Rescue of infant progressive familial intrahepatic cholestasis type 3 mice by repeated dosing of AAV gene therapy

Novel ABCB4 mutation in a female patient with progressive familial intrahepatic cholestasis type 3: a case report and literature review

Introduction and importance

Progressive familial intrahepatic cholestasis (PFIC) is an uncommon disorder inherited in an autosomal recessive manner. PFIC type 3 (PFIC-3) results from mutations in the ABCB4 gene. This type typically advances from chronic cholestasis, which may occur with or without jaundice.

Case presentation

A 16-year-old female presented with abdominal pain, later developing liver complications. Genetic testing revealed a novel ABCB4 gene mutation linked to cholestasis. Diagnosed with PFIC-3, she was treated with ursodeoxycholic acid (UDCA) and vitamins, leading to improved liver function. Despite uncertain clinical significance of the mutation, predictions suggested it was damaging. Her liver function fully recovered, and she remained in remission during follow-up visits.

Clinical discussion

PFIC3 is a rare, autosomal recessive disorder causing cholestasis and liver damage. Our study reported a young female with a novel ABCB4 mutation who responded well to UDCA. Diagnosis relies on comprehensive evaluation, and treatment options include UDCA, surgery, and liver transplantation.

Conclusion

PFIC-3 gene must be considered while evaluating a young female with symptoms of cholestasis.

Repeated dosing of AAV-mediated liver gene therapy in juvenile rat and mouse models of Crigler-Najjar syndrome type I

Crigler-Najjar syndrome is an ultra-rare monogenic recessive liver disease caused by UGT1A1 gene mutations. Complete UGT1A1 deficiency results in severe unconjugated hyperbilirubinemia in newborns that, if not treated, may lead to brain damage and death. Treatment is based on intensive phototherapy, but its efficacy decreases with age, rendering liver transplantation the only curative option. Adeno-associated virus (AAV)-mediated gene therapy has shown long-term correction in adult patients, but loss of viral DNA and therapeutic efficacy are expected in younger patients associated with liver growth. Effective vector re-administration is hindered by anti-AAV neutralizing antibodies generated during the first administration. Here, we investigated AAV vector re-administration by modulating the immune response with rapamycin-loaded nanoparticles (ImmTOR) in Gunn rats (Ugt1a -/- ) and Ugt1a -/- mice. We administered a liver-specific AAV8 vector expressing a codon-optimized hUGT1A1 cDNA (1.0E11 vg/kg) in P25-P28 mutant animals and, upon loss of efficacy after 3 to 5 weeks, a higher second dose (1.0E12 or 5.0E12 vg/kg) was given. ImmTOR co-administration reduced anti-AAV neutralizing antibodies and immunoglobulin Gs generation in male animals of both models allowing effective re-dosing, underscored by a significant and long-term decrease in plasma bilirubin, although efficacy was affected by low-titer residual anti-AAV antibodies suggesting that re-administration in patients may require combination with other methods.

In Vivo Selection of S/MAR Sequences to Favour AAV Episomal Maintenance in Dividing Cells

Adeno-associated viral (AAV) vector-mediated gene therapy has emerged as a promising alternative to liver transplantation for monogenic metabolic hepatic diseases. AAVs are non-integrative vectors that are maintained primarily as episomes in quiescent cells like adult hepatocytes. This quality, while advantageous from a safety perspective due to a decreased risk of insertional mutagenesis, becomes a disadvantage when treating dividing cells, as it inevitably leads to the loss of the therapeutic genome. This is a challenge for the treatment of hereditary liver diseases that manifest in childhood. One potential approach to avoid vector genome loss involves putting scaffold/matrix attachment regions (S/MARs) into the recombinant AAV (rAAV) genome to facilitate its replication together with the cellular genome. We found that the administration of AAVs carrying the human β-interferon S/MAR sequence to neonatal and infant mice resulted in the maintenance of higher levels of viral genomes. However, we also observed that its inclusion at the 3' end of the mRNA negatively impacted its stability, leading to reduced mRNA and protein levels. This effect can be partially attenuated by incorporating nonsense-mediated decay (NMD)-inhibitory sequences into the S/MAR containing rAAV genome, whose introduction may aid in the development of more efficient and longer-lasting gene therapy rAAV vectors.

