AL amyloidosis: from molecular mechanisms to targeted therapies

AbstractSystemic amyloidosis is caused by misfolding and extracellular deposition of circulating proteins as amyloid fibrils, resulting in the dysfunction of vital organs. The most common systemic amyloidosis, light-chain (AL) amyloidosis, is caused by misfolded light chains produced by a small, dangerous B-cell clone. The process of amyloid formation, organ targeting, and damage is multifaceted and, after disease initiation, the complexity of the downstream pathogenic cascade increases, rendering its control a challenge. Because of the progressive nature of the disease, early diagnosis to prevent end-stage organ damage is vital. Improving awareness and systematic use of biomarkers of organ damage in screening populations at risk may improve the still unsatisfactory diagnostic process. Amyloid imaging is now emerging as an important companion of biomarkers in formulating the diagnosis and prognosis and monitoring the effects of therapy. An accurate diagnosis is the basis for appropriate therapy that is risk-adapted and response-tailored. Effective treatments targeting the clone and rapidly and profoundly reducing the amyloid light chains have produced marked improvements in overall survival, making AL amyloidosis the most successful model of all amyloidoses. New therapies targeting the amyloid deposits are now under development, together with novel agents modulating light chain aggregation and proteotoxicity. The future of AL amyloidosis treatment is combination therapy and will require an innovative collaborative model for a rapid translation from bench to bedside with the ultimate aim of achieving a cure for this complex disease.

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Barriers to Small Molecule Drug Discovery for Systemic Amyloidosis

Molecules ◽

10.3390/molecules26123571 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3571

Author(s):

Gareth J. Morgan

Keyword(s):

Small Molecules ◽

Light Chain ◽

Amyloid Fibrils ◽

Systemic Amyloidosis ◽

Light Chains ◽

Al Amyloidosis ◽

Amyloid Formation ◽

Amyloid Fibril Formation ◽

Amyloid Light Chain

Inhibition of amyloid fibril formation could benefit patients with systemic amyloidosis. In this group of diseases, deposition of amyloid fibrils derived from normally soluble proteins leads to progressive tissue damage and organ failure. Amyloid formation is a complex process, where several individual steps could be targeted. Several small molecules have been proposed as inhibitors of amyloid formation. However, the exact mechanism of action for a molecule is often not known, which impedes medicinal chemistry efforts to develop more potent molecules. Furthermore, commonly used assays are prone to artifacts that must be controlled for. Here, potential mechanisms by which small molecules could inhibit aggregation of immunoglobulin light-chain dimers, the precursor proteins for amyloid light-chain (AL) amyloidosis, are studied in assays that recapitulate different aspects of amyloidogenesis in vitro. One molecule reduced unfolding-coupled proteolysis of light chains, but no molecules inhibited aggregation of light chains or disrupted pre-formed amyloid fibrils. This work demonstrates the challenges associated with drug development for amyloidosis, but also highlights the potential to combine therapies that target different aspects of amyloidosis.

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Light chain amyloidosis

Mediterranean Journal of Hematology and Infectious Diseases ◽

10.4084/mjhid.2018.022 ◽

2018 ◽

Vol 10 (1) ◽

pp. e2018022 ◽

Cited By ~ 17

Author(s):

Paolo Milani ◽

Giampaolo Merlini ◽

Giovanni Palladini

Keyword(s):

Plasma Cell ◽

Light Chain ◽

Molecular Mechanisms ◽

Cell Clone ◽

Renal Involvement ◽

Response To Therapy ◽

Al Amyloidosis ◽

Cell Transplant ◽

Cardiac Damage ◽

Risk Patients

Light chain (AL) amyloidosis is caused by a usually small plasma-cell clone that is able to produce the amyloidogenic lights chains. They are able to misfold and aggregate, deposit in tissues in the form of amyloid fibrils and lead to irreversible organ dysfunction and eventually death if treatment is late or ineffective. Cardiac damage is the most important prognostic determinant. The risk of dialysis is predicted by the severity of renal involvement, defined by the baseline proteinuria and glomerular filtration rate, and by response to therapy. The specific treatment is chemotherapy targeting the underlying plasma-cell clone. This needs be risk adapted, according to the severity of cardiac and/or multi-organ involvement. Autologous stem cell transplant (preceded by induction and/or followed by consolidation with bortezomib-based regimens) can be considered for low-risk patients (~20%). Bortezomib combined with alkylators is used in the majority of intermediate-risk patients, and with possible dose escalation in high-risk subjects. Novel, powerful anti-plasma cell agents were investigated in the relapsed/refractory setting, and are being moved to upfront therapy in clinical trials. In addition, the use of novel approaches based on antibodies targeting the amyloid deposits or small molecules interfering with the amyloidogenic process gave promising results in preliminary studies. Some of them are under evaluation in controlled trials. These molecules will probably add powerful complements to standard chemotherapy. The understanding of the specific molecular mechanisms of cardiac damage and the characteristics of the amyloidogenic clone are unveiling novel potential treatment approaches, moving towards a cure for this dreadful disease.

