Durable responses after donor lymphocyte infusion for patients with residual multiple myeloma following non-myeloablative allogeneic stem cell transplant

Allogeneic stem cell transplantation in multiple myeloma: is there still a place?

The introduction of novel agents dramatically improved response and outcomes of multiple myeloma (MM) and led to a sharp decline in the use of allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Thus, recent guidelines do not recommend anymore allo-HSCT as consolidation in the first-line treatment of newly diagnosed MM, even in high-risk patients. In a relapsed/refractory setting, allo-HSCT is not routinely recommended but should only be performed within clinical trials in young and high-risk patients. Nonetheless, allo-HSCT still represents a potential curative approach that has been used for decades in the treatment of MM and plasma cell neoplasms with favorable results and may still represent a treatment option for carefully selected patients. Despite that promising results were obtained with CAR T-cell therapies and bispecific antibodies in triple- and penta-exposed/refractory MM, these patients will inevitably relapse. To date, less is known about outcomes of allo-HSCT in patients exposed to novel immunotherapeutic drugs. Therefore, allo-HSCT could represent a reasonable treatment choice for younger and high-risk patients who have relapsed after CAR T-cell therapies and bispecific antibodies as well as an alternative for patients not eligible to these treatments and in those countries where immunotherapies are not yet available. In the choice of conditioning, reduced intensity conditioning regimens are currently recommended for the lower toxicity and mortality. Moreover, the use of alternative donors, particularly haploidentical, has progressively increased in last years with results comparable to full matched donors. Finally, post-transplantation maintenance strategies are encouraged whenever feasible.

The graft versus leukemia effect: donor lymphocyte infusions and cellular therapy

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for many hematologic malignancies as well as non-malignant conditions. Part of the curative basis underlying HSCT for hematologic malignancies relies upon induction of the graft versus leukemia (GVL) effect in which donor immune cells recognize and eliminate residual malignant cells within the recipient, thereby maintaining remission. GVL is a clinically evident phenomenon; however, specific cell types responsible for inducing this effect and molecular mechanisms involved remain largely undefined. One of the best examples of GVL is observed after donor lymphocyte infusions (DLI), an established therapy for relapsed disease or incipient/anticipated relapse. DLI involves infusion of peripheral blood lymphocytes from the original HSCT donor into the recipient. Sustained remission can be observed in 20-80% of patients treated with DLI depending upon the underlying disease and the intrinsic burden of targeted cells. In this review, we will discuss current knowledge about mechanisms of GVL after DLI, experimental strategies for augmenting GVL by manipulation of DLI (e.g. neoantigen vaccination, specific cell type selection/depletion) and research outlook for improving DLI and cellular immunotherapies for hematologic malignancies through better molecular definition of the GVL effect.

Harnessing the Immune System to Fight Multiple Myeloma

Multiple myeloma (MM) is a heterogeneous plasma cell malignancy differing substantially in clinical behavior, prognosis, and response to treatment. With the advent of novel therapies, many patients achieve long-lasting remissions, but some experience aggressive and treatment refractory relapses. So far, MM is considered incurable. Myeloma pathogenesis can broadly be explained by two interacting mechanisms, intraclonal evolution of cancer cells and development of an immunosuppressive tumor microenvironment. Failures in isotype class switching and somatic hypermutations result in the neoplastic transformation typical of MM and other B cell malignancies. Interestingly, although genetic alterations occur and evolve over time, they are also present in premalignant stages, which never progress to MM, suggesting that genetic mutations are necessary but not sufficient for myeloma transformation. Changes in composition and function of the immune cells are associated with loss of effective immune surveillance, which might represent another mechanism driving malignant transformation. During the last decade, the traditional view on myeloma treatment has changed dramatically. It is increasingly evident that treatment strategies solely based on targeting intrinsic properties of myeloma cells are insufficient. Lately, approaches that redirect the cells of the otherwise suppressed immune system to take control over myeloma have emerged. Evidence of utility of this principle was initially established by the observation of the graft-versus-myeloma effect in allogeneic stem cell-transplanted patients. A variety of new strategies to harness both innate and antigen-specific immunity against MM have recently been developed and intensively tested in clinical trials. This review aims to give readers a basic understanding of how the immune system can be engaged to treat MM, to summarize the main immunotherapeutic modalities, their current role in clinical care, and future prospects.

Allogeneic Stem Cell Transplantation in Patients with High-Risk Multiple Myeloma: Utopia or Continuous Challenge in Aiming for Cure?

