Beyond consolidation: auto-SCT and immunotherapy for plasma cell myeloma

CAR T Cells and Other Cellular Therapies for Multiple Myeloma: 2018 Update

Cellular therapies are a rapidly evolving approach to myeloma treatment, which bring a unique mechanism of action with the potential to overcome drug resistance and induce long-term remissions. Two primary approaches are being studied: non-gene-modified strategies, which rely on the endogenous anti-myeloma T-cell repertoire, and gene-modified strategies, which introduce a new T-cell receptor (TCR) or a chimeric antigen receptor (CAR) to confer novel antigen specificity. CAR T cells show the greatest activity to date. Multiple antigen targets, including B-cell maturation antigen (BCMA), CD19, CD38, CD138, and SLAMF7, are being explored for myeloma, and BCMA has emerged as the most promising. Preliminary data from four phase I studies of BCMA CAR T cells, each using a different CAR construct, that involved 90 evaluable patients with relapsed/refractory disease have been reported. These data show response rates of 60% to 100%, including minimal residual disease (MRD)-negative complete remissions, at effective doses (> 10⁸ CAR-positive cells) after lymphodepleting conditioning. Response durability has been more variable, likely related to differences in CAR T-cell products, lymphodepleting regimens, patient selection criteria, and/or underlying biology/prognostic factors. In the two most recent studies, however, most patients remained progression free with median follow-up time of 6 to 10 months; some ongoing remissions lasted more than 1 year. Toxicities are similar to those from CD19 CAR T cells and include cytokine release syndrome and neurotoxicity that is reversible but can be severe. Multiple BCMA CAR T-cell studies are ongoing. Future directions include combinations with immunomodulatory drugs, checkpoint inhibitors, or other CAR T cells, as well as use of gene-edited cellular products to enhance the safety and efficacy of this approach.

Soluble PD-L1: A biomarker to predict progression of autologous transplantation in patients with multiple myeloma

Autologous hematopoietic stem cell transplantation (AuHSCT) is standard in treating eligible multiple myeloma (MM) patients. However, the outcome after treatment is highly variable. We used ELISA to analyze the levels of soluble PD-L1 (suPD-L1) in bone marrow (BM) plasma from 61 patients with MM at 100 days after AuHSCT. Patients were classified into high (H) and normal-to-low (NL) groups depending on their suPD-L1 levels. Among patients who had a very good partial response (VGPR) or better after AuHSCT, those in the H-group had a shorter response period (RpSCT) as well as shorter overall survival (OS) than those in the NL-group. Multivariate analyses confirmed that a high suPD-L1 level and high-risk cytogenetic abnormalities are independent factors for RpSCT. Our data suggest that suPD-L1 in the BM plasma of MM patients who have VGPR or better after AuHSCT could be used as a biomarker to predict outcome.

Ex Vivo Oncolytic Virotherapy with Myxoma Virus Arms Multiple Allogeneic Bone Marrow Transplant Leukocytes to Enhance Graft versus Tumor

Allogeneic stem cell transplant-derived T cells have the potential to seek and eliminate sites of residual cancer that escaped primary therapy. Oncolytic myxoma virus (MYXV) exhibits potent anti-cancer efficacy against human cancers like multiple myeloma (MM) and can arm transplant-derived T cells to become more effective cancer killers in vitro and in an immunodeficient xenotransplant murine model. Here, we tested ex vivo MYXV virotherapy against residual murine MM in immunocompetent mice using an allogeneic mouse-mouse model. In contrast to all human MM cell lines previously tested, the murine MM cell line tested here was highly resistant to direct MYXV infection and oncolysis in vitro. Despite this in vitro resistance, we found that ex vivo MYXV-armed allogeneic bone marrow (BM) transplantation dramatically ablated pre-seeded residual MM in vivo. Unexpectedly, we show that both neutrophils and activated T cells from the donor function as virus-armed carrier cells, and MYXV-preloaded cells enhanced MM killing. Our results demonstrate a novel therapeutic paradigm for residual cancer, in which multiple classes of allotransplant leukocytes can be armed by MYXV ex vivo to enhance the graft-versus-tumor effects.

The Importance of Positive Immunomagnetic Cell Separation Prior to Autologous Hematopoetic Stem Cell Transplantation for Advanced Stage Lymphomas

We present the method of immunomagnetic stem cell separation with the ISOLEX 300i device (Isolex® 300i Magnetic Cell Selection System, Nextell Therapeutics Inc. Irvine California 21618 USA) and the results obtained using this method in patients admitted to the Hematology and Bone Marrow Transplantation Clinic of Tîrgu Mureş, Romania. Cell selection has a great importance in separating stem cells from tumor cells, therefore contributing to the success of autologous stem cell transplantation.