Gene Therapy for Inherited Liver Disease: To Add or to Edit

Patients suffering from an inherited severe liver disorder require lifelong treatment to prevent premature death. Until recently, the only curative treatment option was liver transplantation, which requires lifelong immune suppression. Now, liver-directed gene therapy, which is a much less invasive procedure, has become a market-approved treatment for hemophilia A and B. This may pave the way for it to become the treatment of choice for many other recessive inherited liver disorders with loss-of-function mutations. Inherited liver disease with toxic-gain-of-function or intrinsic hepatocyte damage may require alternative applications, such as integrating vectors or genome editing technologies, that can provide permanent or specific modification of the genome. We present an overview of currently available gene therapy strategies, i.e., gene supplementation, gene editing, and gene repair investigated in preclinical and clinical studies to treat inherited severe liver disorders. The advantages and limitations of these gene therapy applications are discussed in relation to the underlying disease mechanism.

Emerging mRNA Technology for Liver Disease Therapy

Liver diseases have consistently posed substantial challenges to global health. It is crucial to find innovative methods to effectively prevent and treat these diseases. In recent times, there has been an increasing interest in the use of mRNA formulations that accumulate in liver tissue for the treatment of hepatic diseases. In this review, we start by providing a detailed introduction to the mRNA technology. Afterward, we highlight types of liver diseases, discussing their causes, risks, and common therapeutic strategies. Additionally, we summarize the latest advancements in mRNA technology for the treatment of liver diseases. This includes systems based on hepatocyte growth factor, hepatitis B virus antibody, left-right determination factor 1, human hepatocyte nuclear factor α, interleukin-12, methylmalonyl-coenzyme A mutase, etc. Lastly, we provide an outlook on the potential of mRNA technology for the treatment of liver diseases, while also highlighting the various technical challenges that need to be addressed. Despite these difficulties, mRNA-based therapeutic strategies may change traditional treatment methods, bringing hope to patients with liver diseases.

Molecular Insights of Cholestasis in MDR2 Knockout Murine Liver Organoids

MDR3 (multidrug resistance 3) deficiency in humans (MDR2 in mice) causes progressive familial intrahepatic cholestasis type 3 (PFIC3). PFIC3 is a lethal disease characterized by an early onset of intrahepatic cholestasis progressing to liver cirrhosis, a preneoplastic condition, putting individuals at risk of hepatocellular carcinoma (HCC). Hepatocyte-like organoids from MDR2-deficient mice (MDR2KO) were used in this work to study the molecular alterations caused by the deficiency of this transporter. Proteomic analysis by mass spectrometry allowed characterization of 279 proteins that were differentially expressed in MDR2KO compared with wild-type organoids. Functional enrichment analysis indicated alterations in three main cellular functions: (1) interaction with the extracellular matrix, (2) remodeling intermediary metabolism, and (3) cell proliferation and differentiation. The affected cellular processes were validated by orthogonal molecular biology techniques. Our results point to molecular mechanisms associated with PFIC3 that may drive the progression to liver cirrhosis and HCC and suggest proteins and cellular processes that could be targeted for the development of early detection strategies for these severe liver diseases.

Integration and the risk of liver cancer-Is there a real risk?

Adeno-associated virus (AAV)-based gene therapies are in clinical development for haemophilia and other genetic diseases. Since the recombinant AAV genome primarily remains episomal, it provides the opportunity for long-term expression in tissues that are not proliferating and reduces the safety concerns compared with integrating viral vectors. However, AAV integration events are detected at a low frequency. Preclinical studies in mouse models have reported hepatocellular carcinoma (HCC) after systemic AAV administration in some settings, though this has not been reported in large animal models. The risk of HCC or other cancers after AAV gene therapy in clinical studies thus remains theoretical. Potential risk factors for HCC after gene therapy are beginning to be elucidated through animal studies, but their relevance to human studies remains unknown. Studies to investigate the factors that may influence the risk of oncogenesis as well as detailed investigation of cases of cancer in AAV gene therapy patients will be important to define the potential risk of AAV genotoxicity.

