T Cell Immunity Toward Viral- and Tumor-Antigens Is Preserved in MDS Patients

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by bone marrow failure and a propensity to progress to acute myeloid leukemia (AML). A core component of the underlying pathogenesis in MDS is deregulation of inflammatory cytokines, such as tumor growth factor-β (TGFβ), which impact the function of immune cells and hence their capacity to mount anti-infective or anti-tumor responses. However, little is known about antigen-specific T cell function in patients with MDS. We hypothesized that virus-specific T cell (VST) function might be preserved in patients with MDS, and that the functional capacity of T cells reactive against tumor-associated antigens aberrantly overexpressed by clonal MDS cells such as Cyclin A1 (CCNA1) and Proteinase (PR3) might also be preserved and exploited for immunotherapeutic purposes. Following informed consent, we collected peripheral blood samples from 10 patients (pts) with MDS and 17 healthy donors. Most pts (9 out of 10) were transfusion dependent and 3 subsequently underwent an allogeneic HSCT. Table 1 summarizes the other clinical characteristics, karyotypic and mutational profile at the time of blood collection. Compared with T cells isolated from healthy donors, MDS patient-derived T cells had a similar CD4 to CD8 ratio (1.5-2.5:1 for healthy donors and 3:1 for MDS pts), but displayed a more exhausted profile at baseline (CD3+TIM3+: 1% in healthy donors and 5% in MDS pts) and produced higher levels of inflammatory cytokines [IFNγ (18±3pg/ml vs 36±16pg/ml, healthy donor vs MDS; p=0.12), and IL-8 (56±32 vs 704±446 pg/ml, p=0.01)]. Next, to assess the capacity of MDS pts to mount ex vivo functional virus-directed responses, we stimulated patient-derived PBMCs (n=5) with overlapping peptide libraries (pepmixes) spanning immunogenic AdV, CMV, EBV, BK and HHV-6 antigens. Similar to healthy donor-derived T cell lines (n=5, 3 specific for 4 viruses and 2 for 5 viruses), all 5 MDS patient-derived lines demonstrated specificity for one or more of the target viruses (1 for 5 viruses, 1 for 4, 2 for 3 and 1 for 1 virus) as observed by IFNγ ELISpot assay with comparable magnitude (range Adv: 43-730 vs 384-941 in healthy donors, CMV: 0-1599 vs 0-3002, EBV: 0-1486 vs 0-541, BK: 0-839 vs 38-275 and HHV6: 0-794 vs 5-407 SFU/2x105 cells, respectively). We next examined the feasibility of expanding autologous MDS-antigen directed T cell products (n=10) to determine whether an adoptive immunotherapeutic approach might be applicable for MDS treatment. Thus, we exposed patient-derived PBMCs to autologous dendritic cells (DC) loaded with pepmixes spanning 6 MDS-associated antigens (CCNA1, survivin, WT1, PRAME, PR3 and NYESO1). After 3 rounds of stimulation, the products obtained were predominantly CD3+ T cells (mean 88±1.3%) that were polyclonal (CD4: 46±5% and CD8: 41±4%) containing predominantly memory T cells (TEM: 36±6% TCM: 37±5% and Tnaïve =13±3%). Six lines (60%) showed specific recognition to at least one of the target antigens: 4 lines specific for PRAME, 1 for CCNA1, 1 for WT1 and 1 for NYESO1 (range 0-40, 0-184, 0-1386 and 0-179 SFU/2x105 cells, respectively by IFNγ ELIspot). T cell lines were capable of specifically secreting multiple effector cytokines in response to targets (TNFα: 12% and IFNγ: 16% in response to PRAME in a representative patient-derived T cell line). Furthermore, this line was capable of killing PRAME+ targets in a 4hr 51Cr release assay [60% specific lysis, E:T 20:1]. In conclusion, functional virus-directed T cell immunity in patients with MDS is preserved, potentially explaining the lower rates of viral reactivation seen in these patients compared with other infections. Moreover, T cells specific for MDS-expressed tumor antigens can also be successfully expanded ex vivo from patients. Taken together this raises the possibility of applying an adoptive immunotherapeutic approach for the treatment of MDS. Disclosures Ramos: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Tessa Therapeutics: Research Funding. Leen:Allovir: Consultancy, Other: Cofounder, Ownership Interest; Marker Therapeutics: Consultancy, Other: Cofounder, Ownership Interest.

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Induction of T Cell Immunity Using a Multipeptide Cocktail Containing XBP1, CD138 and CS1 Peptides in Smoldering Multiple Myeloma

Blood ◽

10.1182/blood.v120.21.5039.5039 ◽

2012 ◽

Vol 120 (21) ◽

pp. 5039-5039

Author(s):

Jooeun Bae ◽

Rao H. Prabhala ◽

Weihua Song ◽

Yu-Tzu Tai ◽

Kenneth C. Anderson ◽

...

Keyword(s):

Multiple Myeloma ◽

T Cells ◽

T Cell ◽

T Lymphocytes ◽

Board Of Directors ◽

Advisory Committees ◽

Smoldering Multiple Myeloma ◽

Human T Cell ◽

Cell Immunity ◽

Equity Ownership

Abstract Abstract 5039 Smoldering multiple myeloma (SMM) patients are at high risk for progression to active multiple myeloma (MM), making them candidates for novel immunotherapeutic strategies to prevent or delay disease progression. Among potential strategies, the ability to induce cytotoxic T lymphocytes (CTL) against multiple immunogenic epitopes provides a framework for overcoming major therapeutic challenges including heterogeneity of tumor associated antigen expression, frequent mutations of specific antigens, and variability of the human T-cell repertoire among individuals. In this study, we provide evidence that a cocktail of four immunogenic HLA-A2 specific peptides, heteroclitic XBP1 US184–192, heteroclitic XBP1 SP367–375, native CD138260–268 and native CS1239–247, induces specific CTL response in T cells from SMM patients. Following repeated rounds of multipeptide stimulation, we induced development of CD8+ CTL from SMM patients' T cells. The multipeptide specific-CTL demonstrated polyfunctional immune activities including high levels of IFN-g production, cell proliferation and cytotoxicity against MM cells in an HLA-A2 restricted manner. The multipeptide-specific CTL displayed increased memory (CD45RO+) and activated (CD69+) CD3+CD8+ T lymphocytes, suggesting that a multipeptide vaccine has the potential to induce durable memory by generating specific memory CTL with characteristics of effector T cells against MM cells. In addition, the multipeptide-specific CTL demonstrated peptide-specific responses to each of the relevant epitopes including heteroclitic XBP1 US184–192, heteroclitic XBP1 SP367–375, native CD138260–268 and native CS1239–247, but not against an irrelevant HLA-A2-specific MAGE-3271–279 peptide in various functional assays including antigen-triggered CD137 (4-1BB) expression, IFN-g production and CD107a up-regulation. Therefore, these results suggest the potential of inducing a broad spectrum of immune responses against selected XBP1 unspliced, XBP1 spliced, CD138 and CS1 target antigens in SMM using multipeptide vaccination. In conclusion, these studies provide the framework for clinical trials of vaccination in patients with SMM to delay or prevent progression to active MM. Disclosures: Bae: Oncopep Inc. : Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Anderson:Oncopep Inc. : Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Munshi:Oncopep Inc: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

