scholarly journals Barriers to Small Molecule Drug Discovery for Systemic Amyloidosis

Molecules ◽  
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.

scholarly journals Barriers to Small Molecule Drug Discovery for Systemic Amyloidosis

2021 ◽  
Author(s):  
Gareth Morgan
Keyword(s):  
Small Molecules ◽  
Amyloid Fibrils ◽  
Systemic Amyloidosis ◽  
Light Chains ◽  
Al Amyloidosis ◽  
Amyloid Formation ◽  
Immunoglobulin Light Chain ◽  
Amyloid Fibril Formation ◽  
Precursor Proteins

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. Although many small molecules have been proposed as inhibitors of amyloid formation, few have been successful in clinical trials. Amyloid formation is complex and several individual steps could be targeted by small molecules. 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 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 amyloidogenesis.

scholarly journals A comparison of immunohistochemistry and mass spectrometry for determining light chain amyloid fibril protein from formalin-fixed renal biopsy tissue in a single Chinese center

2019 ◽  
Author(s):  
Ying Sun ◽  
Jian Sun ◽  
Wei Sun ◽  
Junyi Pang ◽  
Yubing Wen ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Renal Biopsy ◽  
Light Chain ◽  
Protein Identification ◽  
Amyloid Fibrils ◽  
Al Amyloidosis ◽  
Precise Diagnosis ◽  
Ffpe Tissues ◽  
Amyloid Light Chain ◽  
Formalin Fixed

Abstract Background Amyloidosis, a disease caused by abnormal protein deposition in tissues, is classified according to the protein precursor that form amyloid fibrils. Diagnosis of amyloidosis is type-specific as the identification of amyloid protein determines the following treatment. However, around a quarter of amyloidosis cases cannot be accurately subtyped by most commonly used immunohistochemistry (IHC). In order to obtain precise diagnosis, our study is focusing on another protein identification methods, laser microdissection and mass spectrometry (LDMS). Methods 20 cases of Amyloid Light-chain (AL) amyloidosis without further subtype were included. IHC and LDMS were used to detect light chains on formalin-fixed paraffin-embedded (FFPE) tissues from renal biopsy. Results 100% consistence between positive IHC and LDMS results were observed, however, chances of subtyping using LDMS is increased to 94% compared to IHC which is only 76%. Conclusion LDMS is a valuable tool in regard to subtyping amyloidosis.

scholarly journals Dissecting the Molecular Features of Systemic Light Chain (AL) Amyloidosis: Contributions from Proteomics

Medicina ◽  
2021 ◽  
Vol 57 (9) ◽  
pp. 916
Author(s):  
Paola Rognoni ◽  
Giulia Mazzini ◽  
Serena Caminito ◽  
Giovanni Palladini ◽  
Francesca Lavatelli
Keyword(s):  
Light Chain ◽  
Amyloid Fibrils ◽  
Cell Clone ◽  
Experimental Models ◽  
Critical Discussion ◽  
Al Amyloidosis ◽  
Primary Role ◽  
Molecular Features ◽  
Amyloid Light Chain ◽  
Models Of Disease

Amyloidoses are characterized by aggregation of proteins into highly ordered amyloid fibrils, which deposit in the extracellular space of tissues, leading to organ dysfunction. In AL (amyloid light chain) amyloidosis, the most common form in Western countries, the amyloidogenic precursor is a misfolding-prone immunoglobulin light chain (LC), which, in the systemic form, is produced in excess by a plasma cell clone and transported to target organs though blood. Due to the primary role that proteins play in the pathogenesis of amyloidoses, mass spectrometry (MS)-based proteomic studies have gained an established position in the clinical management and research of these diseases. In AL amyloidosis, in particular, proteomics has provided important contributions for characterizing the precursor light chain, the composition of the amyloid deposits and the mechanisms of proteotoxicity in target organ cells and experimental models of disease. This review will provide an overview of the major achievements of proteomic studies in AL amyloidosis, with a presentation of the most recent acquisitions and a critical discussion of open issues and ongoing trends.