OPINION STATEMENT

Nowadays, several novel agents have been introduced in the treatment of multiple myeloma, not only resulting in high response rates and prolonged survival but also offering good quality of life. However, the potential of cure, especially for patients with advanced or unfavorable disease features, remains elusive. Allogeneic hematopoietic stem cell transplantation, based mainly on the graft vs. myeloma effect, can offer prolonged disease control and probability of cure but unfortunately at the cost of considerable transplant-related toxicity rates. Therefore, the role of allogeneic hematopoietic stem cell transplantation in the treatment of multiple myeloma has been called into question. Recently, several studies, particularly those with long-term follow-up, demonstrated a trend of survival superiority for allografted patients with high-risk disease. These data fuel again the interest in allogeneic stem cell transplantation for selected patients with high-risk multiple myeloma, especially if the high remission rates which can be achieved with the currently used treatment protocols could be long-life sustained through the additional exploitation of the long-lasting anti-multiple myeloma effect, originating from the allograft.

Bispecific Antibodies: A New Era of Treatment for Multiple Myeloma

Despite the introduction of novel agents such as proteasome inhibitors, immunomodulatory drugs, and autologous stem cell transplant, multiple myeloma (MM) largely remains an incurable disease. In recent years, monoclonal antibody-based treatment strategies have been developed to target specific surface antigens on MM cells. Treatment with bispecific antibodies (bsAbs) is an immunotherapeutic strategy that leads to an enhanced interaction between MM cells and immune effector cells, e.g., T-cells and natural killer cells. With the immune synapse built by bsAbs, the elimination of MM cells can be facilitated. To date, bsAbs have demonstrated encouraging results in preclinical studies, and clinical trials evaluating bsAbs in patients with MM are ongoing. Early clinical data show the promising efficacy of bsAbs in relapsed/refractory MM. Together with chimeric antigen receptor-modified (CAR)-T-cells, bsAbs represent a new dimension of precision medicine. In this review, we provide an overview of rationale, current clinical development, resistance mechanisms, and future directions of bsAbs in MM.

Plasma Cell Leukemia: Definition, Presentation, and Treatment

Purpose of Review

We discuss current topics on the definition of plasma cell leukemia and the distinction between plasma cell leukemia and multiple myeloma. Moreover, we review the latest literature on how to treat plasma cell leukemia.

Recent Findings

Plasma cell leukemia is clinically and genetically distinct from multiple myeloma. Plasma cell leukemia is defined by the observation in blood of more than 20% clonal plasma cells by differential count of the leucocytes or by counting more than 2 × 10⁹ per liter circulating clonal plasma cells. However, patients with lower levels of circulating plasma cells have the same adverse prognosis, which challenges the disease definition. Survival has improved after implementation of high-dose chemotherapy with stem-cell support, bortezomib, and lenalidomide in the treatment; yet, the prognosis remains poor. The results of allo-transplants have been disappointing.

Summary

The diagnostic criteria of PCL are currently discussed in the international myeloma community. Despite some improvement in survival, the prognosis remains adverse. New, more targeted treatment modalities, including immunotherapies, will hopefully improve the outcome in the near future.

Comparison of Outcomes of Allogeneic Hematopoietic Cell Transplantation for Multiple Myeloma Using Three Different Conditioning Regimens

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy for patients with multiple myeloma, as it provides a graft-versus-myeloma effect alongside a myeloma-free graft. Although reduced-intensity conditioning regimens decrease nonrelapse mortality (NRM), there is a paucity of data with regard to the ideal conditioning regimen in myeloma. We conducted a retrospective comparison of 3 different preparative regimens used for allo-HCT for multiple myeloma at our institution in recent clinical trials: busulfan/fludarabine (BuFlu), fludarabine/melphalan 100 mg/m² (FM100), and fludarabine/melphalan 140 mg/m² (FM140). NRM, progression-free survival (PFS) at 3 years, and overall survival (OS) at 3 years were the primary endpoints. Secondary endpoints included time to engraftment, and the incidence of grades II through IV acute graft-versus-host disease and chronic graft-versus-host disease. A total of 73 patients received allo-HCT with these regimens. NRM at 3 years was seen in 3 (21%), 5 (28%), and 6 (24%) patients in the BuFlu, FM100, and FM140 groups, respectively. Three-year PFS in the BuFlu, FM100, and FM140 groups was 16% (hazard ratio [HR], 1.2; 95% confidence interval [CI], 0.6 to 2.1), 26% (HR, 0.6; 95% CI, 0.3 to 1.2), and 11% (reference), respectively. Three-year OS in the BuFlu, FM100, and FM140 groups was 39% (HR, 1.1; 95% CI, 0.5 to 2.2), 43% (HR, 0.7; 95% CI, 0.3 to 1.4), and 32% (reference), respectively. High-risk cytogenetics and relapsed disease prior to allo-HCT were found to be independent predictors of inferior OS on multivariate analysis, with a HR of 2.1 (P = .02) and 2.6 (P = .004), respectively. In contrast, the preparative regimen did not emerge as a predictor of PFS or OS. Durable clinical remission can be achieved in 11% to 25% of patients with multiple myeloma with the use of allo-HCT without any significant difference in the safety or efficacy of the conditioning regimen. High-risk cytogenetics and relapsed disease prior to transplant were associated with inferior PFS and OS.

