Amyloid nomenclature 2024: update, novel proteins, and recommendations by the International Society of Amyloidosis (ISA) Nomenclature Committee.

The ISA Nomenclature Committee met at the XIX International Symposium of Amyloidosis in Rochester, MN, 27 May 2024. The in-person event was followed by many electronic discussions, resulting in the current updated recommendations. The general nomenclature principles are unchanged. The total number of human amyloid fibril proteins is now 42 of which 19 are associated with systemic deposition, while 4 occur with either localised or systemic deposits. Most systemic amyloidoses are caused by the presence of protein variants which promote misfolding. However, in the cases of AA and ATTR the deposits most commonly consist of wild-type proteins and/or their fragments. One peptide drug, previously reported to create local iatrogenic amyloid deposits at its injection site, has been shown to induce rare instances of systemic deposition. The number of described animal amyloid fibril proteins is now 16, 2 of which are unknown in humans. Recognition of the importance of intracellular protein aggregates, which may have amyloid or amyloid-like properties, in many neurodegenerative diseases is rapidly increasing and their significance is discussed.

SMaRT M-Seq: an optimized step-by-step protocol for M protein sequencing in monoclonal gammopathies.

In patients with monoclonal gammopathies, tumor B cells or plasma cells secrete a monoclonal antibody (M protein) that not only serves as a biomarker for tumor tracking but can also cause potentially life-threatening organ damage. This damage is driven by the patient-specific sequence of the M protein. Methods for sequencing M proteins have been limited by their high cost and time-consuming nature, and while recent approaches using next-generation sequencing or mass spectrometry offer advancements, they may require tumor cell sorting, are limited to subsets of immunoglobulin genes or patients, and/or lack extensive validation. To address these limitations, we have recently developed a novel method, termed Single Molecule Real-Time Sequencing of the M protein (SMaRT M-Seq), which combines the unbiased amplification of expressed immunoglobulin genes via inverse PCR from circularized cDNA with long-read DNA sequencing, followed by bioinformatic and immunogenetic analyses. This approach enables the unambiguous identification of full-length variable sequences of M protein genes across diverse patient cohorts, including those with low tumor burden. Our protocol has undergone technical validation and has been successfully applied to large patient cohorts with monoclonal gammopathies. Here we present the step-by-step protocol for SMaRT M-Seq. By enabling the parallel sequencing of M proteins from a large number of samples in a cost-effective and time-efficient manner, SMaRT M-Seq facilitates access to patient-specific M protein sequences, advancing personalized medicine approaches and enabling deeper mechanistic studies in monoclonal gammopathies.

Graded Organ Response and Progression Criteria for Kidney Immunoglobulin Light Chain Amyloidosis.

Importance: Kidney light chain (AL) amyloidosis is associated with a risk of progression to kidney replacement therapy (KRT) and death. Several studies have shown that a greater reduction in proteinuria following successful anticlonal therapy is associated with improved outcomes. Objective: To validate graded kidney response criteria and their association with kidney and overall survival (OS). Design, Setting, and Participants: This retrospective, multicenter cohort was conducted at 10 referral centers for amyloidosis from 2010 to 2015 and included patients with kidney AL amyloidosis that was evaluable for kidney response and who achieved at least hematologic partial response within 12 months of diagnosis. The median follow-up was 69 (54-88) months. Data analysis was conducted in 2023. Exposure: Four kidney response categories based on the reduction in pretreatment 24-hour urine protein (24-hour UP) levels: complete response (kidCR, 24-hour UP ≤200 mg), very good partial response (kidVGPR, >60% reduction in 24-hour UP), partial response (kidPR, 31%-60% reduction), and no response (kidNR, ≤30% reduction). Kidney response was assessed at landmark points (6, 12, and 24 months) and best kidney response. Main Outcomes and Measures: Cumulative incidence of progression to KRT and OS. Results: Seven-hundred and thirty-two patients (335 women [45.8%]) were included, with a median (IQR) age of 63 (55-69) years. The median (IQR) baseline 24-hour proteinuria and estimated glomerular filtration rate was 5.3 (2.8-8.5) g per 24 hours and 72 (48-92) mL/min/1.73m2, respectively. In a competing-risk analysis, the 5-year cumulative incidence rates of progression to KRT decreased with deeper kidney responses as early as 6 months from therapy initiation (11%, 12%, 2.1%, and 0% for kidNR, kidPR, kidVGPR, and kidCR, respectively; P = .002) and were maintained at 12 months and 24 months and best kidney response. Patients able to achieve kidCR/kidVGPR by 24 months and at best response had significantly better OS compared with kidPR/kidNR. Kidney progression, defined as a 25% or greater decrease in estimated glomerular filtration rate, was associated with cumulative incidence of progression to KRT and OS. Conclusions and Relevance: The results of this cohort study suggest that graded kidney response criteria offers clinically and prognostically meaningful information for treating patients with kidney AL amyloidosis. The response criteria potentially inform kidney survival based on the depth of reduction in 24-hour proteinuria levels and demonstrate an OS advantage for those able to achieve kidCR/kidVGPR compared with kidPR/kidNR. Taken together, achievement of at least kidVGPR by 12 months is needed to ultimately improve kidney and patient survival.

