Prime Editing (PE5max/PEmax) for DMD c.1A>T (p.Met1Leu) in Duchenne muscular dystrophy

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.
2. 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.
3. 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.