Impact of minimal residual negativity using next generation flow cytometry on outcomes in light chain amyloidosis

Autologous stem cell transplantation in AL amyloidosis: Muddy waters

Immunoglobulin light chain (AL) amyloidosis is a malignant plasma cell dyscrasia causing multi-organ morbidity. High dose melphalan and autologous stem cell transplantation (ASCT) is a preferred consolidation approach and is safe with improved patient selection criteria. With the advent of bortezomib and daratumumab based induction therapy, nearly all patients can achieve deep hematological responses but follow up for daratumumab based induction is short. Consequently, the traditional approach of induction followed by ASCT is called into question. Given the multi-organ involvement of AL, endpoints beyond depth of response and hematological progression free survival (PFS) are important. Major organ dysfunction PFS (MOD-PFS) adds to PFS and is a composite endpoint of PFS, renal and cardiac organ progression, and overall survival. It is currently unknown which consolidative approach (ASCT or non-ASCT) will generate improved outcomes across the MOD-PFS spectrum a question the recently opened S2213 trial will attempt to answer.

HOVON 104, long-term follow-up of bortezomib-dexamethasone induction therapy followed by autologous stem cell transplantation in newly diagnosed AL amyloidosis patients

The HOVON 104 studied bortezomib-dexamethasone induction therapy and autologous stem cell transplantation in 50 patients, of whom 35 received an autologous stem cell transplantation (ASCT). We demonstrate a 5-year overall survival (OS) of 73% and progression-free survival (PFS) of 52% for all 50 patients with a median follow-up of 61.3 months. For the 35 transplanted patients, calculated from the date of ASCT, the 5-year OS and PFS were 91% and 68%, respectively. After ASCT, the rate of organ response improved over time but stabilized around 3 years. A complete cardiac response was seen in around 60% of patients and remained stable from 2 years onward. Reaching complete renal response was slower over time and achieved by 61% of the renal-affected patients at 5 years. We confirm the excellent outcomes after ASCT and demonstrate a 60% complete organ response with longer follow-up.

A bibliometric analysis of light chain amyloidosis from 2005 to 2024: research trends and hot spots

Background

Light chain (AL) amyloidosis stands as the most prevalent subtype of systemic amyloidosis, encompassing a group of rare diseases. Here, we evaluated the scientific landscape of AL amyloidosis to investigate research trends and identify hotspots within the field.

Methods

Relevant studies on AL amyloidosis published over the past two decades were retrieved from the Web of Science Core Collection. The publications between 2005 and 2024 were subjected to bibliometric analyses, leveraging tools including CiteSpace, VOSviewer, RStudio and MS Excel to analyse and visualize the annual publication trend, co-occurrence patterns, collaborative networks among countries, organizations, and authors. Burst keywords and references were also examined to obtain the research history, and emerging hotspots.

Results

The bibliometric analysis included 2,864 articles published between 2005 and 2024. The most productive journal is Amyloid-Journal of Protein Folding Disorders. The United States, along with several developed nations, emerges as a dominant force in international AL amyloidosis research. "AL amyloidosis" and "cardiac amyloidosis" were the primary hotspots over the past two decades, and "Biomarkers," "Cardiac amyloidosis," and "treatment" would be future trends.

Conclusion

This bibliometric analysis examined the research developments in AL amyloidosis over the past two decades using bibliometric software. Recent research in this field primarily focuses on two main areas: clinical diagnosis and treatment of AL amyloidosis, as well as cardiac amyloidosis. Emphasis is placed on understanding the mechanisms underlying immunoglobulin light chain aggregation and deposition to mitigate organ involvement.

Role of Autologous Stem Cell Transplantation in Systemic Light Chain Amyloidosis

Systemic light chain (AL) amyloidosis is a multisystem disorder characterized by extracellular deposition of misfolded insoluble amyloid fibrils resulting in progressive organ dysfunction. AL. amyloidosis most commonly affects the heart, kidneys, gastrointestinal tract and peripheral nerves. Early mortality is chiefly determined by the degree of cardiac involvement. The aim of therapy is to rapidly reduce amyloidogenic light chain production by targeting the underlying clonal plasma or lymphoma cell population. High dose therapy with melphalan followed by autologous peripheral blood stem cell transplant (ASCT) continues to remain a highly effective treatment and is considered a standard of care for transplant eligible patients, which offers long term disease control in patients with AL amyloidosis. In recent years, several new therapeutic options have emerged (including anti-CD38 monoclonal antibodies) which are very effective alone or in combination in eradicating clonal plasma cells. In this review, we discuss the role of ASCT in the current setting of a rapidly evolving treatment landscape for patients with AL amyloidosis and provide our practice recommendations.

Minimal residual disease in systemic light chain amyloidosis: a systematic review and meta-analysis

PURPOSE

Minimal residual disease (MRD) is a validated prognostic factor in several hematological malignancies. However, its role in systemic light chain (AL) amyloidosis remains controversial, and this systematic review and meta-analysis aims to fill this gap.

METHODS

We searched for relevant studies on Pubmed, Embase, and Cochrane Controlled Register of Trials, nine studies involving 451 patients were included and meta-analyzed. This systematic review has been registered in PROSPERO (CRD42023494169).

