Immunogenetic characterization of clonal plasma cells in systemic light-chain amyloidosis

Maintenance therapy promotes profound organ and haematologic response in light-chain amyloidosis patients not undergoing autologous stem cell transplantation

BACKGROUND

Evidence on maintenance therapy following frontline induction is sparse in primary light-chain amyloidosis (AL), especially for those who do not undergo autologous haematopoietic stem cell transplantation (ASCT).

METHODS

We enrolled primary AL patients who achieved at least haematologic very good partial response (VGPR) by the 4th month at the frontline from December 2008 to June 2023 at Zhongshan Hospital, Fudan University. Those who followed maintenance therapy were identified as the maintenance group (n = 44), whereas those entering the observational phase were classified as the observational group (n = 24).

RESULTS

After 7.2(interquartile range, 4.7-18.6) months of maintenance therapy, 9(20.5%), 14(31.8%) and 5 (11.4%) patients achieved improvement in haematologic, cardiac and renal response respectively. Five (11.4%) patients had minimal residual disease (MRD) response conversion from positive to negative based on maintenance therapy. In the observation group, none of the patients had haematologic response improvement, with 3(12.5%) and 1(4.2%) patient showing cardiac and renal response improvement during follow-up.

CONCLUSION

This study identified the clinical benefits of maintenance therapy in patients with AL who did not undergo ASCT in real-world practice.

Antibody Aggregation: A Problem Within the Biopharmaceutical Industry and Its Role in AL Amyloidosis Disease

Due to the large size and rapid growth of the global therapeutic antibody market, there is major interest in understanding the aggregation of protein products as it can compromise efficacy, concentration, and safety. Various production and storage conditions have been identified as capable of inducing aggregation of polyclonal and monoclonal antibody (mAb) therapies such as low pH, freezing, light exposure, lyophilisation and increased ionic strength. The addition of stabilising excipients to these therapeutics helps to combat the formation of aggregates with future aggregation inhibition mechanisms involving the introduction of point mutations and glycoengineering within aggregation prone regions (APRs). Antibody aggregation also plays an integral role in the pathogenesis of a condition known as amyloid light chain (AL) amyloidosis which is characterised by the production of improperly folded and amyloidogenic immunoglobulin light chains (LCs). Current diagnostic tools rely heavily on histological staining with their future moving towards amyloid component identification and proteomic analysis. For many years, treatment options designed for multiple myeloma (MM) have been applied to AL amyloidosis patients by depleting plasma cell numbers. More recently, treatment strategies more specific to this condition have been developed with many designed to recognize amyloid fibrils and trigger their degradation without causing systemic plasma cell cytotoxicity. Amyloid fibrils in AL disease and aggregates in antibody therapeutics are both formed through the oligomerisation of misfolded / modified proteins attempting to reach a thermodynamically stable, free energy minimum that is lower than the respective monomers themselves. Although the final morphologies are different, by understanding the principles underlying such aggregation, we expect to find common insights that may contribute to the development of new and effective methods of antibody aggregation and/or amyloidosis management. We envision that this area of research will continue to be very relevant in both industry and clinical settings.

A review of recent clinical trials to evaluate disease-modifying therapies in the treatment of cardiac amyloidosis

Cardiac amyloidosis (CA) is a serious condition that results in infiltrative cardiomyopathy and heart failure with preserved ejection fraction (HFpEF) that is caused by the extracellular deposition of amyloid fibrils within heart tissue. While many important features of CA have been known for years, its prevalence in elderly patients with HF is increasingly being recognized. Plasma cells produce monoclonal immunoglobulin light chains which results in the formation and aggregation of amyloid fibrils that are responsible for AL amyloidosis. CA is classified as originating from either transthyretin (ATTR) or light chain (AL) amyloidosis. ATTR CA may result from a genetic mutation in the TTR gene, which is inherited (ATTRv), or from age-related deposition from wild-type ATTR (ATTRwt). Cardiac involvement in AL amyloidosis is attributed to either of two mechanisms: the extracellular deposition of amyloid fibril in the myocardium, or direct cardiotoxicity from the fibril aggregates. Typing of amyloid fibrils, a critical determinant of therapy, has also improved with wider availability of laser capture and mass spectrometry of histologic specimens. Specific and accurate evaluation of CA is now possible using cardiac magnetic resonance imaging and bone scintigraphy tracers. Survival in CA has improved markedly as novel chemotherapy agents have become available, but challenges remain in advanced disease. Broadening the amyloid-specific therapeutic landscape to include RNA inhibitors, fibril formation stabilizers and inhibitors, and immunotherapeutic targeting of amyloid deposits holds promise and may improve outcomes in systemic and cardiac amyloidoses. Treatment strategies for CA has recently undergone transformative changes, leading to some progress in outcomes for certain patients. Here, we discuss the basic features of CA as well as the emergence of novel, disease-modifying strategies that have been recently evaluated in clinical trials for the treatment of CA.