Successes in translation.

Translational research is key in advancing the diagnosis and therapy of systemic amyloidoses. This paper summarises our presentations at the ISA Workshop on Translation in Systemic Amyloidoses held in Athens on September 25-26, 2023. The critical advances made by the pioneers in the field are reviewed, with particular attention to the discoveries and developments of utmost importance to our understanding of what amyloid is and how the substance affects functions. Examples of translational research regarding the mechanisms of cardiac damage in light chain amyloidosis, the role of biomarkers in improving our understanding of the biology of the disease and patients' management, and the molecular mechanisms involved in the cytotoxicity are described. Advances in basic research continue to open new therapeutic avenues.

Helical superstructures between amyloid and collagen in cardiac fibrils from a patient with AL amyloidosis.

Systemic light chain (LC) amyloidosis (AL) is a disease where organs are damaged by an overload of a misfolded patient-specific antibody-derived LC, secreted by an abnormal B cell clone. The high LC concentration in the blood leads to amyloid deposition at organ sites. Indeed, cryogenic electron microscopy (cryo-EM) has revealed unique amyloid folds for heart-derived fibrils taken from different patients. Here, we present the cryo-EM structure of heart-derived AL amyloid (AL59) from another patient with severe cardiac involvement. The double-layered structure displays a u-shaped core that is closed by a ß-arc lid and extended by a straight tail. Noteworthy, the fibril harbours an extended constant domain fragment, thus ruling out the variable domain as sole amyloid building block. Surprisingly, the fibrils were abundantly concatenated with a proteinaceous polymer, here identified as collagen VI (COLVI) by immuno-electron microscopy (IEM) and mass-spectrometry. Cryogenic electron tomography (cryo-ET) showed how COLVI wraps around the amyloid forming a helical superstructure, likely stabilizing and protecting the fibrils from clearance. Thus, here we report structural evidence of interactions between amyloid and collagen, potentially signifying a distinct pathophysiological mechanism of amyloid deposits.

Delayed identification of monoclonal protein is associated with early death in isolated cardiac AL amyloidosis.

BACKGROUND: Early identification of immunoglobulin light-chain amyloidosis (AL) is crucial due to its rapid progression. Monoclonal light-chain (M-LC) testing is the first step in the diagnostic workup for patients with suspected cardiac amyloidosis (CA). We aimed to determine whether the time interval between the first CA suspicion and M-LC testing can be related to AL amyloidosis survival outcomes. METHODS: All patients (n = 94) with isolated cardiac AL amyloidosis diagnosed at our center between 2016 and 2020 were included. Those with pre-existing known monoclonal protein (monoclonal gammopathy of undetermined significance or smoldering multiple myeloma) were excluded. Time intervals to diagnostic tests and diagnosis were calculated and assessed for their survival prediction ability. RESULTS: The time interval between first CA suspicion (on echocardiography) and M-LC testing correlated with early mortality, and the best cutoff predicting survival, was 6 weeks. The 26 patients (∼28% of entire cohort) who underwent M-LC-studies >6 weeks after first suspicion more frequently presented Mayo stage IIIb (65% vs. 35%, p = .008), showing poorer overall survival than those (n = 68, 72%) referred for early M-LC studies (median 3 vs. 14 months, p = .039). CONCLUSIONS: Monoclonal protein testing should be the first-step in the diagnostic workup for patients with echocardiographic/other instrumental red flags raising CA suspicion.

