# Mifepristone alone and in combination with scAAV9-SMN1 gene therapy improves disease phenotypes in Smn2B/- spinal muscular atrophy mice

## TL;DR

This study shows that mifepristone, alone or with gene therapy, improves SMA symptoms in mice by targeting metabolic issues and motor neuron loss.

## Contribution

The study introduces mifepristone as a potential multi-tissue SMA therapy that complements existing SMN-directed treatments.

## Key findings

- Mifepristone reduces Klf15 expression in cellular and animal models of SMA.
- Mifepristone improves survival and neuromuscular pathology in SMA mice.
- Combining mifepristone with scAAV9-SMN1 gene therapy enhances treatment outcomes in a sex- and tissue-specific manner.

## Abstract

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by deletions or mutations in the survival motor neuron 1 (SMN1) gene. SMA is characterised by alpha motor neuron loss in the spinal cord and subsequent muscle atrophy. There are currently three approved SMN-directed therapies for SMA patients. While these therapies have transformed what was once a life-limiting condition into one that can be managed and even improved, they are unfortunately not cures, highlighting the need for additional supporting second-generation therapies. These should not only target the neuromuscular system but also peripheral and metabolic perturbations that are present in both SMA models and patients. Krüppel-like factor 15 (Klf15) is a transcription factor that maintains metabolic homeostasis, is involved in the glucocorticoid-glucocorticoid receptor (GR) signalling pathway and is dysregultated in several peripheral and metabolic tissues in SMA mice. Here, we used murine and human cellular models as well as SMA mice and Caenorhabditis Elegans (C. elegans) to assess the therapeutic potential of reducing Klf15 activity with mifepristone, a glucocorticoid antagonist, combined with a SMN-targeted gene therapy. We report that mifepristone reduces Klf15 expression across several in vitro models, ameliorates neuromuscular pathology in SMA smn-1(ok355) C. elegans and improves survival of SMA Smn2B/- mice. Furthermore, we show that combining mifepristone with an approved SMN-directed gene therapy (scAAV9-SMN1) results in improved tissue- and sex-specific responses to treatment. Our study demonstrates that a multi-tissue targeting SMN-independent drug, alone and in combination with an approved SMN-dependent therapy, has the potential to improve SMA disease pathology.

The online version contains supplementary material available at 10.1038/s41598-025-24050-3.