Gene Therapy in Patients with the Crigler-Najjar Syndrome.

BACKGROUND: Patients with the Crigler-Najjar syndrome lack the enzyme uridine diphosphoglucuronate glucuronosyltransferase 1A1 (UGT1A1), the absence of which leads to severe unconjugated hyperbilirubinemia that can cause irreversible neurologic injury and death. Prolonged, daily phototherapy partially controls the jaundice, but the only definitive cure is liver transplantation. METHODS: We report the results of the dose-escalation portion of a phase 1-2 study evaluating the safety and efficacy of a single intravenous infusion of an adeno-associated virus serotype 8 vector encoding UGT1A1 in patients with the Crigler-Najjar syndrome that was being treated with phototherapy. Five patients received a single infusion of the gene construct (GNT0003): two received 2×1012 vector genomes (vg) per kilogram of body weight, and three received 5×1012 vg per kilogram. The primary end points were measures of safety and efficacy; efficacy was defined as a serum bilirubin level of 300 µmol per liter or lower measured at 17 weeks, 1 week after discontinuation of phototherapy. RESULTS: No serious adverse events were reported. The most common adverse events were headache and alterations in liver-enzyme levels. Alanine aminotransferase increased to levels above the upper limit of the normal range in four patients, a finding potentially related to an immune response against the infused vector; these patients were treated with a course of glucocorticoids. By week 16, serum bilirubin levels in patients who received the lower dose of GNT0003 exceeded 300 µmol per liter. The patients who received the higher dose had bilirubin levels below 300 µmol per liter in the absence of phototherapy at the end of follow-up (mean [±SD] baseline bilirubin level, 351±56 µmol per liter; mean level at the final follow-up visit [week 78 in two patients and week 80 in the other], 149±33 µmol per liter). CONCLUSIONS: No serious adverse events were reported in patients treated with the gene-therapy vector GNT0003 in this small study. Patients who received the higher dose had a decrease in bilirubin levels and were not receiving phototherapy at least 78 weeks after vector administration. (Funded by Genethon and others; ClinicalTrials.gov number, NCT03466463.).

Prevalence and Relevance of Pre-Existing Anti-Adeno-Associated Virus Immunity in the Context of Gene Therapy for Crigler-Najjar Syndrome.

Adeno-associated virus (AAV) vector-mediated gene therapy is currently evaluated as a potential treatment for Crigler-Najjar syndrome (CN) (NCT03466463). Pre-existing immunity to AAV is known to hinder gene transfer efficacy, restricting enrollment of seropositive subjects in ongoing clinical trials. We assessed the prevalence of anti-AAV serotype 8 (AAV8) neutralizing antibodies (NAbs) in subjects affected by CN and investigated the impact of low NAb titers (<1:5) on liver gene transfer efficacy in an in vivo passive immunization model. A total of 49 subjects with a confirmed molecular diagnosis of CN were included in an international multicenter study (NCT02302690). Pre-existing NAbs against AAV8 were detected in 30.6% (15/49) of screened patients and, in the majority of positive cases, cross-reactivity to AAV2 and AAV5 was detected. To investigate the impact of low NAbs on AAV vector-mediated liver transduction efficiency, adult wild-type C57BL/6 mice were passively immunized with pooled human donor-derived immunoglobulins to achieve titers of up to 1:3.16. After immunization, animals were injected with different AAV8 vector preparations. Hepatic vector gene copy number was unaffected by low anti-AAV8 NAb titers when column-purified AAV vector batches containing both full and empty capsids were used. In summary, although pre-existing anti-AAV8 immunity can be found in about a third of subjects affected by CN, low anti-AAV8 NAb titers are less likely to affect liver transduction efficiency when using AAV vector preparations manufactured to contain both full and empty capsids. These findings have implications for the design of liver gene transfer clinical trials and for the definition of inclusion criteria related to seropositivity of potential participants.

Successful plasmapheresis for acute and severe unconjugated hyperbilirubinemia in a child with crigler najjar type I syndrome.

Crigler-Najjar syndrome type I (CN-I, MIM #218800) is a rare and severe autosomal disorder. It is caused by deficiency of the liver enzyme responsible for bilirubin elimination, the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1; EC 2.4.1.17). Biologically, the disease manifests itself with severe and persistent unconjugated hyperbilirubinemia. Kernicterus is a well-known complication of severe unconjugated hyperbilirubinemia in infants and young children, especially in patients with CN-I.Few articles have shown the efficiency of plasmapheresis for extreme hyperbilirubinemia.In this report, we describe the efficiency of plasmapheresis for a rapid control of acute and severe unconjugated hyperbilirubinemia in a 6-year-old CN-I patient who had previously developed kernicterus in the neonatal period. In spite of intensification of phototherapy, the patient developed severe hyperbilirubinemia (up to 830 µmol/l, with bilirubin/albumin ratio at 1.2). With two plasmapheresis procedures, bilirubin serum concentration decreased to 420 µmol/ and bilirubin/albumin ratio to 0.55. Following the acute episode of very severe unconjugated hyperbilirubinemia, the child recovered and neurological examination was unchanged, thus suggesting that plasmapheresis possibly prevented further worsening of kernicterus.

Investigating glycogenosis type III patients with multi-parametric functional NMR imaging and spectroscopy.

Debranching enzyme deficiency (Glycogen storage disease (GSD) type III) causes progressive muscle wasting myopathy. A comprehensive nuclear magnetic resonance study involving spectroscopy (NMRS) and imaging (NMRI) evaluated status and function of calf muscles in 18 GSDIII patients. At rest, (31)P NMRS showed elevated pH and accumulation of anomalous phosphomonoesters, (13)C NMRS quantified excess glycogen accumulation and NMRI demonstrated progressive fat replacement that paralleled muscle weakness. Multi-parametric functional NMR, performed at recovery from a single bout of aerobic exercise, simultaneously assessed oxidative phosphorylation from (31)P NMRS, muscle perfusion and BOLD, a marker of blood oxygenation, from arterial spin labeled NMRI, and oxygen uptake from deoxymyoglobin proton NMRS. While blocked glycogenolysis caused inadequate substrate supply to the mitochondria, combined measurements suggested that altered perfusion was also responsible for impaired post-exercise phosphocreatine recovery and could contribute to exercise intolerance in GSDIII. These non-invasive investigations provide new indices to quantify the progression of GSDIII.