Mini-Midi-Maxi? How to harness the graft-versus-myeloma effect and target molecular remission after allogeneic stem cell transplantation

In search of the optimal platform for Post-Allogeneic SCT immunotherapy in relapsed multiple myeloma: a systematic review

Allogeneic stem cell transplantation (allo-SCT) has the potential to induce sustained remissions in patients with multiple myeloma (MM). Currently, allo-SCT is primarily performed in high-risk MM patients, most often in the setting of early relapse after first-line therapy with autologous SCT. However, the implementation of allo-SCT for MM is jeopardized by high treatment-related mortality (TRM) rates as well as high relapse rates. In this systematic review, we aimed to identify a safe allo-SCT strategy that has optimal 1-year results regarding mortality, relapse and severe GvHD, creating opportunities for post-transplantation strategies to maintain remissions in the high-risk group of relapsed MM patients. Eleven studies were included. Median PFS ranged from 5.2 to 36.8 months and OS was 13.0 to 63.0 months. The relapse related mortality at 1 year varied between 0 and 50% and TRM between 8 and 40%. Lowest GvHD incidences were reported for conditioning regimens with T-cell depletion using ATG or graft CD34+ selection. Similar strategies could lay the foundation for a post-transplant immune platform, this should be further evaluated in prospective clinical trials.

OCTET-CY: a phase II study to investigate the efficacy of post-transplant cyclophosphamide as sole graft-versus-host prophylaxis after allogeneic peripheral blood stem cell transplantation

OBJECTIVE

Post-transplant cyclophosphamide is increasingly used as graft-versus-host disease (GvHD) prophylaxis in the setting of bone marrow transplantation. No data have been published on the use of single-agent GvHD prophylaxis with post-transplant cyclophosphamide in the setting of peripheral blood stem cell transplantation (PBSCT).

METHODS

In a phase II trial, 11 patients with myeloma or lymphoma underwent conditioning with fludarabine and busulfan followed by T-replete PBSCT and application of 50 mg/kg/d of cyclophosphamide on day+3 and +4 without other concurrent immunosuppression (IS).

RESULTS

Median time to leukocyte, neutrophil, and platelet engraftment was 18, 21, and 18 d. The incidence of grade II-IV and grade III-IV GvHD was 45% and 27%, with a non-relapse mortality (NRM) of 36% at one and 2 yr. After median follow-up of 927 d, overall and relapse-free survival was 64% and 34%. Three patients did not require any further systemic IS until day+100 and thereafter. Analysis of immune reconstitution demonstrated rapid T- and NK-cell recovery. B- and CD3+/CD161+NK/T-cell recovery was superior in patients not receiving additional IS.

CONCLUSION

Post-transplant cyclophosphamide as sole IS in PBSCT is feasible and allows rapid immune recovery. Increased rates of severe acute GvHD explain the observed NRM and may advise a temporary combination partner such as mTor-inhibitors in the PBSCT setting.

Functional autoantibodies against SSX-2 and NY-ESO-1 in multiple myeloma patients after allogeneic stem cell transplantation

BACKGROUND

Multiple myeloma (MM) is the malignancy with the most frequent expression of the highly immunogenic cancer-testis antigens (CTA), and we have performed the first analysis of longitudinal expression, immunological properties, and fine specificity of CTA-specific antibody responses in MM.

METHODS

Frequency and characteristics of antibody responses against cancer-testis antigens MAGE-A3, NY-ESO-1, PRAME, and SSX-2 were analyzed using peripheral blood (N = 1094) and bone marrow (N = 200) plasma samples from 194 MM patients.

RESULTS

We found that antibody responses against CTA were surprisingly rare, only 2.6 and 3.1 % of patients evidenced NY-ESO-1- and SSX-2-specific antibodies, respectively. NY-ESO-1-specific responses were observed during disease progression, while anti-SSX-2 antibodies appeared after allogeneic stem cell transplantation and persisted during clinical remission. We found that NY-ESO-1- and SSX-2-specific antibodies were both capable of activating complement and increasing CTA uptake by antigen-presenting cells. SSX-2-specific antibodies were restricted to IgG3, NY-ESO-1 responses to IgG1 and IgG3. Remarkably, NY-ESO-1-positive sera recognized various non-contiguous regions, while SSX-2-specific responses were directed against a single 6mer epitope, SSX-2(85-90).

CONCLUSIONS

We conclude that primary autoantibodies against intracellular MM-specific tumor antigens SSX-2 and NY-ESO-1 are rare but functional. While their contribution to disease control still remains unclear, our data demonstrate their theoretic ability to affect cellular anti-tumor immunity by formation and uptake of mono- and polyvalent immune complexes.