scholarly journals Dissection of the amyloid formation pathway in AL amyloidosis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Pamina Kazman ◽  
Ramona M. Absmeier ◽  
Harald Engelhardt ◽  
Johannes Buchner
Keyword(s):  
Light Chain ◽  
Solvent Accessibility ◽  
Fibril Formation ◽  
Lag Phase ◽  
Al Amyloidosis ◽  
Amyloid Formation ◽  
Hydrophobic Core ◽  
Structural Transitions ◽  
Formation Pathway

AbstractIn antibody light chain (AL) amyloidosis, overproduced light chain (LC) fragments accumulate as fibrils in organs and tissues of patients. In vitro, AL fibril formation is a slow process, characterized by a pronounced lag phase. The events occurring during this lag phase are largely unknown. We have dissected the lag phase of a patient-derived LC truncation and identified structural transitions that precede fibril formation. The process starts with partial unfolding of the VL domain and the formation of small amounts of dimers. This is a prerequisite for the formation of an ensemble of oligomers, which are the precursors of fibrils. During oligomerization, the hydrophobic core of the LC domain rearranges which leads to changes in solvent accessibility and rigidity. Structural transitions from an anti-parallel to a parallel β-sheet secondary structure occur in the oligomers prior to amyloid formation. Together, our results reveal a rate-limiting multi-step mechanism of structural transitions prior to fibril formation in AL amyloidosis, which offers, in the long run, opportunities for therapeutic intervention.

scholarly journals Multiorgan involvement by amyloid light chain amyloidosis

2019 ◽  
Vol 47 (4) ◽  
pp. 1778-1786 ◽  
Author(s):  
Guoliang Li ◽  
Dan Han ◽  
Suhua Wei ◽  
Huaiyu Wang ◽  
Limei Chen
Keyword(s):  
Light Chain ◽  
Amyloid Fibrils ◽  
Normal Structure ◽  
Al Amyloidosis ◽  
Initial Symptom ◽  
Close Monitoring ◽  
Clinical Complexity ◽  
Amyloid Light Chain ◽  
Low Incidence ◽  
Chemotherapy Strategy

Amyloid light chain (AL) amyloidosis is a protein conformational disease. AL amyloidosis results from aggregation of misfolded proteins that are deposited in tissues as amyloid fibrils. Diagnosis of AL amyloidosis can be challenging due to its low incidence and clinical complexity. Therapy requires a risk-adapted approach involving dose reductions and schedule modifications of chemotherapy regimens along with close monitoring of hematologic and organ responses. We herein describe a patient whose condition was diagnosed as systemic AL amyloidosis and presented with splenic rupture as the initial symptom. Congo red staining of the kidney biopsy was positive. The normal structure of the liver and spleen had been replaced by amyloid deposition. The chemotherapy strategy involved a combination of bortezomib, cyclophosphamide, thalidomide, and dexamethasone.

Al amyloidosis with cardiac involvement: cardiotoxicity of aggregation prone peptides deriving from variable domains of immunoglobulin light chains

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
P.E Nikolaou ◽  
G.I Nasi ◽  
I Sulaiman ◽  
P Spatharas ◽  
S Kikionis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Death ◽  
Light Chain ◽  
Hot Spots ◽  
Cytotoxic Effect ◽  
Light Chains ◽  
Al Amyloidosis ◽  
H9c2 Cells ◽  
Variable Domains

