High Efficacy of Therapeutic Equine Hyperimmune Antibodies Against SARS-CoV-2 Variants of Concern

Moreira-Soto, Andres; Arguedas, Mauricio; Brenes, Hebleen; Buján, Willem; Corrales-Aguilar, Eugenia; Díaz, Cecilia; Echeverri, Ann; Flores-Díaz, Marietta; Gómez, Aarón; Hernández, Andrés; Herrera, María; León, Guillermo; Macaya, Román; Kühne, Arne; Molina-Mora, José Arturo; Mora, Javier; Sanabria, Alfredo; Sánchez, Andrés; Sánchez, Laura; Segura, Álvaro; Segura, Eduardo; Solano, Daniela; Soto, Claudio; Stynoski, Jennifer L.; Vargas, Mariángela; Villalta, Mauren; Reusken, Chantal B. E. M.; Drosten, Christian; Gutiérrez, José María; Alape-Girón, Alberto; Drexler, Jan Felix

SARS-CoV-2 variants of concern show reduced neutralization by vaccine-induced and therapeutic monoclonal antibodies; therefore, treatment alternatives are needed. We tested therapeutic equine polyclonal antibodies (pAbs) that are being assessed in clinical trials in Costa Rica against five globally circulating variants of concern: alpha, beta, epsilon, gamma and delta, using plaque reduction neutralization assays. We show that equine pAbs efficiently neutralize the variants of concern, with inhibitory concentrations in the range of 0.146–1.078 μg/mL, which correspond to extremely low concentrations when compared to pAbs doses used in clinical trials. Equine pAbs are an effective, broad coverage, low-cost and a scalable COVID-19 treatment.