RESULTS

Our study found that in the group of patients who achieved very good partial response (VGPR) or better, MRD negativity was correlated with higher cardiac and renal response rates [pooled risk ratio (RR) = 0.74 (95% CI 0.62-0.89), 0.74 (95% CI 0.64-0.87), respectively]. Patients with MRD positivity had a higher hematologic progression rate within two years after MRD detection [pooled RR = 10.31 (95% CI 2.02-52.68)]; and a higher risk of hematologic + organ progression in the first year [pooled RR = 12.57 (95% CI 1.73-91.04)]. Moreover, MRD negativity was correlated with a better progression-free survival (PFS) [pooled hazard ratio (HR) = 0.27 (95% CI 0.17-0.45)]; but it did not significantly improve the overall survival (OS) [pooled HR = 0.34 (95% CI 0.11-1.07)].

CONCLUSION

In AL amyloidosis, our study supports that MRD negativity correlates with higher cardiac or renal response rates and indicates a better PFS in the follow-up. However, the correlation between OS and the status of MRD is not significant.

Systemic Amyloidosis and Kidney Transplantation: An Update

Amyloidosis is a heterogeneous disorder characterized by abnormal protein aggregate deposition that often leads to kidney involvement and end-stage kidney disease. With advancements in diagnostic techniques and treatment options, the prevalence of patients with amyloidosis requiring chronic dialysis has increased. Kidney transplantation is a promising avenue for extending survival and enhancing quality of life in these patients. However, the complex and heterogeneous nature of amyloidosis presents challenges in determining optimal referral timing for transplantation and managing post-transplantation course. This review focuses on recent developments and outcomes of kidney transplantation for amyloidosis-related end-stage kidney disease. This review also aims to guide clinical decision-making and improve management of patients with amyloidosis-associated kidney disease, offering insights into optimizing patient selection and post-transplant care for favorable outcomes.

AL amyloidosis: Singapore Myeloma Study Group consensus guidelines on diagnosis, treatment and management

AL amyloidosis is the most common form of systemic amyloidosis. However, the non-specific nature of presenting symptoms requires the need for a heightened clinical suspicion to detect unexplained manifestations in the appropriate clinical setting. Early detection and treatment are crucial as the degree of cardiac involvement emerges as a primary prognostic predictor of survival in a patient with AL amyloidosis. Following the diagnosis of AL amyloidosis with appropriate tissue biopsies, prompt treatment with a bortezomib, cyclophosphamide and dexamethasone-based first-line induction with or without daratumumab should be initiated. The goal of treatment is to achieve the best haematologic response possible, ideally with involved free light chain <20 mg/L, as it offers the best chance of organ function improvement. Treatment should be changed if patients do not achieve a partial response within 2 cycles of treatment or very good partial response after 4 cycles or after autologous stem cell transplant, as achievement of profound and prolonged clonal responses translates to better organ response and long-term outcomes. Early involvement of multidisciplinary subspecialists such as renal physicians, cardiologists, neurologists, and gastroenterologists for optimal maintenance and support of involved organs is recommended for optimal management of patients with AL amyloidosis.

Graded Cardiac Response Criteria for Patients With Systemic Light Chain Amyloidosis

PURPOSE

Binary cardiac response assessment using cardiac biomarkers is prognostic in light chain amyloidosis. Previous studies suggested four-level cardiac responses using N-terminal prohormone of brain natiuretic peptide improves prognostic prediction. This study was designed to validate graded cardiac response criteria using N-terminal prohormone of brain natiuretic peptide/brain natiuretic peptide.

PATIENTS AND METHODS

This retrospective, multicenter study included patients with light chain amyloidosis who achieved at least a hematologic partial response (PR) and were evaluable for cardiac response. Four response criteria were tested on the basis of natriuretic peptide response depth: cardiac complete response (CarCR), cardiac very good partial response (CarVGPR), cardiac PR (CarPR), and cardiac no response (CarNR). Response was classified as best response and at fixed time points (6, 12, and 24 months from therapy initiation). The study primary outcome was overall survival.

RESULTS

651 patients were included. Best CarCR, CarVGPR, CarPR, and CarNR were achieved in 16%, 26.4%, 22.9%, and 34.7% of patients, respectively. Patients in cardiac stage II were more likely to achieve CarCR than patients in cardiac stage IIIA and IIIB (22% v 13.5% v 3.2%; P < .001). A deeper cardiac response was associated with a longer survival (5-year overall survival 93%, 79%, 65%, and 33% for CarCR, CarVGPR, CarPR, and CarNR, respectively; P < .001). Fixed time-point analyses and time-varying covariates Cox regression analysis, to minimize survivorship bias, affirmed the independent survival advantage of deeper cardiac responses. Four-level response performed better than two-level response as early as 12 months from therapy initiation.

CONCLUSION

Graded cardiac response criteria allow better assessment of cardiac improvement compared with the traditional binary response system. The study re-emphasizes the importance of early diagnosis, which increases the likelihood of deep cardiac responses.

