ASL mRNA-LNP Therapeutic for the Treatment of Argininosuccinic Aciduria Enables Survival Benefit in a Mouse Model

Argininosuccinic aciduria (ASA) is a metabolic disorder caused by a deficiency in argininosuccinate lyase (ASL), which cleaves argininosuccinic acid to arginine and fumarate in the urea cycle. ASL deficiency (ASLD) leads to hepatocyte dysfunction, hyperammonemia, encephalopathy, and respiratory alkalosis. Here we describe a novel therapeutic approach for treating ASA, based on nucleoside-modified messenger RNA (modRNA) formulated in lipid nanoparticles (LNP). To optimize ASL-encoding mRNA, we modified its cap, 5 & PRIME; and 3 & PRIME; untranslated regions, coding sequence, and the poly(A) tail. We tested multiple optimizations of the formulated mRNA in human cells and wild-type C57BL/6 mice. The ASL protein showed robust expression in vitro and in vivo and a favorable safety profile, with low cytokine and chemokine secretion even upon administration of increasing doses of ASL mRNA-LNP. In the ASL(Neo/Neo) mouse model of ASLD, intravenous administration of the lead therapeutic candidate LNP-ASL CDS2 drastically improved the survival of the mice. When administered twice a week lower doses partially protected and 3 mg/kg LNP-ASL CDS2 fully protected the mice. These results demonstrate the considerable potential of LNP-formulated, modified ASL-encoding mRNA as an effective alternative to AAV-based approaches for the treatment of ASA.

Automated summary

This study describes a novel therapeutic approach for the treatment of argininosuccinic aciduria (ASA), using nucleoside-modified messenger RNA (modRNA) formulated in lipid nanoparticles (LNP). Multiple modifications of ASL mRNA were tested and resulted in robust ASL protein expression in vitro and in vivo. The lead therapeutic candidate, LNP-ASL CDS2, significantly improved the survival of mice in an ASL-deficient mouse model. These findings demonstrate the considerable potential of LNP-formulated modified ASL-encoding mRNA as a treatment for ASA.