CAR T-cell Therapy For Multiple Myeloma Research Articles

Targeting cancer-associated fibroblasts in the bone marrow prevents resistance to CART-cell therapy in multiple myeloma

AbstractPivotal clinical trials of B-cell maturation antigen-targeted chimeric antigen receptor T (CART)-cell therapy in patients with relapsed/refractory multiple myeloma (MM) resulted in remarkable initial responses, which led to a recent US Food and Drug Administration approval. Despite the success of this therapy, durable remissions continue to be low, and the predominant mechanism of resistance is loss of CART cells and inhibition by the tumor microenvironment (TME). MM is characterized by an immunosuppressive TME with an abundance of cancer-associated fibroblasts (CAFs). Using MM models, we studied the impact of CAFs on CART-cell efficacy and developed strategies to overcome CART-cell inhibition. We showed that CAFs inhibit CART-cell antitumor activity and promote MM progression. CAFs express molecules such as fibroblast activation protein and signaling lymphocyte activation molecule family-7, which are attractive immunotherapy targets. To overcome CAF-induced CART-cell inhibition, CART cells were generated targeting both MM cells and CAFs. This dual-targeting CART-cell strategy significantly improved the effector functions of CART cells. We show for the first time that dual targeting of both malignant plasma cells and the CAFs within the TME is a novel strategy to overcome resistance to CART-cell therapy in MM.

BCMA CAR-T Therapy Is Safe and Effective for Refractory/Relapsed Multiple Myeloma With Central Nervous System Involvement.

Central nervous system (CNS) involvement is a rare complication of multiple myeloma (MM) that portends an extremely poor prognosis. Although chimeric antigen receptor (CAR)-T cell therapy is considered a promising strategy for patients with MM, the role of CAR-T cell therapy in MM involving the CNS has not been fully elucidated. In this study, we retrospectively analyzed 4 cases of B-cell maturation antigen CAR-T cell therapy for patients with relapsed/refractory MM involving the CNS. Patients received a range of 2-7 lines of prior therapy, including 1 autologous hematopoietic stem cell transplant. The most common adverse event was cytokine release syndrome, which was observed in all 4 patients, including 2 with grade 1 and 2 with grade 2. No patient was complicated with immune effector cell-associated neurotoxicity syndrome. Within the follow-up (median: 257 d, range: 116-392 d), 3 of 4 patients reached complete remission (CR), and 1 patient reached partial response. At the data cutoff, 1 patient continued to remain in CR at day 220, and the patient with partial response died at day 116. The other 2 patients relapsed at 317 and 111 days with CR durations of 287 and 81 days, respectively. Our results show promising effectiveness and acceptable safety of CAR-T cell therapy for heavily pretreated patients with CNS MM.

Novel progresses of chimeric antigen receptor (CAR) T cell therapy in multiple myeloma.

Multiple myeloma (MM) is a malignant proliferative disease of plasma cells, which leads to suppressed hematopoietic and osteolytic diseases. Despite the use of traditional chemotherapy, hematopoietic stem cell transplantation (HSCT) and targeted drugs, MM still cannot be completely cured. In recent years, chimeric antigen receptor (CAR) T cells have revolutionized immunotherapy and cancer treatment. The great success of CAR-T cells in leukemia and lymphoma has promoted its development in MM. The primary requisite for developing clinically effective CAR-T cells suitable for MM is to identify the appropriate targets. In early clinical trials, CAR-T cells targeting B-cell maturation antigen (BCMA) have shown significant anti-MM activity. Currently popular targets in clinical research and preclinical research include CD138, CD38, CS1, CD19, κ light chain, CD56, CD44v6, Lewis Y, NY-ESO-1, CD229, etc. Common toxicities such as cytokine release syndrome (CRS) and neurotoxicity also occur but controllable. MM cells are mainly localized in bone marrow, therefore, the bone marrow microenvironment has a significant effect on the therapeutic effect of CAR-T cells. Targeting both MM cells and the bone marrow microenvironment is currently the most promising treatment. In this review, we provide a comprehensive overview of CAR-T cell therapy in MM, as well as outline potential targets and methods that can overcome local immunosuppression and improve the efficacy of CAR-T cells.

CAR T-Cells in Multiple Myeloma Are Ready for Prime Time.