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Nonchemotherapy Treatment of Immunoglobulin Light Chain Amyloidosis

Acta Haematologica ◽

10.1159/000507724 ◽

2020 ◽

Vol 143 (4) ◽

pp. 373-380

Author(s):

Layla Van Doren ◽

Suzanne Lentzsch

Keyword(s):

Plasma Cell ◽

Light Chain ◽

Cell Clone ◽

Standard Of Care ◽

Organ Damage ◽

Current Therapy ◽

Al Amyloidosis ◽

Immunoglobulin Light Chain ◽

Light Chain Amyloidosis ◽

Immunoglobulin Light Chain Amyloidosis

Immunoglobulin light chain amyloidosis (AL amyloidosis) is a rare, life-threatening disease characterized by the deposition of misfolded proteins in vital organs such as the heart, the lungs, the kidneys, the peripheral nervous system, and the gastrointestinal tract. This causes a direct toxic effect, eventually leading to organ failure. The underlying B-cell lymphoproliferative disorder is almost always a clonal plasma cell disorder, most often a small plasma cell clone of <10%. Current therapy is directed toward elimination of the plasma cell clone with the goal of preventing further organ damage and reversal of the existing organ damage. Autologous stem cell transplantation has been shown to be a very effective treatment in patients with AL amyloidosis, although it cannot be widely applied as patients are often frail at presentation, making them ineligible for transplantation. Treatment with cyclophosphamide, bortezomib, and dexamethasone has emerged as the standard of care for the treatment of AL amyloidosis. Novel anti-plasma cell therapies, such as second generation proteasome inhibitors, immunomodulators, monoclonal antibodies targeting a surface protein on the plasma cell (daratumumab, elotuzumab), and the small molecular inhibitor venetoclax, have continued to emerge and are being evaluated in combination with the standard of care. However, there is still a need for therapies that directly target the amyloid fibrils and reverse organ damage. In this review, we will discuss current and emerging nonchemotherapy treatments of AL amyloidosis, including antifibril directed therapies under current investigation.

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What is new in diagnosis and management of light chain amyloidosis?

Blood ◽

10.1182/blood-2016-01-629790 ◽

2016 ◽

Vol 128 (2) ◽

pp. 159-168 ◽

Cited By ~ 97

Author(s):

Giovanni Palladini ◽

Giampaolo Merlini

Keyword(s):

Plasma Cell ◽

Light Chain ◽

Cell Clone ◽

Rescue Therapy ◽

Response Assessment ◽

Organ Damage ◽

Al Amyloidosis ◽

Cardiac Damage ◽

Staging Systems ◽

Therapy Treatment

Abstract Light chain (AL) amyloidosis is caused by a usually small plasma cell clone producing a misfolded light chain that deposits in tissues. Survival is mostly determined by the severity of heart involvement. Recent studies are clarifying the mechanisms of cardiac damage, pointing to a toxic effect of amyloidogenic light chains and offering new potential therapeutic targets. The diagnosis requires adequate technology, available at referral centers, for amyloid typing. Late diagnosis results in approximately 30% of patients presenting with advanced, irreversible organ involvement and dying in a few months despite modern treatments. The availability of accurate biomarkers of clonal and organ disease is reshaping the approach to patients with AL amyloidosis. Screening of early organ damage based on biomarkers can help identify patients with monoclonal gammopathy of undetermined significance who are developing AL amyloidosis before they become symptomatic. Staging systems and response assessment based on biomarkers facilitate the design and conduction of clinical trials, guide the therapeutic strategy, and allow the timely identification of refractory patients to be switched to rescue therapy. Treatment should be risk-adapted. Recent studies are linking specific characteristics of the plasma cell clone to response to different types of treatment, moving toward patient-tailored therapy. In addition, novel anti-amyloid treatments are being developed that might be combined with anti-plasma cell chemotherapy.