Long-Term Results of Prophylactic Donor Lymphocyte Infusions for Patients with Multiple Myeloma after Allogeneic Stem Cell Transplantation

The major reason for treatment failure after allografting in multiple myeloma (MM) is relapse. Donor lymphocyte infusions (DLIs) are considered a valuable post-transplant strategy mainly for relapsed patients but using them to prevent relapse in MM has been reported rarely. In the present study, we examined the efficacy of prophylactic DLIs after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in myeloma patients with a long-term follow-up of more than 5 years. A total of 61 patients with MM who did not relapse or develop disease progression after allo-HSCT were treated with prophylactic DLI in an escalating fashion (overall 132 DLI procedures) to deepen remission status and prevent relapse. Overall response rate to DLI was 77%. Thirty-three patients (54%) upgraded their remission status, 41 patients (67%) achieved or maintained complete remission, and 26% achieved a molecular remission. Incidence of acute graft-versus-host disease (GVHD) grade II to IV was 33% and no DLI-related mortality was noted. After a median follow-up of 68.7 months from first DLI the estimated 8-year progression-free survival (PFS), and overall survival (OS) in a landmark analysis was 43% (95% confidence interval [CI], 28% to 57%) and 67% (95% CI, 53% to 82%), respectively, with best outcome for patients who acquired molecular remission (8-year PFS was 62% and 8-year OS was 83%). Prophylactic escalating DLI in a selected cohort of MM patients to prevent relapse after allograft resulted in a low incidence of severe GVHD and encouraging long-term results, especially if molecular remission is achieved.

From transplant to novel cellular therapies in multiple myeloma: European Myeloma Network guidelines and future perspectives

Survival of myeloma patients has greatly improved with the use of autologous stem cell transplantation and novel agents, such as proteasome inhibitors, immunomodulatory drugs and monoclonal antibodies. Compared to bortezomib- and lenalidomide-based regimens alone, the addition of high-dose melphalan followed by autologous transplantation significantly improves progression-free survival, although an overall survival benefit was not observed in all trials. Moreover, follow up of recent trials is still too short to show any difference in survival. In the light of these findings, novel agent-based induction followed by autologous transplantation is considered the standard upfront treatment for eligible patients (level of evidence: 1A). Post-transplant consolidation and maintenance treatment can further improve patient outcome (1A). The availability of several novel agents has led to the development of multiple combination regimens such as salvage treatment options. In this context, the role of salvage autologous transplantation and allotransplant has not been extensively evaluated. In the case of prolonged remission after upfront autologous transplantation, another autologous transplantation at relapse can be considered (2B). Patients who experience early relapse and/or have high-risk features have a poor prognosis and may be considered as candidates for clinical trials that, in young and fit patients, may also include an allograft in combination with novel agents (2B). Ongoing studies are evaluating the role of novel cellular therapies, such as inclusion of antibody-based triplets and quadruplets, and chimeric antigen receptor-T cells. Despite encouraging preliminary results, longer follow up and larger patient numbers are needed before the clinical use of these novel therapies can be widely recommended.

Allogeneic Hematopoietic Cell Transplantation for Myeloma: When and in Whom Does It Work

The growing list of available therapies for patients with multiple myeloma has resulted in tremendously high response rates and prolonged survival. However, the cure remains elusive. A continued effort at developing strategies to utilize all available treatment modalities in the most effective manner is needed. Allogeneic hematopoietic cell transplantation (allo-HCT) is a robust platform, associated with high response rates, and provides a unique foundation on which immune therapies and novel agents can be employed to improve clinical outcomes. Patients with high-risk myeloma and those relapsing after novel agent-based therapies or early after an autologous HCT should be considered for allo-HCT, ideally in a clinical trial setting. Results from several ongoing studies are expected to provide important information that will help determine the place of allo-HCT in the myeloma treatment algorithm.