The survival of patients with multiple myeloma (MM) has been dramatically improved in the last decade thanks to the incorporation of second-generation proteasome inhibitors (PI), immunomodulatory drugs (IMID), and, more recently, anti-CD38 monoclonal antibodies (MoAb). Nevertheless, still, a major proportion of MM patients will relapse, underscoring the need for new therapies in this disease. Moreover, survival in patients failing the current standard of care regimens (including PI, IMIDs, and anti-CD38 MoAb), which is now defined as triple-class refractory, remains dismal, and new drugs with different mechanism of action are needed. B-cell maturation antigen (BCMA)-targeted therapies and in particular chimeric antigen receptor T cell (CAR T-cell) treatment have emerged as promising platforms to overcome refractoriness to conventional drugs. In this manuscript, we review the current available data regarding CAR T-cell therapy for MM, with a special focus on target selection, clinical results, limitations, and future strategies.

Chimeric antigen receptor T cell therapy in multiple myeloma: promise and challenges.

Despite a sea change in the therapeutic landscape, multiple myeloma (MM), a cancer of antibody producing plasma cells, remains incurable requiring continued intervention for disease control. In this context, chimeric antigen receptor (CAR) T cell therapy has emerged as a promising immunotherapeutic approach with unprecedented results in heavily treated relapsed and/or refractory MM patients. Although B cell maturation antigen (BCMA) is the current lead target for CAR-T cell therapy in MM, several other antigenic targets are also being investigated. Relapses, however, are inevitable in spite of the promising early responses, and may be mediated by antigenic modulation, poor persistence and "immunostat" in tumor microenvironment. Akin to multi-agent chemotherapy, multi-targeted CAR-T antigens and combinatorial approaches are underway to overcome the resistance mechanisms. Further, CAR-T specific toxicity concerns such as cytokine release syndrome and neurotoxicity, as well as manufacturing time lag are other key challenges. Allogeneic CAR that offers "off-the-shelf" options, and mRNA transfected CAR are being developed to mitigate the access and safety issues. In this review we provide the comprehensive review of the most current clinical trial data for CAR-T in myeloma, challenges associated with this therapy and discuss its future in myeloma therapeutics.

Dual Targeting to Overcome Current Challenges in Multiple Myeloma CAR T-Cell Treatment.

In the era of highly promising novel targeted-immunotherapy strategies for multiple myeloma (MM), the first series of clinical trials with CAR T-cells targeting the plasma cell-specific B-cell maturation antigen (BCMA) have shown excellent response rates. In the long-term, however, MM appears to escape the therapy likely due to initial low and heterogeneous expression or downregulation of BCMA expression. Several other molecules targeted by CAR T-cells in MM are expressed at high levels on MM cells, but many of these attractive targets are also expressed on various, sometimes vital non-malignant cells, posing major risks for on-target, off-tumor side effects. CAR T-cell therapy for MM therefore faces two urgent challenges: (i) improving the efficacy of BCMA CAR T-cells and (ii) establishing a MM-selectivity even when CAR T-cells are directed against not entirely MM-specific target antigens. In this review, we will outline the current attempts to tackle these challenges, with a specific focus on how dual CAR targeting might be applied to tackle both issues.

Development of CAR-T cell therapies for multiple myeloma.

Currently available data on chimeric antigen receptor (CAR)-T cell therapy has demonstrated efficacy and manageable toxicity in heavily pretreated multiple myeloma (MM) patients. The CAR-T field in MM is rapidly evolving with >50 currently ongoing clinical trials across all phases, different CAR-T design, or targets. Most of the CAR-T trials are performed in China and the United States, while European centers organize or participate in only a small fraction of current clinical investigations. Autologous CAR-T cell therapy against B cell maturation antigen shows the best evidence of efficacy so far but main issues remain to be addressed: duration of response, longer follow-up, prolonged cytopenia, patients who may benefit the most such as those with extramedullary disease, outcome prediction, and the integration of CAR-T cell therapy within the MM treatment paradigm. Other promising targets are, i.a.,: CD38, SLAMF7/CS1, or GPRC5D. Although no product has been approved to date, cost and production time for autologous products are expected to be the main obstacles for broad use, for which reason allogeneic CAR-T cells are currently explored. However, the inherent risk of graft-versus-host disease requires additional modification which still need to be validated. This review aims to present the current status of CAR-T cell therapy in MM with an overview on current targets, designs, and stages of CAR-T cell development. Main challenges to CAR-T cell therapy will be highlighted as well as strategies to structurally improve the CAR-T cell product, and thereby its efficacy and safety. The need for comparability of the most promising therapies will be emphasized to balance risks and benefits in an evidence-based but personalized approach to further improve outcome of patients with MM.

