Maintenance therapy in multiple myeloma

Despite recent advances, multiple myeloma remains an incurable disease. Induction therapy followed by autologous transplantation has become the standard of care. The idea of maintenance therapy in multiple myeloma is not new. Starting with chemotherapy in 1975, to interferon in 1998, to novel agents recently, a multitude of agents have been explored in patients with multiple myeloma. In spite of the novel agents, multiple myeloma continues to be an incurable disease with the progression-free survival after autologous transplant rarely exceeding 3 years. The goal of using maintenance therapy has been to improve the outcomes following autologous transplantation by increasing the progression-free survival, deepening remissions and perhaps increasing overall survival. It has been shown that patients with a stringent complete response (CR) have a better outcome [Kapoor et al. 2013]. It is becoming increasingly common to check minimal residual disease (MRD) as a means of assessing depth of response. It has also been shown that patients with no MRD have not only a better progression-free survival but also a better overall survival compared with patients who are MRD positive. This makes it even more important to find agents for maintenance therapy, which can further deepen and maintain responses. Here, we present a comprehensive review of the agents studied as maintenance for multiple myeloma and their efficacy, both in terms of overall survival, progression-free survival and toxicity.

Towards Stratified Medicine in Plasma Cell Myeloma

Plasma cell myeloma is a clinically heterogeneous malignancy accounting for approximately one to 2% of newly diagnosed cases of cancer worldwide. Treatment options, in addition to long-established cytotoxic drugs, include autologous stem cell transplant, immune modulators, proteasome inhibitors and monoclonal antibodies, plus further targeted therapies currently in clinical trials. Whilst treatment decisions are mostly based on a patient’s age, fitness, including the presence of co-morbidities, and tumour burden, significant scope exists for better risk stratification, sub-classification of disease, and predictors of response to specific therapies. Clinical staging, recurring acquired cytogenetic aberrations, and serum biomarkers such as β-2 microglobulin, and free light chains are in widespread use but often fail to predict the disease progression or inform treatment decision making. Recent scientific advances have provided considerable insight into the biology of myeloma. For example, gene expression profiling is already making a contribution to enhanced understanding of the biology of the disease whilst Next Generation Sequencing has revealed great genomic complexity and heterogeneity. Pathways involved in the oncogenesis, proliferation of the tumour and its resistance to apoptosis are being unravelled. Furthermore, knowledge of the tumour cell surface and its interactions with bystander cells and the bone marrow stroma enhance this understanding and provide novel targets for cell and antibody-based therapies. This review will discuss the development in understanding of the biology of the tumour cell and its environment in the bone marrow, the implementation of new therapeutic options contributing to significantly improved outcomes, and the progression towards more personalised medicine in this disorder.

Oral ixazomib maintenance therapy in multiple myeloma

Continuous therapy has proven to be an effective therapeutic strategy to improve the outcome of both young and elderly multiple myeloma patients. Remarkably, lenalidomide and bortezomib showed to play a crucial role in this setting due to their safety profile allowing long-term exposure. Ixazomib, the first oral proteasome inhibitor to be evaluated in multiple myeloma, exerts substantial anti-myeloma activity as a single agent and particularly in combination with immunomodulatory drugs and it may be an attractive option for maintenance therapy. Here we address the issue of maintenance therapy as part of a therapeutic approach of multiple myeloma patients focusing on the potential role of ixazomib.

Advances in understanding prognosis in myeloma

In the last two decades outcomes in multiple myeloma (myeloma) have greatly improved, due to the introduction of newer, more effective therapies. This improvement is not uniform. Response to treatment and survival remains heterogeneous, with some patients living for 1-2 years whilst others are alive and progression-free at 10 years. This variation in outcome is due to patient characteristics plus features intrinsic to the myeloma tumour. Alongside the introduction of novel therapies there has been a greater understanding of disease biology and mechanisms of resistance. This has led to an increase in the number of prognostic markers that can be used in myeloma. This is important not only for more accurate counselling of patients in terms of disease outcome, but also in paving the way for risk-adapted therapy. Both newer and traditional prognostic markers need to be used in the context of planned therapy. Indeed, the prognostic value of certain markers varies according to which therapy the patient receives. As such, these prognostic factors will require constant re-evaluation as agents with new mechanisms of action are added into the myeloma treatment algorithm. This article summarises current concepts of prognostic markers in myeloma.

Role of MRD status in relation to clinical outcomes in newly diagnosed multiple myeloma patients: a meta-analysis

Driven by access to better drugs, on average, newly diagnosed multiple myeloma patients have over 10 years overall survival. Using modern combination therapies – with or without the addition of high-dose melphalan and autologous stem cell transplantation – up to 80% of patients reach a complete response. As a logical and necessary step forward, clinical studies have explored strategies to detect minimal residual disease (MRD) and its correlation with clinical outcomes. In this context, MRD has been proposed as a regulatory endpoint for drug approval in newly diagnosed multiple myeloma. To better define the role of MRD negativity in relation to clinical outcomes, we undertook a meta-analysis including published clinical trials of newly diagnosed multiple myeloma patients. We applied a random effects model which weighted studies using the inverse-variance method. Studies were combined on the scale of the logarithm of the hazard ratio (HR) and the corresponding standard error. We found that remaining MRD positive was associated with worse progression-free survival (HR=2.85; 95% confidence interval (CI) 2.17–3.74; P<0.001) and overall survival (HR=2.08; 95% CI 1.44–3.01; P<0.001). Our results show that MRD negativity is a strong predictor of clinical outcomes, supportive of MRD becoming a regulatory endpoint for drug approval in newly diagnosed multiple myeloma.

Optimal maintenance and consolidation therapy for multiple myeloma in actual clinical practice

Multiple myeloma is an incurable malignant plasma cell-originating cancer. Although its treatment outcomes have improved with the use of glucocorticoids, alkylating drugs, and novel agents, including proteasome inhibitors (bortezomib and carfilzomib) and immunomodulatory drugs (thalidomide, lenalidomide, and pomalidomide), relapse remains a serious problem. Strategies to improve outcomes following autologous stem cell transplantation and frontline treatments in non-transplant patients include consolidation to intensify therapy and improve the depth of response and maintenance therapy to achieve long-term disease control. Many clinical trials have reported increased progression-free and overall survival rates after consolidation and maintenance therapy. The role of consolidation/maintenance therapy has been assessed in patients eligible and ineligible for transplantation and is a valuable option in clinical trial settings. However, the decision to use consolidation and/or maintenance therapy needs to be guided by the individual patient situation in actual clinical practice. This review analyzes the currently available evidence from several reported clinical trials to determine the optimal consolidation and maintenance therapy in clinical practice.