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Adoptive T-Cell Therapy for Acute Lymphoblastic Leukemia Targeting Multiple Tumor Associated Antigens

Blood ◽

10.1182/blood-2018-99-115465 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2693-2693

Author(s):

Swati Naik ◽

Premal Lulla ◽

Ifigeneia Tzannou ◽

Robert A. Krance ◽

George Carrum ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Disease Relapse ◽

Advisory Committees ◽

Leukemic Relapse ◽

Post Infusion ◽

Equity Ownership ◽

T Cell Lines

Abstract Background: Leukemic relapse remains the major cause of treatment failure in hematopoietic stem cell transplant (HSCT) recipients. While the infusion of donor lymphocytes to prevent and treat relapse has been clinically implemented this strategy does not provide durable remissions and carries the risk of life-threatening graft-versus-host disease (GVHD). More recently the adoptive transfer of T cells that have been engineered to express CD19-targeted chimeric antigen receptors (CARs), has shown potent anti-leukemic activity in HSCT recipients with recurrent disease. However, disease relapse with the emergence of CD19 negative tumors is an emerging clinical issue post-administration of these mono-targeted T cells. To overcome these limitations, we developed a protocol for the generation of donor-derived T cell lines that simultaneously targeted a range of tumor associated antigens (multiTAAs) that are frequently expressed by B- and T-cell ALL including PRAME, WT1 and Survivin for adoptive transfer to high risk recipients transplanted for ALL. Methods/Results: We were consistently able to generate donor-derived multiTAA-specific T cells by culturing PBMCs in the presence of a Th1-polarizing/pro-proliferative cytokine cocktail, using autologous DCs as APCs and loading them with pepmixes (15 mer peptides overlapping by 11 amino acids) spanning all 3 target antigens. The use of whole antigen increases the range of patient HLA polymorphisms that can be exploited beyond those matched to single peptides, while targeting multiple antigens simultaneously reduces the risk of tumor immune evasion. To date, we have generated 14 clinical grade multiTAA-specific T cell lines comprising CD3+ T cells (mean 94±9%) with a mixture of CD4+ (mean 21±28%) and CD8+ (mean 52±24 %) cells, which expressed central [CD45RO+/CD62L+: 14±9%] and effector memory markers [CD45RO+/CD62L-: 80±11%] associated with long term in vivo persistence. The expanded lines recognized the targeted antigens WT1, PRAME and Survivin by IFNg ELIspot with activity against >1 targeted antigens in all cases. None of the lines reacted against non-malignant patient-derived cells (4±3% specific lysis; E: T 20:1) - a study release criterion. Thus far we have treated 8 high risk ALL patients with donor derived TAA T cells post-transplant to prevent disease relapse (Table 1). Infusions were well tolerated with no dose-limiting toxicity, GVHD, CRS or other adverse events. Two patients were not evaluable per study criteria as they received >0.5mg/kg of steroids within 4 weeks of infusion and were replaced. Five of the 6 remaining patients infused remain in CR a median of 11.2 months post-infusion (range 9-22 months). We detected the expansion of tumor-reactive T cells in patient peripheral blood post-infusion against both targeted (WT1, Survivin, PRAME) and non-targeted antigens (SSX2, MAGE-A4, -A1, -A2B, -C1, MART1, AFP and NYESO1) reflecting epitope and antigen spreading. The single patient who relapsed showed no evidence of tumor-directed T cell expansion despite receiving 3 additional infusions at 4 week intervals. Conclusion: In summary, infusion of donor multi-TAA-specific T cells to patients with ALL post allogeneic HSCT is feasible, safe and as evidenced by expansion and antigen spreading in patients, may contribute to disease control. This strategy may present a promising addition to current immunotherapeutic approaches for prophylaxis for leukemic relapse in HSCT recipients. Table 1. Table 1. Disclosures Vera: Marker: Equity Ownership. Heslop:Marker: Equity Ownership; Cytosen: Membership on an entity's Board of Directors or advisory committees; Cell Medica: Research Funding; Gilead Biosciences: Membership on an entity's Board of Directors or advisory committees; Tessa Therapeutics: Research Funding; Viracyte: Equity Ownership. Leen:Marker: Equity Ownership.

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Eltrombopag: More Than Just a Thrombopoietin Receptor Agonist (TPO-RA) in Immune Thrombocytopenia (ITP)

Blood ◽

10.1182/blood-2019-122848 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2364-2364

Author(s):

Anwar A. Sayed ◽

Amna Malik ◽

Grace Ayoola ◽

Elisa Lucchini ◽

Sasfia Candrianita ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Cd8 T Cells ◽