Bad players in AL amyloidosis in the current era of treatment

INTRODUCTION

Systemic AL amyloidosis (ALA) is a clonal plasma cell (PC) disease characterized by deposition of amyloid fibrils in different organs and tissues. Traditionally, the prognosis of ALA is poor and is primarily defined by cardiac involvement. The modern prognostic models are based on cardiac markers and free light chain difference (dFLC). Cardiac biomarkers have low specificity and are dependent on renal function, volume status, and cardiac diseases other than ALA. New therapies significantly improved the prognosis of the disease. The advancements in technologies - cardiac echocardiography (ECHO) and cardiac MRI (CMR), as well as new biological markers, relying on cardiac injury, inflammation, endothelial damage, and clonal and non-clonal PC markers are promising.

AREAS COVERED

An update on the prognostic significance of cardiac ALA, number of involved organs, response to treatment, including minimal residual disease (MRD), ECHO, MRI, and new biological markers will be discussed. The literature search was done in PubMed and Google Scholar, and the most recent and relevant data are included.

EXPERT OPINION

Prospective multicenter trials, evaluating multiple clinical and laboratory parameters, should be done to improve the risk assessment models in ALA in the modern era of therapy.

IgM-Related Immunoglobulin Light Chain (AL) Amyloidosis

Waldenström macroglobulinemia (WM) is a rare lymphoplasmacytic disorder characterized by an IgM paraprotein. The clinical presentation of WM varies and can include common manifestations such as anemia and hyperviscosity, in addition to less common features such as cryoglobulinemia, IgM-related neuropathy, and immunoglobulin light chain (AL) amyloidosis. Amyloidosis is a protein-folding disorder in which vital organ damage occurs due to the accumulation of misfolded protein aggregates. The most common type of amyloidosis in patients with an IgM paraprotein is AL amyloidosis, although other types of amyloidosis may occur. IgM-related amyloidosis has distinct clinical features when compared with other subtypes of AL amyloidosis. This review highlights the diagnostic criteria of IgM-related AL amyloidosis, as well as the clinical characteristics and treatment options for this disorder.

The potential role of mass spectrometry for the identification and monitoring of patients with plasma cell disorders: Where are we now and which questions remain unanswered?

Mass spectrometry (MS) techniques provide a highly sensitive methodology for the assessment and monitoring of paraproteins compared to standard electrophoretic techniques. The International Myeloma Working Group (IMWG) recently approved the use of intact light chain matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in lieu of immunofixation in the clinical assessment of patients and the assessment of patients enrolled on clinical trials. The increased sensitivity of these assays may help to detect and monitor monoclonal proteins (MP) in many patients with previously non-measurable disease, will reduce complete response (CR) rates and increase detection of low-level MP. The ability to track the unique mass or amino acid sequence of the MP also eliminates interference from therapeutic monoclonal antibodies (tmAbs) in most patients with IgG kappa myeloma. The intact light chain assays also provide structural information about the monoclonal light chain, including the presence of N-linked glycosylation, which has been shown to be commoner on amyloidogenic light chains and may have prognostic significance in monoclonal gammopathy of undetermined significance (MGUS). In this review, we discuss these issues alongside differences in the analytical and practical aspects related to the different MS assays under development and the challenges for MS.

Biomarkers in AL Amyloidosis

Systemic AL amyloidosis is a rare complex hematological disorder caused by clonal plasma cells which produce amyloidogenic immunoglobulins. Outcome and prognosis is the combinatory result of the extent and pattern of organ involvement secondary to amyloid fibril deposition and the biology and burden of the underlying plasma cell clone. Prognosis, as assessed by overall survival, and early outcomes is determined by degree of cardiac dysfunction and current staging systems are based on biomarkers that reflect the degree of cardiac damage. The risk of progression to end-stage renal disease requiring dialysis is assessed by renal staging systems. Longer-term survival and response to treatment is affected by markers of the underlying plasma cell clone; the genetic background of the clonal disease as evaluated by interphase fluorescence in situ hybridization in particular has predictive value and may guide treatment selection. Free light chain assessment forms the basis of hematological response criteria and minimal residual disease as assessed by sensitive methods is gradually being incorporated into clinical practice. However, sensitive biomarkers that could aid in the early diagnosis and that could reflect all aspects of organ damage and disease biology are needed and efforts to identify them are continuous.

Future Perspectives

Opportunities and challenges in the field of systemic amyloidosis can be grouped into 4 categories. First, a deeper understanding of the pathogenesis of the disease is required. Second, a greater awareness of the disease, which will lead to an earlier diagnosis, is imperative. Third, end points for interventional trials are required to convey us to our fourth aspirations, which are novel therapies for patients with light chain amyloidosis.

Acquired and inherited amyloidosis: Knowledge driving patients' care

Until recently, systemic amyloidoses were regarded as ineluctably disabling and life-threatening diseases. However, this field has witnessed major advances in the last decade, with significant improvements in therapeutic options and in the availability of accurate and non-invasive diagnostic tools. Outstanding progress includes unprecedented hematological response rates provided by risk-adapted regimens in light chain (AL) amyloidosis and the approval of innovative pharmacological agents for both hereditary and wild-type transthyretin amyloidosis (ATTR). Moreover, the incidence of secondary (AA) amyloidosis has continuously reduced, reflecting advances in therapeutics and overall management of several chronic inflammatory diseases. The identification and validation of novel therapeutic targets has grounded on a better knowledge of key molecular events underlying protein misfolding and aggregation and on the increasing availability of diagnostic, prognostic and predictive markers of organ damage and response to treatment. In this review, we focus on these recent advancements and discuss how they are translating into improved outcomes. Neurological involvement dominates the clinical picture in transthyretin and gelsolin inherited amyloidosis and has a significant impact on disease course and management in all patients. Neurologists, therefore, play a major role in improving patients' journey to diagnosis and in providing early access to treatment in order to prevent significant disability and extend survival.

