mRNA-3351

**mRNA-3351** is an investigational mRNA-based therapeutic that encodes for the human enzyme UDP-glucuronosyltransferase 1A1 (UGT1A1). It is designed to restore the missing or dysfunctional UGT1A1 protein in patients with Crigler-Najjar syndrome type 1, an ultra-rare, genetically inherited disorder caused by mutations in the UGT1A1 gene resulting in the inability to metabolize bilirubin[1][2][3][5]. This leads to severe jaundice and risk of neurological damage or death without treatment. mRNA-3351 is delivered using Moderna’s proprietary lipid nanoparticle (LNP) formulation. The therapy aims to reduce toxic bilirubin buildup by enabling patient cells to produce functional UGT1A1, thus potentially replacing lifelong phototherapy or liver transplantation[1][2][3][5]. Moderna has granted a Rare Pediatric Disease designation for mRNA-3351 from the FDA, and it is being developed collaboratively with the Institute for Life Changing Medicines (ILCM) who is responsible for clinical development[1][2][3][5].