viral Vector-Based Gene Therapy

Gene therapy has brought tremendous hope for patients with severe life-threatening monogenic diseases. Although studies have shown the efficacy of gene therapy, serious adverse events have also emerged, including thrombotic microangiopathy (TMA) following viral vector-based gene therapy. In this review, we briefly summarize the concept of gene therapy, and the immune response triggered by viral vectors. We also discuss the incidence, presentation, and potential underlying mechanisms, including complement activation, of gene therapy-associated TMA. Further studies are needed to better define the pathogenesis of this severe complication of gene therapy, and the optimal measures to prevent it.

Liver gene transfer for metabolite detoxification in inherited metabolic diseases

Inherited metabolic disorders (IMDs) are a growing group of genetic diseases caused by defects in enzymes that mediate cellular metabolism, often resulting in the accumulation of toxic substrates. The liver is a highly metabolically active organ that hosts several thousands of chemical reactions. As such, it is an organ frequently affected in IMDs. In this article, we review current approaches for liver-directed gene-based therapy aimed at metabolite detoxification in a variety of IMDs. Moreover, we discuss current unresolved challenges in gene-based therapies for IMDs.

Type II Crigler-Najjar syndrome: a case report and literature review

Background

Crigler-Najjar syndrome (CNS) is caused by mutations in uridine 5'-diphosphate glucuronyltransferase (UGT1A1) resulting in enzyme deficiency and hyperbilirubinemia. Type II CNS patients could respond to phenobarbital treatment and survive. This study presents a rare case of type II CNS.

Case summary

The proband was a 29-year-old male patient admitted with severe jaundice. A hepatic biopsy showed bullous steatosis of the peri-central veins of the hepatic lobule, sediment of bile pigment, and mild periportal inflammation with normal liver plate structure. The type II CNS was diagnosed by routine genomic sequencing which found that the proband with the Gry71Arg/Tyr486Asp compound heterozygous mutations in the UGT1A1 gene. After treatment with phenobarbital (180 mg/day), his bilirubin levels fluctuated between 100 and 200 μmol/L for 6 months and without severe icterus.

Conclusion

Type II CNS could be diagnosed by routine gene sequencing and treated by phenobarbital.

271st ENMC international workshop: Towards a unifying effort to fight Kennedy's disease. 20-22 October 2023, Hoofddorp, Netherlands

The workshop held in the Netherlands from October 20-22, 2023, united 27 scientists from academia, healthcare, and industry representing 11 countries, alongside four patient and charity representatives. Focused on Kennedy's Disease (KD), also known as spinal and bulbar muscular atrophy (SBMA), the workshop aimed to consolidate knowledge, align on clinical trial designs, and promote participative medicine for effective treatments. Discussions emphasized KD's molecular mechanisms, highlighting its status as a neuromuscular disorder with motor neuron degeneration. Strategies for therapeutic intervention, including AR activity modulation and targeting post-translational modifications, were proposed. The need for diagnostic, prognostic, and target engagement biomarkers was stressed. Challenges in patient stratification and clinical trial recruitment were acknowledged, with the International KD/SBMA Registry praised for its role. The workshop concluded with a patient-focused session, underscoring challenges in KD diagnosis and the vital support provided by patient associations.

Genetic prediction of causal association between serum bilirubin and hematologic malignancies: a two-sample Mendelian randomized and bioinformatics study

Introduction

An increasing number of cohort studies have shown a correlation between serum bilirubin and tumors, but no definitive causal relationship has been established between serum bilirubin and hematological malignancies.Therefore, the aim of the present study was to assess the causal relationship of serum bilirubin, including total bilirubin (TBIL) and direct bilirubin (DBIL), with hematological malignancies, including leukemia, lymphoma, and myeloma.

Methods

We used a genome-wide association study (GWAS) collection of TBIL, DBIL, and hematological malignancies data. Using two-sample Mendelian randomization(MR), we assessed the impact of TBIL and DBIL on hematological malignancies. For this study, the inverse variance weighting method (IVW) was the primary method of MR analysis. In the sensitivity analysis, the weighted median method, MR Egger regression, and MR-PRESSO test were used. To understand the mechanisms behind TBIL and DBIL, we used three different approaches based on screening single nucleotide polymorphisms (SNPs) and their associated genes, followed by bioinformatics analysis.

Results

The IVW test results showed evidence of effects of TBIL (odds ratio [OR]: 4.47, 95% confidence interval [CI]: 1.58-12.62) and DBIL (OR: 3.31, 95% CI: 1.08-10.18) on the risk of acute myeloid leukemia (AML).The findings from bioinformatics indicated that TBIL could potentially undergo xenobiotic metabolism through cytochrome P450 and contribute to chemical carcinogenesis.

Discussion

In this study, two-sample MR analysis revealed a causal relationship between TBIL, DBIL, and AML.