Indoleamine 2,3-dioxygenase 1 (IDO1) activity correlates with immune system abnormalities in multiple myeloma

Background

Multiple myeloma (MM) is a plasma cell malignancy with a multifaceted immune dysfunction. Indoleamine 2,3-dioxygenase 1 (IDO1) degrades tryptophan into kynurenine (KYN), which inhibits effector T cells and promote regulatory T-cell (Treg) differentiation. It is presently unknown whether MM cells express IDO1 and whether IDO1 activity correlates with immune system impairment.

Methods

We investigated IDO1 expression in 25 consecutive patients with symptomatic MM and in 7 patients with either monoclonal gammopathy of unknown significance (MGUS; n=3) or smoldering MM (SMM; n=4). IDO1-driven tryptophan breakdown was correlated with the release of hepatocyte growth factor (HGF) and with the frequency of Treg cells and NY-ESO-1-specific CD8⁺ T cells.

Results

KYN was increased in 75% of patients with symptomatic MM and correlated with the expansion of CD4⁺CD25⁺FoxP3⁺ Treg cells and the contraction of NY-ESO-1-specific CD8⁺ T cells. In vitro, primary MM cells promoted the differentiation of allogeneic CD4⁺ T cells into bona fide CD4⁺CD25^hiFoxP3^hi Treg cells and suppressed IFN-γ/IL-2 secretion, while preserving IL-4 and IL-10 production. Both Treg expansion and inhibition of Th1 differentiation by MM cells were reverted, at least in part, by d,l-1-methyl-tryptophan, a chemical inhibitor of IDO. Notably, HGF levels were higher within the BM microenvironment of patients with IDO⁺ myeloma disease compared with patients having IDO^- MM. Mechanistically, the antagonism of MET receptor for HGF with SU11274, a MET inhibitor, prevented HGF-induced AKT phosphorylation in MM cells and translated into reduced IDO protein levels and functional activity.

Conclusions

These data suggest that IDO1 expression may contribute to immune suppression in patients with MM and possibly other HGF-producing cancers.

Diagnostic performance of whole-body MRI for the detection of persistent or relapsing disease in multiple myeloma after stem cell transplantation

OBJECTIVES

To compare the diagnostic performance of whole-body MRI (WBMRI) with haematological parameters for detecting persistent or relapsing disease in patients with multiple myeloma after stem cell transplantation.

METHODS

Sixty-six WBMRI acquisitions were performed in 33 patients with multiple myeloma at two time points after stem cell transplantation. Extent of disease and inter-test dynamics of intra- and extramedullary myeloma manifestations were compared (kappa statistics) with Uniform Response Criteria, comprising haematological parameters.

RESULTS

Using data from 66 sequential WBMRI acquisitions in 33 patients, 10 patients (30.3 %) were classified as having progressive disease and 23 (69.7 %) as being in remission. Eight (80 %) of the ten patients with progressive disease revealed intramedullary lesions, and two patients (20 %) had intra- and extramedullary lesions. WBMRI and laboratory tests were concordant in 26/33 (78.8 %) patients. We found an agreement of 51.2 %, 95 % confidence interval 19.8 %-82.6 %, between results from WBMRI and haematological parameters. WBMRI had a sensitivity of 63.6 %, specificity of 86.4 %, PPV of 70.0 %, NPV of 82.6 % and accuracy of 78.8 % for detection of remission.

CONCLUSIONS

WBMRI allows the detection and exact localisation of intra- and extramedullary myeloma manifestations after stem cell transplantation, but shows only moderate agreement with routinely performed laboratory tests for determination of remission.

18F-FDG PET/CT for detection and localization of residual or recurrent disease in patients with multiple myeloma after stem cell transplantation

PURPOSE

The aim of the study was to determine the diagnostic performance of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT for the detection and localization of residual or recurrent disease in patients with multiple myeloma (MM) after stem cell transplantation.

METHODS

A total of 197 whole-body (18)F-FDG PET/CT scans were performed in 99 patients with MM at different time points in the course of disease after autologous or allogeneic stem cell transplantation. Post-transplant PET/CT scans and clinical remission status as determined by the clinical gold standard (Uniform Response Criteria) were analysed and compared.

RESULTS

A total of 576 focal osseous and extramedullary lesions were detected in 79 scans. Additional diffuse bone marrow involvement was detected in 17 patients. (18)F-FDG PET/CT had a sensitivity of 54.6%, a specificity of 82.1%, a positive predictive value of 82.3%, a negative predictive value of 54.2% and an overall accuracy of 65.5%. The sensitivity of (18)F-FDG PET/CT was shown to depend on the disease category according to the Uniform Response Criteria for myeloma.

