AAV-SPL 2.0, a Modified Adeno-Associated Virus Gene Therapy Agent for the Treatment of Sphingosine Phosphate Lyase Insufficiency Syndrome.
Publication Year:
2023
PubMed ID:
37958544
Public Summary:
Sphingosine phosphate lyase insufficiency syndrome (SPLIS) is a rare genetic condition caused by mutations in the SGPL1 gene. This gene encodes an essential enzyme needed to metabolize a group of lipids called sphingolipids. Children with SPLIS suffer from fibrotic kidney disease which progresses rapidly to kidney failure. They also have neurological problems, immune and hormone deficiencies, and skin problems. Currently there is no cure for SPLIS, and most children do not live past the age of five. We previously showed that when Sgpl1 knockout mice which serve as a model for SPLIS are given a gene therapy that delivers a healthy working copy of the human SGPL1 gene, their survival increased from three weeks to several months. Treatment also delayed the development of many SPLIS features in the mice. In the current study, improvements were made in the adeno-associated virus vector used to deliver the human SGPL1 gene, in hopes of improving the potency of the biologic agent. This new version, called AAV-SPL 2.0, uses a different, potentially stronger promoter to drive the expression of the SGPL1 gene. When given to kidney cells, AAV-SPL 2.0 gene therapy outperforrmed the original agent by 30%. When given to Sgpl1 knockout mice, the new version showed slight improvement in survival to about 5 months or longer. Despite this improvement, over time the treated mice developed kidney disease, which was likely responsible for their demise. Improved kidney targeting may be required to further optimize AAV-SPL gene therapy as a potentially lifesaving treatment for SPLIS.
Scientific Abstract:
Sphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) is an inborn error of metabolism caused by inactivating mutations in SGPL1, the gene encoding sphingosine-1-phosphate lyase (SPL), an essential enzyme needed to degrade sphingolipids. SPLIS features include glomerulosclerosis, adrenal insufficiency, neurological defects, ichthyosis, and immune deficiency. Currently, there is no cure for SPLIS, and severely affected patients often die in the first years of life. We reported that adeno-associated virus (AAV) 9-mediated SGPL1 gene therapy (AAV-SPL) given to newborn Sgpl1 knockout mice that model SPLIS and die in the first few weeks of life prolonged their survival to 4.5 months and prevented or delayed the onset of SPLIS phenotypes. In this study, we tested the efficacy of a modified AAV-SPL, which we call AAV-SPL 2.0, in which the original cytomegalovirus (CMV) promoter driving the transgene is replaced with the synthetic "CAG" promoter used in several clinically approved gene therapy agents. AAV-SPL 2.0 infection of human embryonic kidney (HEK) cells led to 30% higher SPL expression and enzyme activity compared to AAV-SPL. Newborn Sgpl1 knockout mice receiving AAV-SPL 2.0 survived >/= 5 months and showed normal neurodevelopment, 85% of normal weight gain over the first four months, and delayed onset of proteinuria. Over time, treated mice developed nephrosis and glomerulosclerosis, which likely resulted in their demise. Our overall findings show that AAV-SPL 2.0 performs equal to or better than AAV-SPL. However, improved kidney targeting may be necessary to achieve maximally optimized gene therapy as a potentially lifesaving SPLIS treatment.