Treatment of AL Amyloidosis: Mayo Stratification of Myeloma and Risk-Adapted Therapy (mSMART) Consensus Statement 2020 Update

Immunoglobulin light chain (AL) amyloidosis is a clonal plasma cell disorder leading to progressive and life-threatening organ failure. The heart and the kidneys are the most commonly involved organs, but almost any organ can be involved. Because of the nonspecific presentation, diagnosis delay is common, and many patients are diagnosed with advanced organ failure. In the era of effective therapies and improved outcomes for patients with AL amyloidosis, the importance of early recognition is further enhanced as the ability to reverse organ dysfunction is limited in those with a profound organ failure. As AL amyloidosis is an uncommon disorder and given patients' frailty and high early death rate, management of this complex condition is challenging. The treatment of AL amyloidosis is based on various anti-plasma cell therapies. These therapies are borrowed and customized from the treatment of multiple myeloma, a more common disorder. However, a growing number of phase 2/3 studies dedicated to the AL amyloidosis population are being performed, making treatment decisions more evidence-based. Supportive care is an integral part of management of AL amyloidosis because of the inherent organ dysfunction, limiting the delivery of effective therapy. This extensive review brings an updated summary on the management of AL amyloidosis, sectioned into the 3 pillars for survival improvement: early disease recognition, anti-plasma cell therapy, and supportive care.

Comprehensive Review of AL amyloidosis: some practical recommendations

Amyloid light chain (AL) amyloidosis is among the more common and more severe of the amyloidoses usually involving the slow proliferation of a bone-marrow-residing plasma cell (PC) clone and the secretion of unstable immunoglobulin-free light chains (FLC) that infiltrate peripheral tissues and result in detrimental end-organ damage. Disease presentation is rather vague, and the hallmark of treatment is early diagnosis before irreversible end-organ damage. Once diagnosed, treatment decision is transplant-driven whereby ~20% of patients are eligible for autologous stem cell transplantation (ASCT) with or without bortezomib-based induction. In the setting of ASCT-ineligibility, bortezomib plays a central role in upfront treatment with the recent addition of daratumumab to the current emerging standard of care. In general, management of AL amyloidosis is aimed at achieving deep, durable responses with very close monitoring for early detection of relapse/refractory disease. This article provides a comprehensive review of the management of patients with AL amyloidosis including goals of therapy, current treatment guidelines in the setting of both ASCT-eligibility and ineligibility, treatment response monitoring recommendations, toxicity management, and treatment of relapse/refractory disease.

Clinical value of minimal residual disease assessed by multiparameter flow cytometry in amyloid light chain amyloidosis

PURPOSE

To assess the feasibility and prognostic value of minimal residual disease (MRD) evaluated by multiparameter flow cytometry (MFC) in newly diagnosed amyloid light chain (AL) amyloidosis.

METHODS

Clinical data from 25 consecutive newly diagnosed AL amyloidosis patients with MRD data tested at 3 months after first-line therapy completion were retrospectively analysed in a single centre from 2012 to 2019. First-line therapy included 8 courses of VD or 4 courses of VD plus sequential autologous stem cell transplantation (ASCT), both without maintenance therapy.

RESULTS

Of 25 patients with very good partial response (VGPR) or better, 19 (76%) achieved MRD negativity. Baseline characteristics were not different between MRD-negative and MRD-positive patients. More ASCT patients than non-ASCT patients (90.0% vs 53.3%, p = 0.043) achieved MRD negativity. In the MRD-negative and MRD-positive groups, cardiac response was observed in 93% and 25% (p = 0.019) and any organ response in 94% and 50%, respectively (p = 0.023). At a median follow-up of 25.1 months, MRD-negative patients showed significantly longer progression-free survival (PFS) from diagnosis than MRD-positive patients (24.52 vs 76.39 months, p = 0.004).

CONCLUSIONS

MRD negativity measured by MFC at 3 months after first-line therapy completion in patients with AL amyloidosis is measurable and associated with improved organ response rates and PFS over a long follow-up.

Second Stem Cell Transplantation for Relapsed Refractory Light Chain (AL) Amyloidosis

Autologous stem cell transplantation (ASCT) is an effective treatment modality in light chain (AL) amyloidosis but can be offered only to a subset of patients. The feasibility, benefit, and risks of second ASCT (ASCT2) have been rarely reported. The objective of this study was to assess the utility of ASCT2 in AL amyloidosis and to identify the target population with the greatest benefit. This retrospective study examined all AL patients who underwent ASCT2 for relapsed refractory disease between 2003 and 2020. Twenty-six patients were included. The use of ASCT2 has increased over time, from 2.5% of all ASCTs from 2003 to 2011 to 5% from 2012 to 2020 (P = .056). The median time between the first ASCT (ASCT1) and ASCT2 was 7.2 years (range, 0.6 to 17.7). Fifty-four percent of patients received at least one line of therapy between ASCTs. Second stem cell mobilization prior to ASCT2 was required in 42% of patients. Full-dose melphalan (200 mg/m²) was given to 73% of patients. Two patients had failed to engraft by day 100 but eventually recovered to normal blood counts. Both had second stem cell mobilization prior to ASCT2 with prior melphalan exposure. Four patients (15%) died before day 100. Progression-free and overall survival were significantly longer from ASCT2 for those who had durable remission after ASCT1 (≥5 years) and for those who did not receive therapy between ASCTs. ASCT2 is feasible and can produce favorable outcomes, especially among those with durable response to ASCT1. ASCT2, if chosen, should preferably be performed after durable response to ASCT1 and at first progression.

