Therapy cut deaths by one-fifth in the seronegativeCan be used in combination with other treatmentsFinding bodes well for other antibody treatmentsLONDON, June 16 (Reuters) – A COVID-19 antibody cocktail developed by Regeneron Pharmaceuticals Inc (REGN.O) and Roche (ROG.S) reduced deaths in hospitalised patients whose own immune systems had failed to produce a response, a large…