Abstract Background/Introduction Light chain (AL) amyloidosis is an uncommon malignancy manifested by systemic extracellular deposition of immunoglobulin light chain fibrils. The cardiac phenotype is characterised by ventricular wall thickening and stands as the most prominent cause of morbidity and mortality. Although, it has been established that the circulating light chains directly impair cardiomyocyte function, the cytotoxic effect of specific amyloidogenic peptides that may appear due to excessive cleavage of light chains remains unspecified. Purpose In the present work, we aimed to detect amyloidogenic “hot-spots” on the variable domains of light chains associated with cardiac AL amyloidosis (IGLV1-44 and IGLV3-01) or inferior outcomes (IGLV6-57) and define their cytotoxic effect in vitro. Methods At first, we used the curated database ALBase and we performed a multiple sequence alignment of the IGLV1-44, IGLV3-01 and IGLV6-57 inputs that derived only from patients with AL amyloidosis. “Aggregation-prone” hot-spots in the conserved amino acid sequences were identified with the aid of AMYLPRED2, a tool which combines 11 independent computational methods and provides a consensus result of potent amyloidogenic regions. Five peptides were rationally selected and synthetically produced in order to be tested in vitro. The amyloidogenic properties of the peptides were evaluated with Transmission Electron Microscopy and Congo red staining, while the rate of fibril formation at lower concentrations was monitored with Thioflavin T and confirmed with Scanning Electron Microscopy. In order to assess the cytotoxic effect of the non-polymerized peptides, H9C2 cells were incubated with the peptides for 24 hours at 200μg/mL and 100μg/mL and cell death was determined by lactate dehydrogenase release assay. Results Interestingly, sequence alignment on the variable domains of cardiac related light chains revealed the presence of several conserved domains in patients with AL amyloidosis. The chosen peptides were proven to be amyloidogenic suggesting that the variable domains share common amyloidogenic cores. Treatment of H9C2 cells with the peptides at 200μg/mL led to significant reduction in cell viability compared to vehicle treated cells (p<0.001). Two of the peptides deriving from the IGLV6-57 and IGLV3-01 significantly increased cell death at 100μg/mL (p<0.01 and p<0.001 respectively). During the 24h treatment the tested peptides comprised of soluble species and not amyloid fibrils suggesting that monomeric and oligomeric intermediates are highly toxic. Conclusion We discovered five novel amyloidogenic prone regions of cardiac related variable domains that are associated with cellular toxicity and could be exploited for targeted therapeutic interventions. Funding Acknowledgement Type of funding source: None

scholarly journals Pathology and Proteomics-Based Diagnosis of Localized Light-Chain Amyloidosis in Dogs and Cats

2020 ◽  
Vol 57 (5) ◽  
pp. 658-665
Author(s):  
Ayumi Kadota ◽  
Susumu Iwaide ◽  
Shinya Miyazaki ◽  
Ikki Mitsui ◽  
Noboru Machida ◽  
...  
Keyword(s):  
Potassium Permanganate ◽  
Light Chain ◽  
Congo Red ◽  
Light Chains ◽  
Al Amyloidosis ◽  
Specificity And Sensitivity ◽  
Amyloid Deposits ◽  
Liquid Chromatography Tandem Mass ◽  
Congo Red Staining ◽  
Amyloid Light Chain

Amyloidosis is classified according to the amyloid precursor protein, and accurate diagnosis of the amyloidosis type may guide appropriate treatment. Immunohistochemistry and Congo red staining are the most frequently used methods used to distinguish types of amyloidosis, but problems with specificity and sensitivity indicate the need for an alternative diagnostic method. In this study, we evaluated laser microdissection-liquid chromatography-tandem mass spectrometry (LMD-LC-MS/MS) for the diagnosis of amyloid light-chain (AL) amyloidosis in animals. Plasmacytomas with amyloid deposits from 15 dogs and 2 cats were subjected to Congo red staining with or without potassium permanganate pretreatment, immunohistochemistry for kappa and lambda light chains, and LMD-LC-MS/MS. Congo red staining was diagnostic in 12 of 17 cases based on resistance to potassium permanganate pretreatment, but in 5 of 17 cases the pretreatment unexpectedly reduced Congo red staining or abrogated the birefringence and a definitive diagnosis could not be reached. Immunohistochemistry detected kappa or lambda light chains in 6 of 17 cases. With LMD-LC-MS/MS, immunoglobulin lambda light chain was detected in all 17 cases. The amyloid signature proteins ApoA-I, ApoA-IV, and ApoE were detected in 9, 1, and 3 of the 15 canine cases by LMD-LC-MS/MS, but not in the feline cases. In conclusion, LMD-LC-MS/MS consistently determined the amyloid type in all examined specimens, while Congo red staining after potassium permanganate treatment and immunohistochemistry were less sensitive tests.

scholarly journals Early Serum Free Light Chain Response after High-Dose Melphalan and Stem Cell Transplantation Predicts Hematologic Response in AL Amyloidosis

