Property-Driven Design and Development of Lipids for Efficient Delivery of siRNA

Abstract

Ionizable cationic lipids are critical components involved in nanoparticle formulations, which are utilized in delivery platforms for RNA therapeutics. While general criteria regarding lipophilicity and measured pK a in formulation are understood to have impacts on utility in vivo, greater granularity with respect to the impacts of the structure on calculated and measured physicochemical parameters and the subsequent performance of those ionizable cationic lipids in in vivo studies would be beneficial. Herein, we describe structural alterations made within a lipid class exemplified by 4, which allow us to tune calculated and measured physicochemical parameters for improved performance, resulting in substantial improvements versus the state of the art at the outset of these studies, resulting in good in vivo activity within a range of measured basicity (pK a = 6.0–6.6) and lipophilicity (cLogD = 10–14).

Hepatocyte-specific activity of TSC22D4 triggers progressive NAFLD by impairing mitochondrial function

“…ATX lipid was synthesized as described previously [ 13 ]. LNPs were prepared as described previously [ 14 ] by mixing appropriate volumes of lipids in ethanol with an aqueous phase containing siRNA duplexes using a Nanoassemblr microfluidic device, followed by downstream processing. For the encapsulation of siRNA, desired amount of siRNA ( Tsc22d4 or non-targeting control siRNA) was dissolved in 5 mM citrate buffer (pH 3.5).…”

Nanomaterial Delivery Systems for mRNA Vaccines

“…Arcturus uses a self-amplifying, full-length, unmodified mRNA encoding a pre-fusion SARS-CoV-2 full-length spike protein in an LNP that uses an ionizable lipid with a thioester to link the amine-bearing headgroup to lipid tails via two additional ester groups. Two possible ionizable lipids in this family are Lipid 10a (in Table 4 of [111]) or Lipid 2,2 (8,8) 4C CH3 (on p. 33 of [57]) (Table 2). The latter has three branches, resembling the Moderna Lipid H, but with a degradable thioester linked to the headgroup.…”

Lipid nanoparticles employed in mRNA-based COVID-19 vaccines: An overview of materials and processes used for development and production

“…For example, the reported pKa of the Lipid H, used by Moderna, is 6.75, and Acuitas ALC-0315 lipid used by BioNTech/Pfizer is 6.09 (4). It is worth mentioning that, in this case, in silico pKa calculations proved to be unsuitable, always implying values at least 2-3 units higher that the measured ones, possibly due to high energy of solvation within the LNP lipid phase (26).…”