Gene therapy of Wilson disease: A "golden" opportunity using rAAV on the 50th anniversary of the discovery of the virus

Wilson disease in children and young adults - State of the art

Wilson disease (WD) is an autosomal recessive disorder caused by mutations of the ATP7B gene, with a reported prevalence of 1:30,000-50,000. ATP7B encodes an enzyme called transmembrane copper-transporting ATPase, which is essential for copper incorporation into ceruloplasmin and for copper excretion into the bile. A lack or dysfunction of this enzyme results in a progressive accumulation of copper in several organs, especially in the liver, the nervous system, corneas, kidneys, and heart. Children with WD can present with asymptomatic liver disease, cirrhosis, or acute liver failure, with or without neurological and psychiatric symptoms. Approximately 20%-30% of WD patients present with ALF, while most of the other patients have chronic progressive hepatitis or cirrhosis if untreated. Although genetic testing has become a more important diagnostic tool for WD, the diagnosis remains based on both clinical features and laboratory investigations. The aims of treatment are to reduce copper levels and prevent its accumulation in the liver and other organs, especially in the central nervous system. Liver transplantation in WD is a life-saving option for patients presenting with liver failure and encephalopathy. For WD patients treated with chelating agents, adherence to the therapy is essential for long-term success. In this review, we also address specific issues in young adults as compared to children.

Hepatocyte organoids and cell transplantation: What the future holds

Historically, primary hepatocytes have been difficult to expand or maintain in vitro. In this review, we will focus on recent advances in establishing hepatocyte organoids and their potential applications in regenerative medicine. First, we provide a background on the renewal of hepatocytes in the homeostatic as well as the injured liver. Next, we describe strategies for establishing primary hepatocyte organoids derived from either adult or fetal liver based on insights from signaling pathways regulating hepatocyte renewal in vivo. The characteristics of these organoids will be described herein. Notably, hepatocyte organoids can adopt either a proliferative or a metabolic state, depending on the culture conditions. Furthermore, the metabolic gene expression profile can be modulated based on the principles that govern liver zonation. Finally, we discuss the suitability of cell replacement therapy to treat different types of liver diseases and the current state of cell transplantation of in vitro-expanded hepatocytes in mouse models. In addition, we provide insights into how the regenerative microenvironment in the injured host liver may facilitate donor hepatocyte repopulation. In summary, transplantation of in vitro-expanded hepatocytes holds great potential for large-scale clinical application to treat liver diseases.

Wilson disease in children and adolescents

Wilson disease (WD) is a rare, recessively inherited disorder of copper metabolism mainly affecting liver and brain. In childhood, it is known to have a predominant hepatic phenotype. It is likely that the low awareness for WD-associated neuropsychiatric signs and symptoms in this age group means that neurological Wilson's disease is underdiagnosed in children and young people. Practitioners should be alert for this complication in children with or without liver disease. Management of children with WD requires a dedicated multidisciplinary approach involving hepatologists, geneticists, neurologists and psychiatrists to ensure subtle neuropsychiatric symptoms are identified early and addressed appropriately. This review highlights recent advances in hepatic and neuropsychiatric symptoms of WD in childhood, specific diagnostic tools and pitfalls and summarises existing and potential future treatment options.

Management of Wilson Disease Diagnosed in Infancy: An Appraisal of Available Experience to Generate Discussion

Increased access to molecular genetic testing is changing the demographics for diagnosing inherited disorders and imposing new challenges for medical management. Wilson disease (WD), typically diagnosed in older children and adults, can now be detected in utero and in infants (children younger than 24 months, including neonates) via genetic testing. An evidence-based approach to management of these neonates and extremely young children, who are typically asymptomatic, has been hampered by lack of clinical experience. We present a case of an infantile diagnosis of WD, review available experience, and discuss current trends in antenatal genetic testing of parents and fetus that may lead to a very early diagnosis of WD. Based on physiological and nutritional considerations, we propose an algorithmic approach to management of infantile WD as a starting point for further discussion. Future collaboration amongst specialists is essential to identify evidence-based approaches and best practice for managing treatment of infants with genetically diagnosed WD.

