Allogeneic Blood or Marrow Transplantation with Post-Transplantation Cyclophosphamide as Graft-versus-Host Disease Prophylaxis in Multiple Myeloma

Revisiting the Role of Alkylating Agents in Multiple Myeloma: Up-to-Date Evidence and Future Perspectives

From the 1960s to the early 2000s, alkylating agents (e.g., melphalan, cyclophosphamide, and bendamustine) remained a key component of standard therapy for newly-diagnosed or relapsed/refractory multiple myeloma (MM). Later on, their associated toxicities (including second primary malignancies) and the unprecedented efficacy of novel therapies have led clinicians to increasingly consider alkylator-free approaches. Meanwhile, new alkylating agents (e.g., melflufen) and new applications of old alkylators (e.g., lymphodepletion before chimeric antigen receptor T-cell [CAR-T] therapy) have emerged in recent years. Given the expanding use of antigen-directed modalities (e.g., monoclonal antibodies, bispecific antibodies, and CAR-T therapy), this review explores the current and future role of alkylating agents in different treatment settings (e.g., induction, consolidation, stem cell mobilization, pre-transplant conditioning, salvage, bridging, and lymphodepleting chemotherapy) to ellucidate the role of alkylator-based regimens in modern-day MM management.

Chimeric Antigen Receptor T Cell Therapy versus Hematopoietic Stem Cell Transplantation: An Evolving Perspective

Cellular therapy modalities, including autologous (auto-) hematopoietic cell transplantation (HCT), allogeneic (allo-) HCT, and now chimeric antigen receptor (CAR) T cell therapy, have demonstrated long-term remission in advanced hematologic malignancies. Auto-HCT and allo-HCT, through hematopoietic rescue, have permitted the use of higher doses of chemotherapy. Allo-HCT also introduced a nonspecific immune-mediated targeting of malignancy resulting in protection from relapse, although at the expense of similar targeting of normal host cells. In contrast, CAR T therapy, through genetically engineered immunotherapeutic precision, allows for redirection of autologous immune effector cells against malignancy in an antigen-specific and MHC-independent fashion, with demonstrated efficacy in patients who are refractory to cytotoxic chemotherapy. It too has unique toxicities and challenges, however. Non-Hodgkin lymphoma (including large B cell lymphoma, mantle cell lymphoma, and follicular lymphoma), B cell acute lymphoblastic leukemia, and multiple myeloma are the 3 main diseases associated with the use of fully developed CAR T products with widespread deployment. Recent and ongoing clinical trials have been examining the interface among the 3 cellular therapy modalities (auto-HCT, allo-HCT, and CAR T) to determine whether they should be "complementary" or "competitive" therapies. In this review, we examine the current state of this interface with respect to the most recent data and delve into the controversies and conclusions that may inform clinical decision making.

The Role of Allogeneic Stem Cell Transplantation in Multiple Myeloma: A Systematic Review of the Literature

Multiple myeloma (MM) is an indolent B-cell malignancy, where treatment is aimed at preventing organ dysfunction from light chain accumulation (slowing disease progression) and inducing remission. Allogeneic stem cell transplant (allo-SCT), through graft versus myeloma (GVM) effects, has the potential to induce remission to a potentially curative-like state. In this systematic review, we aimed to understand this relationship to the risks and severity of disease in categorized patients and gain an updated comprehension of the future of allo-SCT in MM treatment. We conducted this review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and searched the PubMed database to obtain the specified literature with both the use of keywords and Medical Subject Headings (MeSH). A total of 16 relevant articles were included for discussion after the quality appraisal was completed, as appropriate, by either the Cochrane tool or Newcastle-Ottawa checklist. Our review concludes that while allo-SCT may benefit high-risk patients, successful procedures may incorporate a tandem autologous hematopoietic stem cell transplant approach in combination with novel pharmacologic contributions for which there is an observed synergy in the modulation of the immunologic microenvironment. Furthermore, tailored patient selection by evaluating pre-transplant factors including high-risk cytogenetics, age, and pre-salvage International Staging System (ISS) can predict post-transplantation success including non-relapse mortality. Successive research should continue to revise and update treatment options as the evolving therapeutic drug regimens may change over the course of indolent disease.

