These are different antibodies, antibodies are specialized so Dupixent doesn't help against SARS 2. The virus has maybe 1,000 different points where antibodies can dock to. The immune system does not create all of the possible antibodies, there is some random factor, and some antibody types are sorted out because they also bind to human tissue. The manufacturers of the monoclonal antibodies try to identify one of the most effective antibody type ("neutralizing" antibody), they try to make sure they don't bind elsewhere, and they make sure that the targeted part of the virus doesn't mutate much (so that variants cannot evade). Some manufacturers mix two or more different antibodies ("polyclonal antibody cocktail").