CONCLUSION

In patients with MM in the post-transplant setting, (18)F-FDG PET/CT may (1) contribute to the detection and localization of disease, (2) provide information about the extent of distinct myeloma manifestations and the total disease burden and (3) add information about the metabolic activity of disease, but (4) has substantially lower sensitivity for this purpose compared to the pretreatment setting.

Patients with multiple myeloma develop SOX2-specific autoantibodies after allogeneic stem cell transplantation

The occurrence of SOX2-specific autoantibodies seems to be associated with an improved prognosis in patients with monoclonal gammopathy of undetermined significance (MGUS). However, it is unclear if SOX2-specific antibodies also develop in established multiple myeloma (MM). Screening 1094 peripheral blood (PB) sera from 196 MM patients and 100 PB sera from healthy donors, we detected SOX2-specific autoantibodies in 7.7% and 2.0% of patients and donors, respectively. We identified SOX2_211–230 as an immunodominant antibody-epitope within the full protein sequence. SOX2 antigen was expressed in most healthy tissues and its expression did not correlate with the number of BM-resident plasma cells. Accordingly, anti-SOX2 immunity was not related to SOX2 expression levels or tumor burden in the patients' BM. The only clinical factor predicting the development of anti-SOX2 immunity was application of allogeneic stem cell transplantation (alloSCT). Anti-SOX2 antibodies occurred more frequently in patients who had received alloSCT (n = 74). Moreover, most SOX2-seropositive patients had only developed antibodies after alloSCT. This finding indicates that alloSCT is able to break tolerance towards this commonly expressed antigen. The questions whether SOX2-specific autoantibodies merely represent an epiphenomenon, are related to graft-versus-host effects or participate in the immune control of myeloma needs to be answered in prospective studies.

Trends in allogeneic stem cell transplantation for multiple myeloma: a CIBMTR analysis

Allogeneic hematopoietic cell transplantation in multiple myeloma is limited by prior reports of high treatment-related mortality. We analyzed outcomes after allogeneic hematopoietic cell transplantation for multiple myeloma in 1207 recipients in 3 cohorts based on the year of transplantation: 1989-1994 (n = 343), 1995-2000 (n = 376), and 2001-2005 (n = 488). The most recent cohort was significantly older (53% > 50 years) and had more recipients after prior autotransplantation. Use of unrelated donors, reduced-intensity conditioning and the blood cell grafts increased over time. Rates of acute graft-versus-host (GVHD) were similar, but chronic GVHD rates were highest in the most recent cohort. Overall survival (OS) at 1-year increased over time, reflecting a decrease in treatment-related mortality, but 5-year relapse rates increased from 39% (95% confidence interval [CI], 33%-44%) in 1989-1994 to 58% (95% CI, 51%-64%; P < .001) in the 2001-2005 cohort. Projected 5-year progression-free survival and OS are 14% (95% CI, 9%-20%) and 29% (95% CI, 23%-35%), respectively, in the latest cohort. Increasing age, longer interval from diagnosis to transplantation, and unrelated donor grafts adversely affected OS in multivariate analysis. Survival at 5 years for subjects with none, 1, 2, or 3 of these risk factors were 41% (range, 36%-47%), 32% (range, 27%-37%), 25% (range, 19%-31%), and 3% (range, 0%-11%), respectively (P < .0001).

[Chimerism analysis after allogeneic haematopoietic stem cell transplantation. Interest of cell sorting: general review]

Haematopoietic stem cells transplantation, widely used these last decades, represent the ultimate treatment resource for patients with haematological malignancies. Long range success of this treatment is particularly affected by relapse of the initial disease, graft rejection or graft versus host disease. Chimerism analysis after transplantation had been used since several years to document engraftment, to determine the risk of relapse and to adapt therapy promptly when necessary. Usefulness of this analysis for the outcome of transplanted patients, as well as the impact of using high sensitive techniques coupled with specific cell populations sorted have been demonstrated by retrospective studies. Follow-up of chimerism would allow to operate efficiently before the onset of clinical signs in leukaemic patients with high risk of relapse and to control the expression of minimal residual disease when specific molecular markers could not be monitored.

