AAV9 gene therapy shows biochemical improvement, stable motor scores in GM1 gangliosidosis phase 1-2 trial

This phase 1-2, open-label, dose-escalation study evaluated a single intravenous infusion of adeno-associated virus serotype 9 (AAV9) encoding β-galactosidase in nine children with type II GM1 gangliosidosis (late-infantile or juvenile onset), with a follow-up of 36 months. The primary endpoint was safety. Secondary endpoints included changes in cerebrospinal fluid (CSF) GM1 ganglioside concentration and β-galactosidase activity, clinical assessments (Clinical Global Impression-Improvement [CGI-I] score, scale 1-7), and neuroimaging patterns.

Over the 3-year period, 124 adverse events occurred. The investigator deemed 30 of these as possibly, probably, or definitely related to the gene therapy: 8 gastrointestinal events, 21 laboratory abnormalities associated with inflammation, and 1 tachycardia event. Five serious adverse events occurred, including one hospitalization for vomiting attributed to the gene therapy. Serum aspartate and alanine aminotransferase levels increased in all participants and returned to baseline by 18 months.

Regarding secondary endpoints, all participants showed an increase in CSF β-galactosidase level and a decrease in CSF GM1 ganglioside level. Expressive communication and gross motor scores appeared stable, while fine motor and receptive communication scores decreased. The median CGI-I score was 3 (indicating minimal improvement) at 2 years and 4 (indicating no change) at 3 years; the abstract notes that in historical controls, scores have been shown to increase (indicating worsening) over time. Neuroimaging showed patterns consistent with reduced rates of cerebral atrophy and favorable changes in myelination compared with baseline.

The study concluded that the therapy was associated with adverse events, including severe vomiting in one participant and elevated liver enzymes in all. Secondary endpoint results suggested improvements in biochemical markers and neuroimaging patterns and stable or reduced rates of developmental deterioration in some measures.

Imagine watching your child lose the ability to move and communicate because of a rare, fatal brain disease with no treatment. That's the reality of GM1 gangliosidosis. In a first-of-its-kind trial with nine children, doctors tested a single dose of gene therapy delivered into the bloodstream. The goal was to replace the missing enzyme that causes toxic buildup in the brain. The treatment wasn't easy. All children had elevated liver enzymes that took up to 18 months to return to normal, and one child was hospitalized for severe vomiting linked to the therapy. But there were hopeful signs. The toxic substance in the spinal fluid went down, and the needed enzyme went up. Brain scans suggested the rate of brain shrinkage slowed and there were positive changes in the brain's wiring. While skills like expressive communication and large movements appeared stable, fine motor skills and understanding language still declined. Overall, doctors rated the children as having minimal improvement or no change over 2-3 years, which is notable because without treatment, children with this disease typically get much worse. This early trial shows the therapy engages with the disease and may alter its course, offering a crucial first step for families desperate for options.