Ex Vivo ◽

Granzyme B ◽

Immunomodulatory Effect ◽

Dependent Manner ◽

Advisory Committees ◽

Dose Dependent

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by a skewed proinflammatory T cell profile. Thrombopoietin-receptor agonists (TPO-RA) have largely replaced immunosuppressants in the management of this disorder, with some patients achieving remission after a period of treatment with TPO-RA. The potential immune modulatory role of TPO-RA has not been fully investigated. The two current TPO-RA licensed for use in ITP; Eltrombopag (Elt) and Romiplostim (Romi) act on different parts of the TPO-R and have similar response rates. However, patients can respond to one agent but not the other. Elt has been described to have a strong iron chelating effect, and hence we propose that it may have an additive immunomodulatory effect on the T cells, absent in Romi. We determined the immunomodulatory effect of Elt by assessing the proliferation and functionality of T-cell lines and primary T-cells. T cell proliferation was assessed using both CFSE proliferation assay and MTT cell viability assay. T cell phenotype and functionality were assessed by multicolor surface and intracellular flow cytometric staining. Cells were co-cultured with Elt and Romi in vitro and ex vivo with both Jurkat and DG75 cells lines as well as primary cells, respectively. Deferoxamine (DFX) was used as a positive control for iron-chelation, and human TPO was used as a positive control for TPO-RA. All treatment doses were based on their calculated therapeutic serum levels. Mann Whitney U and Kruskal-Wallis H statistical tests were applied where applicable, and a P value of less than 0.05 were considered significant. Elt significantly decreased Jurkat T cells proliferation in a dose-dependent manner compared to no treatment and Romi. DFX, an iron chelator, also decreased Jurkat T cell proliferation to comparable levels of Elt. Interestingly, this anti-proliferative effect of Elt was only observed on Jurkat T cells, but not DG75 B cell line. Ex vivo CFSE proliferation assay was performed on primary CD4 and CD8 T cells assessing the antiproliferative effect of Elt. Elt significantly reduced proliferation compared to no treatment. DFX exhibited a similar antiproliferative effect on primary T cells, however, less potent compared to Elt. Neither Romi nor TPO affected the proliferation of Jurkat cells, DG75 cells or primary T cells. The functionality of CD4 and CD8 T cells was assessed based on the capacity of T cells to produce intracellular TNFα, IFNγ and Granzyme B. Elt significantly reduced the percentages of TNFα+/IFNγ+ CD4+ and CD8+ T cells in a dose-dependent manner. This reduction was also observed, albeit to a lesser extent, when T cells were treated with DFX. Furthermore, Granzyme B expression in CD8+ T cells was significantly reduced when cells were treated Elt, compared to no treatment. Romi did not affect the frequency of CD8+ TNFα+/IFNγ+ populations nor the expression of Granzyme B in CD8+ T cells. CD4+ and CD8+ T cells did not express TPO-R on their surface. To confirm the immunomodulatory role of Elt in vivo, the terminally-differentiated effector (CD45RA+CD62L-) CD8+ T cells were assessed in 13 Elt-treated patients and 11 Romi-treated patients. Patients on Elt had significantly reduced frequency of effector CD8 T cells compared to Romi-treated patients (44% vs 76.8%; p<0.01). Taken together, these novel findings suggest an off target immunomodulatory nature of Elt besides its thrombopoietic effect. This dose-dependent immunomodulatory effect is not TPO-R dependent and targets T cells primarily. This study is the first to display such property of Elt and could explain why there is a differential response to Elt and Romi. We hypothesise that Elt may be more effective in patients with T cell mediated disease, whilst patients with predominantly antibody mediated disease are more likely respond to Romi. These findings can also offer an explanation for Elt effectiveness in other T cell-mediated autoimmune conditions such as Aplastic Anemia. Disclosures Cooper: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Rigel: Consultancy, Membership on an entity's Board of Directors or advisory committees; Principia: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.

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Poor Clinical Outcome in Pediatric Immunotherapy Is Mediated By a Pre-Existing Overactive IL-18-IFNy Immune Phenotype

Blood ◽

10.1182/blood-2021-148013 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 168-168

Author(s):

Katelyn Burleigh ◽

Anna Kus ◽

Alice Long ◽

Michael C. Jensen ◽

Seth Masters ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Early Time ◽

Advisory Committees ◽

Time Points ◽

The Poor ◽

Healthy Donors ◽

Car T ◽

Group 2

Abstract Background: CAR-T cells have revolutionized the treatment of relapsed B-cell acute lymphoblastic leukemia (ALL), however the field is plagued by 50% relapse, 10-15% non-response, 20% severe toxicity (cytokine release syndrome (CRS) and neurotoxicity) rates. Studies on CAR patient outcomes thus far have largely focused on the contribution of characteristics of the CAR product and post-CAR symptoms 1-8, largely overlooking the potential role of the patient's pre-CAR immunophenotype beyond T-cells in driving therapeutic response and toxicity. We hypothesized that a patient's inflammatory status prior to immunotherapy could be used clinically to inform interventional and therapeutic mechanistic strategies. Taking inspiration from the clinical presentation overlap between CRS and hemophagocytic lymphohistocytosis (HLH), we hypothesized a common pathophysiology. IL-18 signaling in HLH disorders is well known to play a causative role in anomalous T-cell function 9. Importantly, IL-18 is also linked to tumor regression and progression 10-13. This coupled with the poor overall 5-year survival of secondary HLH patients associated with malignancies 14,15 suggested to us that an overactive IFNγ (T-cell)-IL-18 (myeloid) axis may also drive post-CAR toxicity, as well as overall therapeutic efficacy. Methods: To test whether patient-specific immunity and an overactive IFNy-IL-18 axis could predict toxicity, response, and survival, we applied a machine learning classifier to cytokine and cell-type profiles of blood samples obtained to prior and at early time points following CD19 CAR T cell infusion of retrospective cohort based on response/non-response, across the continuum of toxicity severity (both CRS and neurotoxicity) and matched availability of samples from 30 of 43 patients on the PLAT phase1 trial (NCT02028455) 2,16. Results/Discussion: We found evidence for a pre-existing overactive HLH-like axis in some patients; this included both patients with no response to CAR-T therapy as well as patients who experienced high levels of toxicity and diminished long-term survival. Stratification based on this axis was significantly associated with survival rates - Group 2 patients with high levels of IFNy-IL-18 had a median survival of 16.8 months post-CAR, (versus >48 months post-CAR, Group 1). Importantly, we identified an immune sub-type (CD161+IFNy+ T cells which are hyper responsive to IL-18) that is increased in this poor survival Group 2 prior to therapy, which suggests that patients could be effectively stratified prior to CAR infusion. Given the poor clinical outcome associated with high levels of CD161+IFNy+ T cells, we hypothesized that high levels may be a marker for primed pro-inflammatory myeloid activation, independent of cancer. Thus, we reasoned that donor monocytes from healthy donors with high levels of CD161+IFNy+ T cells could be induced with continued interferon signaling/priming into a Group 2 low survival/neurotoxicity phenotype. Healthy donors with elevated CD161+IFNy+ T cells had increased pro-inflammatory potential including IL-18 signaling in response to IFNy prime. We drove healthy donors to an elevated CD161+ IFNy phenotype utilizing an IL-12 prime, suggesting that patents with high levels of CD161+ cells had a monocytic priming event (e.g., pathogenic exposure, genetic predisposition, vaccination, etc.) prior to therapy that drove the poor clinical outcomes. Based on this data, we propose that a child's cytokine pre-inflammatory status might be independent of cancer and drives immunotherapeutic response and therefore tumor response and toxicity. Conclusions: In summary, we have identified that an HLH-like signaling axis pre- and early time points post- CAR therapy stratify patient outcomes predicting the onset of poor clinical outcomes prior to their clinical onset such as neurotoxicity, non-response, and relapse. We have also identified biomarker signatures prior and at early time points post-CAR such as cytokines (IFNγ-IL-18 signaling) and immune cell subsets (CD161+ IFNγ+ cells) responsible for the HLH-like signaling axis that could serve as potential future interventional targets. Finally, this study highlights the need to study patient-specific immune characteristics prior to CAR therapy, as these may be predictive of CAR success and failure and may help to identify novel therapeutic approaches and targets improving clinical outcomes. Figure 1 Figure 1. Disclosures Burleigh: ShapeTx: Current holder of stock options in a privately-held company. Jensen: BMS: Patents & Royalties; Umoja Biopharma: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bluebird Bio: Research Funding. Masters: IFM therapeutics: Membership on an entity's Board of Directors or advisory committees. Vince: Avammune Therepeutics: Membership on an entity's Board of Directors or advisory committees; Exopharm: Membership on an entity's Board of Directors or advisory committees. Gardner: Novartis: Consultancy; BMS: Patents & Royalties.