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

Blood Cancer Journal ◽

10.1038/s41408-021-00428-0 ◽

2021 ◽

Vol 11 (2) ◽

Cited By ~ 2

Author(s):

Giovanni Palladini ◽

Bruno Paiva ◽

Ashutosh Wechalekar ◽

Margherita Massa ◽

Paolo Milani ◽

...

Keyword(s):

Minimal Residual Disease ◽

Organ Dysfunction ◽

Light Chain ◽

Residual Disease ◽

Cell Clone ◽

Cardiac Response ◽

Al Amyloidosis ◽

Next Generation ◽

Organ Response ◽

Minimal Residual

AbstractLight 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.

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Quantitative Immunoprecipitation Free Light Chain Mass Spectrometry (QIP-FLC-MS) Simplifies Monoclonal Protein Assessment and Provides Added Clinical Value in Systemic AL Amyloidosis

Blood ◽

10.1182/blood-2019-128175 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4375-4375 ◽

Cited By ~ 1

Author(s):

Faye Amelia Sharpley ◽

Hannah Victoria Giles ◽

Richa Manwani ◽

Shameem Mahmood ◽

Sajitha Sachchithanantham ◽

...

Keyword(s):

Mass Spectrometry ◽

Light Chain ◽

Residual Disease ◽

Renal Involvement ◽

Light Chains ◽

Al Amyloidosis ◽

Free Light Chains ◽

Accurate Identification ◽

Monoclonal Protein ◽

Serum And Urine

Introduction Early diagnosis, effective therapy and precise monitoring are central for improving clinical outcomes in systemic light chain (AL) amyloidosis. Diagnosis and disease response assessment is primarily based on the presence of monoclonal immunoglobulins and free light chains (FLC). The ideal goal of therapy associated with best outcomes is a complete responses (CR), defined by the absence of serological clonal markers. In both instances, detection of the monoclonal component (M-component) is based on serum FLC assessment together with traditional serum and urine electrophoretic approaches, which present inherent limitations and lack sensitivity particularly in AL where the levels are typically low. Novel mass spectrometry methods provide sensitive, accurate identification of the M-component and may prove instrumental in the timely management of patients with low-level amyloidogenic light chain production. Here we assess the performance of quantitative immunoprecipitation FLC mass spectrometry (QIP-FLC-MS) at diagnosis and during monitoring of AL amyloidosis patients treated with bortezomib-based regimens. Methods We included 46 serial patients with systemic AL amyloidosis diagnosed and treated at the UK National Amyloidosis Centre (UK-NAC). All patients had detailed baseline assessments of organ function and serum FLC measurements. Baseline, +6- and +12-month serum samples were retrospectively analysed by QIP-FLC-MS. Briefly, magnetic microparticles were covalently coated with modified polyclonal sheep antibodies monospecific for free kappa light chains (anti-free κ) and free lambda light chains (anti-free λ). The microparticles were incubated with patient sera, washed and treated with acetic acid (5% v/v) containing TCEP (20 mM) in order to elute FLC in monomeric form. Mass spectra were acquired on a MALDI-TOF-MS system (Bruker, GmbH). Results were compared to serum FLC measurements (Freelite®, The Binding Site Group Ltd), as well as electrophoretic assessment of serum and urine proteins (SPE, sIFE, UPE and uIFE). Results Cardiac (37(80%) patients) and renal (31(67%) patients) involvement were most common; 25(54%) patients presented with both. Other organs involved included liver (n=12), soft tissue (n=4), gastrointestinal tract (n=3) and peripheral nervous system (n=2). Baseline Freelite, SPE, sIFE and uIFE measurements identified a monoclonal protein in 42(91%), 22(48%), 34(74%) and 21(46%) patients, respectively. A panel consisting of Freelite + sIFE identified the M-component in 100% of the samples. QIP-FLC-MS alone also identified an M-component in 100% of the samples and was 100% concordant with Freelite for typing the monoclonal FLC (8 kappa, 34 lambda). In 4 patients, QIP-FLC-MS identified an additional M-protein that was not detected by the other techniques. In addition, 4/8(50%) kappa and 4/38(11%) lambda patients showed a glycosylation pattern of monoclonal FLCs at baseline by mass spectrometry. Interestingly, the frequency of renal involvement was significantly lower for patients with non-glycosylated forms (25% vs 76%, p=0.01), while no similar relationship was found for any other organs. During the 1-year follow-up period, 17 patients achieved a CR; QIP-FLC-MS identified serum residual disease in 13(76%) of these patients. Conclusion In our series, QIP-FLC-MS was concordant with current serum methods for identifying the amyloidogenic light chain type and provided, against all other individual tests, improved sensitivity for the detection of the monoclonal protein at diagnosis and during monitoring. The ability to measure the unique molecular mass of each monoclonal protein offers clone-specific tracking over time. Glycosylation of free light chains is over-represented in AL patients which may allow earlier diagnosis and better risk-assessment of organ involvement. Persistence of QIP-FLC-MS positive M component in patients otherwise in CR may allow targeted therapy. Overall, QIP-FLC-MS demonstrates potential to be exploited as a single serum test for precise serial assessment of monoclonal proteins in patients with AL amyloidosis. Disclosures Wechalekar: GSK: Honoraria; Janssen-Cilag: Honoraria; Amgen: Research Funding; Takeda: Honoraria; Celgene: Honoraria.