Next generation flow cytometry for MRD detection in patients with AL amyloidosis

The treatment of AL amyloidosis aims to eradicate the plasma cell clone and eliminate toxic free light chain production. Only in a minority of patients the plasma cell clone is completely eradicated; residual light chain production may still exist while clonal relapse may occur. We used sensitive next-generation flow cytometry (NGF) to detect minimal residual disease (MRD) in AL amyloidosis patients at complete haematologic response. MRD evaluation was feasible in 51 of 52 (98%) tested patients and at a median sensitivity of 2.3 × 10^-6 MRD was undetectable in 23 (45%). An organ response occurred in 86% of MRDneg vs 77% in MRDpos; renal response in 15/17(88%) of MRDneg vs in 14/16(87.5%) of MRDpos and cardiac response in 10/10(100%) of MRDneg vs 11/15(73%) of MRDpos patients. After a median follow-up of 24 months post MRD testing, no MRDneg patient had a haematologic relapse vs 6/28(21%) MRDpos (p = .029). Pooling haematologic and organ progressions, 9 (32%) MRDpos patients had disease progression vs only 1 (4%) MRDneg patient (p = .026). In conclusion, MRD detection using NGF has profound clinical implications, so that AL patients with undetectable MRD have a very high probability of organ response and a very low probability of haematologic relapse.

Characterization and prognostic implication of delayed complete response in AL amyloidosis

INTRODUCTION

Little is known on continued response following completion of therapy in light chain (AL) amyloidosis.

METHODS

We studied 373 AL amyloidosis patients who achieved complete response (CR) or very good partial response (VGPR) to first-line therapy.

RESULTS

By end of therapy (EOT), 46% of patients achieved a CR and 54% a VGPR. With no further therapy, 17.5% of patients were upstaged from VGPR to CR (delayed CR), with a median of 9 months. Compared with CR and VGPR at EOT, patients with a delayed CR were characterized by higher proportion of t(11;14) and lower rate of trisomies. Autologous stem cell transplant was more frequent in the delayed CR group. Patients with a delayed CR were characterized by minimal residual disease negativity and organ response rates similar to patients with CR at EOT and higher than patients achieving VGPR at EOT. Patients with a delayed CR had a longer PFS/OS compared to patients with CR or VGPR by EOT (median PFS 149 vs 92 vs 52 months, P < .001; 10-year OS 87% vs 71% vs 56%, P < .001).

CONCLUSIONS

This study characterizes delayed CR in AL amyloidosis, highlights its prognostic impact which is at least similar to those who achieved CR at EOT, and underlines another aspect of response monitoring.

Minimal residual disease negativity by next-generation flow cytometry is associated with improved organ response in AL amyloidosis

Light chain (AL) amyloidosis is caused by a small B-cell clone producing light chains that form amyloid deposits and cause organ dysfunction. Chemotherapy aims at suppressing the production of the toxic light chain (LC) and restore organ function. However, even complete hematologic response (CR), defined as negative serum and urine immunofixation and normalized free LC ratio, does not always translate into organ response. Next-generation flow (NGF) cytometry is used to detect minimal residual disease (MRD) in multiple myeloma. We evaluated MRD by NGF in 92 AL amyloidosis patients in CR. Fifty-four percent had persistent MRD (median 0.03% abnormal plasma cells). There were no differences in baseline clinical variables in patients with or without detectable MRD. Undetectable MRD was associated with higher rates of renal (90% vs 62%, p = 0.006) and cardiac response (95% vs 75%, p = 0.023). Hematologic progression was more frequent in MRD positive (0 vs 25% at 1 year, p = 0.001). Altogether, NGF can detect MRD in approximately half the AL amyloidosis patients in CR, and persistent MRD can explain persistent organ dysfunction. Thus, this study supports testing MRD in CR patients, especially if not accompanied by organ response. In case MRD persists, further treatment could be considered, carefully balancing residual organ damage, patient frailty, and possible toxicity.

Measurable residual disease in multiple myeloma and light chain amyloidosis: more than meets the eye

The emergence of highly effective multiple myeloma (MM) treatments may bring cure within reach and highlights the need for highly sensitive measurable residual disease (MRD) techniques to replace conventional response assessments. MRD is being incorporated as an endpoint in an increasing number of studies and had been repeatedly shown to be both a predictive marker of response to treatment and a prognostic marker for future relapse. However, those results should be cautiously interpreted due to non-uniform reporting and the need for longer follow up to assess for sustained MRD negativity. This review aims to critically analyze the key MRD aspects including the current evidence supporting the use of MRD in clinical practice and the pitfalls of the various methods used to assess MRD. The utility of MRD for light chain (AL) amyloidosis will also be discussed.