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 26-26
Author(s):  
Vanessa Fiorini Furtado ◽  
Dina Brauneis ◽  
Shayna Sarosiek ◽  
Karen Quillen ◽  
Vaishali Sanchorawala
Keyword(s):  
Light Chain ◽  
Research Funding ◽  
Amyloid Fibrils ◽  
Advisory Board ◽  
Free Light Chain ◽  
Light Chains ◽  
High Dose ◽  
Al Amyloidosis ◽  
Serum Free Light Chain ◽  
High Dose Melphalan

Introduction Immunoglobulin light chain (AL) amyloidosis is a rare disease caused by a clonal plasma cell dyscrasia producing monoclonal light chains that misfold and form amyloid fibrils which can deposit in a variety of tissues and organs. This deposition of amyloid fibrils can lead to progressive organ impairment, multi-organ failure, and death if left untreated. High-dose melphalan and autologous stem cell transplantation (HDM/SCT) is known to improve patient outcomes with hematologic complete responses (CR) rates of 25-67%. Hematologic CR is currently defined as the absence of monoclonal protein in serum and urine by immunofixation electrophoreses and normal serum free light chain ratio (FLCR). Studies have shown that even among patients achieving a normal FLCR after initial therapy with HDM, persistent elevation of the involved FLC (hiFLC) predicts poor prognosis. Serum half-life of FLCs is approximately 2-6 hours, even with diminished glomerular filtration rates, and could be a tool for early treatment response evaluation. We sought to determine the extent to which early FLC responses after HDM/SCT predict hematologic complete response (CR) at 6 months. Methods We analyzed patients with AL amyloidosis who underwent HDM/SCT from 2012-2019 at Boston Medical Center. Exclusion criteria included death within 100 days, lack of FLC data at any time point, pre-SCT normal FLC concentrations and ratio, and chronic renal insufficiency (serum creatinine >1.3 mg/dL) with a normal FLC ratio. All subjects received a total of 140-200 mg/m2 melphalan IV in equally divided doses on days -3 and -2. Stem cells were infused on day 0. FLC measurements were obtained early in the peri-SCT period (< 1 month), at 6 months, and at 12 months after HDM/SCT. The patients were evaluated for response according to the consensus response criteria at 6 months. Statistical analysis to compare CR at 6 months and early post-SCT free light chain levels was performed by Chi-square with significance considered at p<0.05. Results Of the 113 patients with AL amyloidosis treated with HDM/SCT during the specified time period, 32 were excluded (4 died within 100 days of SCT, 15 had normal FLCs pre-SCT, 5 lacked data, and 8 had chronic renal insufficiency (Cr >1.3 mg/dL) with normal FLCR. A total of 81 subjects (females=30) were analyzed. Median follow-up from SCT was 27.6 months (range, 6-145). Median time of early post-SCT FLC measurement was 8 days (range, 7-30). Median age at diagnosis was 58 years (range 30-79) and the iFLC was lambda in 81.5% (n = 66) of patients. Median number of bone marrow plasma cells was 10% (range, 1-50). The mean absolute involved FLC was 196 mg/L ±221 prior to SCT, 60 mg/L ± 77 in the early post-SCT period, 92 mg/L ± 152 at 6 months post-SCT. In early post-SCT period, 39.5% (n=32) had iFLC <20 mg/L, 28% (n=16/57) had dFLC<10 mg/L, and 84% (n=48/57) had normal FLCR. Early post-SCT dFLC <10 mg/dL and early post-SCT iFLC <20 mg/L were statistically associated with prediction of hematologic CR at 6 months (p=0.025 and p=0.001, respectively). However, early post-SCT normal FLCR was not associated with predicting hematologic CR at 6 months. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of early post-SCT iFLC <20 mg/L, dFLC <10 mg/L and normal FLCR to predict hematologic CR at 6 months are presented in table 1. Conclusion This study concludes that achievement of dFLC <10 mg/L and iFLC <20 mg/L in the early post-SCT period is associated with prediction of hematologic CR at 6 months. Early post-SCT dFLC <10 mg/L could be considered a tool for early evaluation of treatment response following HDM/SCT in AL amyloidosis. Key words: immunoglobulin light chains; AL amyloidosis, HDM/SCT Disclosures Sarosiek: Spectrum: Research Funding. Sanchorawala:Caelum: Research Funding; Prothena: Research Funding; Celgene: Research Funding; Takeda: Research Funding; Proclara: Other: advisory board; Abbvie: Other: advisory board; UpToDate: Patents & Royalties; Oncopeptide: Research Funding; Regeneron: Other: advisory board; Caleum: Other: advisory board; Janssen: Research Funding.

