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Preprint WatchMildOctober 16th, 2026

Neonatal Delivery of Exon Skipping Therapeutics Maximizes Brain Dystrophin Rescue in the Mdx52 Mouse Model of Duchenne Muscular Dystrophy

VACCA, O.; Doisy, M.; Nagy, C.; Saoudi, A.; Phongsavanh, X. M.; Le Coz, O.; Vaillend, C.; Goyenvalle, A.

Neonatal, central nervous system directed AAV9-U7snRNA exon 51 skipping produces sustained brain dystrophin restoration of 20 to 50 percent of Dp427 in the mdx52 mouse, where antisense oligonucleotide delivery is only transient, so early CNS-directed dystrophin rescue is a tractable route to the cognitive comorbidities of Duchenne muscular dystrophy.

Mild contradiction

1 prior failure

One documented clinical failure (Phase 1 or 2) overlaps with the claimed mechanism.

This preprint reports that neonatal intracerebroventricular delivery of an AAV9-U7snRNA exon 51 skipping construct produced sustained exon skipping across hippocampus, cortex and cerebellum in mdx52 mice, restoring 20 to 50 percent of Dp427 dystrophin in brain, whereas antisense oligonucleotide delivery gave only transient rescue. The mechanistic claim is that the central nervous system comorbidities of Duchenne muscular dystrophy are addressable if dystrophin restoration starts early and is delivered directly to the brain. Claidex holds one recorded DMD failure, ataluren in nonsense-mutation Duchenne muscular dystrophy, where the Phase 3 extension was stopped by sponsor decision rather than on an efficacy or safety read (ataluren-dmd-nonsense-mutation-duchenne-phase3-extension-sponsor-termination). That failure does not contradict this preprint. The two address different mutation classes and different modalities, and the recorded stop reason carries no mechanistic information about dystrophin restoration. The flag is MILD on that basis. The claim worth watching is the implicit one about timing: a therapeutic window that closes in the neonatal period would make adult-onset trials a poor test of the hypothesis, which is a design consideration rather than a contradiction of anything Claidex has recorded.

Abstract excerpt

Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene, resulting in the loss of dystrophin expression. Beyond progressive muscle degeneration, nearly half of patients exhibit cognitive and behavioral impairments, highlighting the need for effective central nervous system (CNS) therapies. In this study, we investigated whether neonatal delivery could maximize brain dystrophin rescue in mdx52 mice using exon 51 skipping strategies. We compared systemic and intracerebroventricular (ICV) delivery of an antisense oligonucleotide (ASO-51) and an AAV9-mediated U7snRNA approach (scAAV9-U7-Ex51), administered neonatally. Neonatal intravenous ASO-51 induced widespread but transient exon skipping, resulting in limited brain dystrophin restoration. ICV administration markedly increased CNS exon skipping but did not overcome the limited persistence of ASO, leading to progressive loss of exon skipping and dystrophin rescue. In contrast, neonatal ICV delivery of scAAV9-U7-Ex51 achieved robust, widespread, and sustained exon 51 skipping throughout the brain, including the hippocampus, cortex, and cerebellum, resulting in 20-50% restoration of Dp427 expression. These findings demonstrate that early CNS-directed delivery enhances brain dystrophin restoration and establish AAV-U7-mediated exon skipping as a promising strategy for addressing CNS comorbidities in DMD.

Matching Claidex post-mortems

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This is an automated contradiction flag, not an editorial judgment on the preprint's quality. Flags identify where the preclinical literature and the clinical failure record diverge.