**3. mAbs targeting SLAMF7**

A group of surface proteins belonging to the signaling lymphocytic activation molecule family (SLAMF) has elicited considerable interest in recent years due to the high expression of four family members (SLAMF2, 3, 6, and 7) on both normal plasma cells and those from MM patients at all stages of disease. No trials of SLAMF2 targeting mAbs have been initiated and clinical studies of the SLAMF3 and SLAMF6 mAbs SGN-CD48A and azintuxizumab vedotin (ABBV-838), respectively, both were halted early in phase I trials. On the other hand, SLAMF7 (CS1 or CD319) has emerged as the principal focus for new anti-myeloma mAb development in this group of targets with the introduction of elotuzumab (Empliciti®), a humanized IgG1κ mAb [33]. Preclinical studies revealed that the anti-myeloma activity of elotuzumab is the result of ADCC involving direct activation and engagement of NK cells [34]. FDA approval in 2015 of elotuzumab, which lacks activity as a single agent, was the result of the ELOQUENT-2 trial (NCT01239797) involving 646 randomly assigned RRMM patients who received the mAb plus dexamethasone

with or without lenalidomide. The cohort receiving elotuzumab exhibited a PFS of 19.4 months and an ORR of 68% at one year and 41% at two years, compared to 14.9 months and 57% and 27% for the control [35]. These results were confirmed further by a subsequent four-year follow-up study [36]. Similar benefits of elotuzumab in RRMM were observed in combination with pomalidomidedexamethasone in the ELOQUENT-3 trial (NCT02654132) [37], which included patients refractory to both lenalidomide and a proteasome inhibitor and resulted in the 2018 FDA approval of this combination [38]. Favorable data also have been generated in a trial (NCT01478048) in which bortezomib-dexamethasone was included with elotuzumab [39].