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Myeloid Derived Suppressor Cells (MDSCs) Regulate Tumor Growth, Immune Response and Regulatory T Cell (Treg) Development in the Multiple Myeloma Bone Marrow Microenvironment

Blood ◽

10.1182/blood.v120.21.565.565 ◽

2012 ◽

Vol 120 (21) ◽

pp. 565-565

Author(s):

Gullu Topal Gorgun ◽

Gregory Whitehill ◽

Jennifer Lindsey Anderson ◽

Teru Hideshima ◽

Jacob P. Laubach ◽

...

Keyword(s):

Bone Marrow ◽

T Cells ◽

T Cell ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Tumor Development ◽

Suppressor Cells ◽

Advisory Committees ◽

Healthy Donors

Abstract Abstract 565 Background: The interaction of myeloma (MM) cells with bone marrow accessory cells induces genomic, epigenomic and functional changes which promote tumor development, progression, cell adhesion mediated-drug resistance (CAM-DR), and immune suppression. As in other cancers, bidirectional interaction between MM cells and surrounding cells regulates tumor development on the one hand, while transforming the BM microenvironment into a tumor promoting and immune suppressive milieu on the other. Recent developments in targeted therapies have indicated that generation of the most effective therapeutic strategies requires not only targeting tumor or stroma cells, but also methods to overcome blockade of anti-tumor immune responses. In addition to lymphoid immune suppressor cells such as regulatory T cells (Tregs), distinct populations of myeloid cells such as myeloid derived suppressor cells (MDSCs) can effectively block anti-tumor immune responses, thereby representing an important obstacle for immunotherapy. While MDSCs are rare or absent in healthy individuals, increased numbers of MDSCs have been identified in tumor sites and peripheral circulation. Recent studies have in particular focused on MDSCs in the context of tumor promoting, immune suppressing, stroma in solid tumors. However, their presence and role in the tumor promoting, immune suppressive microenvironment in MM remains unclear. Methods: Here we assessed the presence, frequency, and functional characteristics of MDSCs in patients with newly diagnosed or relapsed MM compared to MM patients with response and healthy donors. We first identified a distinct MDSC population (CD11b+CD14−HLA-DR-/lowCD33+CD15+) with tumor promoting and immune suppressive activity in both PB and BM of MM patients. Moreover, we determined the immunomodulatory effects of lenalidomide and bortezomib on induction of MDSCs by MM cells, as well as on MDSC function. Results: MDSCs were significantly increased in both PB and BM of patients with active MM compared to healthy donors and MM in response (p<0.01). To determine whether the CD11b+CD14−HLA-DR-/lowCD33+CD15+ myeloid cell population represents functional MDSCs, we first assessed tumor promoting role of MDSCs in the MM microenvironment by culturing MM cell lines with MM patient bone marrow stroma cells (BMSC), with or without depletion of MDSCs. Importantly, BMSC-mediated MM growth decreased to baseline levels of MM cells alone when MDSCs were removed from the BMSC microenvironment. Moreover, MDSCs isolated from MM-BM using magnetic-Ab and/or FACS sorting cell separation, directly induced MM cell growth and survival, evidenced by 3H-thymidine incorporation and MTT assays. Since the interaction between tumor and stromal accessory cells is bidirectional, we next analysed the impact of MM cells on MDSC development. Importantly, MM cell lines cultured with PBMCs from healthy donors induced a 7 fold increase in MDSCs. We also examined the immune suppressive functions of MDSCs in cultures of autologous T cells with T cell stimulators, in the presence and absence of MDSCs from MM-PB or MM-BM. Freshly isolated MDSCs from both MM-PB and MM-BM induced significant inhibition of autologous T cell proliferation. Moreover, MDSC-associated immune inhibitory molecules arginase-1 (ARG-1) and reactive oxygen species (ROS), as well as inhibitory cytokines IL-6 and IL-10, were significantly increased in BM MDSCs, evidenced by intracellular flow cytometry analysis. In addition, MM BM MDSCs induced development of Treg from autologous naïve CD4+T cells. Finally, we analysed whether MDSCs impacted response to bortezomib and lenalidomide. Culture of MDSCs with MM cell lines, with or without bortezomib (5nM) and lenalidomide (1uM), demonstrated that less MM cell cytotoxicity in the presence of MDSCs. Conclusions: Our data show that MDSCs are increased in the MM microenvironment and mediate tumor growth and drug resistance, as well as immune suppression. Therefore targeting MDSCs represents a promising novel immune-based therapeutic strategy to both inhibit tumor cell growth and restore host immune function in MM. Disclosures: Raje: Onyx: Consultancy; Celgene: Consultancy; Millennium: Consultancy; Acetylon: Research Funding; Amgen: Research Funding; Eli-Lilly: Research Funding. Munshi:Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy. Richardson:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees.

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Lymphocyte and Hematopoietic Stem and Progenitor Cell (HSPC) Subsets Mobilized By Either Plerixafor or G-GCSF: A Retrospective Comparison of Grafts Harvested in Healthy Allogeneic Stem Cell Donors

Blood ◽

10.1182/blood.v124.21.2451.2451 ◽

2014 ◽

Vol 124 (21) ◽

pp. 2451-2451 ◽

Cited By ~ 1

Author(s):

Georgine E. De Greef ◽

Eric Braakman ◽

Wendimagegn G Alemayehu ◽

Larissa De Graaf ◽

Peter van Geel ◽

...