Cancer testis antigen MAGE C1 can be used to monitor levels of circulating malignant stem cells in the peripheral blood of multiple myeloma patients

PURPOSE

Monitoring the levels of malignant disease-causing cells in multiple myeloma, as opposed to the clinical symptoms alone, is an important move forward in the management of this disease. While current methods including multiparametric flow cytometry and PCR analysis of the clonal plasma cells can be used in a patient-specific manner, their use is limited and the fundamental malignant progenitor cell is not being monitored. The expression of cancer testis antigen MAGE C1 has been linked to the malignant stem cell in this disease, and thus, we investigated the use of both flow cytometric and qRTPCR approaches to monitor its expression as an alternative monitoring methodology in this pilot study.

METHODS

We compared the levels of MAGE C1 in the peripheral blood to serum M protein and serum beta 2 microglobulin levels at 3-monthly intervals over a 2-year period, for 12 patients on chemotherapy regimens and 4 patients undergoing stem cell transplantation.

RESULTS AND CONCLUSIONS

The analysis indicated that the novel flow cytometric analysis of MAGE C1 expression in the peripheral blood was extremely relevant as a potential minimal residual disease-monitoring tool. Expression of this cancer testis antigen was detectable in all patients throughout treatment, with comparable increases and decreases to serum M protein and/or serum beta 2 microglobulin, but with the advantage of being able to detect disease at a more sensitive level. Furthermore, due to the increased sensitivity, the ability to pre-empt disease relapse before clinical changes were evident, was preliminarily indicated. The qRTPCR approach showed potential as a monitoring tool in the chemotherapy patient cohort, with the mRNA MAGE C1 levels following a similar pattern of expression observed in the flow cytometry analysis.

Immunotherapies targeting CD38 in Multiple Myeloma

Recently, the monoclonal antibody daratumumab was approved as a single agent for the treatment of patients with relapsed/refractory Multiple Myeloma (MM). Daratumumab is an antibody targeting surface molecule CD38 on myeloma cells and the agent is already widely being used based on its good tolerability and proven efficacy. We believe, however, that the efficacy of this drug and other anti-CD38 monoclonal antibodies can be further improved by combining it with other types of immunotherapies. Furthermore, surface molecule CD38 can be used as a target for immunotherapies other than just naked monoclonal antibodies. In this report, we review the expression pattern of CD38 among normal tissues and in different types of plasma cell dyscrasias including their progenitor cells, minimal residual disease, and circulating tumor cells. We summarize the physiological role of CD38 as well as its role in the pathophysiology of MM and we present the most recent clinical trials using CD38 as a target. In addition, we highlight possible combination immunotherapies incorporating anti-CD38 monoclonal antibodies and we demonstrate alternative immunotherapeutic approaches targeting the same antigen such as CD38-specific chimeric antigen receptor (CAR) T cells.

Diagnosis of chronic lymphoproliferative disorders by flow cytometry using four-color combinations for immunophenotyping: A proposal of the brazilian group of flow cytometry (GBCFLUX)

BACKGROUND

Multiparametric flow cytometry (MFC) is a powerful tool for the diagnosis of hematological malignancies and has been useful for the classification of chronic lymphoproliferative disorders (CLPD) according to the WHO criteria. Following the purposes of the Brazilian Group of Flow Cytometry (GBCFLUX), the aim of this report was to standardize the minimum requirements to achieve an accurate diagnosis in CLPDs, considering the different economic possibilities of the laboratories in our country. Most laboratories in Brazil work with 4-fluorescence flow cytometers, which is why the GBCFLUX CLPD Committee has proposed 4-color monoclonal antibody (MoAb) panels.

METHODS/RESULTS

Panels for screening and diagnosis in B, T and NK lymphoproliferative disorders were developed based on the normal differentiation pathways of these cells and the most frequent phenotypic aberrations. Important markers for prognosis and for minimal residual disease (MRD) evaluation were also included. The MoAb panels presented here were designed based on the diagnostic expertise of the participating laboratories and an extensive literature review.

CONCLUSION

The 4-color panels presented to aid in the diagnosis of lymphoproliferative neoplasms by GBCFLUX aim to provide clinical laboratories with a systematic, step-wise, cost-effective, and reproducible approach to obtain an accurate immunophenotypic diagnosis of the most frequent of these disorders. © 2016 International Clinical Cytometry Society.

Management of high-risk Myeloma: an evidence-based review of treatment strategies

INTRODUCTION

Despite the progress made in the treatment of patients with multiple myeloma over recent decades, a significant cohort with high-risk disease as defined by specific clinical and genetic criteria continue to respond poorly to standard treatment. These patients represent a particular challenge to the treating physician and require early identification as well as personalized treatment strategies.

AREAS COVERED

In this review, we discuss the prognostic impact of adverse clinical, radiological and genetic factors, evaluate available scoring systems and highlight key aspects of the therapeutic management of high-risk myeloma. MEDLINE and recent scientific meetings' databases were searched for the keywords 'high-risk' and 'multiple myeloma' and relevant studies relating to both diagnostic and therapeutic approaches were identified. Expert commentary: A case is made for intensive induction using combinations of novel agents, early high-dose therapy supported by autologous stem cell transplantation and the widespread use of maintenance therapies. Novel therapeutic options, especially in the field of immunotherapy, are currently explored in clinical trials and have the potential to further improve outcomes for patients with high-risk multiple myeloma.

The MUK five protocol: a phase II randomised, controlled, parallel group, multi-centre trial of carfilzomib, cyclophosphamide and dexamethasone (CCD) vs. cyclophosphamide, bortezomib (Velcade) and dexamethasone (CVD) for first relapse and primary refractory multiple myeloma

Background

Multiple myeloma is a plasma cell tumour with an annual incidence in the UK of approximately 40–50 per million i.e. about 4500 new cases per annum. The triple combination cyclophosphamide, bortezomib (Velcade®) and dexamethasone (CVD) is an effective regimen at relapse and has emerged in recent years as the standard therapy at first relapse in the UK. Carfilzomib has good activity as a single agent in the relapsed setting, and it is expected that efficacy will be improved when used in combination with dexamethasone and cyclophosphamide.

