Analytical Characterization of Heterogeneities in mRNA-Lipid Nanoparticles Using Sucrose Density Gradient Ultracentrifugation.

Rational design and robust formulation processes are critical for optimal delivery of mRNA by lipid nanoparticles (LNPs). Varying degrees of heterogeneity in mRNA-LNPs can affect their biophysical and functional properties. Given the profound complexity of mRNA-LNPs, it is critical to develop comprehensive and orthogonal analytical techniques for a better understanding of these formulations. To this end, we developed a robust ultracentrifugation method for density-based separation of subpopulations of mRNA-LNPs. Four LNP formulations encapsulating human erythropoietin (hEPO) with varying functionalities were synthesized using two ionizable lipids, A and B, and two helper lipids, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and 1,2-dierucoyl-sn-glycero-3-phosphoethanolamine (DEPE), along with cholesterol and DMG-PEG-2K. Upon ultracentrifugation on a sucrose gradient, a distinct pattern of "fractions" was observed across the gradient, from the less dense topmost fraction to the increasingly denser bottom fractions, which were harvested for comprehensive analyses. Parent LNPs, A-DOPE and B-DOPE, were resolved into three density-based fractions, each differing significantly in the hEPO expression following intravenous and intramuscular routes of administration. Parent B-DEPE LNPs resolved into two density-based fractions, with most of the payload and lipid content being attributed to the topmost fraction compared to the lower one, indicating some degree of heterogeneity, while parent A-DEPE LNPs showed remarkable homogeneity, as indicated by comparable in vivo potency, lipid numbers, and particle count among the three density-based fractions. This study is the first to demonstrate the application of density gradient-based ultracentrifugation (DGC) for a head-to-head comparison of heterogeneity as a function of biological performance and biophysical characteristics of parent mRNA-LNPs and their subpopulations.

Inhalable dry powder product (DPP) of mRNA lipid nanoparticles (LNPs) for pulmonary delivery.

Pulmonary delivery of mRNA via inhalation is a very attractive approach for RNA-based therapy for treatment of lung diseases. In this work, we have demonstrated successful development of an mRNA-lipid nanoparticle (LNP) dry powder product (DPP), wherein the LNPs were spray dried using hydroalcoholic solvent along with mannitol and leucine as excipients. The desired critical attributes for the DPP were accomplished by varying the excipients, lipid composition, concentration of LNPs, and weight percentage of mRNA. Leucine alone or in combination with mannitol improved the formulation by increasing the mRNA yield as well as decreasing the particle size. Intratracheal administration of the DPP in mice resulted in luciferase expression in the trachea and lungs indicating successful delivery of functional mRNA. Our results show formulation optimization of mRNA LNPs administered in the form of DPP results in an efficacious functional delivery with great promise for future development of mRNA therapeutics for lung diseases.