Immunologic approaches for the treatment of multiple myeloma

The FDA approval of two monoclonal antibodies in 2015has heralded a new era of targeted immunotherapies for multiple myeloma (MM). In this review we discuss the recent approaches using different immunological components to treat MM. In particular, we review current monoclonal antibody based therapies, engineered T- and NK cell products, 'off-target' immunomodulation, and strategies utilizing allogeneic cell transplantation in MM. We discuss how an immunologic approach offers promise for the treatment of this genetically heterogeneous disease, and how patients with acquired drug resistance may particularly benefit from these therapies. We also describe some of the limitations of the current strategies and speculate on the future of personalized immunotherapies for MM.

Allogeneic Hematopoietic Cell Transplantation in Multiple Myeloma: Focus on Longitudinal Assessment of Donor Chimerism, Extramedullary Disease, and High-Risk Cytogenetic Features

Although generally not applied as first-line treatment of multiple myeloma, allogeneic hematopoietic cell transplantation (allo-SCT) can still be chosen as ultimate escalation approach in high-risk patients, preferentially within the framework of clinical trials. In this study, we investigated whether decreasing donor chimerism (DC) is predictive for relapse. In addition, we comprehensively determined the impact of several other disease- and treatment-related factors on outcome. One hundred fifty-five multiple myeloma patients whose DC status was followed serially by the short tandem repeat-based techniques at a single lab were included in this retrospective study. Outcome variables were studied in univariate and multivariable analyses. Available were 2.324 DC samples (median, 12 per patient). Loss of full DC was associated with shorter progression-free survival (PFS) (HR, 1.7; 95% CI, 1.1 to 2.6) but did not impact overall survival. Two-thirds of patients with International Myeloma Working Group-defined relapses still displayed a full DC in peripheral blood or bone marrow. Extramedullary manifestations were observed in 33% of patients, accounting for the discrepancy between DC analysis and the actual disease status. In multivariable analysis, the 2 most relevant variables for an unfavorable PFS were progressive disease before allo-SCT (HR, 3.0; 95% CI, 1.5 to 5.9) and allo-SCT at least the second relapse (HR, 2.8; 95% CI, 1.5 to 4.9), whereas for overall survival progressive disease or partial response before allo-SCT had the strongest negative effects (HR, 4.2; 95% CI, 1.9 to 9, and HR, 2.0; 95% CI, 1.0 to 3.8, respectively). Adverse cytogenetics such as del17p, t(4,14) or amp(1q21) were not associated with shorter survival after allo-SCT. Extensive DC sampling beyond robust engraftment does not appear to provide additional information helpful for disease management in most patients and is challenged by a significant incidence of extramedullary disease. In our series, allo-SCT overcame unfavorable cytogenetics.

A phase I study of CD25/regulatory T-cell-depleted donor lymphocyte infusion for relapse after allogeneic stem cell transplantation

Donor lymphocyte infusions are used to treat relapse after allogeneic hematopoietic stem cell transplantation, but responses are inadequate. In addition to effector cells, infusions contain CD25⁺ regulatory T cells (Treg) that may suppress graft-versus-tumor responses. We undertook a phase I study of donor lymphocyte infusions depleted of CD25⁺ T cells in patients with hematologic malignancies who had relapsed after transplantation. Twenty-one subjects received CD25/Treg-depleted infusions following removal of CD25⁺ cells using antibody-conjugated magnetic beads. Sixteen subjects received prior cytoreductive therapy. Four were in complete remission at the time of infusion. Two dose levels were administered: 1×10⁷ (n=6) and 3×10⁷ CD3⁺ cells/kg (n=15). A median 2.3 log-depletion of CD4⁺CD25⁺FOXP3⁺ Treg was achieved. Seven subjects (33%) developed clinically significant graft-versus-host disease by 1 year, including one patient who died. At dose level 1, five subjects had progressive disease and one had stable disease. At dose level 2, nine subjects (60%) achieved or maintained responses (8 complete responses, 1 partial response), including seven with active disease at the time of infusion. A shorter period between relapse and infusion was associated with response at dose level 2 (P=0.016). The 1-year survival rate was 53% among patients treated with dose level 2. Four of eight subjects with acute myeloid leukemia remained in remission at 1 year. When compared to unmodified donor lymphocyte infusions in 14 contemporaneous patients meeting study eligibility, CD25/Treg depletion was associated with a better response rate and improved event-free survival. Circulating naïve and central memory CD4⁺ T cells increased after CD25/Treg-depleted infusion, but no immunophenotypic signature for response was noted. CD25/Treg-depleted donor infusion appears feasible and capable of inducing graft-versus-tumor responses without excessive graft-versus-host disease. (ClinicalTrials.gov NCT#00675831).