Methods

MUK Five is a phase II open label, randomised, controlled, parallel group, multi-centre trial that will compare the activity of carfilzomib, cyclophosphamide and dexamethasone (CCD) with that of CVD, given over an equivalent treatment period (24 weeks), in participants with multiple myeloma at first relapse, or refractory to no more than 1 line of treatment. In addition, the study also aims to assess the utility of a maintenance schedule of carfilzomib in these participants. The primary objective of the trial is to assess whether CCD provides non-inferior activity in terms of ≥ VGPR rates at 24 weeks, and whether the addition of maintenance treatment with carfilzomib to CCD provides superior activity in terms of progression-free survival, as compared to CCD with no maintenance. Secondary objectives include comparing toxicity profiles, further summarizing and comparing the activity of the different treatment arms and analysis of the effect of each treatment arm on minimal residual disease status.

Discussion

The development of carfilzomib offers the opportunity to further explore the anti-tumour efficacy of proteasome inhibition and, based on the available evidence, it is important and timely to obtain data on the activity, toxicity and tolerability of this drug. In contrast to ongoing phase III trials, this phase II trial has a unique subset of participants diagnosed with multiple myeloma at first relapse or refractory to no more than 1 line of treatment and will also evaluate the utility of maintenance with carfilzomib for up to 18 months and investigate minimal residual disease status to provide information on depth of response and the prognostic impact thereof.

Trial registration

The trial is registered under ISRCTN17354232, December 2012.

CD229 is expressed on the surface of plasma cells carrying an aberrant phenotype and chemotherapy-resistant precursor cells in multiple myeloma

Multiple Myeloma (MM) is a plasma cell (PC) malignancy, which despite significant therapeutic advances, is still considered incurable. This is due to the persistence of chemotherapy-resistant minimal residual disease in the patients' bone marrow (BM) after an effective induction therapy. Immunotherapies targeting surface molecules expressed on the bulk of tumor cells and the chemotherapy-resistant, myeloma-propagating cells could play a central role in this clinical setting. We recently described surface molecule CD229 as a potential therapeutic target for MM. In our current study we assessed the expression of CD229 on different PC subtypes and on cells with a myeloma-propagating phenotype in a total of 77 patients with PC dyscrasias independently at 2 different cancer centers. We found that CD229 was strongly and homogeneously overexpressed on the PC of patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering myeloma, MM, and PC leukemia. CD229 was particularly overexpressed on those PC showing an abnormal phenotype such as expression of CD56. Most importantly, CD229 was also highly expressed on those cells in the patients' BM displaying the phenotype of chemotherapy-resistant and myeloma-propagating cells. In conclusion, our combined findings suggest that immunotherapies targeting CD229 will not only be effective for the bulk of tumor cells but will also help to eradicate chemotherapy-resistant cells remaining in the patients' BM after induction treatment. Hopefully, the design of CD229-specific monoclonal antibodies or chimeric antigen receptor-transduced T cells will help to achieve prolonged remissions or even cures in MM patients.

Minimal residual disease monitoring and immune profiling in multiple myeloma in elderly patients

The value of minimal residual disease (MRD) in multiple myeloma (MM) has been more frequently investigated in transplant-eligible patients than in elderly patients. Because an optimal balance between treatment efficacy and toxicity is of utmost importance in patients with elderly MM, sensitive MRD monitoring might be particularly valuable in this patient population. Here, we used second-generation 8-color multiparameter-flow cytometry (MFC) to monitor MRD in 162 transplant-ineligible MM patients enrolled in the PETHEMA/GEM2010MAS65 study. The transition from first- to second-generation MFC resulted in increased sensitivity and allowed us to identify 3 patient groups according to MRD levels: MRD negative (<10(-5); n = 54, 34%), MRD positive (between <10(-4) and ≥10(-5); n = 20, 12%), and MRD positive (≥10(-4); n = 88, 54%). MRD status was an independent prognostic factor for time to progression (TTP) (hazard ratio [HR], 2.7; P = .007) and overall survival (OS) (HR, 3.1; P = .04), with significant benefit for MRD-negative patients (median TTP not reached, 70% OS at 3 years), and similar poorer outcomes for cases with MRD levels between <10(-4) and ≥10(-5) vs ≥10(-4) (both with a median TTP of 15 months; 63% and 55% OS at 3 years, respectively). Furthermore, MRD negativity significantly improved TTP of patients >75 years (HR, 4.8; P < .001), as well as those with high-risk cytogenetics (HR, 12.6; P = .01). Using second-generation MFC, immune profiling concomitant to MRD monitoring also contributed to identify patients with poor, intermediate, and favorable outcomes (25%, 61%, and 100% OS at 3 years, respectively; P = .01), the later patients being characterized by an increased compartment of mature B cells. Our results show that similarly to transplant candidates, MRD monitoring is one of the most relevant prognostic factors in elderly MM patients, irrespectively of age or cytogenetic risk. This trial was registered at www.clinicaltrials.gov as #NCT01237249.

Minimal Residual Disease Assessment in the Context of Multiple Myeloma Treatment

With contemporary therapeutic strategies in multiple myeloma, heretofore unseen depth and rate of responses are being achieved. These strategies have paralleled improvements in outcome of multiple myeloma patients. The integration of the next generation of proteasome inhibitors and antibody therapeutics promise continued improvements in therapy with the expectation of consistent depth of response not quantifiable by current clinical methods. As such, there is a growing need to develop adequate tools to evaluate deeper disease response after therapy and to refine the response criteria including the minimal residual disease. Several emerging techniques are being evaluated for these purposes including multi-parameter flow cytometry, allele-specific oligonucleotide polymerase chain reaction, next-generation sequencing, and imaging modalities. In this review, we highlight the recent developments and evaluate advantages and limitations of the current technologies to assess minimal residual disease. We also discuss future applications of these methodologies in potentially guiding multiple myeloma treatment decisions.

Treatment With Carfilzomib-Lenalidomide-Dexamethasone With Lenalidomide Extension in Patients With Smoldering or Newly Diagnosed Multiple Myeloma

IMPORTANCE

Carfilzomib-lenalidomide-dexamethasone therapy yields deep responses in patients with newly diagnosed multiple myeloma (NDMM). It is important to gain an understanding of this combination's tolerability and impact on minimal residual disease (MRD) negativity because this end point has been associated with improved survival.