Diagnosis and Treatment of AL Amyloidosis

Systemic light chain (AL) amyloidosis is caused by an usually small B cell clone that produces a toxic light chain forming amyloid deposits in tissue. The heart and kidney are the major organs affected, but all others, with the exception of the CNS, can be involved. The disease is rapidly progressive, and it is still diagnosed late. Screening programs in patients followed by hematologists for plasma cell dyscrasias should be considered. The diagnosis requires demonstration in a tissue biopsy of amyloid deposits formed by immunoglobulin light chains. The workup of patients with AL amyloidosis requires adequate technology and expertise, and patients should be referred to specialized centers whenever possible. Stagings are based on cardiac and renal biomarkers and guides the choice of treatment. The combination of daratumumab, cyclophosphamide, bortezomib and dexamethasone (dara-CyBorD) is the current standard of care. Autologous stem cell transplant is performed in eligible patients, especially those who do not attain a satisfactory response to dara-CyBorD. Passive immunotherapy targeting the amyloid deposits combined with chemo-/immune-therapy targeting the amyloid clone is currently being tested in controlled clinical trials. Response to therapy is assessed based on validated criteria. Profound hematologic response is the early goal of treatment and should be accompanied over time by deepening organ response. Many relapsed/refractory patients are also treated with daratumumab combination, but novel regimens will be needed to rescue daratumumab-exposed subjects. Immunomodulatory drugs are the current cornerstone of rescue therapy, while immunotherapy targeting B-cell maturation antigen and inhibitors of Bcl-2 are promising alternatives.

Prevalence of plasma cell and lymphoproliferative disorders among blood relatives of patients with light chain amyloidosis

With limited existing data on hereditary factors in light chain (AL) amyloidosis, we conducted a study of patients with plasma cell dyscrasias or lymphoproliferative disorders in their family history. Among 1621 patients, we identified 44 probands (2·7%) with 52 relatives affected. The most common disorders in family members were multiple myeloma (48%) and AL amyloidosis (18%). Light chain isotype was 100% congruent in families with known clonal immunoglobulin for both members. Despite matching light chain isotype, organ involvement varied between members in families with multiple cases of AL amyloidosis. These findings help generate hypotheses about familial influences in AL amyloidosis.

Analysis of Genetic Alterations in Ocular Adnexal Mucosa-Associated Lymphoid Tissue Lymphoma With Whole-Exome Sequencing

Next-generation sequencing studies on ocular adnexal marginal zone lymphoma of mucosa-associated lymphoid tissue (OAML) have to date revealed several targets of genetic aberrations. However, most of our current understanding of the pathogenesis and prognosis of OAML is primarily based on studies conducted in populations from Europe and the US. Furthermore, the majority were based on formalin-fixed paraffin-embedded (FFPE) tissue, which generally has poor integrity and creates many sequencing artifacts. To better investigate the coding genome landscapes of OAML, especially in the Chinese population, we performed whole-exome sequencing of 21 OAML cases with fresh frozen tumor tissue and matched peripheral blood samples. IGLL5, as a novel recurrently mutated gene, was found in 24% (5/21) of patients, with a higher relapse rate (P=0.032). In addition, mutations of MSH6, DIS3, FAT1, and TMEM127 were found in 10% of cases. These novel somatic mutations indicate the existence of additional/alternative lymphomagenesis pathways in OAML. Moreover, the difference between our and previous studies suggests genetic heterogeneity of OAML between Asian and Western individuals.

