Abstract: Vaccination with dendritic cell (DC)/multiple myeloma (MM) fusions has been shown to induce the expansion of circulating multiple myeloma–reactive lymphocytes and consolidation of clinical response following autologous hematopoietic cell transplant (auto-HCT). Patients and Methods: In this randomized phase II trial (NCT02728102), we assessed the effect of DC/MM fusion vaccination, GM-CSF, and lenalidomide maintenance as compared with control arms of GM-CSF and lenalidomide or lenalidomide maintenance alone on clinical response rates and induction of multiple myeloma–specific immunity at 1-year posttransplant. Results: The study enrolled 203 patients, with 140 randomized posttransplantation. Vaccine production was successful in 63 of 68 patients. At 1 year, rates of CR were 52.9% (vaccine) and 50% (control; P = 0.37, 80% CI 44.5%, 61.3%, and 41.6%, 58.4%, respectively), and rates of VGPR or better were 85.3% (vaccine) and 77.8% (control; P = 0.2). Conversion to CR at 1 year was 34.8% (vaccine) and 27.3% (control; P = 0.4). Vaccination induced a statistically significant expansion of multiple myeloma–reactive T cells at 1 year compared with before vaccination (P = 0.024) and in contrast to the nonvaccine arm (P = 0.026). Single-cell transcriptomics revealed clonotypic expansion of activated CD8 cells and shared dominant clonotypes between patients at 1-year posttransplant. Conclusions: DC/MM fusion vaccination with lenalidomide did not result in a statistically significant increase in CR rates at 1 year posttransplant but was associated with a significant increase in circulating multiple myeloma–reactive lymphocytes indicative of tumor-specific immunity. Site-specific production of a personalized cell therapy with centralized product characterization was effectively accomplished in the context of a multicenter cooperative group study.

Abstract: In a prior phase 2 study, personalized cancer vaccination with autologous dendritic cells (DCs) fused with primary MM tumor cells (DC/MM fusions) induced the expansion of circulating MM-reactive lymphocytes and was associated with conversion to complete response (CR) post-autoHCT in the absence of maintenance therapy. 1 We now present a multicenter randomized phase II study that examined the efficacy of DC/MM fusion vaccination with lenalidomide maintenance therapy after autoHCT, compared with lenalidomide maintenance alone. The study offered a first-of-its-kind academic collaborative effort of personalized cell therapy using an open-source format, site-specific production, and centralized product characterization/release criteria verification. Under the aegis of the BMT CTN (CTN 1401), 203 patients enrolled from 18 participating centers. Sixty-three patients dropped out of the study from enrollment to randomization for an overall dropout rate of 31%, concordant with the expected rate of 30% pre-specified in the protocol. Among the 140 patients, 68 were randomized to the vaccine arm, 37 to the lenalidomide/GM-CSF arm, and 35 to the lenalidomide alone arm. Ninety-one (65.0%) patients had high-risk MM. A collaborative process was established for the standardization of vaccine manufacturing including tumor cell harvest and cryopreservation, DC generation from leukapheresis collection, creation and quantification of the DC/tumor fusion vaccine, and the process of characterizing each cellular product. Of the 140 patients who underwent tumor collection, the median percentage of plasma cells in bone marrow aspirate differential was 45%. Mean CD86 expression and viability of the DC preparations were 80.6% and 79.3%, respectively. The mean fusion efficiency of the DC/MM product, as determined by co-expression of standard DC (CD86) and MM (CD38) markers, was 47.9%. Mean fusion cell viability was 78.6%. Vaccine was successfully generated for 63/68 patients (93%) assigned to the vaccine arm of the study. Thirty-six of the 68 (52.9%) evaluable patients on the vaccine arm (80% confidence interval 44.5%, 61.3%) and 34 of the 68 (50.0%) of the non-vaccine arms (80% confidence interval 41.6%, 58.4%) achieved CR/sCR at 1-year post-transplant (p=0.3). Of the patients not achieving CR at time of randomization post-transplant, conversion to CR at 1-year was 34.8% for the vaccine arm and 27.3% for the non-vaccine arm (p=0.4). sCR/CR/VGPR at 1-year was achieved by 85.3% and 77.8% of patients on the vaccine and non-vaccine arms, respectively (p=0.2). The rates of post-transplant grade 3-4 toxicities were 76.5%, 62.5% for the vaccine, and non-vaccine arms, respectively (p=0.07). There were no grade 5 toxicities in any of the cohorts. The overall grade 2-3 infection rate was 22.9% (23.5% on the vaccine arm, 13.5% on the