Preclinical efficacy, safety, and immunogenicity of PHH-1V, a second-generation COVID-19 vaccine, in non-human primates

SARS-CoV-2 emerged in December 2019 and quickly spread worldwide, continuously striking with an unpredictable evolution. Despite the success in vaccine production and mass vaccination programmes, the situation is not still completely controlled, and therefore accessible second-generation vaccines are required to mitigate the pandemic. We previously developed an adjuvanted vaccine candidate coded PHH-1V, based on a heterodimer fusion protein comprising the RBD domain of two SARS-CoV-2 variants. Here, we report data on the efficacy, safety, and immunogenicity of PHH-1V in cynomolgus macaques. PHH-1V prime-boost vaccination induces high levels of RBD-specific IgG and IgA binding and neutralising antibodies against several SARS-CoV-2 variants of concern, as well as a balanced Th1/Th2 cellular immune response. Remarkably, PHH-1V vaccination prevents SARS-CoV-2 replication in the lower respiratory tract and significantly reduces viral load in the upper respiratory tract after an experimental infection. These results highlight the potential use of the PHH-1V vaccine in humans, currently undergoing Phase III clinical trials. ### Competing Interest Statement Authors indicated as "1" are employees of HIPRA, a private pharmaceutical company that develops and manufactures biological medicines such as vaccines. IrsiCaixa, UPF, Cynbiose, CIRI, VirNext have received financial support from HIPRA. Several patent applications have been filed by HIPRA SCIENTIFIC S.L.U. and Laboratorios HIPRA, S.A. on different SARS-CoV-2 vaccine candidates and SARS-CoV-2 subunit vaccines, including the novel recombinant RBD fusion heterodimer PHH-1V. Antonio Barreiro, Antoni Prenafeta, Luis Gonzalez, Laura Ferrer, Ester Puigvert, Jordi Palmada, Teresa Prat and Carme Garriga are the inventors of these patent applications.