OR08

AAV-mediated gene therapy of acid ceramidase deficiency by intravenous and CSF-directed vector administration

J Dernard(1) M Marinello(1) M Derome(1) V Latournerie(1) D Bonnin(1) L Mangin(1) S Martin(1) J A Medin(2) A Buj-Bello(1)

1:Genethon, UMR_S951, Inserm, Univ Evry, Université Paris Saclay, EPHE; 2:Medical College of Wisconsin

Farber disease and spinal muscular atrophy with progressive myoclonic epilepsy are two ultra-rare lysosomal storage disorders resulting from loss-of-function mutations in the ASAH1 gene encoding for acid ceramidase (ACDase). This enzyme catalyzes the conversion of ceramide, a bioactive lipid, into sphingosine and fatty acid. ACDase deficiency leads to the intracellular accumulation of ceramides with an inflammatory response in tissues. These two diseases manifest differently but are part of a clinical continuum with variable severity affecting the nervous system and/or peripheral tissues. Currently, there is no curative treatment, highlighting a significant unmet medical need.

In the present study, we assessed the efficacy of a gene therapy approach with an AAV9 vector expressing human ACDase in a severe mouse model of acid ceramidase deficiency (Asah1ᴾ³⁶¹ᴿᐟᴾ³⁶¹ᴿ) by two routes of administration, intravenous and intracerebroventricular. We performed a dose escalation study by intravenous injection with three vector doses and found that the low dose was suboptimal, whereas most pathological parameters were corrected at mid dose. Detailed histological analysis of treated mutant mice 6 months post-injection revealed that the high dose was able to correct the presence of inflammatory infiltrates in tissues, including the central nervous system (CNS). We also report that intracerebroventricular vector administration prolonged lifespan, improved body growth and enhanced motor activity. While treatment effectively mitigated CNS symptoms, it did not fully address peripheral organ manifestations.

Our findings provide proof-of-concept that systemic AAV-mediated ASAH1 gene replacement can correct the whole-body phenotype of Asah1ᴾ³⁶¹ᴿᐟᴾ³⁶¹ᴿ mice and pave the way for clinical translation in patients.