lenalidomide/GM-CSF arm, and 31.4% on the lenalidomide alone arm). Quantification of circulating MM-reactive T cells was performed for an initial cohort of 20 patients who completed 1-year post-transplant assessments. Patients in the vaccine arm demonstrated a significant expansion of MM-reactive CD8 cells, representing 2.9%, 3.5%, and 15.9% of the lymphocyte population prior to post-transplant maintenance, following 1 cycle of lenalidomide and following 3 vaccinations at 1-year post-transplant, respectively (Figure). In contrast, there was no increase in MM-specific CD8 T cells in the control arm with levels of 1.1, 2.0. and 0.6, respectively. Single-cell transcriptomic analysis performed on the peripheral T-cell repertoire of 14 patients from the vaccine arm at serial time points demonstrated progressive expansion of dominant CD8, CD4, and NKT cell clones with an activated phenotype. Vaccination was associated with the recovery of T-cell clonal diversity. This multicenter trial demonstrated successful site-specific production. DC/MM fusion vaccination with lenalidomide maintenance after autoHCT did not result in a significant increase in CR rates at 1-year but was associated with measurable anti-MM immune reactivity for which the impact on response duration will require longer term follow-up. 1. Rosenblatt, J. et al. Vaccination with dendritic cell/tumor fusions following autologous stem cell transplant induces immunologic and clinical responses in multiple myeloma patients. Clin. Cancer Res. 19, 3640-3648 (2013) Figure 1 Figure 1. Disclosures Shah: CareDx: Consultancy; GSK: Consultancy; Teneobio: Research Funding; Kite: Consultancy; Nektar: Research Funding; Poseida: Research Funding; Oncopeptides: Consultancy; Bluebird Bio: Research Funding; CSL Behring: Consultancy; Indapta Therapeutics: Consultancy; Janssen: Research Funding; Sanofi: Consultancy; Sutro Biopharma: Research Funding; Precision Biosciences: Research Funding; BMS/Celgene: Research Funding; Karyopharm: Consultancy; Amgen: Consultancy. Stroopinsky: The Blackstone Group: Consultancy. Anderson: Sanofi-Aventis: 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; Pfizer: Membership on an entity's Board of Directors or advisory committees; Millenium-Takeda: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Scientific Founder of Oncopep and C4 Therapeutics: Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Mana Therapeutics: Membership on an entity's Board of Directors or advisory committees. Devine: Magenta Therapeutics: Current Employment, Research Funding; Tmunity: Current Employment, Research Funding; Johnsonand Johnson: Consultancy, Research Funding; Orca Bio: Consultancy, Research Funding; Be the Match: Current Employment; Sanofi: Consultancy, Research Funding; Vor Bio: Research Funding; Kiadis: Consultancy, Research Funding. Holmberg: Sanofi: Research Funding; Millennium-Takeda: Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Merck: Research Funding; Janssen: Research Funding; Up-To-Date: Patents & Royalties. Johnson: Miltenyi Biotec: Research Funding. Lazarus: Bristol Myer Squibb: Membership on an entity's Board of Directors or advisory committees. Malek: Janssen: Other: Advisory board ; Medpacto Inc.: Research Funding; Takeda: Honoraria; BMS: Honoraria, Research Funding; Amgen: Honoraria; Cumberland Inc.: Research Funding; Bluespark Inc.: Research Funding; Sanofi: Other: Advisory Board. McCarthy: Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Juno: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. McKenna: Qihan Bio: Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics: Other: all manufacturing of cell therapy products for clinical trials; Intima: Other: all manufacturing of cell therapy products for clinical trials; Gamida: Other: all manufacturing of cell therapy products for clinical trials; Magenta: Other: all manufacturing of cell therapy products for clinical trials. Munshi: Takeda: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Oncopep: Consultancy, Current equity holder in publicly-traded company, Other: scientific founder, Patents & Royalties; Amgen: Consultancy; Janssen: Consultancy; Karyopharm: Consultancy; Abbvie: Consultancy; Adaptive Biotechnology: Consultancy; Legend: Consultancy; Pfizer: Consultancy; Bristol-Myers Squibb: Consultancy. Nooka: Janssen Oncology: Consultancy, Research Funding; Adaptive technologies: Consultancy; Sanofi: Consultancy; GlaxoSmithKline: Consultancy, Other: Travel expenses; Takeda: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy; Amgen: Consultancy, Research Funding; Oncopeptides: Consultancy; Karyopharm Therapeutics: Consultancy. Soiffer: Jazz Pharmaceuticals, USA: Consultancy; Precision Biosciences, USA: