Rapid and definitive treatment of phenylketonuria in variant-humanized mice with corrective editing

Phenylketonuria (PKU), an autosomal recessive disorder caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene, results in the accumulation of blood phenylalanine (Phe) to neurotoxic levels. Current dietary and medical treatments are chronic and reduce, rather than normalize, blood Phe levels. Among the most frequently occurring PAH variants in PKU patients is the P281L (c.842C>T) variant. Using a CRISPR prime-edited hepatocyte cell line and a humanized PKU mouse model, we demonstrate efficient in vitro and in vivo correction of the P281L variant with adenine base editing. With the delivery of ABE8.8 mRNA and either of two guide RNAs in vivo using lipid nanoparticles (LNPs) in humanized PKU mice, we observe complete and durable normalization of blood Phe levels within 48 h of treatment, resulting from corrective PAH editing in the liver. These studies nominate a drug candidate for further development as a definitive treatment for a subset of PKU patients. The PAH P281L variant is one of the most common variants identified in phenylketonuria (PKU) patients. Here, the authors use base editing, enabled by lipid nanoparticle/mRNA technology, to directly correct the P281L variant in the liver in PKU mice and definitively treat the disease within 2 days.

Automated summary

Phenylketonuria (PKU) is a genetic disorder caused by pathogenic variants in the PAH gene, resulting in harmful levels of phenylalanine (Phe) in the blood. Current treatments are inadequate in normalizing Phe levels. The P281L variant is common in PKU patients. This study demonstrates the correction of the P281L variant in liver cells and mice using base editing, leading to complete and durable normalization of blood Phe levels within 48 hours. This research provides a potential definitive treatment for a subset of PKU patients.