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Conventional Therapy for Amyloid Light-Chain Amyloidosis

Acta Haematologica ◽

10.1159/000507072 ◽

2020 ◽

Vol 143 (4) ◽

pp. 365-372

Author(s):

Paolo Milani ◽

Giovanni Palladini

Keyword(s):

Stem Cell ◽

Plasma Cell ◽

Light Chain ◽

Cell Clone ◽

Alkylating Agents ◽

Proteasome Inhibitors ◽

Response Rates ◽

Al Amyloidosis ◽

Cell Transplant ◽

Conventional Chemotherapy

The vast majority of patients with light-chain (AL) amyloidosis are not eligible for stem cell transplant and are treated with conventional chemotherapy. Conventional regimens are based on various combinations of dexamethasone, alkylating agents, proteasome inhibitors, and immunomodulatory drugs. The choice of these regimens requires a careful risk stratification, based on the extent of amyloid organ involvement, comorbidities, and the characteristics of the amyloidogenic plasma cell clone. Most patients are treated upfront with bortezomib and dexamethasone combined with cyclophosphamide or melphalan. Cyclophosphamide does not compromise stem cell mobilization and harvest and is more manageable in renal failure. Melphalan can overcome the effect of t(11;14), which is associated with lower response rates and shorter survival in subjects treated with bortezomib and dexamethasone, or in combination with cyclophosphamide. Lenalidomide and pomalidomide are the mainstay of rescue treatment. They are effective in patients exposed to bortezomib, dexamethasone, and alkylators, but deep hematologic responses are rare. Ixazomib, alone or in combination with lenalidomide, increases the rate of complete responses in relapsed/refractory patients. Conventional chemotherapy regimens will represent the backbone for future combinations, particularly with anti-plasma-cell immunotherapy, that will further improve response rates and outcomes.

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Recent Advances in the Diagnosis, Risk Stratification, and Management of Systemic Light-Chain Amyloidosis

Acta Haematologica ◽

10.1159/000495455 ◽

2019 ◽

Vol 141 (2) ◽

pp. 93-106 ◽

Cited By ~ 28

Author(s):

Iuliana Vaxman ◽

Morie Gertz

Keyword(s):

Plasma Cell ◽

Light Chain ◽

Cell Clone ◽

Proteasome Inhibitors ◽

Clinical Manifestations ◽

Al Amyloidosis ◽

Amyloid Deposits ◽

Protein Fibrils ◽

Risk Patients ◽

Intensive Search

The term amyloidosis refers to a group of disorders in which protein fibrils accumulate in certain organs, disrupt their tissue architecture, and impair the function of the effected organ. The clinical manifestations and prognosis vary widely depending on the specific type of the affected protein. Immunoglobulin light-chain (AL) amyloidosis is the most common form of systemic amyloidosis, characterized by deposition of a misfolded monoclonal light-chain that is secreted from a plasma cell clone. Demonstrating amyloid deposits in a tissue biopsy stained with Congo red is mandatory for the diagnosis. Novel agents (proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, venetoclax) and autologous stem cell transplantation, used for eliminating the underlying plasma cell clone, have improved the outcome for low- and intermediate-risk patients, but the prognosis for high-risk patients is still grave. Randomized studies evaluating antibodies that target the amyloid deposits (PRONTO, VITAL) were recently stopped due to futility and currently there is an intensive search for novel treatment approaches to AL amyloidosis. Early diagnosis is of paramount importance for effective treatment and prognosis, due to the progressive nature of this disease.