Wilson disease-treatment perspectives

Wilson disease (WD) is a genetic disorder caused by pathological tissue copper accumulation with secondary damage of affected organs (mainly, but not limited to, the liver and brain). The main clinical symptoms of WD are, in concordance with the pathogenesis, hepatic and/or neuropsychiatric. Current treatment options for WD, based on drugs leading to negative copper body balance like chelators or zinc salts, were introduced more than 40 years ago and are generally effective in the majority of WD cases if used lifelong. However, especially in neurological patients, treatment may lead to neurological deterioration, which is often irreversible. Further, almost 50% of neurologically affected WD patients present with persistent neurological deficits despite the use of anti-copper treatment. In addition, up to 30% of patients treated with the widely used drug, d-penicillamine, present with adverse events related to treatment, which often leads to treatment discontinuation. Finally, almost 25% of WD patients do not adhere with anti-copper treatment, partially due to drug-related adverse events and complex treatment regimens (3 times daily, before meals, etc.). These limitations with current treatments have led to the search for other WD treatment possibilities. Currently, research is mainly focused on: (I) new agents with better safety profiles and less neurological deterioration properties compared with traditional chelators, e.g., tetrathiomolybdate salts or central nervous system-penetrable trientine, with the aim to provide more effective copper removal from brain tissue; (II) other non-chelating drugs that lead to removal of copper from cells [e.g., methanobactin (currently in preclinical studies)]; (III) cell and gene therapy. In this article, current research on future treatments for WD is reviewed.

Biochemical Markers for the Diagnosis and Monitoring of Wilson Disease

Wilson disease (WD) is an autosomal recessively-inherited disorder of copper metabolism and characterised by a pathological accumulation of copper. The ATP7B gene encodes for a transmembrane copper transporter essential for biliary copper excretion. Depending on time of diagnosis, severity of disease can vary widely. Almost all patients show evidence of progressive liver disease. Neurological impairments or psychiatric symptoms are common in WD patients not diagnosed during adolescence. WD is a treatable disorder, and early treatment can prevent the development of symptoms in patients diagnosed while still asymptomatic. This is why the early diagnosis of WD is crucial. The diagnosis is based on clinical symptoms, abnormal measures of copper metabolism and DNA analysis. Available treatment includes chelators and zinc salts which increase copper excretion and reduce copper uptake. In severe cases, liver transplantation is indicated and accomplishes a phenotypic correction of the hepatic gene defect. Recently, clinical development of the new copper modulating agent tetrathiomolybdate has started and direct genetic therapies are being tested in animal models. The following review focuses especially on biochemical markers and how they can be utilised in diagnosis and drug monitoring.

Accuracy of the radioactive copper incorporation test in the diagnosis of Wilson disease

BACKGROUND & AIMS

In Wilson disease (WD), copper accumulates in the liver and other tissues because of mutations in the ATP7B copper transporter gene. Early and effective anticopper treatment is crucial. However, routine diagnostic methods based on clinical findings, copper metabolism tests, liver biopsies and DNA analyses do not always provide a conclusive diagnosis. The aim was to evaluate radioactive copper incorporation as a diagnostic test.

METHODS

We included cases with a diagnosis of WD supported by radiocopper testing and later, when available, confirmed by DNA analysis. Incorporation of ⁶⁴ Cu was measured at 2, 24 and 48 hours following intravenous injection. Diagnostic accuracy (area under the receiver operating characteristic curve [AUC]), sensitivity, specificity and predictive value were assessed for 24 hours/2 hours and 48 hours/2 hours ⁶⁴ Cu ratios and compared with serum measurements of ceruloplasmin, copper, non-ceruloplasmin-bound copper and urinary 24-hours copper excretion.

