Gene Therapy for Crigler Najjar Syndrome Type I (AlphaCN)

Inherited enzymopathy of uridine diphosphate glucuronosyltransferase 1A1 (Crigler-Najjar syndrome type I) is an orphan disease, that arises from loss of function UGT1A1 genetic variants. Mutations lead to the enzyme's inability in neutralization of bilirubin conjugates. Clinically this condition is represented by jaundice and severe neurologic disorders, which can lead to death in infancy. Diagnosis of Crigler-Najjar syndrome type I is made through biochemical tests and determination the level of unconjugated bilirubin in blood serum, as well as by molecular genetic methods. There is no specific treatment for the disease, except liver transplantation. In common clinical practice phototherapy and plasmapheresis are applied in order to reduce serum concentration of unconjugated bilirubin and destroy or eliminate it from the body. From the very newborn and further, the lifestyle of young patients is dramatically restricted by the long-lasting exposure to phototherapy.

In Russian Federation there are just a few children annually with such disorder. Under our vision is a girl diagnosed Crigler-Najjar type I, who had either opportunity of liver transplantation and long term immunosuppression or receive a gene therapy within previously promising reports in clinics.

The Crigler-Najar syndrome is a convenient subject of choice for a gene therapy application, because the product of the damaged gene is directly related to a well-studied metabolite in the human body. The norms of bilirubin are known to biochemists, and it is clear how to study it's concentration in plasma. In addition, the level of bilirubin usually correlates well with the levels of liver enzymes, which reflect the condition of the liver and the possible viral load of gene constructs that have liver tropism.

Previously successful applications of gene therapy for this syndrome encouraged us to implement this treatment for the first time on children.

GT-UGT1A1-AAV8-02 (alphaglucuronosyltransferasegene unoparvovec, alphacrigen, OGP-001, AAV-TBG1A1) is comprised of a recombinant adeno-associated virus type 2/8 (rAAV2/8), carrying the normal human UGT1A1 gene. rAAV2/8 does not contain viral genes, but only viral inverted terminal repeats (ITRs), that are essential for genome rescue, replication, packaging, and vector persistence. Instead of viral genes, the vector carries a genetic engineering construct that ensures expression of the human UGT1A1 gene under the control of liver specific promoter of the human thyroxine-binding globulin (TBG) gene.