Genetics of Gallstone Disease and Their Clinical Significance: A Narrative Review

Gallstone (GS) disease is common and arises from a combination of genetic and environmental factors. Although genetic abnormalities specifically leading to cholesterol GSs are rare, there are clinically significant gene variants associated with cholesterol GSs. In contrast, most bilirubin GSs can be attributed to genetic defects. The pathogenesis of cholesterol and bilirubin GSs differs greatly. Cholesterol GSs are notably influenced by genetic variants within the ABC protein superfamily, including ABCG8, ABCG5, ABCB4, and ABCB11, as well as genes from the apolipoprotein family such as ApoB100 and ApoE (especially the E3/E3 and E3/E4 variants), and members of the MUC family. Conversely, bilirubin GSs are associated with genetic variants in highly expressed hepatic genes, notably UGT1A1, ABCC2 (MRP2), ABCC3 (MRP3), CFTR, and MUC, alongside genetic defects linked to hemolytic anemias and conditions impacting erythropoiesis. While genetic cases constitute a small portion of GS disease, recognizing genetic predisposition is essential for proper diagnosis, treatment, and genetic counseling.

Current limitations of gene therapy for rare pediatric diseases: Lessons learned from clinical experience with AAV vectors

Gene therapy using adeno-associated viral (AAV) vectors is a promising therapeutic strategy for multiple inherited diseases. Following intravenous injection, AAV vectors carrying a copy of the missing gene or the genome-editing machinery reach their target cells and deliver the genetic material. Several clinical trials are currently ongoing and significant success has already been achieved with at least six AAV gene therapy products with market approval in Europe and the United States. Nonetheless, clinical trials and preclinical studies have uncovered several limitations of AAV gene transfer, which need to be addressed in order to improve the safety and enable the treatment of the largest patient population. Limitations include the occurrence of immune-mediated toxicities, the potential loss of correction in the long run, and the development of neutralizing antibodies against AAV vectors preventing re-administration. In this review, we summarize these limitations and discuss the potential technological developments to overcome them. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.

Readministration of high-dose adeno-associated virus gene therapy vectors enabled by ImmTOR nanoparticles combined with B cell-targeted agents

Tolerogenic ImmTOR nanoparticles encapsulating rapamycin have been demonstrated to mitigate immunogenicity of adeno-associated virus (AAV) gene therapy vectors, enhance levels of transgene expression, and enable redosing of AAV at moderate vector doses of 2 to 5E12 vg/kg. However, recent clinical trials have often pushed AAV vector doses 10-fold to 50-fold higher, with serious adverse events observed at the upper range. Here, we assessed combination therapy of ImmTOR with B cell-targeting drugs for the ability to increase the efficiency of redosing at high vector doses. The combination of ImmTOR with a monoclonal antibody against B cell activation factor (aBAFF) exhibited strong synergy leading to more than a 5-fold to 10-fold reduction of splenic mature B cells and plasmablasts while increasing the fraction of pre-/pro-B cells. In addition, this combination dramatically reduced anti-AAV IgM and IgG antibodies, thus enabling four successive AAV administrations at doses up to 5E12 vg/kg and at least two AAV doses at 5E13 vg/kg, with the transgene expression level in the latter case being equal to that observed in control animals receiving a single vector dose of 1E14 vg/kg. Similar synergistic effects were seen with a combination of ImmTOR and a Bruton's tyrosine kinase inhibitor, ibrutinib. These results suggest that ImmTOR could be combined with B cell-targeting agents to enable repeated vector administrations as a potential strategy to avoid toxicities associated with vector doses above 1E14 vg/kg.