ALBERT

Description: Introduction: Daratumumab (DARA) is a human CD38-targeting monoclonal antibody that induces deep clinical responses in MM pts through multifaceted mechanisms of action (MOA) including complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis and induction of apoptosis. Flow cytometry analysis revealed a previously unknown immunomodulatory role of DARA, via T-cell induction expansion, T-cell activity enhancement, and reduction of immune suppressive cell populations including CD38+ myeloid-derived suppressor cells, CD38+ regulatory T cells (TRegs), and CD38+ regulatory B cells (BRegs). Next-generation mass cytometry (CyTOF), which allows high parameter evaluation of the immune system, was used to assess the effects of DARA alone or in combination on a more comprehensive profile of immune cell subpopulations. Methods: Relapsed/refractory MM pt samples from a subset of single agent studies; SIRIUS (32 pts; whole blood [WB] only; Lonial S et al. The Lancet, 2016) and GEN501 (5 pts; WB and bone marrow [BM], Lokhorst HM et al. NEJM, 2015) along with GEN503, a study of DARA plus lenalidomide and dexamethasone (9 pts; WB and BM; Plesner T et al. ASH 2015) were analyzed. Fluorochrome or metal-conjugated antibody panel stained samples were evaluated by flow cytometry or cytometry by time-of-flight (CyTOF®) platforms, respectively. FACS analyses were performed and analyzed by FACS Canto II flow cytometers and FACSDiva software. For CyTOF analysis, events were clustered by phenotype by a spanning tree progression of density normalized events (SPADE) algorithm, and each cluster was associated with an immune population via Cytobank® software. Differential analysis of population fractions and marker intensity, over time and between response groups, derived raw P values from t-tests and single cell level bootstrap adjusted P values corrected for multiple dependent hypothesis testing. Results were visualized using SPADE trees (Figure) and Radviz projections, a new method that allows for the comparison of populations and conditions while preserving the relation to original dimensions. Results: Flow cytometry and high-dimensional CyTOF analyses confirmed previous findings including higher CD38 expression on plasma cells compared with other immune populations of natural killer (NK), monocytes, B and T cells, and depletion of both plasma cells and NK cells upon DARA treatment. Interestingly, while NK cells were significantly reduced with DARA treatment, remaining active NK cells (CD16+CD56dim) demonstrated increased expression of activation markers CD69, CD25 and CD137 while also decreasing granzyme B and increasing naive marker CD27. Though functionality tests weren't performed, the ability to evaluate several markers simultaneously suggests these cells possess limited cytotoxicity. Additionally, these studies indicated depletion of CD38 positive immune suppressive subsets of Tregs and Bregs. CD38+ basophil reductions occurred independent of response and may provide insight to short-lived infusion related reactions. Several observations within the T-cell compartment were indicative of a DARA-mediated adaptive response in both WB and BM samples. T cells displayed increases in total numbers and shifted towards higher CD8:CD4 and effector:naïve ratios after 2 months of DARA treatment. Responders had higher expression levels of several activation markers including CD69 and HLA-DR along with increased production of cytolytic enzyme granzyme B in CD8+ T cells following DARA treatment. Interestingly, in the GEN503 sample set, pts who achieved a complete response presented with a distinct BM CD4 T-cell phenotype of high granzyme B positivity versus those that achieved a partial response or very good partial response. This observation suggests pts with an active immune phenotype may achieve deeper responses to DARA in combination with standard of care agents lenalidomide and dexamethasone. Conclusion: CyTOF analysis of pt samples from both single agent and combination DARA studies agree with flow cytometry and support the pharmacodynamics and immune modulatory MOA of DARA while providing additional insight into changes in T-cell subtypes and activation status. Future CyTOF analyses of clinical samples from phase 3 combination studies aim to confirm these observations and expand the understanding of the MOA of DARA. Disclosures Adams: Janssen Research & Development, LLC: Employment. Stevenaert:Janssen: Employment. Van der Borght:Janssen: Employment. Casneuf:Janssen R&D, Beerse, Belgium: Employment; Johnson & Johnson: Equity Ownership. Smets:Janssen: Employment. Bald:Janssen: Employment. Abraham:Janssen: Employment. Ceulemans:Janssen: Employment. Vanhoof:Janssen: Employment; Johnson & Johnson: Equity Ownership. Ahmadi:Janssen: Employment. Usmani:Onyx: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Array: Research Funding; BioPharma: Research Funding; Pharmacyclics: Research Funding; Takeda: Consultancy, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Research Funding; Millenium: Membership on an entity's Board of Directors or advisory committees; Skyline: Membership on an entity's Board of Directors or advisory committees. Plesner:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Lonial:Janssen: Consultancy; BMS: Consultancy; Merck: Consultancy; Novartis: Consultancy; Janssen: Consultancy; Onyx: Consultancy; Onyx: Consultancy; Millenium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; BMS: Consultancy; Celgene: Consultancy. Lokhorst:Genmab: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Mutis:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genmab: Research Funding; Celgene: Research Funding. van de Donk:Janssen: Research Funding; BMS: Research Funding; Amgen: Research Funding; Celgene: Research Funding. Sasser:Janssen Pharmaceuticals R&D: Employment; Johnson & Johnson: Equity Ownership.

