POLLUX evaluated daratumumab plus lenalidomide and dexamethasone (D-Rd) versus the comparator control regimen (lenalidomide and dexamethasone alone ) in relapsed/refractory MM. To further expand upon these findings, we conducted CyTOF immune cell profiling of daratumumab in a large patient population and in the presence of a randomized controlled standard-of-care comparator arm on patient samples collected in the phase 3 POLLUX study ( Identifier: NCT02076009). Collectively, these findings supported a broad immunomodulatory role for daratumumab that may contribute to the observed depth of response. In addition, we demonstrated a shift to CD8 + prevalence with higher granzyme B (GrB) positivity in the T-cell population of responders, supporting monotherapy-induced CD8 + T-cell activation. We confirmed NK cell reduction, and CyTOF profiling revealed that daratumumab induced distinct phenotypic changes in the persisting NK cells, with increased expression of CD27, HLA-DR, CD69, and CD137, suggesting that these cells may be capable of daratumumab-mediated ADCC. Our analysis revealed the downregulation of CD38 expression across a large number of immune cell types, and the selective depletion of the strongly immunosuppressive fraction of T regs that highly express CD38. CyTOF utilizes next-generation, high-parameter, single-cell analysis platforms, overcoming the challenges of classical cytometry by allowing for the simultaneous analysis of cellular composition and marker expression across a wide range of immune cell subpopulations. To further investigate the immunomodulatory effects of daratumumab, we recently utilized mass cytometry by time-of-flight (CyTOF) on WB and/or bone marrow samples from 32 patients treated with daratumumab monotherapy in SIRIUS or GEN501 at baseline and after 2 months of treatment. Interestingly, this reduction in NK cells was not complete, and peripheral blood mononuclear cells (PBMCs) from the patients were still capable of inducing lysis by ADCC of CD38 + tumor cells in vitro, suggesting that persisting NK cells retained cytotoxic functionality. We showed a rapid reduction of natural killer (NK) cells in whole blood (WB) and bone marrow of MM patients after the first dose of daratumumab, to a low level that remained over the course of treatment, and a recovery of these cells after treatment discontinuation. Recently, we revealed an immunomodulatory MOA of daratumumab, including the expansion of cytotoxic T cells, increase in T-cell repertoire clonality, and elimination of CD38 + myeloid-derived suppressor cells, regulatory B cells, and a subpopulation of regulatory T cells (T regs CD4 +CD25 +CD127 dim). The ability of daratumumab to induce deep and durable responses in MM is thought to be in part due to its direct on-tumor mechanism of action (MOA), including complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis, apoptosis, and direct enzymatic inhibition. This study confirms daratumumab’s immunomodulatory MOA in combination with immunomodulatory drugs and provides further insight into immune cell changes and activation status following daratumumab-based therapy.ĭaratumumab is a CD38-targeted monoclonal antibody that has demonstrated activity as monotherapy and in combination with standard-of-care regimens in patients with relapsed/refractory multiple myeloma (MM) and newly diagnosed MM. D-Rd reduced immunosuppressive CD38 + regulatory T cells. D-Rd resulted in a higher proportion of effector memory T cells versus Rd. The expansion of CD8 + T cells correlated with clonality, indicating generation of adaptive immune response with D-Rd.
The proportion of T cells increased preferentially in deep responders to D-Rd, with a higher proportion of CD8 + versus CD4 + T cells. Persisting NK cells were phenotypically distinct, with increased expression of HLA-DR, CD69, CD127, and CD27.
We confirmed previous reports of NK cell reduction with D-Rd. We further evaluated daratumumab’s effects on immune cells in whole blood samples of relapsed/refractory MM patients from both treatment arms of the phase 3 POLLUX study (lenalidomide/dexamethasone or daratumumab plus Rd ) at baseline (D-Rd, 40 Rd, 45) and after 2 months on treatment (D-Rd, 31 Rd, 33) using cytometry by time-of-flight. Phase 1/2 studies GEN501/SIRIUS revealed a novel immunomodulatory mechanism of action (MOA) of daratumumab that enhanced the immune response, reducing natural killer (NK) cells without affecting efficacy or safety. CD38-targeted antibody, daratumumab, is approved for the treatment of multiple myeloma (MM).