Long-term survival of 1338 MM patients treated with tandem autologous vs. autologous-allogeneic transplantation

Contrary to tandem autologous transplant (auto-auto), autologous followed by reduced intensity conditioning allogenic transplantation (auto-allo) offers graft-versus-myeloma (GVM) effect but with higher toxicity. Trials comparing these two strategies relied on availability of HLA-matched sibling donors for arm allocation (biological randomization) and yielded conflicting results. A pooled analysis of multiple trials with extended follow up provides an opportunity to compare these strategies. We obtained individual patient data from participants of four trials comparing auto-auto vs. auto-allo after induction therapy. There were 899 patients in auto-auto and 439 in auto-allo. Median follow up of survivors was 118.5 months. Median overall survival (OS) was 78.0 months in auto-auto and 98.3 months in auto-allo (HR = 0.84, P = 0.02). OS was 36.4% vs. 44.1% at 10 years (P = 0.01) for auto-auto and auto-allo, respectively. Progression-free survival was also improved in auto-allo (HR = 0.84, P = 0.004). Risk of non-relapse mortality was higher in auto-allo (10 year 8.3% vs. 19.7%, P < 0.001), while risk of disease progression was higher in auto-auto (10 year 77.2% vs. 61.6%, P < 0.001). Median post relapse survival was 41.5 months in auto-auto and 62.3 months in auto-allo (HR = 0.71, P < 0.001). This supports the existence of durable GVM effect enhancing myeloma control with subsequent therapies.

Tandem Autologous-Autologous versus Autologous-Allogeneic Hematopoietic Stem Cell Transplant for Patients with Multiple Myeloma: Long-Term Follow-Up Results from the Blood and Marrow Transplant Clinical Trials Network 0102 Trial

Allogeneic hematopoietic cell transplant (HCT) may improve long-term multiple myeloma (MM) control through the graft-versus-myeloma effect. The Blood and Marrow Transplant Clinical Trials Network 0102 trial was a biologic assignment trial comparing tandem autologous transplant (auto-auto) versus autologous followed by reduced-intensity allogeneic (auto-allo) transplant in patients with newly diagnosed MM with standard-risk (n = 625) or high-risk (n = 85; β₂-microglobulin at diagnosis ≥ 4 mg/dL or deletion of chromosome 13 by conventional karyotyping) disease. Although the initial 3-year analysis showed no difference in progression-free survival (PFS) between arms in either risk group, we hypothesized that long-term follow-up may better capture the impact of the graft-versus-myeloma effect. Median follow-up of survivors was over 10 years. Among standard-risk patients there was no difference in PFS (hazard ratio [HR], 1.11; 95% confidence interval [CI], .93 to 1.35; P = .25) or OS (HR, 1.03; 95% CI, .82 to 1.28; P = .82). The 6-year PFS was 25% in the auto-auto arm versus 22% in the auto-allo arm (P = .32), and 6-year overall survival (OS) was 60% and 59%, respectively (P = .85). In the high-risk group, although there was no statistically significant difference in PFS (HR, .66; 95% CI, .41 to 1.07; P = .07) and OS (HR, 1.01; 95% CI, .60 to 1.71; P = .96), a reduction in 6-year risk of relapse of 77% versus 47% (P = .005) was reflected in better PFS of 13% versus 31% (P = .05) but similar OS, at 47% versus 51% (P = .69). Allogeneic HCT can lead to long-term disease control in patients with high-risk MM and needs to be explored in the context of modern therapy.

Allogeneic Haploidentical Blood or Marrow Transplantation with Post-Transplantation Cyclophosphamide in Chronic Lymphocytic Leukemia

Allogeneic blood or marrow transplantation (allo-BMT) remains the only treatment for chronic lymphocytic leukemia (CLL) with curative potential. Although post-transplantation cyclophosphamide (PTCy) reduces allo-BMT toxicity by decreasing the risk of graft-versus-host disease (GVHD), its effect on CLL allo-BMT outcomes is unknown. We studied 64 consecutive patients with CLL who underwent nonmyeloablative (NMA) haploidentical allo-BMT at Johns Hopkins Sidney Kimmel Comprehensive Cancer Center. In this cohort, the 4-year overall survival was 52% (95% confidence interval [CI], 40% to 68%), and progression-free survival was 37% (95% CI, 26% to 54%). Six patients experienced engraftment failure. PTCy prophylaxis was associated with a modest cumulative incidence of 1-year grade II-IV acute GVHD (27%; %95% CI, 15% to 38%) and %%%2-year chronic GVHD (17%; 95% CI, 7% to 26%). We demonstrate that NMA haploidentical allo-BMT with PTCy is a safe and effective treatment option.