OBJECTIVE

To assess the safety and efficacy of carfilzomib-lenalidomide-dexamethasone therapy in NDMM and high-risk smoldering multiple myeloma (SMM).

DESIGN, SETTING, AND PARTICIPANTS

Clinical and correlative pilot study at the National Institutes of Health Clinical Center. Patients with NDMM or high-risk SMM were enrolled between July 11, 2011, and October 9, 2013. Median follow-up was 17.3 (NDMM) and 15.9 months (SMM).

INTERVENTIONS

Eight 28-day cycles were composed of carfilzomib 20/36 mg/m2 on days 1, 2, 8, 9, 15, and 16; lenalidomide 25 mg on days 1 through 21; and dexamethasone 20/10 mg (cycles 1-4/5-8) on days 1, 2, 8, 9, 15, 16, 22, and 23. Patients who achieved at least stable disease subsequently received 24 cycles of lenalidomide extended dosing.

MAIN OUTCOMES AND MEASURES

Primary end points were neuropathy of grade 3 or greater (NDMM) and at least very good partial response rates (SMM). Minimal residual disease was also assessed.

RESULTS

Of 45 patients with NDMM, none had neuropathy of grade 3 or greater. Of 12 patients with high-risk SMM, the most common of any-grade adverse events were lymphopenia (12 [100%]) and gastrointestinal disorders (11 [92%]). All patients with SMM achieved at least a very good partial response during the study period. Among the 28 patients with NDMM and the 12 with SMM achieving at least a near-complete response, MRD negativity was found in 28 of 28 (100% [95% CI, 88%-100%]), 11 of 12 (92% [95% CI, 62%-100%]) (multiparametric flow cytometry), 14 of 21 (67% [95% CI, 43%-85%]), and 9 of 12 (75% [95% CI, 43%-94%]) (next-generation sequencing), respectively. In patients with NDMM, 12-month progression-free survival for MRD-negative vs MRD-positive status by flow cytometry and next-generation sequencing was 100% vs 79% (95% CI, 47%-94%; P < .001) and 100% vs 95% (95% CI, 75%-99%; P = .02), respectively.

CONCLUSIONS AND RELEVANCE

Carfilzomib-lenalidomide-dexamethasone therapy is tolerable and demonstrates high rates of MRD negativity in NDMM, translating into longer progression-free survival in patients achieving MRD negativity. Carfilzomib-lenalidomide-dexamethasone therapy also demonstrates efficacy in high-risk SMM.

Flow cytometry remission by Ig light chains ratio is a powerful marker of outcome in multiple myeloma after tandem autologous transplant: a real-life study

BACKGROUND

The achievement of complete response (CR) significantly correlates with a better clinical outcome in multiple myeloma (MM) patients treated with autologous stem cell transplant (ASCT). The depth of response is one of the most relevant factors to predict patient's outcome, however the definition of CR through standard criteria has shown several limitations.

METHODS

In this study we evaluated the minimal residual disease (MRD) in 50 consecutive MM patients who underwent an up-front tandem ASCT in our center, using a single-tube six-colors flow cytometry assay (FC) based on intra-cytoplasmic immunoglobulin (cy-Ig) light chains ratio evaluated on patient-specific plasma cells (PC) immune profile, in a real-life setting.

RESULTS

With a sensitivity up to 10(-5), clonal-PC were documented by FC in 36.4% (12/33) of patients in conventional CR after second transplant. The number of flow MRD-negative patients significantly increased after induction and first ASCT, but not between first and second transplant. The 5-years progression-free survival (5ys-PFS) of flow MRD-negative patients after second transplant was significantly better than patients who remained MRD-positive considering both all patients (5ys-PFS: 70% vs 5%) and patients in CR according to standard criteria (5ys-PFS: 67% vs 0%).

CONCLUSIONS

FC remission through cy-Ig light ratio on PC sub-populations is a sensitive, highly informative, low-cost and routinely applicable MRD assay, a powerful tool in treatment response evaluation and a crucial marker of outcome in MM.

Multiple myeloma: is it time for biomarker-driven therapy?

Remarkable strides have been made in understanding the molecular mechanisms by which multiple myeloma develops, leading to more sophisticated classification that incorporates not only the traditional diagnostic criteria, but also immunophenotype, genetic, and molecular features. However, even with this added information, considerable heterogeneity in clinical outcomes exists within the identified subtypes. The present paradigm for myeloma treatment is built on the basic step of defining transplant eligibility versus noneligibility, as determined by age, performance status, and cumulative burden of comorbidities. An incredibly complex heterogeneous disease is, therefore, treated in a generalized way with the result that large interpatient variability exists in the outcome. As antimyeloma therapeutics continue to expand it is becoming even more crucial to personalize treatment approaches that provide the most value to a specific patient. Development of biomarkers, either individually or as larger sets or patterns and ranging from analysis of blood or bone marrow to biomedical imaging, is a major focus in the field. Biomarkers such as involved serum free light chain ratio and MRI focal lesions have been implemented in the new definition of multiple myeloma and guide clinicians to initiate treatment in otherwise asymptomatic individuals. Currently, however, there is not enough evidence to support intensifying the treatment for high-risk disease or reducing the treatment for low-risk disease. Minimal residual disease-negative status is an important biomarker that holds promise for monitoring the effectiveness of response-adapted strategies. This article sheds light on the forward landscape and rear-mirror view of biomarkers in myeloma.

Accuracy of Bone Marrow Flow Cytometry Analysis in Patients With Plasma Cell Neoplasm in Thailand: A Single Institutional Study

BACKGROUND

Plasma cell neoplasm is a common hematologic malignancy. Treatment with novel agents results in favorable outcomes. Reliable investigations are required to monitor the residual disease, especially after such effective treatments. Flow cytometric analysis is a speedy and accurate method to detect abnormal cells. The aim of this study was to determine diagnostic performance of flow cytometry in the detection of abnormal plasma cells in bone marrow specimens.

MATERIALS AND METHODS

We included bone marrow samples taken from patients suspected to harbor plasma cell neoplasm at the time of diagnosis or follow-up after treatment from 2013 to 2015. Flow cytometric analyses, using cluster of differentiation (CD)19/CD20/CD27/CD38/CD45/CD56/CD117/CD138 and cytoplasmic κ/λ, were done and results compared with morphologic evaluation of marrow aspirate smear, histology, and immunohistochemistry of marrow biopsy and protein electrophoretic analyses.

