Peripheral Immunotype Correlates with Minimal Residual Disease Status and Is Modulated by Immunomodulatory Drugs in Multiple Myeloma

Data indicate reversal of immune dysfunction with active treatment; however, the precise contribution of specific immune effector and immune suppressor components to achieve a minimal residual disease (MRD) state and immunomodulatory drug-mediated immunomodulatory effects in multiple myeloma (MM) patients remains poorly understood. In this prospective proof-of-principle study we sought to determine the dynamic alterations in natural killer (NK), NK-T, and T cells, including maturation and activating/inhibitory repertoire associated with MRD^pos versus MRD^neg status after autologous stem cell transplantation (ASCT) and during lenalidomide-based maintenance therapy. Of the 46MM patients enrolled, 36 had bone marrow MRD assessment 60+ days post-ASCT, 30 had longitudinal blood immunotyping during maintenance (pretherapy and after cycles 1, 3, and 6), and 20 had both MRD assessment and longitudinal immunotyping. Multicolor flow cytometry was used for MRD and immunotyping. Although the absolute number of NK cells was significantly lower in patients with MRD^pos response, phenotypically NK cells in these patients displayed higher expression of activating receptors KIRDS4 and decreased expression of inhibitory molecules NKG2A compared with the MRD^neg group. Furthermore, we observed significantly lower frequencies of T cells displaying KIR3DL1 in MRD^pos versus MRD^neg patients. Longitudinal immunotyping during lenalidomide maintenance showed loss of mature NK effector function, augmentation of NK-T effector function, and acquisition of PD1 independent anergic state. Our findings also suggest skewing of T cells toward an exhausted state during the maintenance phase in MRD^pos patients. Put together, these observations provide a distinctive signature for MRD^neg and MRD^pos groups. These data support exploration of immune profiling in prospective clinical trials according to MRD-defined responses to identify patients that may benefit from maintenance intensification/modification or maintenance withdrawal.