Donor lymphocyte infusion after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (allo-SCT) is considered the cornerstone in the treatment of several malignant and not malignant hematological diseases. However, relapse of hematological disease after allo-SCT is considered the most challenging point in the field. The risk can be reduced through optimal patients, donor and disease selection before allo-SCT, but harnessing donor immune system is an appealing way to treat or avoid disease relapse. Donor lymphocyte infusion (DLI) is a simple and effective therapy after allo-SCT. In this paper, the efficacy of DLI will be analyzed in different hematological diseases, focusing also on their therapeutic or pre-emptive use.

Allogeneic stem cell transplantation in multiple myeloma: immunotherapy and new drugs

INTRODUCTION

Autologous (auto) stem cell transplantation (SCT) and the development of new drugs have improved the survival of multiple myeloma (MM) patients. By contrast, though potentially curative, the use of allogeneic (allo)-SCT is controversial.

AREAS COVERED

A review has been conducted to examine the current evidence for the use of allo-SCT in MM. We have examined novel cell therapies that may be exploited to induce myeloma-specific immune responses including the new promising frontier of chimeric antigen receptor (CAR)-T and -natural killer (NK) cells.

EXPERT OPINION

One of the major controversies facing researchers in exploring the allo approach is the remarkable recent treatment improvement observed with second- and third-generation proteasome inhibitors and immunomodulatory drugs, monoclonal antibodies and deacetylase inhibitors. Despite these great advances, the disease remains to be incurable and allo-SCT may still play a role in the cure of MM. We think that allo-SCT conserves a role in MM and its curative potential in high-risk patients should be explored in the setting of control clinical trials. Novel cell therapies such as CAR technologies may open new avenues of research toward a potential cure. Data from currently ongoing prospective studies will be helpful to clarify pending clinical questions.

The graft-versus-myeloma effect: chronic graft-versus-host disease but not acute graft-versus-host disease prolongs survival in patients with multiple myeloma receiving allogeneic transplantation

We conducted a study of patients with multiple myeloma (MM) undergoing allogeneic transplantation to evaluate outcome parameters. Fifty-seven consecutive patients with MM received an allogeneic transplantation between 2004 and 2011 at our institution. Patients who had received at least 1 prior autologous transplantation were included. Twenty-six patients underwent allogeneic transplantation for consolidation after a response to their first autograft, and 30 patients received an allogeneic transplantation as salvage therapy. Donor source was evenly distributed between related and unrelated. The median follow-up was 52 months. Thirty-two (57.1%) patients achieved a complete response (CR). At 5 years, 49.2% of all patients were in CR. Sixteen patients received either donor lymphocyte infusions or immune suppression withdrawal for disease progression, with a 62.5% response rate. The 5-year overall survival (OS) for all patients was 59%. The 5-year OS for the 30 patients in the consolidation group was 82% compared with 38% for those in the salvage group. In multivariate analysis, 3 factors remained significantly associated with OS. These include being in the salvage group (hazard ratio [HR], 4.05; P = .0196), acute graft-versus-host disease (aGVHD) (HR, 2.99; P = .034), and chronic graft-versus-host disease (cGVHD), which was highly protective, with a 5-year OS of 78.8% for patients with cGVHD versus 42.6% for patients without cGVHD (HR .17, P = .008). Our data show that allogeneic transplantation for MM can lead to sustained remissions. aGVHD is significantly deleterious to OS and progression-free survival, whereas cGVHD is strongly favorable, supporting an important role for the graft-versus-myeloma effect.

Allogeneic transplantation as anticancer immunotherapy

Allogeneic stem cell transplantation (AlloSCT) utilizes HLA-matched donor bone marrow or peripheral blood stem cell grafts to reconstitute haematopoiesis and immunity in patients with bone marrow failure or hematological malignancies. It is now clear that much of the anti-cancer effect of AlloSCT is due to the ability of engrafting donor derived lymphocyte populations to eradicate residual malignant clones, through a phenomenon known as the graft-versus-tumor (GVT) effect. Recognition of the importance of GVT in the long-term control of cancer has allowed substantial reductions in the pre-transplant conditioning intensity, leading to the development of reduced-intensity or even non-myeloablative transplant regimens in some patient groups. These reduced intensity regimens still allow donor cell engraftment and GVT, whilst reducing the morbidity and mortality associated with traditional myeloablative conditioning. Through clinical observations and experimental models of AlloSCT substantial insights have been provided into the mechanisms of immunological control of malignancy even outside the setting of AlloSCT, providing an opportunity to duplicate these anti-cancer mechanisms via non-allogeneic immunotherapies.