In June, two studies in Science reported an antibody cocktail against SARS-CoV-2 developed from studies in humanized mice and recovering patients. The two antibody cocktail was designed to bind the virus to reduce the risk of a drug-resistant form emerging. Now, expanding upon this work, researchers show this antibody cocktail offers benefits in animal models that mimic the diverse pathology of SARS-CoV-2 infection, both when administered prophylactically and therapeutically. "These findings highlight the therapeutic potential of [this approach] to both protect from and treat SARS-CoV-2 disease," the authors say. While multiple studies have described discovery and characterization of potent neutralizing monoclonal antibodies against SARS-CoV-2, evaluation of the efficacy of these antibodies in vivo is limited, and it's largely focused on the prophylactic setting. As well, no single animal model has emerged as being more relevant for human disease, which has led some to say multiple animal models may be required to mimic various settings of human infection. Building on studies Johanna Hansen et al. and Alina Baum et al. published in Science in June that identified and characterized a double antibody therapy, Baum and colleagues tested this cocktail, REGN-COV2, in rhesus macaques, which manifest mild COVID-19 symptoms, and in golden hamsters, which show symptoms that are much more severe, including rapid weight loss. When administered three days before viral challenge, treatment almost completely blocked establishment of viral infection in macaques, the authors say. This ability, they note, "matches or exceeds the effects recently shown in vaccine efficacy studies using the same animal models." In macaques treated with the drug one day after infection, the authors report faster viral clearance than in controls who'd not been treated. Next, the authors used the hamster model to evaluate the drug's ability to alter the disease course in more severe cases. Hamsters treated with the drug two days before infection exhibited a "dramatic protection from weight loss" and decreased viral load in the lungs, the authors report. They also report benefits for hamsters treated one day after infection, as compared to controls. "In conclusion," say the authors, "our data provide evidence that REGN-COV2 based therapy may offer clinical benefit in both prevention and treatment settings of COVID-19 disease, where it is currently being evaluated."