Optimizing Lipid Nanoparticles for Delivery in Primates.

Lipid nanoparticles (LNPs) are clinically proven to successfully deliver both small interfering RNA (siRNA) therapeutics and larger mRNA payloads for prophylactic vaccine applications. Non-human primates (NHPs) are generally considered to be the most predictive of human responses. However, for ethical and economic reasons, LNP compositions have historically been optimized in rodents. It has been difficult to translate LNP potency data from rodents to NHPs for intravenously (IV) administered products in particular. This presents a major challenge for preclinical drug development. An attempt to investigate LNP parameters, which have historically been optimized in rodents, is carried out, and seemingly innocuous changes are found to result in large potency differences between species. For example, the ideal particle size for NHPs (50-60 nm) is found to be smaller than for rodents (70-80 nm). Surface chemistry requirements are also different, with almost double the amount of poly(ethylene glycol) (PEG)-conjugated lipid needed for maximal potency in NHPs. By optimizing these two parameters, approximately eight-fold increase in protein expression from intravenously administered messenger RNA (mRNA)-LNP in NHP is gained. The optimized formulations are well tolerated when administered repeatedly with no loss of potency. This advancement enables the design of optimal LNP products for clinical development.

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' and 3' 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 ASLNeo/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.