Canine mucopolysaccharidosis VII

Base Editing (ABE8e) via AAV9 delivery is a rationale-driven therapeutic strategy for Canine mucopolysaccharidosis VII targeting the GUSB c.526C>T (p.Leu176Phe) variant (Pathogenic, missense variant, non-coding transcript variant, intron variant). The editing system (ABE8e-nSpCas9 (adenine base editor)) converts the pathogenic A back to G on the target strand, restoring the wild-type codon. Target tissue: CNS. Therapeutic goal: Correct loss-of-function mutations in GUSB in affected dogs (e.g., c.559G>A / p.Arg166His) via in vivo gene replacement or precise editing at the endogenous locus to restore beta-glucuronidase activit. Risk profile: off-target Medium (bystander bases in editing window), delivery complexity Medium, immunogenicity High (AAV pre-existing immunity).

1. Molecular basis: GUSB NM_000181.4(GUSB):c.526C>T (p.Leu176Phe) is classified as Pathogenic (ClinVar variation ID 905). Molecular consequence: missense variant, non-coding transcript variant, intron variant. Protein change: L176F. 2. Epidemiology: Canine mucopolysaccharidosis VII (MPS VII) is a rare, autosomal recessive lysosomal storage disease reported in multiple dog breeds and also in cats and mice as spontaneous models. Genetic summaries indicate that spontaneous canine and feline models faithfully recapitulate human MPS VII with residua 3. Standard of care: There is no widely adopted, approved disease-modifying therapy for canine MPS VII in routine veterinary practice. Management in spontaneous canine/feline models is largely supportive, focusing on symptomatic treatment for skeletal deformities, mobility issues, respiratory compromise, and quality of 4. Pipeline: Canine MPS VII is one of the best-developed large-animal models for LSD gene therapy. Neonatal liver-directed AAV gene therapy with a GUSB transgene has produced systemic enzyme expression, improved skeletal manifestations, and prolonged survival for more than a decade after a single neonatal dose ( 5. ABE clinical validation: ABE8e (Richter et al. 2020, Nat Biotechnol) achieves ~1.7x higher editing efficiency than ABE7.10. VERVE-101 demonstrated first-in-human LNP-ABE liver editing with 55-66% PCSK9 reduction (Raal et al. 2025, NEJM). Beam Therapeutics is advancing multiple ABE programs.

1. No published data specifically correcting GUSB c.526C>T (p.Leu176Phe) with Base Editing (ABE8e); strategy is based on general principles and must be validated preclinically. 2. PAM availability and bystander base analysis for the specific genomic context have not been performed. If no canonical NGG PAM positions the target within the editing window, PAM-flexible variants (SpRY) may be needed. 4. Delivery to CNS 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.

Base Editing (ABE8e) via AAV9 delivery is a rationale-driven therapeutic strategy for Canine mucopolysaccharidosis VII targeting the GUSB c.526C>T (p.Leu176Phe) variant (Pathogenic, missense variant, non-coding transcript variant, intron variant). The editing system (ABE8e-nSpCas9 (adenine base editor)) converts the pathogenic A back to G on the target strand, restoring the wild-type codon. Target tissue: CNS. Therapeutic goal: Correct loss-of-function mutations in GUSB in affected dogs (e.g., c.559G>A / p.Arg166His) via in vivo gene replacement or precise editing at the endogenous locus to restore beta-glucuronidase activit. Risk profile: off-target Medium (bystander bases in editing window), delivery complexity Medium, immunogenicity High (AAV pre-existing immunity).

1. Molecular basis: GUSB NM_000181.4(GUSB):c.526C>T (p.Leu176Phe) is classified as Pathogenic (ClinVar variation ID 905). Molecular consequence: missense variant, non-coding transcript variant, intron variant. Protein change: L176F. 2. Epidemiology: Canine mucopolysaccharidosis VII (MPS VII) is a rare, autosomal recessive lysosomal storage disease reported in multiple dog breeds and also in cats and mice as spontaneous models. Genetic summaries indicate that spontaneous canine and feline models faithfully recapitulate human MPS VII with residua 3. Standard of care: There is no widely adopted, approved disease-modifying therapy for canine MPS VII in routine veterinary practice. Management in spontaneous canine/feline models is largely supportive, focusing on symptomatic treatment for skeletal deformities, mobility issues, respiratory compromise, and quality of 4. Pipeline: Canine MPS VII is one of the best-developed large-animal models for LSD gene therapy. Neonatal liver-directed AAV gene therapy with a GUSB transgene has produced systemic enzyme expression, improved skeletal manifestations, and prolonged survival for more than a decade after a single neonatal dose ( 5. ABE clinical validation: ABE8e (Richter et al. 2020, Nat Biotechnol) achieves ~1.7x higher editing efficiency than ABE7.10. VERVE-101 demonstrated first-in-human LNP-ABE liver editing with 55-66% PCSK9 reduction (Raal et al. 2025, NEJM). Beam Therapeutics is advancing multiple ABE programs.

1. No published data specifically correcting GUSB c.526C>T (p.Leu176Phe) with Base Editing (ABE8e); strategy is based on general principles and must be validated preclinically. 2. PAM availability and bystander base analysis for the specific genomic context have not been performed. If no canonical NGG PAM positions the target within the editing window, PAM-flexible variants (SpRY) may be needed. 4. Delivery to CNS 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.