Duchenne muscular dystrophy

For DMD c.2916T>G (p.Tyr972Ter), nonsense-suppression remains the most direct currently actionable variant-class strategy because this allele creates a premature stop codon, making translational read-through a better mechanistic fit than therapies that require bespoke editing around the exact site.

ClinVar classifies DMD c.2916T>G (p.Tyr972Ter) as pathogenic. Ataluren was developed specifically for nonsense-mutation Duchenne muscular dystrophy and has shown supportive efficacy signals across randomized and pooled analyses in ambulant nmDMD populations (PMID:28781359; PMID:32851872). More recent placebo-controlled data from Study 041 again supported functional benefit in a prespecified nonsense-mutation subgroup (PMID:40843507). Because p.Tyr972Ter is a true stop-gain DMD allele, it fits the same pathogenic class targeted by read-through therapy even though those trials were not powered for codon-level conclusions.

The direct evidence is for nonsense-mutation DMD as a class, not specifically for p.Tyr972Ter. Clinical benefit from ataluren has remained controversial, and the regulatory picture worsened after the European Medicines Agency moved against renewal in 2024. Any real-world interpretation also depends on age, ambulatory status, concomitant steroids, geography, and access. This should therefore be read as a class-based therapeutic rationale for a stop-gain DMD variant, not proof of variant-specific efficacy.

For DMD c.1950T>A (p.Cys650Ter), nonsense-suppression remains the most direct currently actionable variant-class strategy because the lesion is a premature stop codon, making translational read-through better aligned with the molecular defect than therapies that would require bespoke correction at the exact site.

ClinVar classifies DMD c.1950T>A (p.Cys650Ter) as likely pathogenic. The strongest direct clinical precedent for nonsense-mutation Duchenne muscular dystrophy is ataluren, which was designed for premature stop codons and showed supportive efficacy signals across randomized and pooled analyses in ambulant nmDMD cohorts (PMID:28781359; PMID:32851872). Additional placebo-controlled data from Study 041 also reported functional benefit in a prespecified nonsense-mutation subgroup (PMID:40843507). Because p.Cys650Ter is a stop-gain DMD allele, it falls squarely within the variant class targeted by read-through therapy even though no trial was specific to this codon.

The evidence is class-level for nonsense-mutation DMD, not specific to p.Cys650Ter. Ataluren remains controversial across regulators and payers, and the European regulatory position worsened in 2024. Practical interpretation also depends on age, ambulatory status, background corticosteroid use, geography, and access. This should therefore be read as a mechanism-based rationale for a stop-gain DMD variant, not proof of allele-specific efficacy.

For DMD c.2609T>G (p.Leu870Ter), nonsense-suppression therapy is the most direct currently actionable variant-class strategy because the pathogenic event is a premature stop codon, making translational read-through more mechanistically aligned than approaches that require mutation-specific editing design.

ClinVar classifies DMD c.2609T>G (p.Leu870Ter) as pathogenic. The strongest direct clinical precedent for nonsense-mutation Duchenne muscular dystrophy is ataluren, which was developed specifically for premature stop codons and showed ambulatory benefit signals in randomized and pooled analyses of nmDMD cohorts (PMID:28781359; PMID:32851872). More recent placebo-controlled evidence from Study 041 also reported functional benefit in a prespecified nonsense-mutation subgroup consistent with the read-through mechanism (PMID:40843507). Because p.Leu870Ter is a bona fide stop-gain allele, it fits the biological class targeted by nonsense-suppression therapy even though the trials were not designed around this exact codon.

The evidence is for nonsense-mutation DMD as a class, not specifically for p.Leu870Ter. Clinical benefit from ataluren has remained debated across regulators and payers, and regulatory uncertainty increased after the European Medicines Agency recommended non-renewal of ataluren authorization in 2024. Any practical use also depends on disease stage, steroid background, geography, and access. This is therefore a mechanism-based therapeutic interpretation for a stop-gain DMD allele, not proof of variant-specific efficacy.

Prime Editing (PE5max/PEmax) via Dual-AAV delivery is a rationale-driven therapeutic strategy for Duchenne muscular dystrophy targeting the DMD c.1A>T (p.Met1Leu) variant (Pathogenic, missense variant, initiator_codon_variant, intron variant). The editing system (PEmax with engineered pegRNA) search-and-replace editing that directly rewrites the pathogenic transversion back to wild-type without requiring DSBs. Target tissue: Muscle. Therapeutic goal: Correct or bypass out-of-frame DMD mutations in skeletal and cardiac muscle (e.g., by exon reframing, precise repair, or micro-dystrophin replacement) to restore functional dystrophin expression and p. Risk profile: off-target Low (prime editing has inherently low off-target rate), delivery complexity Medium, immunogenicity High.

1. Molecular basis: DMD NM_004006.3(DMD):c.1A>T (p.Met1Leu) is classified as Pathogenic (ClinVar variation ID 4774215). Molecular consequence: missense variant, initiator_codon_variant, intron variant. Protein change: M1L. 2. Epidemiology: Duchenne muscular dystrophy (DMD) is an X-linked recessive neuromuscular disorder with a birth prevalence around 1 in 3,500–5,000 live male births worldwide. Affected boys typically present in early childhood with delayed motor milestones and proximal weakness, lose independent ambulation around 10– 3. Standard of care: Standard management includes chronic glucocorticoid therapy, cardioprotective medications (ACE inhibitors, beta-blockers), respiratory monitoring with early non-invasive ventilation, spinal and orthopedic interventions, and comprehensive rehabilitation and assistive devices. For specific genotypes, 4. Pipeline: Multiple AAV micro-dystrophin gene-replacement programs have progressed into Phase II/III clinical trials, and at least one micro-dystrophin product has received accelerated approval by the FDA based on increased dystrophin expression and functional outcome trends. Additional exon-skipping agents ta 5. Prime editing validation: PEmax (Chen et al. 2021, Cell) enables precise insertions, deletions, and all 12 point mutations without DSBs. Prime Medicine is advancing PE programs into clinical development. LNP and dual-AAV delivery of PE have been demonstrated in preclinical liver and CNS models.

1. No published data specifically correcting DMD c.1A>T (p.Met1Leu) with Prime Editing (PE5max/PEmax); strategy is based on general principles and must be validated preclinically. 3. Dual-AAV delivery requires intein-mediated protein reconstitution with lower efficiency than single-AAV. Pre-existing AAV immunity in the patient population may limit eligibility. 4. Delivery to Muscle tissue remains a major translational bottleneck. Current vectors have limited transduction efficiency in these compartments. 4. Long-term durability, off-target genome-wide effects, and immunogenicity in the target patient population require thorough preclinical and clinical evaluation.