RESULTS

A total of 154 specimens were included. Plasma cell neoplasm was detected in 56 samples (36.4%). Most abnormal plasma cells in this study were CD19-negative (CD19(-))/CD20(-)/CD27(+)/CD38(+)/CD45(-) (or weakly positive)/CD56(+)/CD117(+)/CD138(+). Light chain restriction was found only in 18 samples (32.1%). Sensitivity and specificity of flow cytometric analysis were 91.1% and 96.9%, respectively. For the follow-up cohort, sensitivity and specificity were 86.7% and 66.7%, respectively.

CONCLUSION

Analysis of plasma cell neoplasm using flow cytometry has high sensitivity and specificity. As an adjunct to marrow histology and immunohistochemistry, flow cytometry can be used in diagnosis of plasma cell neoplasm and more importantly in monitoring the disease after treatment. We propose a limited panel of CD19/CD38/CD45/CD56/CD117/CD138 for detecting minimal residual disease in Thai patients.

Is it possible to cure myeloma without allogeneic transplantation?

During the last decades, a better understanding of the biology of multiple myeloma (MM) has led to the application of novel treatment strategies for MM patients. The new anti-myeloma regimens produce higher incidence of durable and of better quality responses and they improve overall survival, challenging the dogma of incurable disease, outside the context of allogeneic transplantation. This review presents all these strategies that aim to cure MM, including continuous treatment i.e. induction, consolidation and maintenance, treatment of asymptomatic MM and monitoring minimal residual disease using modern techniques, such as multi-parameter flow cytometry, molecular assays and advanced imaging.

The Prevalence and Management of Multiple Myeloma-Induced Kidney Disease in China

BACKGROUND

Multiple myeloma (MM) is a clonal B-cell malignancy of the bone marrow. Renal impairment is a common complication of MM. So far, there is no systematic overview of MM-induced kidney disease in China.

SUMMARY

The incidence of MM is 0.6/100,000 in China. Twenty-four, 19.7, and 30.8% of all patients with MM had renal insufficiency [defined by serum creatinine (Scr) ≥2 mg/dl] at diagnosis in China mainland, Hong Kong and Taiwan, respectively. Novel criteria based on the estimated glomerular filtration rate measurements are recommended for the assessment of renal function in patients with MM with stabilized Scr. It is reported that 78% of the MM patients had a creatinine clearance rate (Ccr) <90 ml/min, and 30.5% had a Ccr <30 ml/min. The IgG type was the most prevalent in MM patients; the light-chain and IgD type usually had a higher rate of kidney damage than others. New more effective drugs, blood purification technology and peripheral blood autologous stem cell transplantation have been introduced in clinical practice. Unfortunately, the studies conducted in the patients with renal insufficiency were almost all retrospective, had a small sample size and a short follow-up time. Although new treatments such as bortezomib are more widely used than before, traditional chemotherapy is still used, also because of economic constraints. The RIFLE criteria, which seem to be appropriate to define the severity of acute kidney injury (AKI), have been extensively validated worldwide but rarely in patients with MM. It was the first time to apply the RIFLE system to analyze the natural history of MM patients with AKI retrospectively in our unit. The severity of AKI defined by using the RIFLE criteria (OR = 2.04, p = 0.06) was associated with a marginal better long-term outcome.

KEY MESSAGES

Novel criteria of renal insufficiency should be introduced into practice when treating MM. The treatment of MM patients with kidney disease has been greatly improved recently. It is necessary to conduct further large randomized controlled trials of the long-term outcome in China.

FACTS FROM EAST AND WEST

(1) An Scr level >2 mg/dl has been reported in 16, 21, 24, and 33% of patients with MM in cohort studies of Japan, Europe, China, and Korea, respectively. A Ccr <30 ml/min was observed in 30 and 15% of patients in Chinese and Western MM cohorts, respectively. The commonest cause of severe renal impairment (RI) in patients with MM is myeloma cast nephropathy. (2) The efficacy of novel treatments (bortezomib, carfilzomib, thalidomide, and lenalidomide) has predominantly been assessed in Western patients. Bortezomib and dexamethasone are the current standard of care for MM and severe RI in the West. Severe RI is not a contraindication to autologous stem cell transplantation (ASCT). Most of the data are from the West; there are case reports from China describing good outcomes with ASCT. The removal of free light chain by high cutoff hemodialysis is under evaluation in randomized controlled trials (RCTs) in the West. Studies in this area are not yet conducted in China. In China, new treatments, such as bortezomib, are more widely used than before and favorable results are being reported; however, RCT studies are still needed in this area to confirm the efficacy and safety of this and other novel treatments.

Prognostic impact of immunophenotypic complete response in patients with multiple myeloma achieving better than complete response

To investigate the impact of immunophenotypic complete response [iCR, ≤10(-4) multiple myeloma (MM) cells defined by multicolor flow cytometry (MFC)] on survival in patients with MM, we retrospectively analyzed 78 patients that obtained conventional CR at our hospital. Survivals were landmarked at achievement of CR. The rate of stringent CR (sCR) among patients with CR was 88%, and iCR for CR and sCR patients were 44% and 49%, respectively. Achievement of iCR was associated with significantly longer disease-free survival (DFS) not only in CR patients (p = 0.009) but also in sCR patients (p = 0.002), while sCR attainment per se did not have statistically significant impact on DFS (p = 0.06) or overall survival (OS) (p = 0.587). Univariate and multivariate analyses indicated that attainment of iCR was independently associated with longer 2-year DFS in addition to creatinine (≤2.0 mg/dL) and maintenance therapy. This study highlights the importance of pursuing iCR even in patients with sCR.

A CD138-independent strategy to detect minimal residual disease and circulating tumour cells in multiple myeloma

CD138 (also termed SDC1) has been the gold-standard surface marker to detect multiple myeloma (MM) cells for decades; however, drug-resistant residual and circulating MM cells were shown to have lower expression of this marker. In this study, we have shown that residual MM cells following bortezomib treatment are hypoxic. This combination of drug exposure and hypoxia down-regulates their CD138 expression, thereby making this marker unsuitable for detecting residual or other hypoxic MM cells, such as circulating tumour cells, in MM. Hence, we developed an alternative biomarker set which detects myeloma cells independent of their hypoxic and CD138 expression status in vitro, in vivo and in primary MM patients. The new markers were able to identify a clonal CD138-negative population as minimal residual disease in the bone marrow and peripheral blood of MM patients. Further investigation to characterize the role of this population as a prognostic marker in MM is warranted.