Keyword(s):

T Cells ◽

Stem Cell ◽

T Cell ◽

The Netherlands ◽

Board Of Directors ◽

T Cell Subsets ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Healthy Donors ◽

Cd34 Cells

Abstract Plerixafor (PXF) is a bicyclam molecule, which acts as a reversible inhibitor of SDF-1 binding to CXCR4. A single injection results in immediate release of CD34+ cells into the peripheral blood. Sofar, PXF has been used for stem cell mobilization only in a limited number of allogeneic donors (Devine et al. Blood.2008;112(4):990) The currently ongoing randomized phase 2 Hovon -107 study of the Dutch hemato-oncology group HOVON (www.hovon.nl) aims to compare the feasibility of intravenous (iv) versus subcutaneous (sc) PXF (Genzyme Europe BV) 320 µg/kg subcutaneously (sc) 9 hours before the planned stem cell collection or intravenously (iv) 4 hours before stem cell collection in healthy adult matched sibling donors. Concurrently, all stem cell products are evaluated for the total number of CD45+; CD34+ cells and other hematopoietic stem cell subsets, including more primitive progenitor cells (MPP/CMP: CD34+/CD45RA-/CD90- and HSC :CD34+/CD45RA-/CD90+). Furthermore, the frequency and absolute numbers of CD3+, CD4+; CD8+;CD19+; CD 3-CD16/CD56+ (NK) cells and several T cell subsets, including Foxp3+, Th1, Th2 and Th17 cells, are assessed. Thereby, the HOVON-107 study enabled us to retrospectively compare lymphocyte and CD34+ HSPC subsets in grafts harvested in healthy donors (n=27) following PXF versus a similar evaluation of those subsets in grafts (n=10) harvested following G-CSF(Neupogen) (2 x 500 ug/kg (sc) for 5 days). Data are presented with respect to the composition of stemcell harvests, obtained after a single gift of PXF (13 iv and 14 sc) followed by 15 liters leucopheresis. For comparison of the stem cell products between the two groups the Mann-Whitney U test was applied. Results: Both groups are comparable with respect to age/sex. Mobilization with PFX resulted in similar WBC numbers as compared to G-CSF mobilization. The total number of CD34+ cells was significantly lower after PFX mobilization: median 200 x106; (range 40-560) vs 400 x106 (360-840) after G-CSF (p=0.000). However after PFX mobilization, the CD34+ cells contained a higher frequency of immature HSC and a lower frequency of MPP as compared to G-CSF mobilized grafts. The lower number of CD34+ HSPC and the higher frequency of HSC within CD34+ HSPC resulted in similar numbers of immature HSC in PXF mobilized grafts (PFX 50;1-218 x106 for G-CSF 90;11-200 x106 p=0.411).Although it is known that Plerixafor can mobilize a higher number of T-cells no data are available about the frequencies of distinct T cell subsets in the grafts. PFX mobilization resulted in higher numbers of CD3+T cells and CD19+B cells. The number of CD3-CD16/56+ NK-cells did not differ between both groups. Within the CD3+ T cell population, the CD4/CD8 ratio did not differ between both groups of mobilized grafts. While absolute numbers of T-cells were significantly increased, the frequencies of IFN-gamma+ Th1 cells, IL-4+ Th2 cells; IL-17+ Th17 cells and Foxp3+ regulatory T cells were not significantly different between both groups, resulting in increased Treg and Th1 after PFX (see Table below) In conclusion, allogeneic stem cell grafts harvested in healthy donors following a single dose of Plerixafor contain higher numbers of primitive progenitor cells, and higher numbers of both effector and regulatory T-cells as compared to grafts harvested following G-CSF. The impact of altered subset numbers on clinical endpoints including graft versus host, engraftment, and overall outcome remain to be established. Abstract 2451. TableCD3 (x 109)CD3/4 (x 109)CD3/8 (x 109)CD19 (x 109)CD3-CD16/56+ (x 109)Treg (x 109)Th1 (x 109)Th2 (x 109)Th17 (x 109)PFXMedian Range22.7 9.8-56,7 13.2 6.3-30.56.6 2.8-22.15.7 0.6-18.11.40.5-4.30.7 0.3-2.52.8 0.3-9.30.2 0.0-1.80.20.0-6.8G-CSFMedian Range12.8 7.6-217.5 4.3-15.43.8 2.0-6.03.1 1.9-4.51.30.5-2.90.4 0.2-1.20.9 0.4-2.70.20.1-0.40.1 0.0-0.5P-value0.0010.0050.0030.0020.7320.0220.0160.2890.129 Disclosures De Greef: Sanofi The Netherlands: Membership on an entity's Board of Directors or advisory committees. Petersen:Sanofi the Netherlands: Membership on an entity's Board of Directors or advisory committees. Visser:Sanofi the Netherlands: Membership on an entity's Board of Directors or advisory committees. Niederwieser:Novartis, Gentium, Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

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AML Cell Vaccines Co-Expressing CD80 and IL-15/IL-15 Receptor Alpha Induce Activation and Cytolytic Activity in Post Remission Autologous Patient PBMC Ex Vivo

Blood ◽

10.1182/blood-2021-151614 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 1706-1706

Author(s):

Xinyue Wang ◽

Jeffrey P. Fung ◽

Giulia Parisi ◽

Francesca M. Olguin ◽

Nathaniel Z. Rothschild ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Ex Vivo ◽