A real-life study of daratumumab combinations in newly diagnosed patients with light chain (AL) amyloidosis.

Daratumumab-based regimens are the new standard of care for newly diagnosed patients with AL amyloidosis based on the results of the ANDROMEDA study. However, real-world data on daratumumab efficacy in upfront therapy in unselected patients are scanty. In the framework of a prospective observational study, we investigated the efficacy and safety of daratumumab in 88 newly diagnosed patients, including subjects with IIIb cardiac stage (26%) or myeloma defining events (29%). Daratumumab was administered with bortezomib in 50 (56%) patients, lenalidomide in 31 (35%), and monotherapy in 7 (8%). The rate of serious adverse events was low (16%). The overall hematologic response rate was 75% with 52 (59%) patients attaining at least a very good partial response (VGPR) at six months. Amongst patients evaluable for organ response, the rate of cardiac and renal responses at 6 months was 31% and 21%, respectively. Comparing stage IIIb patients with the remaining ones, the rate of profound hematologic response was not significantly different (≥VGPR 57% vs. 59%, p 0.955) likewise the rate of cardiac (33% vs. 30%, p 0.340) and renal (40% vs. 16%, p 0.908) responses. Daratumumab-based regimens demonstrated to be safe and effective in treatment-naïve AL amyloidosis even in advanced stage disease.

Renal alterations in cats (Felis catus) housed in shelters and affected by systemic AA-amyloidosis: Clinicopathological data, histopathology, and ultrastructural features.

AA-amyloidosis is frequent in shelter cats, and chronic kidney disease is the foremost cause of death. The aims were to describe kidney laboratory and microscopic findings in shelter cats with AA-amyloidosis. Cats were included if kidney specimens were collected post-mortem and laboratory data were available within 6 months before death. Renal lesions were evaluated with optical and electron microscopy. Mass spectrometry was used to characterize amyloid. Nine domestic short-hair cats were included; 4 females and 5 males with a median age of 8 years (range = 2-13). All cats had blood analyses and urinalyses available. Serum creatinine concentrations were increased in 6 cats and symmetric dimethylarginine was increased in all of the cats. All of the cats had proteinuria. Eight of 9 cats had amyloid in the medulla, and 9 had amyloid in the cortex (glomeruli). All cats had amyloid in the interstitium. Six cats had concurrent interstitial nephritis and 1 had membranoproliferative glomerulonephritis. All cats had extrarenal amyloid deposits. Amyloid was AA in each case. In conclusion, renal deposition of amyloid occurs in both cortex and medulla in shelter cats and is associated with azotemia and proteinuria. Renal involvement of systemic AA-amyloidosis should be considered in shelter cats with chronic kidney disease. The cat represents a natural model of renal AA-amyloidosis.

International Myeloma Working Group immunotherapy committee consensus guidelines and recommendations for optimal use of T-cell-engaging bispecific antibodies in multiple myeloma.

Multiple myeloma remains an incurable disease, despite the development of numerous drug classes and combinations that have contributed to improved overall survival. Immunotherapies directed against cancer cell-surface antigens, such as chimeric antigen receptor (CAR) T-cell therapy and T-cell-redirecting bispecific antibodies, have recently received regulatory approvals and shown unprecedented efficacy. However, these immunotherapies have unique mechanisms of action and toxicities that are different to previous treatments for myeloma, so experiences from clinical trials and early access programmes are essential for providing specific recommendations for management of patients, especially as these agents become available across many parts of the world. Here, we provide expert consensus clinical practice guidelines for the use of bispecific antibodies for the treatment of myeloma. The International Myeloma Working Group is also involved in the collection of prospective real-time data of patients treated with such immunotherapies, with the aim of learning continuously and adapting clinical practices to optimise the management of patients receiving immunotherapies.

Patients with a cardiac complete response in AL amyloidosis have survival rates similar to those of a matched general population.

ABSTRACT: The survival of patients achieving a cardiac complete response in light chain amyloidosis, defined as N-terminal pro B-type natriuretic peptide ≤350 pg/mL or B-type natriuretic peptide ≤80 pg/mL, was similar to that of a matched general population, with estimated 5-year survival rates of 93% and 95%, respectively.