Minimal Residual Disease by Next-Generation Sequencing: Pros and Cons

The wealth of data recently generated highlights that minimal residual disease (MRD)-negative status can be achieved in a large proportion of patients. These studies, in addition to a meta-analysis, clearly suggest significant improvement in both event-free survival (EFS) and overall survival (OS) among those patients achieving MRD-negative status, especially with sensitivity of one cell in 1 million bone marrow cells. There is an evolving consensus that achieving MRD-negative status should become the ultimate goal of therapeutic intervention. Further future efforts should now be directed at determining how MRD status can be used to guide and personalize further therapy including type of consolidation and maintenance therapy.

Multiple Myeloma Minimal Residual Disease

Assessment of minimal residual disease (MRD) is becoming standard diagnostic care for potentially curable neoplasms such as some acute leukemias as well as chronic myeloid and lymphocytic leukemia. Although multiple myeloma (MM) remains as an incurable disease, around half of the patients achieve complete remission (CR), and recent data suggests increasing rates of curability with "total-therapy-like" programs. This landscape is likely to be improved with the advent of new antibodies and small molecules. Therefore, conventional serological and morphological techniques have become suboptimal for sensitive evaluation of highly effective treatment strategies. Although, existing data suggests that MRD could be used as a biomarker to evaluate treatment efficacy, help on therapeutic decisions, and act as surrogate for overall survival, the role of MRD in MM is still a matter of extensive debate. Here, we review the different levels of remission used to define depth of response in MM and their clinical significance, as well as the prognostic value and unique characteristics of MRD detection using immunophenotypic, molecular, and imaging techniques. Key facts The higher efficacy of new treatment strategies for MM demand the incorporation of highly sensitive techniques to monitor treatment efficacy MRD could be used as a more potent surrogate biomarker for survival than standard CR We need to understand the pros and cons of the different MRD techniques The time has come to incorporate highly sensitive, cost-effective, readily available, and standardized MRD techniques into clinical trials to assess its role in therapeutic decisions.

Better therapy requires better response evaluation: Paving the way for minimal residual disease testing for every myeloma patient

In 2015, there is a large body of evidence demonstrating that minimal residual disease (MRD) negativity after therapy is a powerful predictor of progression-free survival and overall survival in multiple myeloma. On the basis of available data, we believe MRD provides a meaningful endpoint for regulatory purposes, academic studies, and a valuable prognostic evaluation of individual patients in the clinical setting. Similar to what has been shown in acute and chronic lymphocytic leukemia, based on emerging data, the prognostic impact of MRD in multiple myeloma appears to be independent of induction therapy received. This fact raises fundamental questions regarding best possible treatment strategies (e.g., fixed number of cycles versus response adapted number of cycles) as well as optimal treatment modalities (e.g., newer effective but less intense combination therapies versus high dose melphalan followed by autologous stem cell transplantation), in particular for patients newly diagnosed with multiple myeloma.

Measuring disease levels in myeloma using flow cytometry in combination with other laboratory techniques: Lessons from the past 20 years at the Leeds Haematological Malignancy Diagnostic Service

People with myeloma who obtain a good response to treatment have a better survival if sensitive molecular or flow-cytometric techniques show no detectable minimal residual disease (MRD). The application of MRD techniques to clinical trials is now considered to be increasingly important because treatment approaches are sufficiently effective that using survival outcomes is slowing down the identification of the best new treatments. The articles in this issue consider the laboratory requirements for harmonization of MRD analysis by flow cytometry but there are practical considerations that are also important in implementing a myeloma MRD assay in the cytometry laboratory. In particular, it is important to consider when to request, and how best to utilize, a bone marrow aspirate sample because the procedure is invasive and the cells obtained are valuable for a number of different investigations. This brief article considers some experience obtained over two decades of implementing a service for MRD detection, initially as a scientific bolt-on to clinical trials through to a routine clinical diagnostic assay.

Deep Response in Multiple Myeloma: A Critical Review

Novel and more effective treatment strategies against multiple myeloma (MM) have significantly prolonged patients' survival and raised interest in the depth of response and its association with clinical outcome. Minimal residual disease (MRD) has emerged as one of the most relevant prognostic factors in MM and should be included in a new definition of complete response (CR). Although further standardization is still required, MRD monitoring should be applied in prospective clinical trials as a sensitive tool to compare and evaluate the efficacy of different treatment strategies, particularly in the consolidation and maintenance settings, and implement individualized therapy-monitoring approaches. Here, we review current definition of deep response in MM, advantages and limitations of current MRD assessment assays, clinical evidences for MRD monitoring as a prognostic tool for therapeutic decisions in MM, and challenges to develop uniform criteria for MRD monitoring.

Clinical efficacy and management of monoclonal antibodies targeting CD38 and SLAMF7 in multiple myeloma

Immunotherapeutic strategies are emerging as promising therapeutic approaches in multiple myeloma (MM), with several monoclonal antibodies in advanced stages of clinical development. Of these agents, CD38-targeting antibodies have marked single agent activity in extensively pretreated MM, and preliminary results from studies with relapsed/refractory patients have shown enhanced therapeutic efficacy when daratumumab and isatuximab are combined with other agents. Furthermore, although elotuzumab (anti-SLAMF7) has no single agent activity in advanced MM, randomized trials in relapsed/refractory MM have demonstrated significantly improved progression-free survival when elotuzumab is added to lenalidomide-dexamethasone or bortezomib-dexamethasone. Importantly, there has been no significant additive toxicity when these monoclonal antibodies are combined with other anti-MM agents, other than infusion-related reactions specific to the therapeutic antibody. Prevention and management of infusion reactions is important to avoid drug discontinuation, which may in turn lead to reduced efficacy of anti-MM therapy. Therapeutic antibodies interfere with several laboratory tests. First, interference of therapeutic antibodies with immunofixation and serum protein electrophoresis assays may lead to underestimation of complete response. Strategies to mitigate interference, based on shifting the therapeutic antibody band, are in development. Furthermore, daratumumab, and probably also other CD38-targeting antibodies, interfere with blood compatibility testing and thereby complicate the safe release of blood products. Neutralization of the therapeutic CD38 antibody or CD38 denaturation on reagent red blood cells mitigates daratumumab interference with transfusion laboratory serologic tests. Finally, therapeutic antibodies may complicate flow cytometric evaluation of normal and neoplastic plasma cells, since the therapeutic antibody can affect the availability of the epitope for binding of commercially available diagnostic antibodies.