Targeting Cancer Associated Fibroblasts in the Bone Marrow Prevents Resistance to Chimeric Antigen Receptor T Cell Therapy in Multiple Myeloma

Introduction Cellular immunotherapy is a rapidly progressing field in multiple myeloma (MM). Multiple clinical trials have reported impressive efficacy of B cell maturation antigen (BCMA) directed chimeric antigen receptor cell therapy (BCMA CART) in MM. While trials demonstrated a high response rate, the durable response rate is around 30%. Most patients lose their CART cells, and the disease relapses within the first year, suggesting an inhibition by the MM tumor microenvironment (TME). Therefore strategies to overcome this inhibition would represent a major advance in this field. Cancer associated fibroblasts (CAFs) within the TME play a critical role in promoting tumor growth and immunosuppression. Objective CAFs from MM patients lead BCMA CART cell dysfunction and targeting both MM cells and CAFs can overcome this resistance. Methods CAFs were isolated from the bone marrow (BM) of MM patients and purified using anti fibroblast beads. MM-TME mouse model was established by injecting a 1:1 ratio of BCMA+ OPM2 (MM cell line) to CAFs. Five different CART cells were tested in this study. For single transduced CAR: BCMA, CS1, and fibroblast activation protein (FAP). For dual transduced CAR: BCMA-CS1 and BCMA-FAP CART. These were generated through the double transduction of two lentiviral vectors. Results BCMA CART cell proliferation assay showed inhibition of CART expansion in the presence of CAFs, and this was mediated by TGF-β (Fig A). MM-TME mouse model revealed a significant acceleration of MM progression (Fig B). To identify targets, we verified FAP expression on CAFs. Interestingly, there was a low level of CS1, but not BCMA expressed on CAFs (Fig C). Then, we evaluated the impact of CAFs on functions of BCMA CART cells compared to dual CART cells. When CART cells were stimulated with the BCMA+ MM cell line MM1S, in the presence of CAFs, the proliferation of BCMA CART cells, but not the dual CART cells was significantly inhibited (Fig A). Similarly, in the presence of CAFs, the production of key effector cytokines by BCMA CART cells, but not the dual CART cells was reduced (Fig D). Finally, we studied the impact of CAFs on CART cell functions in vivo. First, using OPM2 xenografts, treatment with BCMA CART cells was able to eradicate MM (Fig E). Then, the MM-TME model was used to assess the effect of targeting CAFs. Mice were treated with 1) control T cells, 2) BCMA CART cells, 3) BCMA-FAP CART cells, or 4) BCMA-CS1 CART cells. A low dose (1 × 106 iv) of CART cell was used to induce relapse. BCMA CART cells led to a transient antitumor activity in this model (mice died within 2 weeks), while dual CART cells resulted in durable remissions, a higher number of circulating T cells, and long term survival (Fig F). Conclusion We demonstrate for the first time that dual targeting both malignant plasma cells and the CAFs within the TME is a novel strategy to overcome resistance to CART cell therapy in MM.

Evolving Data on CAR T-Cell Therapy for Multiple Myeloma, Novel Targets, Conditioning Regimens and Novel Constructs: A Systematic Review