Hemophilia and hepatology, back to the future

Years ago, patients with hemophilia were often cared for because of liver issues. The use of hemoderivatives in the 1970s and 1980s, and the natural history of chronic hepatitis B and C, led to a surge of patients with cirrhosis and related complications after two or three decades. It was not until the approval of entecavir and tenofovir (2005-2008) against the B virus, and of direct-acting antiviral agents (2015) against the C virus, that a truly effective treatment became available for liver disease. Since then, patients with hemophilia disappeared from hepatology clinics and wards, apart from specific isolated problems.

Crigler-Najjar syndrome: looking to the future does not make us forget the present

Recently, the safety and efficacy of gene therapy were evaluated in patients with Crigler-Najjar syndrome (CNS). Although it is a promising curative option for CNS, many doubts still persist about its long-term efficacy and safety. Furthermore, there is a risk of overlooking several unresolved problems still present in current clinical practice. This letter is a call for action on crucial open issues that remain nowadays an unmet need in the management of CNS patients.

Similarities in Structure and Function of UDP-Glycosyltransferase Homologs from Human and Plants

The uridine diphosphate glycosyltransferase (UGT) superfamily plays a key role in the metabolism of xenobiotics and metabolic wastes, which is essential for detoxifying those species. Over the last several decades, a huge effort has been put into studying human and mammalian UGT homologs, but family members in other organisms have been explored much less. Potentially, other UGT homologs can have desirable substrate specificity and biological activities that can be harnessed for detoxification in various medical settings. In this review article, we take a plant UGT homology, UGT71G1, and compare its structural and biochemical properties with the human homologs. These comparisons suggest that even though mammalian and plant UGTs are functional in different environments, they may support similar biochemical activities based on their protein structure and function. The known biological functions of these homologs are discussed so as to provide insights into the use of UGT homologs from other organisms for addressing human diseases related to UGTs.

Adeno-associated viruses for gene therapy - clinical implications and liver-related complications, a guide for hepatologists

Gene therapy has garnered increasing interest over recent decades. Several therapies employing gene transfer mechanisms have been developed, and, of these, adeno-associated virus (AAV) vectors have demonstrated viability for use with in vivo gene therapy. Several AAV-based therapeutics have received regulatory approval in the last few years including those for retinal disease, spinal muscular atrophy or aromatic L-amino acid decarboxylase deficiency. Lately, with the introduction of novel liver-directed AAV vector-based therapeutics for the treatment of haemophilia A and B, gene therapy has attracted significant attention in the hepatology community, with the liver increasingly recognised as a target for gene therapy. However, the introduction of foreign DNA into hepatocytes is associated with a risk of hepatic reactions, with raised ALT (alanine aminotransferase) and AST (aspartate aminotransferase) being - so far - the most commonly reported side effects. The complete mechanisms underlying the ALT flairs remain to be determined and the long-term risks associated with these new treatments is not yet known. The liver community is increasingly being asked to support liver-directed gene therapy to mitigate potential liver associated harm. In this review, we focus on AAV vector-based gene therapy, shedding light on this promising technique and its remarkable success in haemophilia, with a special focus on hepatic complications and their management in daily clinical practice.

Liver-directed gene therapy for inherited metabolic diseases

Gene therapy clinical trials are rapidly expanding for inherited metabolic liver diseases whilst two gene therapy products have now been approved for liver based monogenic disorders. Liver-directed gene therapy has recently become an option for treatment of haemophilias and is likely to become one of the favoured therapeutic strategies for inherited metabolic liver diseases in the near future. In this review, we present the different gene therapy vectors and strategies for liver-targeting, including gene editing. We highlight the current development of viral and nonviral gene therapy for a number of inherited metabolic liver diseases including urea cycle defects, organic acidaemias, Crigler-Najjar disease, Wilson disease, glycogen storage disease Type Ia, phenylketonuria and maple syrup urine disease. We describe the main limitations and open questions for further gene therapy development: immunogenicity, inflammatory response, genotoxicity, gene therapy administration in a fibrotic liver. The follow-up of a constantly growing number of gene therapy treated patients allows better understanding of its benefits and limitations and provides strategies to design safer and more efficacious treatments. Undoubtedly, liver-targeting gene therapy offers a promising avenue for innovative therapies with an unprecedented potential to address the unmet needs of patients suffering from inherited metabolic diseases.

Paediatric research sets new standards for therapy in paediatric and adult cholestasis

Children with Alagille syndrome and progressive familial intrahepatic cholestasis (PFIC) experience debilitating pruritus, for which there have been few effective treatment options. In the past 2 years, the ileal bile acid transporter (IBAT) inhibitors maralixibat and odevixibat have been approved for the management of cholestatic pruritus in these individuals, representing an important step forward in improving their quality of life. Emerging data suggest these drugs might also improve event-free survival, therefore potentially altering the typical disease course currently seen in these disorders. This Review will discuss how genetic advances have clarified the molecular basis of cholestatic disorders, facilitating the development of new therapeutic options that have only been evaluated in children. We focus specifically on the newly licensed IBAT inhibitors for patients with Alagille syndrome and PFIC and explore the next steps for these drugs in relation to other paediatric and adult cholestatic disorders, recognising that they have the potential to benefit a wider group of patients with gastrointestinal and liver disease.