RESULTS

Patients having two pathogenic ATP7B mutations (homozygotes/compound heterozygotes) (n = 74) had significantly lower 24 hours/2 hours and 48 hours/2 hours ⁶⁴ Cu ratios than heterozygote controls (n = 21) (mean 0.14 and 0.12 vs 0.49 and 0.63, respectively; both P < .001). Of note, 24 hours/2 hours and 48 hours/2 hours ⁶⁴ Cu ratios had excellent diagnostic accuracy, with AUCs approaching 1, and only 24-hours urinary copper excretion displayed similar positive features. Other copper metabolism tests studied had lower accuracy, specificity and sensitivity.

CONCLUSIONS

The radioactive copper test had excellent diagnostic accuracy and may be useful in the evaluation of new therapies aimed at restoring ATP7B function.

Wilson disease

Wilson disease (WD) is a potentially treatable, inherited disorder of copper metabolism that is characterized by the pathological accumulation of copper. WD is caused by mutations in ATP7B, which encodes a transmembrane copper-transporting ATPase, leading to impaired copper homeostasis and copper overload in the liver, brain and other organs. The clinical course of WD can vary in the type and severity of symptoms, but progressive liver disease is a common feature. Patients can also present with neurological disorders and psychiatric symptoms. WD is diagnosed using diagnostic algorithms that incorporate clinical symptoms and signs, measures of copper metabolism and DNA analysis of ATP7B. Available treatments include chelation therapy and zinc salts, which reverse copper overload by different mechanisms. Additionally, liver transplantation is indicated in selected cases. New agents, such as tetrathiomolybdate salts, are currently being investigated in clinical trials, and genetic therapies are being tested in animal models. With early diagnosis and treatment, the prognosis is good; however, an important issue is diagnosing patients before the onset of serious symptoms. Advances in screening for WD may therefore bring earlier diagnosis and improvements for patients with WD.

Wilson’s disease: Prospective developments towards new therapies

Wilson’s disease (WD) is an autosomal recessive disorder of copper metabolism, caused by mutations in the ATP7B gene. A clear demand for novel WD treatment strategies has emerged. Although therapies using zinc salts and copper chelators can effectively cure WD, these drugs exhibit limitations in a substantial pool of WD patients who develop intolerance and/or severe side effects. Several lines of research have indicated intriguing potential for novel strategies and targets for development of new therapies. Here, we review these new approaches, which comprise correction of ATP7B mutants and discovery of new compounds that circumvent ATP7B-deficiency, as well as cell and gene therapies. We also discuss whether and when these new therapeutic strategies will be translated into clinical use, according to the key requirements for clinical trials that remain to be met. Finally, we discuss the hope for the current rapidly developing research on molecular mechanisms underlying WD pathogenesis and for the related potential therapeutic targets to provide a solid foundation for the next generation of WD therapies that may lead to an effective, tolerable and safe cure.

Methanobactin reverses acute liver failure in a rat model of Wilson disease

In Wilson disease (WD), functional loss of ATPase copper-transporting β (ATP7B) impairs biliary copper excretion, leading to excessive copper accumulation in the liver and fulminant hepatitis. Current US Food and Drug Administration- and European Medicines Agency-approved pharmacological treatments usually fail to restore copper homeostasis in patients with WD who have progressed to acute liver failure, leaving liver transplantation as the only viable treatment option. Here, we investigated the therapeutic utility of methanobactin (MB), a peptide produced by Methylosinus trichosporium OB3b, which has an exceptionally high affinity for copper. We demonstrated that ATP7B-deficient rats recapitulate WD-associated phenotypes, including hepatic copper accumulation, liver damage, and mitochondrial impairment. Short-term treatment of these rats with MB efficiently reversed mitochondrial impairment and liver damage in the acute stages of liver copper accumulation compared with that seen in untreated ATP7B-deficient rats. This beneficial effect was associated with depletion of copper from hepatocyte mitochondria. Moreover, MB treatment prevented hepatocyte death, subsequent liver failure, and death in the rodent model. These results suggest that MB has potential as a therapeutic agent for the treatment of acute WD.