Introduction: Multiple myeloma (MM) remains an incurable malignancy originating from plasma cell. Chimeric antigen receptor T (CAR T) cells have been used for treating various malignancies and have proven very efficacious especially for some hematologic malignancies. Pre-clinical and phase 1 studies of CAR T-cells designed against various molecular targets in MM patients have demonstrated encouraging anti-tumor activity. With the emerging data and success of antibody based immunotherapy, questions about the clinical efficacy and safety of CAR T-cells continue to emerge. This study aims to provide a systematic review of CAR T-cell therapy in MM through systematic review offering a reference for future research. Methods: On 03/28/19, we performed a search for published studies on CAR T cell therapy in MM using the following databases: Embase, Web of Science, Biosis and Scopus. Following PRISMA guidelines, search results were screened by two independent reviewers. Clinical studies with safety and efficacy data were included in the analysis. In vitro and animal studies and abstracts with duplicate data were excluded. Results: Our literature search produced 1604 results and 21 studies were included in the final review. Of these, 7 were complete manuscripts. Publications were from 2016-2019. 1 was a clinical pilot study, 20 phase 1 trials and 1 study extending to phase 2 with unpublished data. Reported CAR-T cell targets were BCMA (trials [t]=14), CD138 (t=1), CD19 (t=1), Kappa light chain (t=1), multi ligand (t=1), NKG2D (t=1) and 2 studies combining anti BCMA and CD19 CAR T cell infusion. Viral vectors were gamma retrovirus (t=4), lentivirus (t=10), standard retrovirus (t=2), 1 trial without a viral vector and 4 with unknown viral vector. Source of single chain fragment variants were human (t=4), murine (t=3), alpaca (t=1) and 13 unknown. Number of treated MM patients evaluable for efficacy were 4-57. Median prior lines of therapy were 3-12.5 with 3 studies not reporting prior lines of therapy. Pre conditioning treatments were cyclophosphamide (t=4), cyclophosphamide and fludarabine (t=12), high dose melphalan and autologous stem cell transplantation (t=1), 1 trial without preconditioning and 3 with unknown pre conditioning regimen. Dose of CAR-T cell administered ranged from 2.1x10^6-3x10^9. Median follow up time was 2-35 weeks. Overall response rate was 0%-100%. Individual response rate was as follows: strict complete response (CR) 0%-21%, CR 0%-68%, near CR 0%-11%, partial response 0%-75%, minimal response 0%-20%, stable disease 0%-100%, progressive disease 0%-100%. Only two studies reported minimal residual disease negative response of 14%-63%. 11 studies reported median progression free survival (PFS) of 4.15 weeks-15 months. 10 studies reported number of patients with grade 3 or higher complications with a rate of complication of 0-96%. Conclusion: Results of trials using CAR-T cell therapy in MM are promising for heavily treated relapsed MM patients. BCMA has emerged as an appropriate target for CAR T based immunotherapy. Possibility of a longer lasting PFS makes this modality of treatment very desirable. Variability in safety and efficacy data may be related to patient related factors, disease severity, prior lines of therapy and may uniquely be linked with CAR-T cell construct. Larger prospective clinical studies and randomized control trials are needed to further study the role and safety issue with CAR T cell therapy in relapsed and refractory MM. Disclosures Anwer: In-Cyte: Speakers Bureau; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees.

Targeting Cancer Associated Fibroblasts in the Bone Marrow Prevents Resistance to Chimeric Antigen Receptor T Cell Therapy in Multiple Myeloma

