A Thermostable nasal spray dried COVID vaccine candidate.

A nasal dry powder adjuvanted subunit COVID vaccine candidate was manufactured via spray drying and evaluated for physicochemical stability and aerosol performance over the course of 10 months under accelerated conditions. A nanoliposomal adjuvant system containing synthetic TLR 4 agonist GLA and synthetic TLR 7/8 agonist 3 M-052 and a trimeric SARS-CoV-2 spike protein antigen were encapsulated using trehalose and varying amounts of trileucine as excipients. 1 % and 3 % trileucine batches as well as a trehalose-only control batch were spray dried to achieve varying levels of particle surface modification and to study the overall effects on stability and aerosol performance. All batches achieved good yields and low processing losses on drying. Samples were held at 25 °C and 40 °C and monitored for physical and chemical stability. All three batches showed excellent performance over the course of the study. Overall morphology; solid phase; moisture content; contents of GLA and 3 M-052; and aerosol performance were largely maintained after exposure to high temperatures for 10 months. Spike protein antigen remained present in all samples after exposure, and liposomal size distributions remained within acceptable ranges for all but one of the samples. Overall, this vaccine candidate showed performance suitable for distribution independent of the cold chain and would be able to withstand high-temperature conditions encountered during last-mile delivery.