Preliminary Evaluation of Formulations for Stability of mRNA-LNPs Through Freeze-Thaw Stresses and Long-Term Storage

Ionizable lipid nanoparticles were a crucial contribution to the effective packaging and delivery of mRNA informational drugs for vaccines and therapeutic applications. However, thermal instability and the need for ultracold storage present significant challenges during distribution and administration, even during non-pandemic periods like epidemics. Ongoing efforts include engineering novel lipids or optimizing mRNA-LNP formulations with different buffers, excipients, and surfactants to enable extended storage at room temperature (RT) or refrigerated conditions (4 ˚C). Methods: In this study, six sugar-surfactant excipient combinations in tris buffer were evaluated for extending the stability of mRNA-LNPs. The experimentation included two phases of screening: first, the evaluation of six formulations under repeated freeze-thaw (−20 °C) cycles, and second, a long-term storage evaluation of the best formulations at RT, 4 °C, − 20 °C and −80 °C. LNPs were formulated with the ionizable lipids ALC-0315 or SM-102. Results: Sucrose-P188 and mannitol-F127 combinations effectively preserved physicochemical properties like encapsulation efficiency (EE), polydispersity index (PDI), and z-average (size) of mRNA-LNPs. Surfactants in the screened formulations reduced the aggregation of LNPs. Storage at −20 °C with sucrose-P188 extended LNP stability beyond ultra-low temperature requirements, showing potential for removing logistical hurdles to improve global delivery by eliminating the need for ultracold storage. Excipients in non-frozen conditions preserved the LNP quality attributes, but the RNA integrity was affected. On the other hand, mRNA degradation was minimized when frozen, but LNP quality was affected, underscoring the challenging trade-off during storage condition optimization. Conclusions: This work highlights the potential of improved formulations to preserve mRNA-LNP functionality and emphasizes the need for further systematic studies on a library of excipient and surfactant combinations, paving the way for stable storage under less stringent conditions.