P-005: Novel strategy of elotuzumab and zoledronic acid with Th1-like γδT cells against myeloma

Abstract

<h3>Background</h3> We are now in the new era of immunotherapies against multiple myeloma (MM) such as anti-CD38 and anti-SLAMF7 therapeutic monoclonal antibodies (mAbs); however, MM progression falls into attenuation and exhaustion of effector cells via immune checkpoint axes such as PD-1/PD-L1 and TIGIT/CD155, leading to hamper the clinical efficacy of these therapeutic mAbs. <h3>Methods</h3> To overcome this issue, we have been studying the utilization of Vδ2 γδT cells in peripheral blood mononuclear cells, which can be expanded and induced as Th1-like phenotype ex vivo using aminobisphosphonates in combination with IL-2, as effectors for MM treatment. The present study was aimed to develop the novel therapeutic strategies of γδT cells in combination with anti-MM mAbs. <h3>Results</h3> The next generation IMiDs, cereblon E3 ligase modulators (CELMoDs) of iberdomide and CC-92480 have been developed. CELMoDs was able to expand and activate γδT cells at much lower dose compared to IMiDs of lenalidomide and pomalidomide, in combination with zoledronic acid (ZA) ex vivo. Since the expanded Th1-like γδT cells highly expressed CD16, FcγRIIIa without expression of checkpoint molecules such as PD-1, TIGIT, CTLA-4, and LAG-3, we next examined whether anti-MM mAbs, elotuzumab (ELO), daratumumab (DARA), and isatuximab (ISA), induced ADCC in the presence of the γδT cells. DARA and ISA did not induce cytotoxicity against CD38-expressing MM cells in the presence of the γδT cells; however, addition of ELO further increased cytotoxicity of the γδT cells against SLAMF7-expressing MM.1S and OPM-2 cells but not RPMI 8226 cells with marginal SLAMF7 expression, suggesting induction of ELO's ADCC with the γδT cells. We next examined the cytotoxic effect of the combinatory treatment on osteoclasts (OCs) because MM cells resides in the bone marrow and the interaction between MM cells and OCs forms vicious cycle of MM cell growth and bone destruction. Of note, OCs, which can be induced from monocytes using M-CSF and RANK ligand, highly expressed SLAMF7 along with elevation of NFATc1 transcription factor. Although the expanded γδT cells can target OCs, addition of ELO augmented the cytotoxic effect of γδT cells on OCs, suggesting the emergence of ELO's ADCC with Th1-like γδT cells towards OCs. As γδT cells recognize not only neoantigens but also phosphoantigens (pAgs), we treated MM cells and OCs with ZA to enhance the expression of pAgs, and γδT cells then incubated with the ZA-treated cells. ZA-stimulation augmented the cytotoxicity of γδT cells towards MM cells and OCs even in the presence of ELO. <h3>Conclusions</h3> Taken together, our findings demonstrated the effective usage of ELO and Th1-like γδT cells with ZA against MM cells and ambient cells in MM bone marrow. Further study is warranted on the effective revitalization and expansion of Th1-like γδT cells using CELMoDs.