Abstract
Classical homocystinuria (HCU) is an autosomal recessive metabolic disorder caused by mutations in the cystathionine β-synthase (CBS) gene, leading to the accumulation of toxic levels of homocysteine and methionine. Current therapeutic options, including dietary methionine restriction and betaine supplementation, offer suboptimal metabolic control and suffer from extremely poor patient compliance. In this study, we evaluated the therapeutic potential of lipid nanoparticle (LNP)-mediated delivery of mRNA encoding human CBS (hCBS) in a transgenic mouse model of HCU (I278T Cbs-/-). We formulated LNPs containing modified hCBS mRNA using a high-throughput microfluidic mixing process. A single intravenous administration of hCBS mRNA-LNPs resulted in rapid, dose-dependent restoration of functional hepatic CBS enzyme activity. Crucially, this treatment led to a dramatic 91% reduction in plasma total homocysteine (tHcy) levels within 24 hours, alongside a significant increase in downstream transsulfuration metabolites. Repeated weekly dosing over six weeks maintained stable metabolic correction, prevented the development of hepatic lipid accumulation, and improved trabecular bone mineral density in treated mice. These results demonstrate that LNP-mediated mRNA therapy can safely and effectively restore metabolic homeostasis in vivo, highlighting its potential as a highly translatable therapeutic platform for the clinical management of classical homocystinuria.