T Cell Responses ◽

Cytolytic Activity ◽

Advisory Committees ◽

Receptor Alpha ◽

Cell Responses ◽

Effector Pathways

Abstract There is a critical need for more effective therapy for acute myelogenous leukemia (AML). Although many patients achieve remission, most relapse with poor outcomes. Even after allogeneic Stem Cell Transplantation (SCT), 30-50% of patients relapse due to the persistence of residual disease. To address the poor immunogenicity of AML cells and the diminished immune responsiveness of patients, our candidate autologous AML vaccine is lentivirally engineered, in each patient's leukemic cells, to express CD80, IL-15, and IL-15 Receptor alpha (IL-15Rα). In prior studies in a syngeneic 32Dp210 murine AML model, CD80-mediated co-stimulation of T-cells combined with immune activation by the IL-15/IL-15Rα heterodimer showed unprecedented synergy in induction of anti-leukemic cytolytic activity (Shi, Y. et al, 2018). This was observed in both ex vivo co-culture and in vivo where vaccinated leukemic mice had >80% cure rates. No local skin, organ, or systemic toxicity was observed, nor was there evidence of systemic cytokine release of IL-6 or TNFα after SC or IV injection of up to 10 8 transduced irradiated AML cells. We confirmed the feasibility of producing patient-derived AML vaccines by transduction of 16 independent AML samples with a tri-cistronic lentiviral vector (TLV) that contains human CD80, IL-15 and IL-15Rα. Transduction levels were 11-71% of cells (median 38.6%). To define the minimum transduction level required for PBMC activation and to assess synergy of co-expressed human CD80, IL-15, and IL-15Rα, allogenic U937 leukemia cells were initially used as stimulators. Transduced U937 (U937-TLV) had high-level surface expression of CD80 and IL-15, secreted IL-15 (7 ng/ml/24 hours from 2 x 10 6 cells/ml) and activated CD3+ T-cells from an AML patient (Fig.1). Mixtures of irradiated U937-TLV with non-transduced U937 were created at fixed ratios (100%, 80%, 40%, 20%, 10%, 5%, 0%) for overnight co-culture with patient PBMC. At 24 hours, the T-cells were analyzed for activation by measurement of the frequency of CD69+ CD4 or CD8 T cells (Fig. 1), normalized to expression of unstimulated PBMC (0%) and the percentage of maximal CD69 expression with 100% U937-TLV (100%). Background levels of activation due to the presence of allogenic U937 were negligible. Co-culture with as little as 10% transduced U937-TLV reliably activated patient T-cells. To assess the synergy of CD80, IL-15 and IL-15Rα expression, parallel experiments were performed with PBMC co-cultured in IL-15 containing supernatants from U937-TLV cells (Fig. 1). The frequencies of activated T-cells were significantly higher after co-culture with U937/U937-TLV cells than after stimulation with IL-15-containing supernatants from similar ratios of U937/U937-TLV, confirming the synergy of CD80 and IL-15/IL-15Rα in the transduced cells. To better, model the clinical setting, we assessed induction of immune responses of patient T cells to autologous transduced AML. PBMC were stimulated with transduced or non-transduced autologous AML cells vs stimulation with allogeneic U937-TLV, or with anti-CD3/CD28 beads to define maximal stimulation. Negative controls included culture of PBMC alone. All patients had T-cell activation, as measured by induction of CD69, HLA-DR and CD95 (Fas) expression, although there was heterogeneity in the nature of responses, e.g., disparate induction of the markers in individual patients (Fig. 2A and B). Induction of cytotoxic effector pathways was confirmed by detection of CD178 (FasL) and perforin expression (Figure 2C and D). Overall, all patients' PBMC had the capacity to mount T-cell responses of similar magnitude to both allogeneic U937-TLV and autologous vaccine. These studies establish that autologous AML cells transduced with CD80, IL-15 and IL-15Rα can elicit specific anti-leukemic T-cell responses, even in the face of prior lymphodepleting chemotherapy. A strength of this autologous vaccine strategy is that it is agnostic to which AML proteins are immunogenic for each patient. Although uniformly detected, there was heterogeneity in the induction of activation markers and effector pathways, which may reflect host and/or disease-related differences. The mechanisms underlying differences in the nature of responses in patients will be important to understand and will provide the basis for future immune correlative studies for our Phase 1 vaccine trial in transplant ineligible AML patients. Figure 1 Figure 1. Disclosures Kohn: Lyrik Therapeutics: Membership on an entity's Board of Directors or advisory committees; MyoGene Bio: Membership on an entity's Board of Directors or advisory committees; ImmunoVec: Membership on an entity's Board of Directors or advisory committees; Pluto Immunotherapeutics: Membership on an entity's Board of Directors or advisory committees; Allogene: Membership on an entity's Board of Directors or advisory committees; UC Regents: Patents & Royalties; Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Sangamo Biosciences: Membership on an entity's Board of Directors or advisory committees.

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Targeting Lymphomas Using Non-Engineered, Multi-Antigen Specific T Cells

Blood ◽

10.1182/blood-2018-99-113140 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1685-1685 ◽

Cited By ~ 1

Author(s):