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Differential diagnosis of monoclonal gammopathy of undetermined significance

Hematology ◽

10.1182/asheducation.v2012.1.595.3798563 ◽

2012 ◽

Vol 2012 (1) ◽

pp. 595-603 ◽

Cited By ~ 57

Author(s):

Giampaolo Merlini ◽

Giovanni Palladini

Keyword(s):

Differential Diagnosis ◽

Plasma Cell ◽

Monoclonal Gammopathy ◽

Cell Clone ◽

Organ Damage ◽

Organ Injury ◽

Al Amyloidosis ◽

Monoclonal Protein ◽

Undetermined Significance

Abstract Monoclonal gammopathy of undetermined significance (MGUS) is an asymptomatic plasma cell disorder occurring in 4.2% of adults > 50 years of age, which can progress into symptomatic diseases either through proliferation of the plasma cell clone, giving rise to multiple myeloma and other lymphoplasmacellular neoplasms, or through organ damage caused by the monoclonal protein, as seen in light-chain amyloidosis and related conditions. Differential diagnosis of asymptomatic and symptomatic monoclonal gammopathies is the determinant for starting therapy. The criteria for determining end-organ damage should include markers of organ injury caused by the monoclonal protein. Patient assessment and optimal follow-up are now performed using risk stratification models that should also take into account the risk of developing AL amyloidosis. Patients with low-risk MGUS (approximately 40% of all MGUS patients) need limited assessment and very infrequent follow-up. The ongoing development of novel molecular biomarkers and advanced imaging techniques will improve the identification of high-risk patients who may benefit from early therapeutic intervention through innovative clinical trials.

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Serum Reference Intervals and Diagnostic Ranges for Free κ and Free λ Immunoglobulin Light Chains: Relative Sensitivity for Detection of Monoclonal Light Chains

Clinical Chemistry ◽

10.1093/clinchem/48.9.1437 ◽

2002 ◽

Vol 48 (9) ◽

pp. 1437-1444 ◽

Cited By ~ 421

Author(s):

Jerry A Katzmann ◽

Raynell J Clark ◽

Roshini S Abraham ◽

Sandra Bryant ◽

James F Lymp ◽

...

Keyword(s):

Light Chain ◽

Reference Intervals ◽

Systemic Amyloidosis ◽

Light Chains ◽

Light Chain Deposition Disease ◽

Monoclonal Gammopathies ◽

Automated Immunoassay ◽

Light Chain Deposition ◽

Diagnostic Intervals ◽

Detection And Quantification

Abstract Background: The detection of monoclonal free light chains (FLCs) is an important diagnostic aid for a variety of monoclonal gammopathies and is especially important in light-chain diseases, such as light-chain myeloma, primary systemic amyloidosis, and light-chain-deposition disease. These diseases are more prevalent in the elderly, and assays to detect and quantify abnormal amounts of FLCs require reference intervals that include elderly donors. Methods: We used an automated immunoassay for FLCs and sera from a population 21–90 years of age. We used the calculated reference and diagnostic intervals to compare FLC results with those obtained by immunofixation (IFE) to detect low concentrations of monoclonal κ and λ FLCs in the sera of patients with monoclonal gammopathies. Results: Serum κ and λ FLCs increased with population age, with an apparent change for those >80 years. This trend was lost when the FLC concentration was normalized to cystatin C concentration. The ratio of κ FLC to λ FLC (FLC K/L) did not exhibit an age-dependent trend. The diagnostic interval for FLC K/L was 0.26–1.65. The 95% reference interval for κ FLC was 3.3–19.4 mg/L, and that for λ FLC was 5.7–26.3 mg/L. Detection and quantification of monoclonal FLCs by nephelometry were more sensitive than IFE in serum samples from patients with primary systemic amyloidosis and light-chain-deposition disease. Conclusions: Reference and diagnostic intervals for serum FLCs have been developed for use with a new, automated immunoassay that makes the detection and quantification of monoclonal FLCs easier and more sensitive than with current methods. The serum FLC assay complements IFE and allows quantification of FLCs in light-chain-disease patients who have no detectable serum or urine M-spike.

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