Clonotypic Light Chain Peptides Identified for Monitoring Minimal Residual Disease in Multiple Myeloma without Bone Marrow Aspiration

BACKGROUND

Analytically sensitive techniques for measuring minimal residual disease (MRD) in multiple myeloma (MM) currently require invasive and costly bone marrow aspiration. These methods include immunohistochemistry (IHC), flow cytometry, quantitative PCR, and next-generation sequencing. An ideal MM MRD test would be a serum-based test sensitive enough to detect low concentrations of Ig secreted from multifocal lesions.

METHODS

Patient serum with abundant M-protein before treatment was separated on a 1-dimensional SDS-PAGE gel, and the Ig light-chain (LC) band was excised, trypsin digested, and analyzed on a Q Exactive mass spectrometer by LC-MS/MS. We used the peptide's abundance and sequence to identify tryptic peptides that mapped to complementary determining regions of Ig LCs. The clonotypic target tryptic peptides were used to monitor MRD in subsequent serum samples with prior affinity enrichment.

RESULTS

Sixty-two patients were tested, 20 with no detectable disease by IHC and 42 with no detectable disease by 6-color flow cytometry. A target peptide that could be monitored was identified in 57 patients (91%). Of these 57, detectable disease by LC-MS/MS was found in 52 (91%).

CONCLUSIONS

The ability to use LC-MS/MS to measure disease in patients who are negative by bone marrow-based methodologies indicates that a serum-based approach has more analytical sensitivity and may be useful for measuring deeper responses to MM treatment. The method requires no bone marrow aspiration.

Assessment of minimal residual disease in myeloma and the need for a consensus approach

Treatment options for myeloma continue to develop at a rapid pace, and it is becoming increasingly challenging to determine the optimal therapeutic approaches because demonstrating a clear survival benefit now requires many years of follow-up. The detection of minimal residual disease (MRD) is recognized as a sensitive and rapid approach to evaluate treatment efficacy that predicts progression-free and overall survival independent of categorical response assessment and patients' biology. The benefit of MRD analysis is reflected in the many different techniques (multiparameter flow cytometry, quantitative polymerase chain reaction, and high-throughput sequencing) and collaborative groups (including EMN, ESCCA, ICCS, EuroFlow, and EuroMRD) that have performed collaborative projects to harmonize quantitative MRD detection. The time has come to adopt a consensus approach, and this report reviews the benefits and disadvantages of different strategies for MRD detection in myeloma and highlights the requirements for a sensitive, reproducible, and clinically meaningful cellular analytical approach.

Flow cytometry quality requirements for monitoring of minimal disease in plasma cell myeloma

Current therapeutic approaches for plasma cell myeloma (PCM) attain an overall survival of more than 6 years for the majority of newly diagnosed patients. However, PFS and OS are the only accepted FDA clinical endpoints for demonstrating drug efficacy before they can be become frontline therapeutic options. There is, however, recognition that the increasing gap between drug development and approval for mainstream therapeutic use needs to be shortened. As such regulatory bodies such as the FDA are now considering whether biomarker response evaluation, as in measurement of minimal residual disease (MRD) as assessed by flow cytometry (FC), can provide an early, robust prediction of survival and therefore improve the drug approval process. Recently, FC MRD using a standardized eight-color antibody methodology has been shown to have a minimum sensitivity of 0.01% and an upper sensitivity of 0.001%. To ensure that all laboratories using this approach achieve the same levels of sensitivity it is crucially important to have standardized quality management procedures in place. This manuscript accompanies those published in this special issue and describes the minimum that is required for validating and quality monitoring of this highly specific test to ensure any laboratory, irrespective of location, will achieve the expected quality standards required.

Detection of minimal residual disease in B lymphoblastic leukemia using viSNE

BACKGROUND

Minimal residual disease (MRD) following treatment is a robust prognostic marker in B lymphoblastic leukemia. However, the detection of MRD by flow cytometric immunophenotyping is technically challenging, and an automated method to detect MRD is therefore desirable. viSNE, a recently developed computational tool based on the t-Distributed Stochastic Neighbor Embedding (t-SNE) algorithm, has been shown to be capable of detecting synthetic "MRD-like" populations of leukemic cells created in vitro, but whether viSNE can facilitate the immunophenotypic detection of MRD in clinical samples has not been evaluated.

METHODS

We applied viSNE retrospectively to 8-color flow cytometric immunophenotyping data from normal bone marrow samples, and samples from B lymphoblastic leukemia patients with or without suspected MRD on the basis of conventional manual gating.

RESULTS

In each of 14 bone marrow specimens containing MRD or suspected MRD, viSNE identified a putative MRD population; an abnormal composite immunophenotype was confirmed for the putative MRD in each case. MRD populations were not identified by viSNE in control bone marrow samples from patients with increased normal B-cell precursors, or in post-treatment samples from B lymphoblastic leukemia patients who did not have detectable MRD by manual gating.

CONCLUSION

viSNE shows promise as an automated method to facilitate immunophenotypic MRD detection in patients treated for B lymphoblastic leukemia.

The road to treating smoldering multiple myeloma

The management of smoldering multiple myeloma (SMM) has been a challenge to clinicians, ever since the condition was first characterized in 1980. While the risk of progression to symptomatic myeloma is greater for SMM (10% per year) compared to MGUS (1% per year), several SMM patients remain asymptomatic for years without evidence of disease progression. Early clinical trials focusing on early treatment of SMM have been equivocal with no clear benefit. However, the last decade has seen a greater understanding of the pathogenesis of plasma cell disorders, including SMM, and development of better therapeutics. A recent randomized trial has provided evidence of clinical benefit with early treatment of high-risk SMM. In this review, we summarize issues related to the early treatment of SMM including risk stratification and possible outcomes with therapy initiation. In the context of reviewing recent clinical trial data supporting early treatment, we define challenges faced by clinicians and provide future directions to the road to treating SMM.

