Tassilo L. A. Wachsmann

Despite major progress with chimeric antigen receptor T-cell therapy, multiple myeloma (MM) remains largely incurable and most patients relapse. To broaden therapeutic options and overcome antigen escape, we explored T-cell receptor (TCR)–based targeting of intracellular antigens derived from immunoglobulin heavy chain constant domains. Using HLA class-I peptidomics, we identified 9 immunoglobulin G (IgG)– or IgA-derived peptides presented by common HLA alleles (HLA-A∗01:01, HLA-A∗02:01, HLA-A∗03:01, and HLA-B∗07:02). High-avidity T-cell clones recognizing 4 of these epitopes were isolated from HLA-mismatched healthy donors. The transfer of these immunoglobulin-specific TCRs into donor T cells conferred potent and selective recognition of IgG- or IgA-expressing MM cell lines, sparing antigen-negative cells. Safety profiling confirmed strict HLA-restricted specificity without cross-reactivity toward other HLA alleles, non–B-lineage tumor cell lines, or healthy tissues, except for the depletion of isotype-matched B cells. Immunoglobulin-TCR T cells efficiently lysed patient-derived MM cells ex vivo and eradicated established IgA- or IgG-expressing MM tumors in murine xenograft models. Mechanistic studies revealed that dendritic cells could cross-present immunoglobulin peptides at high serum concentrations, potentially enhancing T-cell activation in vivo. Importantly, subtype-specific depletion of B cells implies that immunoglobulin-TCR T-cell therapy could partly preserve humoral immunity, reducing the need for antibody replacement compared with pan–B-cell depletion strategies. Collectively, these findings establish immunoglobulin heavy chain constant domains as promising targets for TCR-based cellular immunotherapy in MM and potentially other immunoglobulin-producing malignancies or autoantibody-mediated autoimmune diseases.

Background Cellular immunotherapy using modified T cells offers new avenues for cancer treatment. T-cell receptor (TCR) engineering of CD8 T cells enables these cells to recognize tumor-associated antigens and tumor-specific neoantigens. Improving TCR T-cell therapy through increased potency and in vivo persistence will be critical for clinical success. Methods We evaluated a novel drug combination to enhance TCR therapy in mouse models for acute myeloid leukemia (AML) and multiple myeloma (MM). Results Combining TCR therapy with the SUMO E1 inhibitor TAK981 and the DNA methylation inhibitor 5-Aza-2’ deoxycytidine resulted in strong antitumor activity in a persistent manner against two in vivo tumor models of established AML and MM. We uncovered that the drug combination caused strong T-cell proliferation, increased cytokine signaling in T cells, improved persistence of T cells, and reduced differentiation towards exhausted phenotype. Simultaneously the drug combination enhanced immunogenicity of the tumor by increasing HLA and co-stimulation and surprisingly reducing inhibitory ligand expression. Conclusion Combining T-cell therapy with TAK981 and 5-Aza-2’ deoxycytidine may be an important step towards improved clinical outcome.

Background T cell receptor (TCR)-engineered cells can be powerful tools in the treatment of malignancies. However, tumor resistance by Human Leukocyte antigen (HLA) class I downregulation can negatively impact the success of any TCR-mediated cell therapy. Allogeneic natural killer (NK) cells have demonstrated efficacy and safety against malignancies without inducing graft-versus-host-disease, highlighting the feasibility for an ‘off the shelf’ cellular therapeutic. Furthermore, primary NK cells can target tumors using a broad array of intrinsic activation mechanisms. In this study, we combined the antitumor effector functions of NK cells with TCR engineering (NK-TCR), creating a novel therapeutic strategy to avoid TCR-associated immune resistance. Methods BOB1, is a transcription factor highly expressed in all healthy and malignant B cell lineages, including multiple myeloma (MM). Expression of an HLA-B*07:02 restricted BOB1-specifc TCR in peripheral blood–derived NK cells was achieved following a two-step retroviral transduction protocol. NK-TCR was then compared with TCR-negative NK cells and CD8-T cells expressing the same TCR for effector function against HLA-B*07:02+ B-cell derived lymphoblastoid cell lines (B-LCL), B-cell acute lymphoblastic leukemia and MM cell lines in vitro and in vivo. Results Firstly, TCR could be reproducibly expressed in NK cells isolated from the peripheral blood of multiple healthy donors generating pure NK-TCR cell products. Secondly, NK-TCR demonstrated antigen-specific effector functions against malignancies which were previously resistant to NK-mediated lysis and enhanced NK efficacy in vivo using a preclinical xenograft model of MM. Moreover, antigen-specific cytotoxicity and cytokine production of NK-TCR was comparable to CD8 T cells expressing the same TCR. Finally, in a model of HLA-class I loss, tumor cells with B2M KO were lysed by NK-TCR in an NK-mediated manner but were resistant to T-cell based killing. Conclusion NK-TCR cell therapy enhances NK cell efficacy against tumors through additional TCR-mediated lysis. Furthermore, the dual efficacy of NK-TCR permits the specific targeting of tumors and the associated TCR-associated immune resistance, making NK-TCR a unique cellular therapeutic.

Chimeric antigen receptor (CAR) T cell therapies have resulted in profound clinical responses in the treatment of CD19-positive hematological malignancies, but a significant proportion of patients do not respond or relapse eventually. As an alternative to CAR T cells, T cells can be engineered to express a tumor-targeting T cell receptor (TCR). Due to HLA restriction of TCRs, CARs have emerged as a preferred treatment moiety when targeting surface antigens, despite the fact that functional differences between engineered TCR (eTCR) T and CAR T cells remain ill-defined. Here, we compared the activity of CAR T cells versus engineered TCR T cells in targeting the B cell malignancy-associated antigen CD20 as a function of antigen exposure. We found CAR T cells to be more potent effector cells, producing higher levels of cytokines and killing more efficiently than eTCR T cells in a short time frame. However, we revealed that the increase of antigen exposure significantly impaired CAR T cell expansion, a phenotype defined by high expression of coinhibitory molecules and effector differentiation. In contrast, eTCR T cells expanded better than CAR T cells under high antigenic pressure, with lower expression of coinhibitory molecules and maintenance of an early differentiation phenotype, and comparable clearance of tumor cells.