Healthcare Resource Utilization and Cost-of-Illness in Systemic Light Chain (AL) Amyloidosis in Europe: Results From the Real-World, Retrospective EMN23 Study.

OBJECTIVES: To report healthcare resource utilization (HCRU) and safety outcomes in systemic light chain (AL) amyloidosis from the EMN23 study. MATERIALS AND METHODS: The retrospective, observational, multinational EMN23 study included 4,480 patients initiating first-line treatment for AL amyloidosis in 2004-2018 and assessed, among other objectives, HCRU and safety outcomes. HCRU included hospitalizations, examinations, and dialysis; safety included serious adverse events (SAEs) and adverse events of special interest (AESIs). Data were descriptively analyzed by select prognostic factors (e.g., cardiac staging by Mayo2004/European) for 2004-2010 and 2011-2018. A cost-of-illness analysis was conducted for the UK and Spain. RESULTS: HCRU/safety and dialysis data were extracted for 674 and 774 patients, respectively. Of patients with assessed cardiac stage (2004-2010: 159; 2011-2018: 387), 67.9% and 61.0% had ≥ 1 hospitalization, 56.0% and 51.4% had ≥ 1 SAE, and 31.4% and 28.9% had ≥ 1 AESI across all cardiac stages in 2004-2010 and 2011-2018, respectively. The per-patient-per-year length of hospitalization increased with disease severity (cardiac stage). Of patients with dialysis data (2004-2010: 176; 2011-2018: 453), 23.9% and 14.8% had ≥ 1 dialysis session across all cardiac stages in 2004-2010 and 2011-2018, respectively. The annual cost-of-illness was estimated at €40,961,066 and €31,904,386 for the UK and Spain, respectively; dialysis accounted for ∼28% (UK) and ∼35% (Spain) of the total AL amyloidosis costs. CONCLUSIONS: EMN23 showed that the burden of AL amyloidosis is substantial, highlighting the need for early disease diagnosis and effective treatments targeting the underlying pathology.

Mining the amyloid-plaque proteome to uncover disease mechanisms in renal amyloidoses.

Beyond typing amyloid deposits and discovering new forms of amyloidosis, laser microdissection and mass spectrometry enable the analysis of the amyloid-plaque proteome constituents-amyloid fibrillar proteins, matrix and cellular components, and absorbed blood-borne proteins. Charalampous et al. analyzed the amyloid-plaque proteomes of the 7 most common renal amyloidoses to gain preliminary mechanistic insights on cellular and molecular perturbations elicited during gradual amyloid deposition and potential tissue repair or damage mechanisms. Clinical correlations identified a prognostic pattern.

Patient-reported outcome measures for transthyretin cardiac amyloidosis: the ITALY study.

BACKGROUND: Transthyretin cardiac amyloidosis (ATTR-CA) has a deep impact on the quality of life (QoL), yet no specific patient-reported outcome measures (PROMs) for ATTR-CA exist. METHODS: The ITALY study involved 5 Italian referral centres (Pisa, Pavia, Ferrara, Florence, Messina) enrolling consecutive outpatients with ATTR-CA. RESULTS: Two 30-item questionnaires were created for wild-type (wt) and variant (v) ATTR-CA. Scores ranged from 100 (best condition) to 0 (worst condition). Out of 140 patients enrolled (77% with ATTRwt-CA), 115 repeated the re-evaluation at 6 months. At baseline, only 30% of patients needed help to fill out the questionnaires. Among baseline variables, all KCCQ and SF-36 domains were univariate predictors of ITALY scores in ATTRwt-CA patients, with the KCCQ Symptom Summary score (beta coefficient 0.759), Social Limitations (0.781), and Overall summary score (0.786) being the strongest predictors. The SF-36 Emotional well-being score (0.608), the KCCQ Overall summary score (0.656), and the SF-36 Energy/fatigue score (0.669) were the strongest univariate predictors of ITALY scores in ATTRv-CA. Similar results were found at 6 months. CONCLUSIONS: The ITALY questionnaires are the first specific PROMs for ATTRwt- and ATTRv-CA. Questionnaire completion is feasible. ITALY scores display close relationships with non-ATTR-specific measures of QoL.

Nanobodies counteract the toxicity of an amyloidogenic light chain by stabilizing a partially open dimeric conformation.