Consultancy; Juno Therapeutics, USA: Other: Data Safety Monitoring Board; Kiadis, Netherlands: Membership on an entity's Board of Directors or advisory committees; Rheos Therapeutics, USA: Consultancy; Gilead, USA: Other: Career Development Award Committee; NMPD - Be the Match, USA: Membership on an entity's Board of Directors or advisory committees; Jasper: Consultancy; Takeda: Consultancy. Uhl: Grifols: Consultancy, Speakers Bureau; Abbott: Consultancy, Speakers Bureau; UpToDate: Patents & Royalties. Young: Amgen: Current equity holder in publicly-traded company; Pfizer: Current equity holder in publicly-traded company; Merck: Current equity holder in publicly-traded company. Rosenblatt: Attivare Therapeutics: Consultancy; Bristol-Myers Squibb: Research Funding; Parexel: Consultancy; Wolters Kluwer Health: Consultancy, Patents & Royalties; Imaging Endpoints: Consultancy; Karyopharm: Membership on an entity's Board of Directors or advisory committees. Waller: Verastem Oncology: Consultancy, Research Funding; Cambium Oncology: Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Pasquini: GlaxoSmithKline: Research Funding; Kite Pharma: Research Funding; Novartis: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding. 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. OffLabel Disclosure: Dendritic Cell/Tumor Fusion Vaccine and GM-CSF

Abstract: Background: Axicabtagene ciloleucel (Axi-cel), a CD19 directed CAR T cell therapy, results in durable response in a subset of patients with relapsed/refractory large B cell lymphoma (LBCL) in the absence of persistent circulating CAR T cells. Aim: We postulated that long-term efficacy of CAR T therapy depends on the downstream triggering of native T cell immunity. We performed single-cell transcriptomics of longitudinal peripheral blood (PB) samples and RNAseq of tumor samples from patients of the ZUMA 1 Axi-cel study. Methods: Single cell immunoprofiling (5’ expression + V(D)J, 10x Genomics) was performed on PB mononuclear cell samples from ZUMA-1 patients (N=32), collected at leukapheresis, 4 weeks, 6 and 12 months post Axi-cel infusion. RNAseq was performed on FFPE lymphoma samples (N=17). Patients were divided into 3 groups: non-responders, relapsed within 1 year from CAR T infusion, and long-term responders. A total of 405,775 cells passed quality check, capturing 73 cellular populations. Results: Long-term responders presented a distinct T cell landscape with increased CD8 T cells and CD8/CD4 ratios prior to CAR T therapy, compared to the other groups, with similar trends observed across time points. They also presented an increased abundance of 3 distinct CD8 T cell populations: (a) cells expressing cytotoxic and NK cell markers, (b) CD8 T effector memory cells characterized by CXCR4, TGFB1, and BCL3, and (c) proinflammatory CD8 T cells. In contrast, patients with early relapse showed increased levels of regulatory T cells pre-/post-CAR T infusion and lower abundance of CD4 cytotoxic T cells.Comparisons of the TCR repertoire pre-/post-CAR T demonstrated a greater clonal expansion of cytotoxic CD4 and CD8 T cell populations in the long-term responders, with high similarity of expanded clones post CAR T. Shared PB T cell clones and tumor antigen sequences derived from the RNAseq samples suggest an antigen-specific response driven by common epitopes. In contrast to the lack of expansion of T reg clones in responders, relapsed patients demonstrated high T reg-clonal expansion 6 months post treatment.Monocyte and NK cells were less prevalent in responders before treatment, driven by differences in phagocytic monocyte and inhibitory NK cell abundance. Modeling the interaction between monocyte and effector cell populations based on ligand receptor expression was suggestive of negative immunoregulatory impact on the T cell populations. Conclusion: The application of single-cell immunoprofiling on longitudinal samples from ZUMA-1 patients demonstrated distinct cellular and clonal profiles among long-term responders. These findings confirm our hypothesis of an important role for the native immune cell repertoire in response to CAR T therapeutics and can be utilized to further our understanding but also to potentially inform patient stratification, management, and treatment. Citation Format: Dimitra Karagkouni, Giulia Cheloni, Yered Pita-Juarez, Daniela Torres, Eleni Kanata, Zachary Avigan, Jessica Liegel, Dina Stroopinsky, Brodie Miles, Gayatri Tiwari, Jenny Kim, Mike Mattie, Jacalyn Rosenblatt, David Avigan, Ioannis Vlachos. Activation and clonotypic expansion of the native T cell repertoire identifies durable response to CD19 CAR T cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2257.

