BENGALURU : Regeneron Pharmaceuticals Inc said on Monday it began late-stage clinical trials to assess the effectiveness of its antibody cocktail in preventing and treating COVID-19, sending its shares up nearly 4%.The trial, run jointly with the National Institute of Allergy and Infectious Diseases (NIAID), would test the therapy's ability to prevent infection in those who have had close exposure to a COVID-19 patient.The late-stage trial, to be conducted across 100 sites and expected to enroll 2,000 patients in the US, begins after an assessment of the antibody cocktail's safety in an early-stage trial by an independent committee."We are pleased to collaborate with NIAID to study REGN-COV2 in our quest to further prevent the spread of the.