Long-term follow-up of an intensified myeloablative conditioning regimen with in vivo T cell depletion followed by allografting in patients with advanced multiple myeloma

We report long-term results after a median follow-up of 105 months in 18 patients with multiple myeloma who received an intensified myeloablative conditioning regimen regimen consisting of modified total body irradiation, busulfan, cyclophosphamide, and antithymocyte globulin, followed by allogeneic stem cell transplantation (SCT). Grade II-IV acute graft-versus-host disease occurred in 7 patients (44%), and treatment-related mortality was 17%. Complete remission (CR) with negative immunofixation after allogeneic SCT occurred in 53% of the patients. For all patients, the estimated overall survival at 12 years was 50% (95% confidence interval [CI], 26%-74%), and the estimated event-free survival (EFS) was 35% (95% CI, 23%-57%). Those patients who achieved CR after SCT had a 12-year estimated PFS of 60%, whereas none of the patients without CR remained progression-free. Our data indicate that an intensified myeloablative conditioning regimen followed by allogeneic SCT can produce long-term survival and freedom from disease in patients with multiple myeloma who achieve CR.

Thymocyte expansion and maturation: crosstalk of CD44v6 on thymocytes and panCD44 on stroma cells

Re-acquisition of immunocompetence after allogeneic bone marrow cell (BMC) transplantation depends on intrathymic maturation of the allogeneic T progenitor cells. We recently reported that CD44 promotes progenitor homing into the thymus and T-cell maturation and now elucidate the molecular mechanisms of CD44-supported thymocyte maturation. Lethally irradiated, tumor-bearing mice, allogeneically reconstituted with T-cell-depleted BMC and a small number of common lymphoid progenitor 2 cells (CLP2) from transgenic (TG) mice, that express ratCD44v4-v7 under the Thy1 promoter, showed accelerated immunocompetent T-cell recovery compared with mice reconstituted with non-transgenic (NTG) CLP2. In addition, graft-versus-host disease was strongly reduced after tumor vaccination. TG, but not NTG double-negative (DN) thymocytes showed high proliferative potential, accompanied by constitutive association of lck with CD44. Importantly, when thymocyte adhesion was strengthened by anti-CD44, co-cultures of DN thymocytes with thymic stroma supported DN thymocyte maturation. The close contact between DN thymocytes and thymic stroma promoted persisting activation of lck and ERK1/2, particularly in CD44v6(+) DN thymocytes. Thus, intrathymic T-cell maturation in allogeneically reconstituted, leukemia-bearing hosts can be considerably accelerated by high CD44v6 expression in early thymocytes, in which proliferation-supporting signals are initiated by a crosstalk between CD44v6 on thymocytes and panCD44 on the thymic stroma.

Post-transplant immunotherapy with donor-lymphocyte infusion and novel agents to upgrade partial into complete and molecular remission in allografted patients with multiple myeloma

OBJECTIVE

To investigate post-transplant immunotherapy with escalating donor-lymphocyte infusions (DLI) and novel agents (thalidomide, bortezomib, and lenalidomide) to target complete remission (CR).

MATERIALS AND METHODS

Thirty-two patients with multiple myeloma who achieved only partial remission after allogeneic stem cell transplantation were treated with DLI. If no CR was achieved, one of the novel agents was added to target CR.

RESULTS

CR defined either by European Group for Blood and Marrow Transplantation criteria, flow cytometry, or molecular methods as assessed by patient-specific immunoglobulin H-polymerase chain reaction or plasma cell chimerism polymerase chain reaction was accomplished in 59%, 63%, and 50% of patients, respectively. Achievement of CR resulted in improved 5-year progressive-free and overall survival, according to European Group for Blood and Marrow Transplantation criteria (53% vs 35%; p=0.03 and 90% vs 62%; p=0.06), flow cytometry (74% vs 15%; p=0.001 and 100% vs 52%; p=0.1), or molecular methods (84% vs 38%; p=0.001 and 100% vs 71%; p=0.03).

CONCLUSIONS

Our finding demonstrates the clinical relevance of posttransplantation therapies to upgrade remission, and of remission's depth for long-term survival in myeloma patients.

A Phase II trial of autologous stem cell transplantation followed by mini-allogeneic stem cell transplantation for the treatment of multiple myeloma: an analysis of Eastern Cooperative Oncology Group ECOG E4A98 and E1A97

