Peripheral Immune Profile and Minimal Residual Disease (MRD) Burden Following Autologous Stem Cell Transplantation (ASCT) in Multiple Myeloma (MM)

BACKGROUND: The immune system plays an essential role in both promoting and inhibiting the growth of MM. Loss of anti-myeloma immunity involves altered activation and polarization of effector cells as well as immunosuppressive cytokines. Immune dysfunction associated with MM can be partially or totally reversed when patients achieve clinical remission. Detection of MRD has become an achievable goal in MM, and is a powerful predictor of progression-free survival and overall survival. We hypothesized that the immune profile of MRDpos patients is distinct from MRDneg patients. PATIENTS AND METHODS: We studied peripheral NK, NK-T and T cell distribution/activation, and measured bone marrow MRD status by flow cytometry in 30 newly diagnosed MM patients 60+ days after ASCT. Patients were divided in 2 groups based on κ/λ ratio and MM-plasma cell (MM-PC) distribution: MRDneg (n=6), with κ/λ ratio ≤1.8 and MM-PC≤15 per million or MRDpos (n=24), with MM-PC>15 per million. Plasma was also collected from 17 of these patients (5 MRDneg and 12 MRDpos) 60+ days after ASCT to quantify inflammatory cytokines, chemokines and growth factors by multiplex protein assay. Linear regression was used to determine association between each tested variable (25 by flow cytometry and 27 by multiplex protein assay) and MRD status. Unsupervised hierarchical cluster analysis was then applied to post-ASCT samples with selected variables that were differentially expressed between MRDneg and MRDpos patients (p RESULTS: More than a third of immune variables tested by flow cytometry (9/25) were significantly differential between MRDpos and MRDneg patients (p CONCLUSION: A comprehensive analysis of 52 immune variables assessing cytotoxic cell distribution, mobilization, killing potential, inflammatory status, immune polarization chemotaxis and angiogenesis revealed distinct differences in peripheral immunity between MRDpos and MRDneg MM patients after ASCT. Fewer circulating NK cells exhibiting a loss of killing potential characterized immune dysfunction among MRDpos patients. On the other hand, MRDneg patients more frequently displayed an inflammatory and pro-angiogenic cytokine profile. Taken together, these observations suggest that MRD represents a state of immune equilibrium where detectable or undetectable myeloma cells remain under surveillance by cellular and soluble immune mediators. As a next step, we are validating our observation in a larger prospective cohort by assessing peripheral immune profile as a predictor for MRD negativity. Disclosures Symanowski:Eli Lilly & Co: Consultancy; Ra Pharma: Consultancy; Caris Life Sciences: Consultancy; Endocyte: Consultancy. Avalos:Seattle Genetics: Membership on an entity9s Board of Directors or advisory committees. Usmani:BioPharma: Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pharmacyclics: Research Funding; Onyx: Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Britsol-Myers Squibb: Consultancy, Research Funding; Millenium: Membership on an entity9s Board of Directors or advisory committees, Speakers Bureau; Array: Research Funding; Janssen: Membership on an entity9s Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Skyline: Membership on an entity9s Board of Directors or advisory committees, Speakers Bureau; Novartis: Speakers Bureau; Takeda: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau. Bhutani:Takeda Oncology: Research Funding, Speakers Bureau; Prothena: Research Funding; Bristol-Myers Squibb: Speakers Bureau; Onyx, an Amgen subsidiary: Speakers Bureau.