Detection of High Molecular Weight Light Chain Oligomers in Urinary Exosomes of Patients with AL Amyloidosis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4886-4886
Author(s):  
Marina Ramirez-Alvarado ◽  
Christopher J Ward ◽  
Bing Q Huang ◽  
Xun Gong ◽  
Marie C Hogan ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Light Chain ◽  
Amyloid Fibrils ◽  
Urine Samples ◽  
Al Amyloidosis ◽  
Amyloid Formation ◽  
Western Blots ◽  
Light Chain Deposition Disease ◽  
Urinary Exosomes

Abstract Abstract 4886 Detection of high molecular weight light chain oligomers in urinary exosomes of patients with AL amyloidosis. Background Exosomes are microvesicles that are part of the multivesicular body (MVB) pathway. They are created by the inward budding of the cell surface membrane and contain both surface bound membrane proteins and cytosolic proteins which can be used to identify the cell of origin. Immunoglobulin light chain amyloidosis (AL) occurs as the result of amyloid formation by the misfolding of monoclonal light chains (LC) and deposition of these amyloid fibrils in various soft tissues. This reaction requires the organization of the monoclonal LC's into protofibrils which are then weave into amyloid fibrils. This study was undertaken to determine whether urinary exosomes of glomerular origin contain intermediate species of amyloid formation. Method Urine samples from patients with AL, light chain deposition disease (LCDD), multiple myeloma (MM) and monoclonal clonal gammopathy of undetermined significance (MGUS) were collected. Urinary exosomes were isolated and separated into fractions by gradient centrifugation. Western blots were performed on the urinary exosome fractions using anti-kappa or anti-lambda antibodies. Glomerular fractions were identified using antibodies directed toward podocin. Results Urine samples were collected from 5 patients with AL, 2 from LCDD, 1 from MM and 1 MGUS. On the Western blot, immunoglobulin LC were seen in all exosomal fractions in patients with AL amyloidosis, LCDD, MM but not MGUS which is similar to normal controls (not shown). In patients with AL, oligomeric species were found in the highest concentrations in fraction 4 and 5 (Figure 1). Fraction 4 and 5 were also stained for podocin, a glomerular protein (not shown). The highest molecular weight species was ∼250 kd which corresponds to a LC decamer. High molecular weight species were also identified in 1 of 2 LCDD patients corresponding to a tetramer. The band was identified in fraction 10 which had polycystin-1 expression suggesting a tubular origin. No high molecular weight LC species was found in patients with MM or MGUS. Conclusion Our study found high molecular weight LC species corresponding to the intermediates involved in protofibril formation in urinary exosomes of patients with AL. Smaller (tetramer) high molecular weight LC species were also found in a patient with LCDD but not in patients with MM and MGUS. Not only were the high molecular weight LC species found exclusively in the diseases characterized by deposition of LC aggregates, they were also found in the segments of the nephron where the deposits were expected: glomerulus for AL and tubular epithelium for LCDD. This is consistent with our current understanding of the pathogenic mechanisms of these diseases. We believe urinary exosomes are a powerful tool in the study of diseases involving self-aggregation of monoclonal proteins. It has tremendous potential in both diagnostic and scientific research in this area. Disclosures Gertz: celgene: Honoraria; millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees.

scholarly journals A Novel Mass Spectrometry Method to Identify the Serum Monoclonal Light Chain Component and Infer Organ Involvement in Systemic Light Chain Amyloidosis

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 4445-4445 ◽  
Author(s):  
Faye Sharpley ◽  
Richa Manwani ◽  
Shameem Mahmood ◽  
Sajitha Sachchithanantham ◽  
Helen Lachmann ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Mass ◽  
Light Chain ◽  
Mass Spectra ◽  
Amyloid Fibrils ◽  
Cardiac Involvement ◽  
Small Sample ◽  
Organ Involvement ◽  
Light Chains ◽  
Al Amyloidosis