Abstract: Background: In Zuma-1 study, approximately 40% of patients with refractory or relapsed large B cell lymphoma (LBCL) show durable response to Axi-cel. The identification of immunologic factors predictive of therapeutic efficacy and tumor escape is a critical area of investigation. The impact of CAR T cell activation on the native T cell repertoire and lymphoma specific immunity has not been elucidated. Aim: We sought to determine the role of host immune activation in response to tumor-associated antigens and the impact of consequent epitope spreading on CAR-T mediated therapeutic efficacy. To this end, we performed longitudinal single cell immunoprofiling of peripheral blood samples from ZUMA-1 patients to capture immune cell subsets and T cell repertoire during axi-cel treatment. Methods: Single cell immunoprofiling (expression + V(D)J sequencing) was performed on PBMC samples from ZUMA-1 patients (N=32), collected at leukapheresis, 4 weeks, and 6 months post CAR-T cell infusion, to examine potential markers associated with response and resistance. scRNA-seq was performed using 10x Genomics Chromium Next GEM Single Cell 5' Kit v1.1. Full-length paired α/β TCR and BCR libraries were obtained using the Chromium Single Cell V(D)J Enrichment, Human T Cell/B cell kits following manufacturer instructions, while γ/δ TCR libraries were generated using custom primers. Results: Analysis has been completed on the pilot implementation comprising 3 patients. A total of 22,403 cells passed quality-check capturing 31 cellular populations (Figure 1a). In 2 of the 3 patients analyzed, CD8 T cells, after an initial decrease at 4 weeks post CAR T infusion, exhibited an increase at 6 months post CAR T infusion reaching higher levels than those observed prior to CAR T treatment. The third patient presented an increase of the CD8 T cell compartment at 4 weeks compared to pretreatment (Figure 1a). A similar trend was observed for CD4 T cell population, with an increase at 6 months post CAR-T to a level higher than prior to CAR T infusion (Figure 1a). On the contrary, the myeloid cell compartment depicted a gradual decrease from leukapheresis to 6 months post CAR T (Figure 1a). B cells were observed only in 1 of the 3 patients at 6 months (Figure 1a). α/β TCR, γ/δ TCR and BCR clonotypes were identified and projected on the 2-dimensional embedding (Figure 1b). Full-length paired α/β TCR at single cell level showed that some of the most abundant clonotypes at baseline continued to be prominent in post CAR T timepoints (Figure 1c). An extensive expansion of new clonotypes was observed at 6 months after infusion. Moreover, in 2 of the 3 patients, we observed that T cell clonal diversity converged at 4 weeks, and diverged in one patient at 6 months post treatment (Figure 1d). The analysis of the remaining 29 patients (87 samples) is ongoing. Conclusion: The application of single cell immunoprofiling on longitudinal samples from Axi-cel-treated LBCL patients successfully captured the changes in the cellular transcriptional landscape, cell proportions, and TCR/BCR space across the time axis in high resolution. It is anticipated that the full analysis of 32 patients can elucidate the transcriptional program in response to CAR T cell therapy. Figure 1: (A) Two-dimensional uniform manifold approximation and projection (UMAP) of all cells passing QC (n=22,403), separated per patient and timepoint. (B) T and B cell receptor clonality at single cell resolution. T and B cells with one or more clones are colored. (C) α/β clonotype frequency per timepoint for each patient. (D) T Cell receptor Shannon diversity index per timepoint for the 3 profiled patients. Dashed lines connect the different timepoints from the same patient. Figure 1 Figure 1. Disclosures Stroopinsky: The Blackstone Group: Consultancy. Bot: Kite, a Gilead Company: Current Employment; Gilead Sciences: Consultancy, Current equity holder in publicly-traded company, Other: Travel support. Mattie: Kite: Current Employment. Chou: Kite Pharma: Current Employment. Rosenblatt: Karyopharm: Membership on an entity's Board of Directors or advisory committees; Parexel: Consultancy; Wolters Kluwer Health: Consultancy, Patents & Royalties; Bristol-Myers Squibb: Research Funding; 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.