George Carrum ◽

Premal Lulla ◽

Ifigeneia Tzannou ◽

Ayumi Watanabe ◽

Manik Kuvalekar ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

B Cell ◽

Board Of Directors ◽

Research Funding ◽

Advisory Committees ◽

Post Infusion ◽

Equity Ownership ◽

T Cell Lines ◽

Large B Cell

Abstract Immunotherapy is emerging as a potent therapy for a range of hematologic malignancies including lymphomas. Indeed adoptive transfer of T cells genetically engineered to express the CD19 chimeric antigen receptor (CAR) has now received FDA approval for the treatment of patients with refractory diffuse large B cell lymphomas (DLBCL). We have developed a non-engineered T cell-based therapy to treat patients with all types of lymphomas: Hodgkin's (HL) and non-Hodgkin's lymphoma (NHL). The approach uses single T cell lines that simultaneously target a range of tumor-associated antigens (TAAs) that are frequently expressed by these tumors, including PRAME, SSX2, MAGEA4, NY-ESO-1 and Survivin. We can consistently prepare these lines by culturing PBMCs in the presence of a Th1-polarizing/pro-proliferative cytokine cocktail, and adding autologous DCs as APCs that are loaded with pepmixes (15mer peptides overlapping by 11 amino-acids) spanning all 5 target antigens. The use of whole antigen should remove the HLA restriction imposed by the use of transgenic TCRs specific for single peptides, while targeting multiple antigens simultaneously would reduce the risk of tumor immune evasion. We have generated 42 clinical-grade multiTAA-specific T cell lines, comprising CD3+ T cells (mean 98±1.1%) with a mixture of CD4+ (mean 48±4.3%) and CD8+ (mean 37±4%) T cells, which expressed central and effector memory markers (CD45RO+/CD62L+/CCR7+ -- mean 14±3%; CD45RO+/CD62L+/CCR7- -- 10±2.2%; CD45RO+/CD62L-/CCR7- -- 28.3±3.6%) (n=42). The expanded lines recognized the targeted antigens PRAME, SSX2, MAGEA4, NY-ESO-1 and Survivin (range 0-463, 0-496, 0-330, 0-379 and 0-304 spot forming units (SFU)/2x105 input cells, respectively in IFNg ELIspot, n=34). None of the lines reacted against non-malignant autologous recipient cells (3±3.8% specific lysis; E:T 20:1). We have treated 33 patients: 13 with HL, 17 with aggressive NHL (diffuse large B-cell, mantle cell, or T cell lymphomas) and 3 with indolent NHLs (FL and marginal zone lymphoma). Patients received 0.5-2x107 multiTAA-T cells/m2. Of 18 patients who were infused as adjuvant therapy all but 2 remain in remission (range 3-42 months post-infusion). Fifteen patients have received multiTAA-specific T cells to treat active disease, all of whom had failed a median of 4 lines of prior therapy. Of these, 5 had transient disease stabilization followed by disease progression, 4 have ongoing stable disease, 3-18 months post-multiTAA-specific T cells while the remaining 6 (3 with HL and 3 with DLBCL) have all had complete and durable responses ( 4 to 41 months), as assessed by PET imaging. These clinical responses correlated with the detection of tumor-reactive T cells in patient peripheral blood post-infusion directed against both targeted antigens as well as non-targeted TAAs including MAGEA2B and MAGE C1, indicating induction of antigen/epitope spreading. Notably, no patient, including the complete responders, had infusion-related systemic- or neuro-toxicity. Thus, infusion of autologous multiTAA-targeted T cells directed to PRAME, SSX2, MAGEA4, NY-ESO-1 and Survivin has been safe and provided durable clinical benefit to patients with lymphomas. Disclosures Brenner: Marker: Equity Ownership. Heslop:Marker: Equity Ownership; Cell Medica: Research Funding; Tessa Therapeutics: Research Funding; Viracyte: Equity Ownership; Gilead Biosciences: Membership on an entity's Board of Directors or advisory committees; Cytosen: Membership on an entity's Board of Directors or advisory committees. Rooney:Marker: Equity Ownership. Vera:Marker: Equity Ownership. Leen:Marker: Equity Ownership.

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Treatment with DC/AML Fusion Vaccine and CD3xCD123 Bi-Specific T-Cell Engager (CD123-CODV-TCE) for Treatment of Acute Myeloid Leukemia

Blood ◽

10.1182/blood-2021-148219 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 904-904

Author(s):

Dina Stroopinsky ◽

Anita G. Koshy ◽

Jessica J. Liegel ◽

Myrna Nahas ◽

Giulia Cheloni ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Ex Vivo ◽

Leukemia Cells ◽

Publicly Traded ◽

Advisory Committees ◽

Isotype Control ◽

Ifn Γ

Abstract Introduction: Immunotherapy for AML holds promise in overcoming chemotherapy resistance and in preserving immunologic memory necessary for durable remissions.A bispecific T-cell engaging antibody targeting CD3 and CD123 (CD123-CODV-TCE) has been shown to stimulate T cells to target CD123-expressing leukemic cells in vitroand in mouse models 1. While the short-term immune stimulation mediated by the CD123TCE has the potential to result in clinical response, long-term disease control will require the development of immune memory. We have developed a personalized cancer vaccine in which patient's dendritic cells are fused with autologous leukemia cells resulting in presentation of a wide range of antigens to the immune system. Here, we describe a novel combination of CD123TCE with a DC/AML fusion vaccine ex vivo and in a xenograft murine model. We hypothesized that the CD123TCE will direct the vaccine-educated T cells to not only more effectively eradicate target leukemia cells but also evoke a repertoire of memory T cells and long-term response. Methods/Results: AML cells expressing CD123 were isolated from bone marrow mononuclear cells (BMMCs) from AML patients (n=3). DCs were generated from autologous adherent peripheral blood mononuclear cells (PBMCs) obtained at the time of disease remission as previously described 2,3. Concurrently, CD3+ T cells were isolated from the non-adherent fraction of PBMCs using magnetic bead separation. Fusion cells were generated by co-culturing the DC and tumor cells at a ratio of 3:1 in the presence of polyethylene glycol (PEG). Vaccine educated T cells were then generated by co-culture of T cells with the autologous fusion cells at a ratio of 10:1 for 5-7 days followed by T cell expansion via CD3/CD28 ligation. The capacity of the vaccine-educated T cells to target autologous leukemia cells with the addition of CD123TCE was assessed. The results demonstrated a statistically significant increase in Granzyme B activity in the target AML cells following co-culture with vaccine-educated T cells and the addition of the CD123TCE, compared to T cells + isotype control (n=3). Furthermore, vaccine stimulation in combination with CD123TCE led to a robust increase in induction of tumor specific activated T cells as detected by CD137 expression and intracellular IFN-γ production after co-culture of vaccine-educated T cells with autologous tumor cells in the presence of CD123TCE. The addition of CD123TCE to vaccine-educated T cells resulted in mean 25.4% and 9.6% intracellular IFN-γ expression for CD8 and CD4 T cells, respectively, compared to 8.5 and 3.1% IFN-γ expression following the addition of isotype control (n=3). Next, we examined the efficacy of the combined treatment with vaccine-educated T cells and CD123TCE in-vivo, in two independent xenograft experiments. NSG mice were irradiated with 300rads and challenged with 1x10 6 patient-derived CD123+ tumor cells via retro-orbital injections. After detection of human AML engraftment in the PB on day 76, the mice were inoculated IV with 1X10 6 resting, or ex vivo fusion vaccine educated autologous T cells IV. Subsequently, cohorts of mice were treated with CD123TCE or an appropriate isotype control every 3 days IP. A significant decrease in human leukemia burden was detected in the peripheral blood, spleen and bone marrows of analyzed animals after treatment with vaccine educated T cells and isotype control, or resting T cells and CD123TCE, compared to untreated mice (n=5). Strikingly, no detectable AML was found in peripheral blood, spleens and bone marrows of mice treated with vaccine educated T cells in combination with TCE (n=5). Of note, treatment with vaccine educated T cells led to an expansion of human CD3+ T cells in tissues obtained from the analyzed animals. These human T cells persisted in mice treated with the CD123TCE with a two-fold increase in tumor-specific CD8+ T cells, as assessed by intracellular IFN-γ secretion following ex vivo stimulation with autologous tumor lysate. Conclusions: We demonstrated that the combination of DC/AML fusion vaccine and CD123TCE led to increase in tumor specific T cell immunity, both ex-vivo and in a xenograft murine model when compared to uneducated T cells with CD123TCE or educated T cells with isotype control molecule. Most significantly, the combination treatment was shown to eradicate AML in this model with all animals remaining disease-free several months post inoculation. Disclosures Stroopinsky: The Blackstone Group: Consultancy. Nahas: Kite Pharma: Current Employment. Fraenkel: Sanofi: Current Employment. Yildirim: Sanofi: Current Employment. Bonnevaux: Sanofi: Current Employment. Guerif: Sanofi: Current Employment. Kufe: Genus Oncology: Current equity holder in publicly-traded company; Canbas: Consultancy; REATA: Consultancy, Current equity holder in publicly-traded company; Hillstream BioPharma: Current equity holder in publicly-traded company. Rosenblatt: Parexel: Consultancy; Wolters Kluwer Health: Consultancy, Patents & Royalties; Bristol-Myers Squibb: Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Imaging Endpoints: Consultancy; Attivare Therapeutics: Consultancy. Avigan: Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Kite Pharma: Consultancy, Research Funding; Juno: Membership on an entity's Board of Directors or advisory committees; Partner Tx: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Aviv MedTech Ltd: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Legend Biotech: Membership on an entity's Board of Directors or advisory committees; Chugai: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; Parexcel: Consultancy; Takeda: Consultancy; Sanofi: Consultancy.