Light chain amyloidosis (AL) is a systemic disease where fibrillar deposition of misfolded immunoglobulin light chains (LCs) severely affects organ function and results in poor prognosis for patients, especially when heart involvement is severe. Particularly relevant in this context is the cardiotoxicity exerted by still uncharacterized soluble LC species. Here, with the final goal of identifying alternative therapeutic strategies to tackle AL amyloidosis, we produced five llama-derived nanobodies (Nbs) specific against H3, a well-characterized amyloidogenic and cardiotoxic LC from an AL patient with severe cardiac involvement. We found that Nbs are specific and potent agents capable of abolishing H3 soluble toxicity in C. elegans in vivo model. Structural characterization of H3-Nb complexes revealed that the protective effect of Nbs is related to their ability to bind to the H3 VL domain and stabilise an unexpected partially open LC dimer in which the two VL domains no longer interact with each other. Thus, while identifying potent inhibitors of LC soluble toxicity, we also describe the first non-native structure of an amyloidogenic LC that may represent a crucial step in toxicity and aggregation mechanisms.

The Cryo-EM STRUCTURE of Renal Amyloid Fibril Suggests Structurally Homogeneous Multiorgan Aggregation in AL Amyloidosis.

Immunoglobulin light chain amyloidosis (AL) is caused by the aberrant production of amyloidogenic light chains (LC) that accumulate as amyloid deposits in vital organs. Distinct LC sequences in each patient yield distinct amyloid structures. However different tissue microenvironments may also cause identical protein precursors to adopt distinct amyloid structures. To address the impact of the tissue environment on the structural polymorphism of amyloids, we extracted fibrils from the kidney of an AL patient (AL55) whose cardiac amyloid structure was previously determined by our group. Here we show that the 4.0 Å resolution cryo-EM structure of the renal fibril is virtually identical to that reported for the cardiac fibril. These results provide the first structural evidence that LC amyloids independently deposited in different organs of the same AL patient share a common fold.

Management of multiple myeloma-related renal impairment: recommendations from the International Myeloma Working Group.

Here, the International Myeloma Working Group (IMWG) updates its clinical practice recommendations for the management of multiple myeloma-related renal impairment on the basis of data published until Dec 31, 2022. All patients with multiple myeloma and renal impairment should have serum creatinine, estimated glomerular filtration rate, and free light chains (FLCs) measurements together with 24-h urine total protein, electrophoresis, and immunofixation. If non-selective proteinuria (mainly albuminuria) or involved serum FLCs value less than 500 mg/L is detected, then a renal biopsy is needed. The IMWG criteria for the definition of renal response should be used. Supportive care and high-dose dexamethasone are required for all patients with myeloma-induced renal impairment. Mechanical approaches do not increase overall survival. Bortezomib-based regimens are the cornerstone of the management of patients with multiple myeloma and renal impairment at diagnosis. New quadruplet and triplet combinations, including proteasome inhibitors, immunomodulatory drugs, and anti-CD38 monoclonal antibodies, improve renal and survival outcomes in both newly diagnosed patients and those with relapsed or refractory disease. Conjugated antibodies, chimeric antigen receptor T-cells, and T-cell engagers are well tolerated and effective in patients with moderate renal impairment.

Amyloidogenic light chains impair plasma cell survival.

Systemic light chain amyloidosis (AL) is a clonal plasma cell disorder characterized by the deposition of misfolded immunoglobulin light chains (LC) as insoluble fibrils in organs. The lack of suitable models has hindered the investigation of the disease mechanisms. Our aim was to establish AL LC-producing plasma cell lines and use them to investigate the biology of the amyloidogenic clone. We used lentiviral vectors to generate cell lines expressing LC from patients suffering from AL amyloidosis. The AL LC-producing cell lines showed a significant decrease in proliferation, cell cycle arrest, and an increase in apoptosis and autophagy as compared with the multiple myeloma LC-producing cells. According to the results of RNA sequencing the AL LC-producing lines showed higher mitochondrial oxidative stress, and decreased activity of the Myc and cholesterol pathways. The neoplastic behavior of plasma cells is altered by the constitutive expression of amyloidogenic LC causing intracellular toxicity. This observation may explain the disparity in the malignant behavior of the amyloid clone compared to the myeloma clone. These findings should enable future in vitro studies and help delineate the unique cellular pathways of AL, thus expediting the development of specific treatments for patients with this disorder.