Description: Advances in Acute Myeloid Leukemia (AML) research have shown that the bone marrow microenvironment may distinctly vary across disease subtypes, and that this variation is associated with disease risk and response to conventional therapies. Novel therapies aimed at altering the tumor microenvironment, such as T-cell redirection, CAR-T and checkpoint inhibition, are emerging as promising treatment options for AML patients; however, there remains a critical need to determine how response to immune modulation may vary within different subsets of AML. Thus, in collaboration with the Beat AML Consortium, we carried out comprehensive mass cytometry profiling of patient bone marrow samples of nearly 100 Beat AML subjects and characterized their ex vivo response to several immune modulators. As a complement to this study, we leveraged the Beat AML Consortium dataset (including next-generation sequencing, functional cell-based assays, small molecule screening and clinical information) to investigate connections between disease subtype, immune function and clinical outcome. The mass cytometry time of flight (CyTOF) immune profiling, combined with matched genomic, cytogenetic, and outcome data from the same subjects, provided a unique opportunity to investigate features of the immune environment at single-cell resolution and test for their association with clinical covariates in a large treatment-naïve cohort. Interestingly, flow cytometry analysis of T-cells isolated from patient bone marrow showed a distinct subset of AML subjects with highly proliferative T-cells and a group of AML subjects with non-proliferative T-cells. To characterize molecular determinants of T-cell function in the AML microenvironment, we compared the transcriptional profiles of tumor specimens from subjects within these two groups. The data revealed a distinct set of differentially expressed genes associated with T-cell proliferation; pathway enrichment analysis indicated that these genes were involved in leukocyte migration, inflammation and response to hypoxia. Genes related to immune function were also enriched, likely due to the presence of immune cell infiltrates and stromal cells in addition to tumor cells from the AML specimens used for RNA-Seq. To estimate the extent of immune and stromal cells in the AML bone marrow, we next computed the approximate cellularity of the RNA-Seq samples using the xCell algorithm. The results of this analysis indicated enrichment of several types of immune cells in the RNA-Seq specimens from the proliferator group, including monocytes, neutrophils and activated dendritic cells. These observations were validated by preliminary results of the CyTOF immune cell profiling of the same subjects. Ongoing work is focused on the biological interpretation of CyTOF data collected for these subjects, including evaluating the association of functional marker expression on T-cell and myeloid cell populations with T-cell proliferation. Furthermore, we are exploring the functional impact of variation in T-cell fitness and immune cell composition on response to several immune modulators in a series of ex vivo experiments using Beat AML patient samples. Initial findings suggest that for a subset of patients, low baseline levels of T-cell proliferation did not prevent response to immune modulation. We are interrogating the Beat AML dataset for common molecular features of patients in this responder group. Overall, this study evaluates determinants of immune function and variation within the tumor microenvironment of AML patients to advance current knowledge of AML disease biology and to assess the impact of immune fitness on response to immune modulation. These results will contribute to early target identification and development, and importantly shed light on features of the AML bone marrow environment associated with response to therapy. Disclosures Brady: Janssen R&D: Employment. Soong:Janssen R&D: Employment. Lind:Celgene: Research Funding; Monojul: Research Funding; Amgen: Research Funding; Janssen Pharmaceutical R&D: Research Funding; Fluidigm: Honoraria. Schaffer:Janssen Research & Development: Employment, Equity Ownership. Hodkinson:Janssen R&D: Employment. Adams:Janssen Pharmaceutical R&D: Employment. Abraham:Janssen R&D: Employment. Safabakhsh:Janssen R&D: Employment. Tyner:AstraZeneca: Research Funding; Aptose: Research Funding; Array: Research Funding; Genentech: Research Funding; Constellation: Research Funding; Gilead: Research Funding; Incyte: Research Funding; Janssen: Research Funding; Takeda: Research Funding; Vivid Biosciences: Membership on an entity's Board of Directors or advisory committees. Druker:Aileron Therapeutics: Consultancy; MolecularMD: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Oregon Health & Science University: Patents & Royalties; Aptose Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Cepheid: Consultancy, Membership on an entity's Board of Directors or advisory committees; McGraw Hill: Patents & Royalties; Vivid Biosciences: Membership on an entity's Board of Directors or advisory committees; GRAIL: Consultancy, Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Bristol-Meyers Squibb: Research Funding; ARIAD: Research Funding; Novartis Pharmaceuticals: Research Funding; ALLCRON: Consultancy, Membership on an entity's Board of Directors or advisory committees; Third Coast Therapeutics: Membership on an entity's Board of Directors or advisory committees; Leukemia & Lymphoma Society: Membership on an entity's Board of Directors or advisory committees, Research Funding; Beta Cat: Membership on an entity's Board of Directors or advisory committees; Millipore: Patents & Royalties; Celgene: Consultancy; Gilead Sciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Patient True Talk: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Fred Hutchinson Cancer Research Center: Research Funding; Monojul: Consultancy; Henry Stewart Talks: Patents & Royalties. Huang:Janssen R&D: Employment, Equity Ownership.