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Safety and Efficacy of Multiantigen-Targeted T Cells for Multiple Myeloma

Blood ◽

10.1182/blood-2018-99-113118 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1014-1014 ◽

Cited By ~ 2

Author(s):

Premal Lulla ◽

Ifigeneia Tzannou ◽

George Carrum ◽

Carlos A. Ramos ◽

Rammurti Kamble ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Peripheral Blood ◽

Research Funding ◽

Advisory Committees ◽

T Cell Clones ◽

Cell Clones ◽

Equity Ownership ◽

T Cell Lines

Abstract Despite an array of approved agents for the treatment of multiple myeloma (MM), most patients eventually relapse after conventional treatments. The adoptive transfer of tumor-targeted T cells has demonstrated efficacy in the treatment of patients with chemo-refractory hematological malignancies including MM. While the majority of T cell-based immunotherapeutic studies in the clinic explore genetically modified T cells that target a single tumor-expressed antigen, we have developed a strategy to generate non-engineered T cell lines that simultaneously target multiple MM-expressed antigens, thereby reducing the risk of tumor immune evasion. We manufacture multiTAA-specific T cells targeting the tumor-associated antigens PRAME, SSX2, MAGEA4, NY-ESO-1 and Survivin by culturing patient-derived PBMCs with autologous DCs loaded with pepmixes (15mer peptides overlapping by 11 aminos acids) spanning all 5 target antigens in the presence of a Th1-polarizing/pro-proliferative cytokine cocktail. In our current clinical trial (NCT02291848), we have successfully generated multi-antigen-targeted lines from 18/ of 19 patients thus far, with one in production. The T cell lines comprise of CD3+ T cells (mean 95.6±2.2%) with a mixture of CD4+ (28.9±7.2%) and CD8+ (56.6±7.2%) T cells, which express central and effector memory markers (CD45RO+/CD62L+/CCR7+ -- 1.21±0.2%; CD45RO+/CD62L+/CCR7- -- 15.16±2.5%; CD45RO+/CD62L-/CCR7- -- 56.9±6.3%). All the expanded lines were specific for two to five target antigens with the majority of lines (13 of 18) specific for ≥3, (PRAME: Mean 45, range: 0 to 205 spot forming units (SFU)/2x105 input cells ; SSX2 mean: 57, 0 to 583, NYESO1: mean: 51, 0 to 125 , MAGE-A4 Mean: 67, 0 to 377 and Survivin mean: 53, 0 to 51), and did not react against non-malignant autologous recipient cells (2±3% specific lysis; E:T 20:1). We assessed the clonal diversity of the clinical product using TCR vβ deep sequencing analysis. We found both polyclonality and that the majority (mean 79%; range: 59 to 95%) represented rare T cell clones that were unique to the ex vivo expanded cell line and below levels of detection in the patients peripheral blood prior to infusion, thereby enabling in vivo tracking studies.. To date we have infused 18 patients with at least 2 infusions, 2 weeks apart of doses ranging from 0.5 to 2x107/m2. These patients had received a median of 4 lines of prior therapy including high dose chemotherapy with autologous stem cell rescue. Ten patients were refractory to their latest therapy and had active MM, while 8 were in remission at the time of infusion. At the 6 week evaluation period, of the 10 patients receiving multiTAA-specific T cells to treat active disease, 1 had a complete remission (CR) by the international myeloma working group (IMWG) response criteria, 1 had a partial remission (PR) and 8 others had stable disease (SD). Seven of these 10 patients were infused more than 1 year ago. Although 2 of the 7 subsequently had disease progression, the remaining 5 continue to respond, with sustained CR (1), PR (2) or SD (2). Of the 8 patients in CR at the time of T cell infusion, all remained in CR at the week 6 disease assessment and of the 6 evaluable patients who are >1 year post T cells, only one patient has relapsed, at 7 months after T cell infusion. These clinical responses correlated with the emergence and persistence (>6 months) of "line-exclusive" tumor-reactive T cells in patient peripheral blood, as assessed by longitudinal tracking of infused T cell clones using TCR deep sequencing. These infused product-derived T cells were detected in both peripheral blood (mean 0.43% ±SD of 0.3 of the total repertoire) and the marrow (mean 0.61%±0.24% of total repertoire). The expansion of product-derived T cell clones was higher among patients with active MM than in patients treated in remission (active: 0.60±0.39%, remission: 0.2±0.08%, p=0.048). Notably, no patient, including the complete responder, had infusion-related systemic- or neuro-toxicity. Thus, autologous multiTAA-targeted T cells directed to PRAME, SSX2, MAGEA4, NY-ESO-1 and Survivin can be safely administered to patients with MM, in whom they can subsequently be detected long-term in peripheral blood and marrow, and where they produce sustained tumor responses including CR. It will be of interest to discover whether larger or more frequent doses of these T cells can produce further benefit with maintained safety. Disclosures Brenner: Marker: Equity Ownership. Heslop:Marker: Equity Ownership; Viracyte: Equity Ownership; Cell Medica: Research Funding; Gilead Biosciences: Membership on an entity's Board of Directors or advisory committees; Tessa Therapeutics: Research Funding; Cytosen: Membership on an entity's Board of Directors or advisory committees. Vera:Marker: Equity Ownership. Leen:Marker: Equity Ownership.

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