Refining amyloid complete hematological response: Quantitative serum free light chains superior to ratio

Response assessment in light chain (AL) amyloidosis is based on serum and urine monoclonal protein studies. Newly diagnosed patients (n = 373) who achieved very good partial response or complete response (CR) to first line therapy were assessed for the survival impact of each of the monoclonal protein studies. At end of therapy (EOT), negative serum/urine immunofixation (IFE) was achieved in 61% of patients, 72% achieved normal serum free light chain ratio (sFLCR), and the median involved free light chain (iFLC) and difference between involved to uninvolved light chain (dFLC) were 17 mg/L and 5 mg/L, respectively. Overall, 46% of patients achieved a CR at EOT. At EOT, iFLC ≤20 mg/L and dFLC ≤10 mg/L were additive in survival discrimination to negative serum/urine IFE and were independent predictors of overall survival. In contrast, normalization of sFLCR did not add survival discrimination to serum/urine IFE and was not independent predictor of survival. We propose a new definition for hematological CR to include serum/urine IFE negativity plus iFLC ≤20 mg/L or dFLC ≤10 mg/L, instead of the current definition of serum/urine IFE negativity and normal sFLCR. Complete response using dFLC ≤10 mg/L had the best performance in those with significant renal dysfunction and by light chain isotype, making it the preferred partner to IFE. Validation of these results in a multicenter cohort is warranted.

Monoclonal Antibody Therapies in Systemic Light-Chain Amyloidosis

In systemic light-chain amyloidosis, monoclonal antibodies target antigens that are either membrane-bound or circulating or deposited in the organs. CD38 holds high promise as a target against clonal plasma cells. Multiple anti-CD38 antibodies are either approved for use or being investigated in clinical trials. Daratumumab has been investigated and has clinical efficacy in upfront or refractory settings. High rates of hematologic response are seen with daratumumab, which translates to high organ response rates. Rituximab is usually integrated into the treatment regimen for IgM amyloidosis. Anti-amyloid therapies have shown preclinical proof of principle, but lack confirmation of improvement.

Systemic AL Amyloidosis: Current Approaches to Diagnosis and Management

AL amyloidosis is characterized by a low-level expansion of an indolent, small plasma cell clone that produces amyloidogenic light chains. Amyloid aggregates or preceding intermediaries cause direct cell damage through their proteotoxicity, and amyloid deposits distort tissue architecture, and, eventually, lead to organ impairment. It is a rare, underdiagnosed disease with a diverse clinical presentation depending on the organ tropism of the amyloid fibrils; cardiac and renal involvement is most common, but any organ can be affected, excluding the central nervous system. A high level of awareness and a systematic approach using newly emerging screening biomarkers is required to achieve early diagnosis. Management should be multidisciplinary as supportive management tailored to management of organ dysfunction is paramount to survival and minimization of treatment-associated toxicity. The initial therapeutic aim is to rapidly eliminate the clonal plasma cell that produces the circulating amyloid precursor and achieve a complete hematologic response, and if possible with undetectable minimal residual disease as assessed by next-generation methods (flow and sequencing), with minimal toxicity. Treatment is tailored to the initial risk assessment of the patients. Treatments are based on regimens adapted from the expanding options that are available for multiple myeloma patients and hematological response rates have improved. Organ response rates are strongly associated with deeper hematologic response but usually lag behind hematological response and are also dependent on the initial organ function reserve. Agents directed against the amyloid deposits have been explored to aid amyloid clearance and improve organ function, but data are still negative.

Novel challenges in the management of immunoglobulin light chain amyloidosis: from the bench to the bedside

INTRODUCTION

Immunoglobulin light chain (AL) amyloidosis is one of the most frequent systemic amyloidosis in Western countries. It is caused by a B-cell clone producing a misfolded light chain (LC) that deposits in organs.

AREAS COVERED

The review examines recent findings on pathophysiology and clinical management of AL amyloidosis. It contains an update on the recent hot topics as novel therapeutic approaches, definition of relapse, and hematologic response assessment. To review literature on AL amyloidosis, a bibliographic search was performed using PubMed.

EXPERT OPINION

Due to the proteotoxicity of amyloidogenic LCs, the therapeutic goal is a rapid and profound decrease in their concentration. The standard treatment is a risk-adapted chemotherapy targeting the B-cell clone. Novel, promising drugs, as daratumumab, are currently under evaluation in newly-diagnosed and relapsed/refractory patients. New sensitive techniques, as mass spectrometry approach and bone marrow minimal residual disease assessment, are available to evaluate depth of response. After first-line therapy, increase in LC concentration may precede worsening of organ dysfunction and should be considered carefully. Further clarification of molecular mechanisms of the disease are shedding light on new possible therapeutic targets. Innovative treatment strategies and novel technologies will improve our ability to treat AL amyloidosis, preventing organ deterioration.

Time to Redefine Risk-Stratification and Response Criteria in Immunoglobulin Light Chain Amyloidosis?