Conventional allogeneic hematopoietic stem cell transplantation (HSCT) for multiple myeloma is associated with high transplantation-related mortality (TRM). Nonmyeloablative allogeneic transplantation (NST) uses the well-known graft-versus-myeloma (GVM) effect to eradicate minimal residual disease. The Eastern Cooperative Oncology Group conducted a Phase II trial of autologous HSCT followed by NST to provide maximal tumor cytoreduction to allow for a subsequent GVM effect. Patients received melphalan 200 mg/m(2) with autologous HSCT, followed by fludarabine 30 mg/m(2) in 5 daily doses and cyclophosphamide 1 g/m(2) in 2 daily doses with matched sibling donor NST. Graft-versus-host disease (GVHD) prophylaxis included cyclosporine and corticosteroids. The primary endpoints were TRM, graft failure, acute GVHD, progression-free survival (PFS), and overall survival (OS). Thirty-two patients were enrolled into the study; 23 patients completed both transplantations (72%). Best responses post-NST were 7 (30%) complete remission (CR), 11 (48%) partial remission (PR), 2 (9%) no response, and 3 (13%) not evaluable. Acute grade III-IV GVHD was observed in 4 patients (17%), and chronic GVHD was seen in 13 patients (57%; 7 limited, 6 extensive). Chronic GVHD resulted in the following responses: 3 (23%) CR, 1 continuing CR, and 6 (46%) PR. Two patients (8.7%) had early TRM. With a median follow up of 4.6 years, the median PFS was 3.6 years, and the 2-year OS was 78%. Our findings indicate that autologous HSCT followed by NST is feasible, with a low early TRM in a cooperative group setting. The overall response rate was 78%, including 30% CR, similar to other reports for autologous HSCT-NST. Because a plateau in PFS or OS was not observed with this treatment approach even in patients achieving CR, we suggest that future studies use posttransplantation maintenance therapy.

Myeloablative radioimmunotherapy in conditioning prior to haematological stem cell transplantation: closing the gap between benefit and toxicity?

High-dose radio-/chemotherapy in the context of autologous and allogeneic haematopoietic stem cell transplantation is a double-edged sword. The requirement for dose intensification is linked to an increase in toxicity to noninvolved organs. Particularly for older patients and patients with comorbidities, efficient but toxicity-reduced schemes are needed. Myeloablative radioimmunotherapy is a targeted, internal radiotherapy that uses radiolabelled monoclonal antibodies (mAb) with affinity to the bone marrow. It involves the administration of high radiation doses (up to 30 Gy) to the bone marrow and spleen but without exposing radiosensitive organs to doses higher than 1-7 Gy. Added to conventional or intensity-reduced conditioning, myeloablative radioimmunotherapy may achieve a pronounced antileukaemic effect with tolerable toxicities. A rational and individual design of the ideal nuclide-antibody combination optimizes therapy. The anti-CD33, anti-CD45 and anti-CD66 mAbs appear to be ideal tracers so far. The beta-emitter (90)Y is coupled by DTPA and is the best nuclide for myeloablation. Approval trials for DTPA anti-CD66 mAb are underway in Europe, and in the near future these therapies may become applicable in practice. This review gives an overview of current myeloablative conditioning radioimmunotherapy. We discuss the selection of the optimal radioimmunoconjugate and discuss how radioimmunotherapy might be optimized in the future by individualization of therapy protocols. We also highlight the potential advantages of combination therapies.

Stem-Cell Transplantation for Multiple Myeloma in the Era of Novel Drugs

The treatment of multiple myeloma (MM) is changing rapidly. During the last 10 years, higher rates of complete response (CR) and prolonged progression-free and overall survival have been seen with high-dose chemotherapy plus autologous stem-cell transplantation (HDT-ASCT). Achievement of CR and good partial response have been shown to be key prognostic factors for prolonged survival, with eradication of minimal residual disease seeming crucial to long-term disease-free survival. Until recently, high rates of CR and other major responses were primarily seen with HDT-ASCT, but insights into the biology of MM have led to the development and approval of new drugs with significant activity, and new induction regimens based on these novel agents are offering improved responses. Thalidomide, bortezomib, and lenalidomide have been combined with corticosteroids, alkylators, and anthracyclines in front-line MM treatment. Phase II studies have indicated that high rates of response and CR may be achieved. The substantial activity seen with these new drug combinations has prompted a re-examination of the role of SCT in MM treatment. Will achievement of major responses with these new regimens translate into improved survival after consolidation with transplantation? Will these improved induction regimens reduce the need for tandem transplantation, or does achievement of CR obviate the need for front-line transplantation altogether? To help address these questions, randomized trials are needed, as well as tests with improved sensitivity to better define depth of remission.

Future challenges

Treatment for patients with myeloma has changed unrecognisably over the last two decades and now includes a sequence of treatments including chemotherapy, biological targeted therapy with or without consideration for high-dose therapy (autologous and allogeneic stem cell transplantation for younger and fit patients). As patients can now expect a doubling of median survival and a 20-30% chance of surviving longer than 10 years, the focus of treatment is shifting to long-term quality of life. This article focuses on future challenges facing clinicians treating myeloma and how best we may optimize our resources.