(549b) Spray Drying to Overcome Cold Storage of RNA-Loaded Lipid Nanoparticles

Lipid Nanoparticles (LNPs) are emerging as delivery vehicles for nucleic acid therapeutics, as evidenced by LNP-based ribonucleic acid (RNA) vaccines for COVID-19. LNPs serve as a delivery platform for encapsulating nucleic acids that are otherwise too unstable in physiological conditions to achieve the desired therapeutic effect. Even when encapsulated, chemical instability of RNA and some of the constituent lipids (over longer time scales than for RNA) necessitates cold chain handling (-20 °C and -70 °C for the Moderna and Pfizer COVID-19 vaccines, respectively) that increases cost and logistical challenges. One way to improve stability is by formulating these products in the solid-state. Solid-state formulations can slow degradation relative to liquid suspensions through two mechanisms: 1) removal of water from the formulation, which is required for many relevant degradation reaction pathways and 2) reduction in molecular mobility in the solid state relative to a liquid. Lyophilization and spray drying have been investigated for drying LNP-based products. Between the two, spray drying is more scalable, offers greater particle engineering capabilities (that may enable pulmonary or nasal delivery), and does not impose a freezing stress on the LNPs.

This talk focuses on spray drying of solid-state LNP formulations. Solid matrix compositions and spray drying process parameters are identified that enable RNA-loaded LNPs to be spray dried and reconstituted with minimal-to-no change in their critical quality attributes (CQAs) of particle size distribution, as measured by dynamic light scattering (DLS), and encapsulation efficiency of RNA, as measured by a RiboGreen fluorescence assay. We investigate the combinations and ratios of these components to best enable a target product profile defined for injectable delivery. The CQAs of spray dried and reconstituted LNPs from matrices composed of various combinations and ratios of these components are compared and implications to product design are discussed. Effects of spray drying process parameters, including liquid to gas mass ratio, atomization pressure, and outlet temperature, are also investigated. Special attention is paid to outlet temperature in order to avoid thermal stress and accelerated RNA degradation kinetics. A novel vacuum spray dryer design was employed to achieve outlet temperatures ranging from 5 – 60 °C. Finally, data is shown for optimized solid-state LNP formulations that result in minimal change to the particle size distribution of the LNPs upon spray drying and reconstitution, maintaining the CQAs of a Z-average diameter of less than 200 nm, polydispersity index less than 0.2, and RNA encapsulation efficiency greater than 80%. CQAs are tracked through accelerated stability studies to demonstrate the benefit of solid-state formulations for product storage and handling.

The results show that careful formulation of solid-state LNPs manufactured via spray drying can provide a scalable path to more widely available LNP-based nucleic acid therapies with improved shelf stability as a dry powder.