As we already know The omicron variant has lot of antigenic change. Many mutations are at peak escape sites, especially E484, G446, K417, & Q 487, Q 493 Q496., resulting in reduction of RBD antibodies binding. the REGEN-COV cocktail is likely ineffective given omicrons mutations especially the REGN10987 component. Moreover, earlier studies shown that monoclonals cocktails evoke new mutations.
Eli Lily antibodies like LY-CoV555 (bamlanivimab) and LY-CoV016, which were already in trouble with current variants, aren't going to do any better