Cellular immunotherapy is a rapidly progressing field in multiple myeloma (MM). Multiple clinical trials have reported impressive efficacy of B cell maturation antigen (BCMA) directed chimeric antigen receptor cell therapy (BCMA CART) in MM. While trials demonstrated an overall response rate of 70-90% in patients with relapsed/refractory MM, the durable response rate is around 30%. Most patients lose their CART cells and the disease relapses within the first year, suggesting an inhibition by the MM tumor microenvironment (TME). Therefore strategies to overcome this inhibition would represent a major advance in CART cell therapy for MM. Cancer associated fibroblasts (CAFs) within the TME play a critical role in promoting tumor growth and in the generation of an immunosuppressive microenvironment. We hypothesized that CAFs from bone marrows of patients with MM (MM-CAFs) inhibit BCMA CART cells and contribute to their failure and that targeting both the malignant plasma cells and CAFs can overcome this resistance. To test this hypothesis, we isolated MM-CAFs and studied their interaction with BCMA CART cells generated from normal donors (41BB costimulated, lentivirally transduced). Our initial findings suggest that MM-CAFs inhibit BCMA CART cell antigen specific proliferation in the presence of the BCMA+ MM cell line OPM2, and this inhibition is predominantly mediated through the secretion of TGF-β (Fig A). MM-CAFs also promoted MM tumor growth in an MM-TME xenograft model established in the laboratory (Fig B). Here, immunocompromised NOD-SCID-γ-/- (NSG) mice were engrafted with 1x106 luciferase+ BCMA+ OPM2, in combination with either 1x106 CAFs or vehicle control intraveneously (IV). Subsequent tumor burden was monitored by bioluminescent imaging of these mice. The presence of CAFs in this model significantly accelerated MM progression (Fig B). Based on these findings, we aimed to develop CART cell therapy targeting both malignant MM cells and their CAFs and to determine whether this strategy can reverse MM-CAF induced CART cell inhibition. To identify targets for these CART cells, we first verified the expression of Fibroblast Associated Protein (FAP), an established CAF target, on MM-CAFs. Flow cytometric analysis of MM-CAFs showed significantly higher expression of FAP, compared to fibroblasts derived from normal bone marrow (Fig C). In addition, our screening flow cytometric analysis identified CS1 as another protein overexpressed by MM-CAFs (Fig C). We therefore designed and generated FAP CART cells (41BB costimulated, lentivirally transduced) and CS1 CART cells (CD28 costimulated, lentivirally transduced). We also generated dual CART cells for both BCMA-FAP CART cells and BCMA-CS1 CART cells. These dual CART cells were generated through the dual transduction of two lentiviral vectors during CART manufacturing. Next, we evaluated the impact of CAFs on effector functions of BCMA CART cells compared to dual targeting CART cells. When CART cells were stimulated with the BCMA+ MM cell line MM1S, in the presence of MM-CAFs, the antigen specific proliferation of BCMA CART cells, but not the dual targeting CART cells was significantly inhibited (Fig A). Similarly, in the presence of MM-CAFs, production of key effector cytokines by BCMA CART cells, but not the dual CART cells was reduced (Fig D). Finally, to verify the significance of our laboratory findings, we investigated the impact of CAFs on CART cell functions in vivo. First, using OPM2 xenografts, treatment with BCMA CART cells were able to completely eradicate MM (Fig E). However, to determine the effect of targeting CAFs, we used our MM-TME model. Here, NSG mice were engrafted with the luciferase+ MM cell line OPM2, along with MM-CAFs, as described in Fig 1B. Mice were then imaged for engraftment and randomized to treatment with 1) untransduced control T cells, 2) BCMA CART cells, 3) BCMA-FAP CART cells, or 4) BCMA-CS1 CART cells. A lower dose (1x106 IV) of CART cell was used to induce relapse post BCMA CART cells. Treatment with BCMA CART cells led to a transient antitumor activity in this MM-TME model (mice died within 2 weeks), while dual targeting CART cells resulted in durable remissions and long term survival of these mice (Fig F). In summary, we demonstrate for the first time that dual targeting both malignant plasma cells and the CAFs within the TME is a novel strategy to overcome resistance to CART cell therapy in multiple myeloma. Figure Disclosures Sakemura: Humanigen: Patents & Royalties. Cox:Humanigen: Patents & Royalties. Parikh:Janssen: Research Funding; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; AbbVie: Honoraria, Research Funding; Acerta Pharma: Research Funding; Ascentage Pharma: Research Funding; Genentech: Honoraria; AstraZeneca: Honoraria, Research Funding. Kay:Celgene: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; MorphoSys: Other: Data Safety Monitoring Board; Agios: Other: DSMB. Kenderian:Lentigen: Research Funding; Kite/Gilead: Research Funding; Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Tolero: Research Funding; Novartis: Patents & Royalties, Research Funding; Morphosys: Research Funding.

Chimeric antigen receptor T-cell therapy for multiple myeloma: a consensus statement from The European Myeloma Network.

Adoptive cellular therapy using chimeric antigen receptor T-cell (CART) therapy is currently being evaluated in patients with relapsed / refractory multiple myeloma (MM). The majority of CAR-T cell programs now being tested in clinical trials are targeting B-cell maturation antigen. Several recent phase I / II trials show promising preliminary results in patients with MM progressing on proteasome inhibitors, immunomodulatory drugs and monoclonal antibodies targeting CD38. CAR-T cell therapy is a potentially life-threatening strategy that can only be administered in experienced centers. For the moment, CAR-T cell therapy for MM is still experimental, but once this strategy has been approved in relapsed/refractory MM, it will become one of the most important indications for this therapy in Europe and world-wide. This manuscript proposes practical considerations for the use of CAR-T cell therapy in MM, and discusses several important issues for its future development.

Chimeric Antigen Receptor-Modified T Cell Therapy in Multiple Myeloma: Beyond B Cell Maturation Antigen.

Chimeric antigen receptor (CAR)-modified T cell therapy is a rapidly emerging immunotherapeutic approach that is revolutionizing cancer treatment. The impressive clinical results obtained with CAR-T cell therapy in patients with acute lymphoblastic leukemia and lymphoma have fueled the development of CAR-T cells targeting other malignancies, including multiple myeloma (MM). The field of CAR-T cell therapy for MM is still in its infancy, but remains promising. To date, most studies have been performed with B cell maturation antigen (BCMA)-targeted CARs, for which high response rates have been obtained in early-phase clinical trials. However, responses are usually temporary, and relapses have frequently been observed. One of the major reasons for relapse is the loss or downregulation of BCMA expression following CAR-T therapy. This has fostered a search for alternative target antigens that are expressed on the MM cell surface. In this review, we provide an overview of myeloma target antigens other than BCMA that are currently being evaluated in pre-clinical and clinical studies.