Immunophenotype of normal vs. myeloma plasma cells: Toward antibody panel specifications for MRD detection in multiple myeloma

In recent years, several studies on large series of multiple myeloma (MM) patients have demonstrated the clinical utility of flow cytometry monitoring of minimal residual disease (flow-MRD) in bone marrow (BM), for improved assessment of response to therapy and prognostication. However, disturbing levels of variability exist regarding the specific protocols and antibody panels used in individual laboratories. Overall, consensus exists about the utility of combined assessment of CD38 and CD138 for the identification of BM plasma cells (PC); in contrast, more heterogeneous lists of markers are used to further distinguish between normal/reactive PCs and myeloma PCs in the MRD settings. Among the later markers, CD19, CD45, CD27, and CD81, together with CD56, CD117, CD200, and CD307, have emerged as particularly informative; however, no single marker provides enough specificity for clear discrimination between clonal PCs and normal PCs. Accordingly, multivariate analyses of single PCs from large series of normal/reactive vs. myeloma BM samples have shown that combined assessment of CD138 and CD38, together with CD45, CD19, CD56, CD27, CD81, and CD117 would be ideally suited for MRD monitoring in virtually every MM patient. However, the specific antibody clones, fluorochrome conjugates and sources of the individual markers determines its optimal (vs. suboptimal or poor) performance in an eight-color staining. Assessment of clonality, via additional cytoplasmic immunoglobulin (CyIg) κ vs. CyIgλ evaluation, may contribute to further establish the normal/reactive vs. clonal nature of small suspicious PC populations at high sensitivity levels, provided that enough cells are evaluated.

Autologous haematopoietic cell transplantation in elderly patients with multiple myeloma

High-dose chemotherapy with melphalan followed by autologous haematopoietic cell transplantation (AHCT) is a standard of care in young patients (<65 years) with multiple myeloma. Most myeloma patients, however, are older than 65 years at the time of diagnosis, and the findings of numerous single-centre and registry studies provide evidence that AHCT can be a feasible and effective treatment option in these patients. Nevertheless, AHCT is not generally recommended as standard treatment in the elderly, due to the fact that a benefit of AHCT over conventional-dose therapy has not been demonstrated by prospective randomized trials. Yet, the use of AHCT has increased substantially in older patients in recent years, and an increasing number of reports suggest comparable outcomes for older and younger patients after AHCT. In this review we summarize the results of AHCT for elderly patients with multiple myeloma.

Regulatory perspective on minimal residual disease flow cytometry testing in multiple myeloma

The FDA has co-sponsored three workshops to address minimal residual disease (MRD) detection in acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), and acute myeloid leukemia (AML) as well as an FDA-NCI roundtable symposium on MRD detection and its use as a response biomarker in Multiple Myeloma (MM). As clinical outcomes in MM continue to improve with the introduction of new therapeutics, consideration of biomarkers and their development as validated surrogate endpoints that can be used in the place of traditional clinical trial endpoints of progression-free survival (PFS) will be fundamental to expeditious drug development. This article will describe the FDA drug approval process, the regulatory framework through which a biomarker can be used as a surrogate endpoint for drug approval, and how MRD detection in MM fits within this context. In parallel, this article will also describe the FDA current device clearance process with emphasis on the analytical development as it might apply to an in vitro diagnostic assay for the detection of MRD in MM. It is anticipated that this Special Issue may possibly represent how MRD might serve as a drug development tool in hematological malignancies.

Bortezomib, thalidomide and dexamethasone, with or without cyclophosphamide, for patients with previously untreated multiple myeloma: 5-year follow-up

This follow-up extension of a randomised phase II study assessed differences in long-term outcomes between bortezomib-thalidomide-dexamethasone (VTD) and VTD-cyclophosphamide (VTDC) induction therapy in multiple myeloma. Newly diagnosed patients (n = 98) were randomised 1:1 to intravenous bortezomib (1·3 mg/m(2); days 1, 4, 8, 11), thalidomide (100 mg; days 1-21), and dexamethasone (40 mg; days 1-4, 9-12), with/without cyclophosphamide (400 mg/m(2); days 1, 8), for four 21-day cycles before stem-cell mobilisation/transplantation. After a median follow-up of 64·8 months, median time-to-next therapy was 51·8 and 47·9 months with VTD and VTDC, respectively. Type of subsequent therapy was similar in both arms. After adjusting for asymmetric censoring, median time to progression was not significantly different between VTD and VTDC [35·7 vs. 34·5 months; Hazard ratio (HR) 1·26, 95% confidence interval: 0·76-2·09; P = 0·370]. Five-year survival was 69·1% and 65·3% with VTD and VTDC, respectively. When analysed by minimal residual disease (MRD) status, overall survival was longer in MRD-negative versus MRD-positive patients with bone marrow-confirmed complete response (HR 3·66, P = 0·0318). VTD induction followed by transplantation provides long-term disease control and, consistent with the primary analysis, there is no additional benefit from adding cyclophosphamide. This study was registered at ClinicalTrials.gov (NCT00531453).

Cancer-testis antigen SLLP1 represents a promising target for the immunotherapy of multiple myeloma

Background

Most patients with multiple myeloma (MM) will relapse after an initial response and eventually succumb to their disease. This is due to the persistence of chemotherapy-resistant tumor cells in the patients’ bone marrow (BM) and immunotherapeutic approaches could contribute to eradicating these remaining cells. We evaluated SLLP1 as a potential immunotherapeutic target for MM.

Methods

We determined SLLP1 expression in myeloma cell lines and 394 BM samples from myeloma patients (n = 177) and BM samples from healthy donors (n = 11). 896 blood samples and 64 BM samples from myeloma patients (n = 263) and blood from healthy donors (n = 112) were analyzed for anti-SLLP1 antibodies. Seropositive patients were evaluated regarding SLLP1-specific T cells.

Results

Most cell lines showed SLLP1 RNA and protein expression while it was absent from normal BM. Of 177 patients 41% evidenced SLLP1 expression at least once during the course of their disease and 44% of newly diagnosed patients were SLLP1-positive. Expression of SLLP1 was associated with adverse cytogenetics and with negative prognostic factors including the patient’s age, number of BM-infiltrating plasma cells, serum albumin, β₂-microglobulin, creatinine, and hemoglobin. Among patients treated with allogeneic stem cell transplantation those with SLLP1 expression showed a trend towards a reduced overall survival. Spontaneous anti-SLLP humoral immunity was detectable in 9.5% of patients but none of the seropositive patients evidenced SLLP1-specific T cells. However, antigen-specific T cells could readily be induced in vitro after stimulation with SLLP1.

Conclusions

SLLP1 represents a promising target for the immunotherapy of MM, in particular for the adoptive transfer of T cell receptor-transduced T cells.