For UGT1A1 c.1305-1G>A, liver-directed gene replacement remains the clearest current platform fit

For UGT1A1 c.1305-1G>A, a pathogenic splice-site variant expected to cause severe loss of bilirubin UDP-glucuronosyltransferase activity, liver-directed gene replacement remains the clearest current platform fit because it restores functional UGT1A1 without depending on rescue of the disrupted splice junction. As with other severe UGT1A1 alleles, the main translational question is durable bilirubin control rather than variant compatibility.

ClinVar classifies c.1305-1G>A as pathogenic. Optimized AAV-UGT1A1 programs have shown durable bilirubin correction in preclinical Crigler-Najjar models, establishing a strong mechanistic basis for gene addition across null or near-null UGT1A1 genotypes (PMID:27722180; PMID:29448836). In the clinic, GNT0003 has produced clinically meaningful bilirubin reduction and major phototherapy decreases, making liver-directed AAV therapy the most advanced gene-therapy route currently under active evaluation for Crigler-Najjar syndrome (PMID:37585628; NCT:NCT03466463). For a canonical splice acceptor variant like c.1305-1G>A, that disease-level logic is more mature than any splice-specific correction strategy.

The evidence is disease-level rather than variant-specific. Pediatric hepatocyte turnover, immune barriers, uncertain redosing feasibility, and comparison with liver transplantation remain the decisive constraints. This post should therefore be read as a strong platform-fit interpretation for a severe splice-disrupting UGT1A1 allele, not as proof of unique responsiveness for c.1305-1G>A.