Abstract: Introduction: Multiple myeloma (MM), a clonal disorder of terminally differentiated plasma cells, is the second most common hematologic malignancy with ~57.9% 5-year survival rate. Current MM therapies are not curative and in most patients MM relapse. Aiming to restore antitumor immunity and counteract MM evolution, we have developed a personalized dendritic(DC)/MM cell fusion vaccine, whereby several tumor antigens are presented in the context of DC mediated co-stimulation. BMT CTN 1401 is a multicenter randomized phase II clinical trial (NCT02728102) evaluating the efficacy of the DC/MM vaccine combined with lenalidomide maintenance (Len) after autoHCT. 203 patients were enrolled from 18 centers. Aim: To evaluate the impact of the DC/MM vaccine on the establishment of anti-MM immune response we profiled the peripheral blood (PB) immune landscape at the single-cell level, with particular focus on the T cell compartment. Method: We performed single-cell immunoprofiling (gene expression + V(D)J sequencing) on 40 patients (3xDC/MM vaccine/Len/GM-CSF: N=20; Len/GM-CSF: N=10; Len: N=10). 160 PB mononuclear cells (PBMC) samples were collected at enrollment, prior to Len, after 1 and 3 vaccines and were processed using the 10x Genomics single cell 5' assay. Here we present the analysis relative to 52 PBMC samples from 13 vaccinated patients included in the initial study cohort. The remaining 108 PBMC samples have already been subjected to single-cell immunoprofiling and the analysis is ongoing. Results: 309,423 cells passed quality-check identifying 47 cell populations, corresponding to 20 major compartments. The T cell compartment (146,373 cells) was divided into 14 different cell populations including activated CD8, CD4, and NKT cells that exhibited a gradual increase during the course of the study. Relatively, TCR sequencing demonstrated a recovery of T cell clonal diversity and a progressive rise in the frequency of expanded clonotypes within the activated CD4 and cytotoxic T cell populations after vaccination. Consistently, we observed a progressively raised number of shared TCR clonotypes within the activated CD8 and CD4 T cell subsets. The identification of common epitope/paratope hotspots among the expanded clonotypes and the different patients revealed a higher proportion of shared TCR clonotype groups across patients after vaccination compared to the early post-transplant period, predominantly after 3 vaccinations. Conclusions: Assessment of PBMC samples from 13 vaccinated patients provided a detailed picture of the PBMC landscape. The constant T cell expansion in patients following vaccination coupled with the shared paratope/epitope hotspots and TCR signatures among patients indicated the TCR cross-reactivity and suggested for the establishment of an anti-MM immune response. Citation Format: Giulia Cheloni, Dimitra Karagkouni, Daniela Torres, David J. Chung, Nina Shah, Natalie S. Callander, Thinle Chodon, Yvonne Efebera, Nancy Geller, Peiman Hematti, Hillard Lazarus, Ehsan Malek, Philip L. McCarthy, Ajay K. Nooka, Jacalyn Rosenblatt, Aaron P. Rapoport, Robert J. Soiffer, Dina Stroopinsky, Edmund K. Waller, Marcelo C. Pasquini, Ioannis Vlachos, David Avigan. Dendritic cell/myeloma fusion vaccine with lenalidomide maintenance following autologous hematopoietic cell transplant induced T cell activation and expansion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6785.