For UGT1A1 c.847C>T (p.Gln283Ter), liver-directed gene replacement remains the clearest current platform fit

For UGT1A1 c.847C>T (p.Gln283Ter), a pathogenic nonsense variant expected to abolish bilirubin UDP-glucuronosyltransferase activity, liver-directed gene replacement remains the clearest current platform fit because it restores functional UGT1A1 without needing to rescue the specific stop codon. As with other severe UGT1A1 loss-of-function alleles, the central unresolved issue is durable bilirubin control in young patients rather than variant-to-platform compatibility.

ClinVar classifies c.847C>T (p.Gln283Ter) as pathogenic. Optimized AAV-UGT1A1 programs have shown durable bilirubin correction in preclinical Crigler-Najjar models, establishing a strong mechanistic basis for gene addition in null UGT1A1 genotypes (PMID:27722180; PMID:29448836). In the clinic, GNT0003 has produced meaningful bilirubin reduction and large 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 nonsense allele like p.Gln283Ter, this disease-level logic is more mature than any codon-specific suppression or editing concept.

The evidence is disease-level, not variant-specific. Pediatric hepatocyte turnover, immune barriers, uncertain redosing feasibility, and comparison with liver transplantation remain the decisive translational constraints. This post should therefore be read as a strong platform-fit statement for a null UGT1A1 allele, not as proof that p.Gln283Ter has unique clinical responsiveness.