Immunoglobulin light chain (AL) amyloidosis results from clonal plasma cell (PC)-derived immunoglobulin light chain-mediated end-organ dysfunction, the extent and severity of which predicts survival. Anti-PC therapies reduce clonal light chain burden, which usually results in improvement of organ function, and consequently overall survival. Response assessment is critical to gauge therapeutic efficacy, to report clinical trial outcomes, and to switch therapy in those without response. Response in AL amyloidosis is 2-fold: hematologic response and organ response (OR). Depth of hematologic response is graded on the basis of serum free light chain (sFLC) parameters, but assessment of OR is binary. The role of normal sFLC ratio or complete remission as a treatment end point has been challenged, thus highlighting the need to quantify involved FLC and residual PC beyond the normal sFLC ratio to possibly account for the ongoing organ damage seen in some patients with complete remission. Mass spectrometry and urinary exosome represent ultrasensitive strategies to estimate involved FLC below the detection threshold of current sFLC assays. The role of new sFLC parameters and minimal residual disease as potential prognostic parameters has been recognized. Brain natriuretic peptide (BNP) and 24-hour proteinuria:estimated glomerular filtration rate ratio were identified to overcome certain limitations of N-terminal-Pro-BNP, 24-hour proteinuria, and estimated glomerular filtration rate for cardiac and renal response assessment, respectively. Use of monoclonal antibodies targeting PC and amyloid deposits has expanded the therapeutic armamentarium of AL amyloidosis, and given their excellent efficacy, early ORs are reported. This review provides insights into recent advances in the risk-stratification and response assessment of patients with AL amyloidosis in light of the changing therapeutic paradigms. Incorporation of these advancements into formal consensus guidelines would require further validation.

Treating Protein Misfolding Diseases: Therapeutic Successes Against Systemic Amyloidoses

Misfolding and extracellular deposition of proteins is the hallmark of a heterogeneous group of conditions collectively termed protein misfolding and deposition diseases or amyloidoses. These include both localized (e.g. Alzheimer’s disease, prion diseases, type 2 diabetes mellitus) and systemic amyloidoses. Historically regarded as a group of maladies with limited, even inexistent, therapeutic options, some forms of systemic amyloidoses have recently witnessed a series of unparalleled therapeutic successes, positively impacting on their natural history and sometimes even on their incidence. In this review article we will revisit the most relevant of these accomplishments. Collectively, current evidence converges towards a crucial role of an early and conspicuous reduction or stabilization of the amyloid-forming protein in its native conformation. Such an approach can reduce disease incidence in at risk individuals, limit organ function deterioration, promote organ function recovery, improve quality of life and extend survival in diseased subjects. Therapeutic success achieved in these forms of systemic amyloidoses may guide the research on other protein misfolding and deposition diseases for which effective etiologic therapeutic options are still absent.

Diverse patterns of antibody variable gene repertoire disruption in patients with amyloid light chain (AL) amyloidosis

Immunoglobulin light chain amyloidosis is the most common form of systemic amyloidosis. AL amyloidosis is caused by a misfolded light chain produced by a clonal population of plasma cells. Disease status currently is defined by measuring the absolute quantity of serum free light chain protein, but this measurement often fails to identify the subclinical presence of clonal cells that may merit additional therapy. Next generation sequencing has the sensitivity to measure the relative amount of dominating light chains within the repertoire of a patient, and this technique is in clinical use to identify clonal populations of plasma cells for multiple myeloma, a related disorder. In this proof-of-concept study, we used bone marrow aspirates of AL amyloidosis positive patients and used reverse transcription of the antibody transcriptome followed by next generation sequencing to identify antibody variable-diversity-joining gene sequences for patients with immunoglobulin light chain amyloidosis, and demonstrate that this technology can be used to identify the dominant clone. The data also reveal differing patterns of overall antibody repertoire disruption in different patients. This method merits further study in larger prospective studies to establish its utility in detecting residual disease for patients with immunoglobulin light chain amyloidosis.

Immunoglobulin light chain amyloidosis: 2020 update on diagnosis, prognosis, and treatment

DISEASE OVERVIEW

Immunoglobulin light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of immunoglobulin light or heavy chain are deposited in tissues. Clinical features depend on organs involved but can include heart failure with preserved ejection fraction, nephrotic syndrome, hepatic dysfunction, peripheral/autonomic neuropathy, and "atypical smoldering multiple myeloma or monoclonal gammopathy undetermined significance (MGUS)."

DIAGNOSIS

Tissue biopsy stained with Congo red demonstrating amyloid deposits with apple-green birefringence is required for diagnosis. Invasive organ biopsy is not required in 85% of patients. Verification that amyloid is composed of immunoglobulin light chains is mandatory. The gold standard is laser capture mass spectroscopy.

PROGNOSIS

N-terminal pro-brain natriuretic peptide (NT-proBNP), serum troponin T, and difference between involved and uninvolved immunoglobulin free light chain (FLC) values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months.

THERAPY

All patients with a systemic amyloid syndrome require therapy to prevent deposition of amyloid in other organs and prevent progressive organ failure. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include systolic blood pressure >90 mmHg, troponin T < 0.06 ng/mL and serum creatinine ≤1.7 mg/dL. Nontransplant candidates can be offered cyclophosphamide-bortezomib-dexamethasone or daratumumab-containing regimens as it appears to be highly active in AL amyloidosis.

