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2031 Donor T Cells Maintain Myeloma-Immune Equilibrium after Autologous Stem Cell Transplantation and Concurrent Immunotherapy Promotes Cure

Program: Oral and Poster Abstracts
Session: 701. Experimental Transplantation: Basic Biology, Pre-Clinical Models: Poster I
Hematology Disease Topics & Pathways:
Biological, multiple myeloma, Diseases, Therapies, checkpoint inhibitors, immunotherapy, Plasma Cell Disorders, Lymphoid Malignancies, transplantation
Saturday, December 1, 2018, 6:15 PM-8:15 PM
Hall GH (San Diego Convention Center)

Simone A Minnie1*, David Smith2*, Kate H Gartlan, PhD2*, Thomas S Watkins2*, Kate A Markey, PhD, MBBS3,4,5, Camille Guillerey, PhD2*, Rachel D Kuns, BSc2*, Kelly R Locke2*, Antiopi Varelias, PhD2*, Ping Zhang2*, Nicholas Huntington, PhD6,7*, Marta Chesi, PhD8, John J Miles, PhD9*, Mark J Smyth, PhD2*, Slavica Vuckovic, PhD10* and Geoffrey R Hill, MD, PhD2,5,11,12

1QIMR Berghofer Medical Research Institute, Brisbane City, Australia
2QIMR Berghofer Medical Research Institute, Brisbane, Australia
3Queensland Institute of Medical Research, Brisbane, Australia
4Memorial Sloan Kettering Cancer Center, New York, NY
5Royal Brisbane and Women's Hospital, Brisbane, Australia
6Molecular Immunology Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
7Department of Medical Biology, The University of Melbourne, Parkville, Australia
8Division of Hematology/Oncology, Mayo Clinic, Scottsdale, AZ
9Centre for Biodiscovery and Molecular Development of Therapeutics, AITHM, James Cook University, Townsville, Australia
10Institute of Haematology, Royal Prince Alfred Hospital, Sydney, Australia
11Fred Hutchinson Cancer Research Centre, Seattle, WA
12Division of Medical Oncology, University of Washington, Seattle

Autologous stem cell transplantation (ASCT) remains an important consolidation treatment for multiple myeloma (MM) patients, even in the era of novel agents. The prolongation of plateau-phase induced by ASCT is generally attributed to intensive cytoreduction. However, ASCT generates inflammation and profound lymphodepletion, which may result in hitherto unexpected immunological effects. To investigate potential immunological contributions to myeloma control after ASCT, we developed preclinical models of transplantation for MM using Vk*MYC myeloma that generates bony lytic lesions, a serum M band and marrow plasmacytosis that are hallmarks of clinical disease.

Myeloma-bearing B6 recipients underwent myeloablative conditioning and were transplanted with naïve B6 bone marrow (BM) grafts with or without T cells from donors that were myeloma-naïve (SCT) or had low M bands at the time of harvest to mimic ASCT. Surprisingly, we demonstrate the broad induction of T cell-dependent myeloma control with enhanced median survival in recipients of grafts containing T cells compared to T cell depleted (TCD) BM alone (SCT= 91 days and ASCT > 100 days post-transplant vs TCD BM alone= 44 days; p<0.0001). Myeloma was most efficiently controlled when recipients were transplanted with memory T cells (CD44+) from autologous grafts (median survival: ASCT-CD44+ T cells >90 days post-transplant vs. CD44 T cells = 50 days; p = 0.0006). Importantly, T cells adoptively transferred from recipients surviving > 120 days (MM-primed) protected secondary recipients compared to T cells from naïve donors (median survival: MM-primed > 120 days post-transplant vs 65 days naïve T cells; p = 0.0003). Furthermore, MM-primed CD8 T cells were restricted in TCR repertoire and provided protection in a myeloma clone-specific fashion, indicative of a tumor-specific T cell response.

Despite this immune-mediated control of myeloma after SCT, progression still occurred in the majority of recipients. We phenotyped CD8+ T cells from the BM of MM-relapsed, MM-controlled and MM-free (that had never seen myeloma) mice 8 weeks after SCT. Expression of the inhibitory receptors, programmed cell death protein 1 (PD-1) and T cell immunoreceptor with Ig and ITIM domains (TIGIT) on BM CD8+ T-cells strongly correlated with myeloma cell number (r = 0.729, p<0.0001 and r = 0.796, p<0.0001 respectively). Additionally, the co-stimulatory/adhesion receptor CD226 (DNAM-1) was markedly downregulated as myeloma progressed (r = - 0.865, p<0.0001), as was interferon-γ secretion (r = - 0.76, p = 0.0022). t-SNE analysis confirmed an irreversible exhaustion signature at myeloma progression, characterized by the absence of DNAM-1 and co-expression of PD-1, TIM-3, TIGIT together with CD101 and CD38. Immune-checkpoint inhibition (CPI) early post-SCT, using antibodies against PD-1 or TIGIT facilitated long-term myeloma control (median survival in both treatment arms > 120 days post-SCT vs. 60 and 68 days respectively; p <0.05). Furthermore, TIGIT blockade limited CD8+ T cell exhaustion, increased CD107a and IFNγ secretion and expanded a memory CD8+ T cell population in the BM. Genetic deletion of either IFNγ or the IFNγ receptor from the donor graft resulted in dramatic myeloma progression after SCT. Consequently, treatment with a CD137 (4-IBB) agonist early after SCT profoundly augmented CD8+IFNγ+GranzymeB+ T-cell expansion in the BM, such that majority of treated animals eliminated myeloma and survived long-term. These data provide insights into an unappreciated mechanism of action of ASCT whereby myeloma immune-equilibrium is established and suggest that combination with immunotherapeutic strategies is a rational approach to generate long term disease control.

Disclosures: Smyth: Bristol Myers Squibb: Other: Research agreement; Tizona Therapeutics: Research Funding.

*signifies non-member of ASH