Abstract Introduction Light chain (AL) amyloidosis is caused by progressive organ dysfunction due to the deposition of structurally abnormal monoclonal light chains (LC) as amyloid fibrils. Serial free light chain measurement is the cornerstone of AL diagnosis but is limited by current methods which measure normal polyclonal and abnormal monoclonal LCs. Since each individual monoclonal LC has a unique amino acid sequence, mass spectrometry (MS) has the ability to detect serum monoclonal LCs. We report a novel MS method for monoclonal LC detection in AL amyloidosis. Methods Twenty patients with systemic AL amyloidosis, diagnosed and treated at the UK National Amyloidosis Centre (UK-NAC), were randomly selected. This included 16 newly diagnosed patients, 2 patients in a complete haematological remission (CR) post-treatment and 2 patients with no amyloidosis (acting as negative controls). All patients had detailed baseline assessments of organ function and serum FLC measurements. Organ involvement was defined according to the international amyloidosis consensus criteria. Magnetic microparticles were covalently coated with modified polyclonal sheep antibodies monospecific for free kappa light chains (anti-free k) and free lambda light chains (anti-free l). The microparticles were incubated with patient sera, washed and treated with acetic acid (5% v/v) containing TCEP (20 mM) in order to elute free light chains in monomeric form. Mass spectra were acquired on a Microflex LT/SH smart matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS; Bruker, GmbH). Results The median number of organs involved was 2 (range 1-4); cardiac involvement was most common in 70% (14/20) patients, followed by renal 40% (8/20), autonomic and soft tissue in 15% (3/20) and peripheral nerve involvement in 5% (1/20). No patients had liver involvement. The median N-terminal pro b-type natriuretic peptide (NT-proBNP) and cardiac troponin T were 3761.5 (range 245-25348 ng/L) and 35.5 (8-170 ng/L) respectively. The median presenting serum albumin was 37 (19-45 g/L) and eGFR 62 (10-100 mls/min). The amyloid deposits were typed as AL lambda in 14(70%), kappa in 2(10%) patients and amyloid of uncertain type in two cases (10%). The median involved FLC was kappa 76 mg/L (range 71-440) and lambda 185 mg/L (44-1023), with difference involved to uninvolved (dFLC) 118 mg/L (33-1015). An intact monoclonal protein was present in 70% (14/20). In all cases, MS correctly identified the presence and type of monoclonal LC, identifying a monoclonal lambda in 14/14 (100%) and a monoclonal kappa in 2/2 (100%); the two patients where a clear monoclonal component could not be identified were patients whose amyloid fibrils failed to be typed by immunohistochemistry or MS. The assay also confirmed normal polyclonal expression of both kappa and lambda LCs in the two control samples. In the two lambda patients in a CR, the MS method identified monoclonal lambda LC expression; in one of these patients next-generation sequencing (NGS) confirmed minimal residual disease (MRD). A clear shift in the LC mass spectra was seen relating to the specific pattern of organ involvement: in patients with renal amyloid the monoclonal LC predominantly displayed a "heavy" molecular mass, (with a mean molecular mass of 11596+/- 436 daltons), whereas in patients with cardiac involvement the monoclonal LC mainly exhibited a "light" mass (with a mean molecular mass of 11443 +/- 102 daltons). Conclusion This small study shows that monoclonal light chains can be accurately detected by MS and be concordant to the tissue amyloid type. A monoclonal LC was detected in 2 patients in serological "CR" - in one case presence of persistent disease was demonstrated by NGS-MRD. Even in this small sample size, there appears to be a marked difference in LC mass for patients with cardiac ("light" LC) vs. renal ("heavy" LC) involvement, raising the interesting possibility that "heavy" LC are trapped by the glomerulus causing renal AL but are unable to penetrate the tight cardiac capillary gap junctions, and vice versa. The unique molecular location of LC on MS offers the possibility of exploiting this technique as a tool to detect amyloidogenic FLC and potentially predict organ involvement in patients with gammopathies. We plan to expand this study to a large cohort of patients to confirm these findings and assess the impact on survival and organ response outcomes. Figure 1 Figure 1. Disclosures Wechalekar: Janssen: Honoraria.

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