Efficacy of bortezomib to intensify the conditioning regimen and the graft-versus-host disease prophylaxis for high-risk myeloma patients undergoing transplantation

This multicenter phase I trial was designed to evaluate the safety and efficacy of bortezomib (Bz) as part of both the conditioning regimen and the graft-versus-host disease (GvHD) prophylaxis. Patients received fludarabine, melphalan and Bz (days -9 and -2). GVHD prophylaxis consisted of Bz (days +1, +4, and +7), sirolimus (Siro) from day -5 and tacrolimus (Tk) from -3 (except the first five patients that did not receive Tk). Twenty-five patients with poor prognostic multiple myeloma were included. Eleven out of the 19 patients had high-risk features. Out of the 21 patients evaluable at day +100, 14 were in CR (67%) and 7 (33%) in PR. Cumulative incidence (CI) of nonrelapse mortality at 1 year was 24%. CI of grades 2-4 and 3-4 acute GvHD was 35% and 10%, respectively; CI of chronic GvHD was 35% and 55% at 1 and 2 years, respectively. Overall and event free survival at 2 years were 64% and 31%, respectively. Bz as part of the conditioning regimen and in the combination with Siro/tacrolimus for GvHD prophylaxis is safe and effective allowing an optimal disease control early after transplant and reducing the risk of GvHD.

Indications for haematopoietic stem cell transplantation for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2019

This is the seventh special EBMT report on the indications for haematopoietic stem cell transplantation for haematological diseases, solid tumours and immune disorders. Our aim is to provide general guidance on transplant indications according to prevailing clinical practice in EBMT countries and centres. In order to inform patient decisions, these recommendations must be considered together with the risk of the disease, the risk of the transplant procedure and the results of non-transplant strategies. In over two decades since the first report, the EBMT indications manuscripts have incorporated changes in transplant practice coming from scientific and technical developments in the field. In this same period, the establishment of JACIE accreditation has promoted high quality and led to improved outcomes of patient and donor care and laboratory performance in transplantation and cellular therapy. An updated report with operating definitions, revised indications and an additional set of data with overall survival at 1 year and non-relapse mortality at day 100 after transplant in the commonest standard-of-care indications is presented. Additional efforts are currently underway to enable EBMT member centres to benchmark their risk-adapted outcomes as part of the Registry upgrade Project 2020 against national and/or international outcome data.

A retrospective analysis of haplo-identical HLA-mismatch hematopoietic transplantation without posttransplantation cyclophosphamide for GVHD prophylaxis in patients with adult T-cell leukemia-lymphoma

Currently, allogeneic hematopoietic stem cell transplantation (allo-HCT) is the only available curative modality for patients with adult T-cell leukemia-lymphoma (ATL). When used in conjunction with posttransplantation cyclophosphamide (PTCY) for graft-versus-host disease prophylaxis, allo-HCT from an HLA haplo-identical donor yields promising outcomes for many diseases other than ATL. However, appropriate comparisons with other donor sources, especially cord blood and conventional HLA haplo-identical donors, are needed to validate the safety and efficacy of this modality. In this study, we retrospectively evaluated the outcome of allo-HCT without PTCY in patients with ATL registered in the Japan Society for Hematopoietic Cell Transplantation TRUMP database between 1985 and 2015. During that period, 46 patients received allo-HCT without PTCY and survivors were followed for a median of 2316.5 days (range: 220-3884 days). Although the estimated 1- and 5-year overall survival rates of the entire cohort were 34.5% and 17.7%, respectively, the cumulative 1- and 5-year non-ATL mortality rates of 41.3% and 55.8%, respectively, were high. The results of our study will serve as a platform for discussions of the safety and efficacy of haplo-HCT for future clinical trials in patients with ATL.

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.