Effect of lenalidomide and pomalidomide combined with IgG1-isotype antibodies on antibody-dependent cellular cytotoxicity (ADCC) via cytokine signaling and effector cell granzyme B and FasL expression

Abstract

3058 Background: Lenalidomide and pomalidomide (CC-4047) display anti-angiogenic and immunomodulatory activities in a variety of in vitro assay systems. Evidence from single agent patient studies indicate enhancement of T cell and NK cell function in patients either with hematological or solid tumors. There is also in vitro and preclinical evidence that both drugs can enhance NK cell mediated ADCC. Methods: We have utilized an in vitro ADCC system to investigate the mechanism(s) whereby lenalidomide and pomalidomide are able to enhance human NK cell and monocyte effector function in response to FCγ receptor signaling initiated by therapeutic antibodies. Results: Pre-treatment of NK cells or monocytes with pomalidomide or lenalidomide (but not thalidomide) greatly enhanced ADCC of Her2/neu overexpressing breast cancer cells pre-coated with trastuzumab and EGFR positive colorectal cancer cells pre-coated with cetuximab. NK cell and monocyte-mediated killing of antibody coated tumor cells was dose-dependent. There was minimal tumor cell killing by antibody alone or by either drug alone or in the presence of panitumumab, an anti-EGFR IgG2a antibody that does not efficiently engage NK cell FCγ receptors. NK cell-mediated killing is associated with distinct changes in intracellular signaling (decreased pSHIP-1, increased PLCγ2, pERK) and increased granzyme B and FasL expression. Monocyte-mediated ADCC takes longer to initiate (16 hrs vs 4 hrs) is also associated with increased granzyme B and FasL and is blocked by anti-IL-12mAb. ADCC is completely blocked by an inhibitor of granzyme B activity and partially blocked by an antibody that blocks FasL-Fas interaction. Conclusions: Pomalidomide and lenalidomide (but not thalidomide) strongly enhance the ability of therapeutic IgG1 antibodies to induce ADCC via NK cell/monocyte-mediated killing of tumor cells in vitro. Furthermore, granzyme B activity and concurrent cytokine signaling is crucial to enable the synergistic combination of either drug with antibodies to tumor-specific surface antigens the potential utility of which is being assesses in upcoming clinical studies. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Celgene Corp Celgene Corp