Preclinical evaluation of a SARS-CoV-2 mRNA vaccine PTX-COVID19-B

Liu, Jun; Budylowski, Patrick; Samson, Reuben; Griffin, Bryan D.; Babuadze, Giorgi; Rathod, Bhavisha; Colwill, Karen; Abioye, Jumai A.; Schwartz, Jordan A; Law, Ryan; Yip, Lily; Ahn, Sang Kyun; Chau, Serena; Naghibosadat, Maedeh; Arita, Yuko; Hu, Queenie; Yue, Feng Yun; Banerjee, Arinjay; Mossman, Karen; Mubareka, Samira; Kozak, Robert A.; Pollanen, Michael S.; Orozco, Natalia Martin; Gingras, Anne-Claude; Marcusson, Eric G.; Ostrowski, Mario A.

Safe and effective vaccines are needed to end the COVID-19 pandemic caused by SARS-CoV-2. Here we report the preclinical development of a lipid nanoparticle (LNP) formulated SARS-CoV-2 mRNA vaccine, PTX-COVID19-B. PTX-COVID19-B was chosen among three candidates after the initial mouse vaccination results showed that it elicited the strongest neutralizing antibody response against SARS-CoV-2. Further tests in mice and hamsters indicated that PTX-COVID19-B induced robust humoral and cellular immune responses and completely protected the vaccinated animals from SARS-CoV-2 infection in the lung. Studies in hamsters also showed that PTX-COVID19-B protected the upper respiratory tract from SARS-CoV-2 infection. Mouse immune sera elicited by PTX-COVID19-B vaccination were able to neutralize SARS-CoV-2 variants of concern (VOCs), including the B.1.1.7, B.1.351 and P.1 lineages. No adverse effects were induced by PTX-COVID19-B in both mice and hamsters. These preclinical results indicate that PTX-COVID19-B is safe and effective. Based on these results, PTX-COVID19-B was authorized by Health Canada to enter clinical trials in December 2020 with a phase 1 clinical trial ongoing (ClinicalTrials.gov number: NCT04765436). One Sentence Summary PTX-COVID19-B is a SARS-CoV-2 mRNA vaccine that is highly immunogenic, safe, and effective in preventing SARS-CoV-2 infection in mice and hamsters and is currently being evaluated in human clinical trials.