Lenalidomide Exhibits Activity In Mantle Cell Lymphoma Through Increased Nk Cell Mediated Cytotoxicity

Introduction: Lenalidomide (Len) is indicated for the treatment of relapsed/refractory (R/R) Mantle Cell Lymphoma (MCL) in the United States and Switzerland. Len binds to the cullin 4 ring E3 ubiquitin ligase complex resulting in ubiquitination and subsequent proteasomal degradation of lymphoid transcription factors Aiolos and Ikaros leading to stimulation of immune cells, such as T-cells. Clinical trial CC-5013-MCL-002 (NCT00875667) is a randomized open-label phase II study in R/R MCL patients in which Len was given orally at 25 mg/day on days 1-21 of each 28-day cycle until progression (N=170). The control arm consisted of investigator choice of single-agent rituximab, gemcitabine, fludarabine, chlorambucil, or cytarabine (N=84). We explored the immune effects of Len treatment in MCL patients enrolled in CC-5013-MCL-002 and further investigated our findings in in vitro MCL co-culture models. Methods: Peripheral blood samples for exploratory analysis were collected at Cycle 1 Day 1 (C1D1, pre-treatment), Cycle 1 Day 4 (C1D4), Cycle 2 Day 15 (C2D15) and at treatment discontinuation. Flow cytometric profiling of T, B and natural killer (NK) cell subsets was performed and differences were analyzed for correlation with clinical outcomes (response rate and progression free survival [PFS]). Cell dependent cytotoxicity was measured in 1) anti-CD3 stimulated peripheral blood mononuclear cells (PBMC) treated with vehicle or 1-10000 nM Len for 3 days and incubated with target tumor cells for an additional 4 hours followed by an apoptosis assay as measured by Annexin V/ToPro-3 flow cytometry and 2) negatively selected CD56+ NK cells stimulated with IL-2 and treated with Len (1 nM to 10 μM) for 18 hrs and incubated with target tumor cells for an additional 4 hours followed by apoptosis assay. Results: At baseline, no significant differences were observed in the absolute levels of immune subsets when comparing non-responders (NR) and responders (R) in either Len (NR=11, R=23) or control (NR=4, R=5) arms. However, in the Len arm, significantly elevated (adj. p The mechanism whereby NK cell modulation contributes to clinical benefit demonstrated by Len in patients was further explored in in vitro co-culture systems with MCL cell lines. Len treated PBMC co-cultured with Jeko-1, Granta-519, and Mino MCL cell lines resulted in 38-47.5% more apoptosis compared to DMSO (p≤0.001). We examined the effect of Len on Aiolos and Ikaros protein expression in CD56+ NK and CD3+ T cells within anti-CD3 antibody stimulated PBMCs treated with DMSO or various concentrations of Len (1 nM to 10 μM) for 72 hours. Degradation of both Aiolos (40%) and Ikaros (95%) was observed after drug treatment in CD56+ NK cells. Aiolos and Ikaros levels were also monitored in CD3+ T cells and showed decreased levels after Len treatment, consistent with previous reports (Gandhi, 2014; Kronke, 2014). Furthermore, purified CD56+ NK cell mediated cytotoxicity produced a similar pro-apoptotic effect as the PBMC assay in all MCL cell lines versus DMSO (p≤0.01). Supernatants from co-cultures of NK cells with MCL cell lines showed significantly elevated granzyme B levels as compared to DMSO controls (p≤0.0001), suggesting that the apoptotic effects observed are induced by granzyme B. Conclusions: Lenalidomide is an immune modulating agent and NK cell modulation in particular may play a role in its clinical activity in MCL. A significant increase in proportions of NK cell subsets (vs total lymphocytes) at C1D4 versus baseline was observed and is a potential response indicator of favorable clinical outcome in R/R MCL patients treated with Len. In vitro, Len enhances cell mediated cytotoxicity of MCL cell lines in two co-culture model systems. Understanding NK cell mediated mechanism(s) has potential to enhance guiding patient selection strategies and rational combination therapies of lenalidomide in MCL. Disclosures Hagner: Celgene: Employment, Equity Ownership. Chiu: Celgene: Employment, Equity Ownership. Ortiz-Estevez: Celgene: Employment, Equity Ownership. Biyukov: Celgene: Employment, Equity Ownership. Brachman: Celgene: Employment, Equity Ownership. Trneny: Celgene: Consultancy, Honoraria, Other: Travel, accommodations, expenses, Research Funding. Morschhauser: Genentech Inc./Roche: Other: Advisory boards. Stilgenbauer: AbbVie, Amgen, Boehringer-Ingelheim, Celgene, Genentech, Genzyme, Gilead, GSK, Janssen, Mundipharma, Novartis, Pharmacyclics, Roche: Consultancy, Honoraria, Research Funding. Milpied: Celgene: Honoraria, Research Funding. Musto: Sandoz: Consultancy; Celgene: Honoraria; Roche: Honoraria; Sanofi: Consultancy; Genzyme: Consultancy; Novartis: Honoraria; Janssen: Honoraria; Mundipharma: Honoraria. Martinelli: AMGEN: Consultancy; Ariad: Consultancy; Pfizer: Consultancy; ROCHE: Consultancy; BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy. Heise: Celgene: Employment, Equity Ownership. Daniel: Celgene: Employment, Equity Ownership. Chopra: Celgene: Employment, Equity Ownership. Carmichael: Celgene: Employment, Equity Ownership. Trotter: Celgene Corporation: Employment. Gandhi: Celgene: Employment, Equity Ownership. Thakurta: Celgene Corporation: Employment, Equity Ownership.