MFGR1877S binds to FGFR3 with high affinity to competitively inhibit native ligand binding and prevent receptor dimerisation, not only in cells with wild-type FGFR3 but also in cells with the most prevalent cancer-associated mutants of FGFR3.72 In addition, MFGR1877S was shown to induce ADCC using in vitro models of multiple myeloma. Here, FGFR3 is linked to plasma cell myeloma.