Genetic pathogenesis of immunoglobulin light chain amyloidosis: basic characteristics and clinical applications

Immunoglobulin light chain amyloidosis (AL) is an indolent plasma cell disorder characterized by free immunoglobulin light chain (FLC) misfolding and amyloid fibril deposition. The cytogenetic pattern of AL shows profound similarity with that of other plasma cell disorders but harbors distinct features. AL can be classified into two primary subtypes: non-hyperdiploidy and hyperdiploidy. Non-hyperdiploidy usually involves immunoglobulin heavy chain translocations, and t(11;14) is the hallmark of this disease. T(11;14) is associated with low plasma cell count but high FLC level and displays distinct response outcomes to different treatment modalities. Hyperdiploidy is associated with plasmacytosis and subclone formation, and it generally confers a neutral or inferior prognostic outcome. Other chromosome abnormalities and driver gene mutations are considered as secondary cytogenetic aberrations that occur during disease evolution. These genetic aberrations contribute to the proliferation of plasma cells, which secrete excess FLC for amyloid deposition. Other genetic factors, such as specific usage of immunoglobulin light chain germline genes and light chain somatic mutations, also play an essential role in amyloid fibril deposition in AL. This paper will propose a framework of AL classification based on genetic aberrations and discuss the amyloid formation of AL from a genetic aspect.

Tumor cells in light-chain amyloidosis and myeloma show different transcriptional rewiring of normal plasma cell development

Although light-chain amyloidosis (AL) and multiple myeloma (MM) are characterized by tumor plasma cell (PC) expansion in bone marrow (BM), their clinical presentation differs. Previous attempts to identify unique pathogenic mechanisms behind such differences were unsuccessful, but there are no studies investigating the differentiation stage of tumor PCs in patients with AL and MM. We sought to define a transcriptional atlas of normal PC development (n=11) in secondary lymphoid organs (SLO), peripheral blood (PB) and BM for comparison with the transcriptional programs (TPs) of tumor PCs in AL (n=37), MM (n=46) and MGUS (n=6). Based on bulk and single-cell RNAseq, we observed thirteen TPs during transition of normal PCs throughout SLO, PB and BM; that CD39 outperforms CD19 to discriminate new-born from long-lived BM-PCs; that tumor PCs expressed the most advantageous TPs of normal PC differentiation; that AL shares greater similarity to SLO-PCs whereas MM is transcriptionally closer to PB-PCs and new-born BM-PCs; that AL and MM patients enriched in immature TPs had inferior survival; and that TPs related with protein N-linked glycosylation are upregulated in AL. Collectively, we provide a novel resource to understand normal PC development and the transcriptional reorganization of AL and other monoclonal gammopathies.

Daratumumab in the Treatment of Light-Chain (AL) Amyloidosis

Systemic light-chain (AL) amyloidosis is caused by a small B cell, most commonly a plasma cell (PC), clone that produces toxic light chains (LC) that cause organ dysfunction and deposits in tissues. Due to the production of amyloidogenic, misfolded LC, AL PCs display peculiar biologic features. The small, indolent plasma cell clone is an ideal target for anti-CD38 immunotherapy. A recent phase III randomized study showed that in newly diagnosed patients, the addition of daratumumab to the standard of care increased the rate and depth of the hematologic response and granted more frequent organ responses. In the relapsed/refractory setting, daratumumab alone or as part of combination regimens gave very promising results. It is likely that daratumumab-based regimens will become new standards of care in AL amyloidosis. Another anti-CD38 monoclonal antibody, isatuximab, is at an earlier stage of development as a treatment for AL amyloidosis. The ability to target CD38 on the amyloid PC offers new powerful tools to treat AL amyloidosis. Future studies should define the preferable agents to combine with daratumumab upfront and in the rescue setting and assess the role of maintenance. In this review, we summarize the rationale for using anti-CD38 antibodies in the treatment of AL amyloidosis.

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.