Ex vivo virotherapy with myxoma virus does not impair hematopoietic stem and progenitor cells

BACKGROUND

Relapsing disease is a major challenge after hematopoietic cell transplantation for hematological malignancies. Myxoma virus (MYXV) is an oncolytic virus that can target and eliminate contaminating cancer cells from auto-transplant grafts. The aims of this study were to examine the impact of MYXV on normal hematopoietic stem and progenitor cells and define the optimal treatment conditions for ex vivo virotherapy.

METHODS

Bone marrow (BM) and mobilized peripheral blood stem cells (mPBSCs) from patients with hematologic malignancies were treated with MYXV at various time, temperature and incubation media conditions. Treated BM cells from healthy normal donors were evaluated using flow cytometry for MYXV infection, long-term culture-initiating cell (LTC-IC) assay and colony-forming cell (CFC) assay.

RESULTS

MYXV initiated infection in up to 45% of antigen-presenting monocytes, B cells and natural killer cells; however, these infections were uniformly aborted in >95% of all cells. Fresh graft sources showed higher levels of MYXV infection initiation than cryopreserved specimens, but in all cases less than 10% of CD34(+) cells could be infected after ex vivo MYXV treatment. MYXV did not impair LTC-IC colony numbers compared with mock treatment. CFC colony types and numbers were also not impaired by MYXV treatment. MYXV incubation time, temperature or culture media did not significantly change the percentage of infected cells, LTC-IC colony formation or CFC colony formation.

CONCLUSIONS

Human hematopoietic cells are non-permissive for MYXV. Human hematopoietic stem and progenitor cells were not infected and thus unaffected by MYXV ex vivo treatment.

CMRF-56(+) blood dendritic cells loaded with mRNA induce effective antigen-specific cytotoxic T-lymphocyte responses

There are numerous transcriptional, proteomic and functional differences between monocyte-derived dendritic cells (Mo-DC) and primary blood dendritic cells (BDC). The CMRF-56 monoclonal antibody (mAb) recognizes a cell surface marker, which is upregulated on BDC following overnight culture. Given its unique ability to select a heterogeneous population of BDC, we engineered a human chimeric (h)CMRF-56 IgG4 mAb to isolate primary BDC for potential therapeutic vaccination. The ability to select multiple primary BDC subsets from patients and load them with in vitro transcribed (IVT) mRNA encoding tumor antigen might circumvent the issues limiting the efficacy of Mo-DC. After optimizing and validating the purification of hCMRF-56(+) BDC, we showed that transfection of hCMRF-56(+) BDC with mRNA resulted in efficient mRNA translation and antigen presentation by myeloid BDC subsets, while preserving superior DC functions compared to Mo-DC. Immune selected and transfected hCMRF-56(+) BDC migrated very efficiently in vitro and as effectively as cytokine matured Mo-DC in vivo. Compared to Mo-DC, hCMRF-56(+) BDC transfected with influenza matrix protein M1 displayed superior MHC peptide presentation and generated potent antigen specific CD8(+) T-cell recall responses, while Wilms tumor 1 (WT1) transfected CMRF-56(+) BDC generated effective primary autologous cytotoxic T-cell responses. The ability of the combined DC subsets within hCMRF-56(+) BDC to present mRNA delivered tumor antigens merits phase I evaluation as a reproducible generic platform for the next generation of active DC immune therapies.

Reprint of: Fast Cars and No Brakes: Autologous Stem Cell Transplantation as a Platform for Novel Immunotherapies

Autologous stem cell transplantation (ASCT) is indicated in a number of hematologic malignancies, including multiple myeloma, non-Hodgkin lymphoma, and Hodgkin lymphoma. Relapse, however, remains 1 of the main causes of post-ASCT failure, and several strategies are being investigated to decrease the risk of relapse of progression. Recent advances in the treatment of hematological malignancies have included adoptive transfer of genetically modified T cells that express chimeric antigen receptors or T cell receptors, as well the use of checkpoint inhibitors. Early clinical results in non-transplantation patients have been very promising. This review will focus on the use of gene-modified T cells and checkpoint inhibitors in stem cell transplantation.

Fast Cars and No Brakes: Autologous Stem Cell Transplantation as a Platform for Novel Immunotherapies

Autologous stem cell transplantation (ASCT) is indicated in a number of hematologic malignancies, including multiple myeloma, non-Hodgkin lymphoma, and Hodgkin lymphoma. Relapse, however, remains 1 of the main causes of post-ASCT failure, and several strategies are being investigated to decrease the risk of relapse of progression. Recent advances in the treatment of hematological malignancies have included adoptive transfer of genetically modified T cells that express chimeric antigen receptors or T cell receptors, as well the use of checkpoint inhibitors. Early clinical results in nontransplantation patients have been very promising. This review will focus on the use of gene-modified T cells and checkpoint inhibitors in stem cell transplantation.