FUTURE CHALLENGES

Delayed diagnosis remains a major obstacle to initiating effective therapy prior to the development of end-stage organ failure.

The diagnostic challenges of cardiac amyloidosis: A practical approach to the two main types

Systemic amyloidosis of the immunoglobulin light-chain (AL) or transthyretin type (ATTR) is a multisystem protein deposition disease that often involves the heart. Delays in diagnosis are very common and can have detrimental consequences on patient outcomes. Because both major types can now be distinguished quickly and treated effectively, clear approaches are required. There have been advances in radioisotope scintigraphy, monoclonal protein testing and mass spectrometry for typing that need coordinated application. We have entered an era in which rapid diagnosis and ready therapy will save lives, therefore we must develop coherent approaches to this multisystem disease. The prognosis for AL has improved significantly with the incorporation of novel agents such as proteasome inhibitors, immunomodulators and monoclonal antibodies against plasma cells. Multiple independent studies have demonstrated the efficacy of these agents in AL, though tolerability can become an issue with dose reductions required in many cases. Median overall survival for patients achieving complete responses after stem cell transplant and consolidation exceeds a decade. The prognosis for ATTR, both age-related wild-type (ATTRwt) and hereditary due to variants of transthyretin (ATTRv), has improved as well due to the availability of the stabilizer tafamidis and the RNA-interference agents patisiran and inotersen. In both AL and ATTR, with elimination or suppression of the pathologic amyloid-forming protein, symptomatic involvement of the heart, kidneys and peripheral nervous system can improve as well. In this review, we present the current state of diagnosing and treating the two major types of systemic amyloidosis, emphasizing the coherent clinical application of the new tools and treatments. Implementation of the approaches we provide will enable rapid identification of amyloid type and rational selection of therapy.

Prognosis and Staging of AL Amyloidosis

The treatment options for systemic light chain amyloidosis (AL) are currently widening in an unprecedented way, brought about by an expanding arsenal of anti-myeloma therapy as well as by novel approaches to target toxic light chains and, most recently, deposited amyloid directly. In this context, accurate estimates of prognosis in AL, which allow for reliable patient advice and for example comparison of different therapies, are particularly important to clinicians. Some biomarkers and especially the genetic background of the underlying clonal disease as evaluated by interphase fluorescence in situ hybridization even have predictive value, enabling an appropriate treatment selection. Derived from the most frequently involved organs in AL, heart and kidney, this review focuses on overall survival and renal survival. A comprehensive overview and summary of reported prognostic factors and biomarkers in AL is given and the most important and validated factors are highlighted. Finally, established staging systems in AL as well as validated and perspective response criteria are presented.

Solid Organ Transplantation in Amyloidosis

Amyloidosis comprises a diverse group of diseases characterized by misfolding of precursor proteins which eventually form amyloid aggregates and preceding intermediaries, which are deposited in target tissues causing progressive organ damage. In all forms of amyloidosis, vital organs may fail; depending on the specific amyloidosis type, this may occur rapidly or progress slowly. Beyond therapies to reduce the precursor protein (chemotherapy for light chain [AL] amyloidosis, anti-inflammatory therapy in serum A amyloid-osis [AA], and antisense RNA therapy in transthyretin amyloidosis [ATTR]), organ transplantation may also be a means to reduce amyloidogenic protein, e.g., in types of amyloid-osis in which the variant precursor is produced by the liver. Heart transplantation is a life-saving approach to the treatment of patients with advanced cardiac amyloidosis; however, amyloidosis may still be considered a contraindication to the procedure despite data supporting improved outcomes, similar to patients with other indications. Kidney transplantation is associated with particularly favorable outcomes in patients with amyloidosis, especially if the precursor protein has been eliminated. Overall, outcomes of solid organ transplantation are improving, but more data are needed to refine the selection criteria and the timing for organ transplantation, which should be performed in highly experienced centers involving multidisciplinary teams with close patient follow-up to detect amyloid recurrence.

CD38 and Anti-CD38 Monoclonal Antibodies in AL Amyloidosis: Targeting Plasma Cells and beyond

Immunoglobulin light chain amyloidosis (AL amyloidosis) is a rare systemic disease characterized by monoclonal light chains (LCs) depositing in tissue as insoluble fibrils, causing irreversible tissue damage. The mechanisms involved in aggregation and deposition of LCs are not fully understood, but CD138/38 plasma cells (PCs) are undoubtedly involved in monoclonal LC production.CD38 is a pleiotropic molecule detectable on the surface of PCs and maintained during the neoplastic transformation in multiple myeloma (MM). CD38 is expressed on T, B and NK cell populations as well, though at a lower cell surface density. CD38 is an ideal target in the management of PC dyscrasia, including AL amyloidosis, and indeed anti-CD38 monoclonal antibodies (MoAbs) have promising therapeutic potential. Anti-CD38 MoAbs act both as PC-depleting agents and as modulators of the balance of the immune cells. These aspects, together with their interaction with Fc receptors (FcRs) and neonatal FcRs, are specifically addressed in this paper. Moreover, the initiallyavailable experiences with the anti-CD38 MoAb DARA in AL amyloidosis are reviewed.