The Amyloidosis Forum: a public private partnership to advance drug development in AL amyloidosis

The mechanism of action, pharmacological characteristics, and clinical utility of the amyloid depleter birtamimab for the potential treatment of AL amyloidosis

Amyloid light chain (AL) amyloidosis is a progressive plasma cell disorder caused by amyloid deposition resulting in organ damage and failure. Current standard-of-care treatments target clonal plasma cells, the source of misfolded light chains (amyloid precursors), yet only half of patients with advanced disease survive ≥6 months. The amyloid depleter birtamimab is an investigational humanized monoclonal antibody that binds misfolded κ and λ light chains with high specificity and was designed to neutralize soluble toxic light chain aggregates and promote phagocytic clearance of deposited amyloid. Post hoc analyses from the Phase 3 VITAL trial suggested birtamimab plus standard of care confers a survival benefit in patients with advanced (Mayo Stage IV) AL amyloidosis. AFFIRM-AL (NCT04973137), a Phase 3 confirmatory trial of birtamimab plus standard of care in patients with Mayo Stage IV AL amyloidosis, is ongoing. This review summarizes birtamimab's mechanism of action, attributes, and potential clinical utility.

Advancing Transthyretin Amyloidosis Drug Development in an Evolving Treatment Landscape: Amyloidosis Forum Meeting Proceedings

INTRODUCTION

Hereditary transthyretin amyloidosis (ATTRv, also referred to as hATTR; ORPHA 271861) and wild-type ATTR amyloidosis (ATTRwt; ORPHA 330001) are rare, progressive, systemic protein misfolding disorders with heterogeneous clinical presentations. ATTRv and ATTRwt amyloidosis are characterized by the deposition of amyloid fibrils in multiple organs including the heart, nerves, eyes, and soft tissues. The management of ATTR amyloidosis is complex because of its multisystemic nature and progression despite available treatment options. Morbidity is high and there are many unmet medical needs for patients. While contemporary ATTR amyloidosis cohorts are diagnosed earlier, have lower risk disease and lower mortality compared with the previous era, these advances coupled with the emergence of effective disease-modifying therapies have confounded the design of future prospective clinical trials and interpretation of historical control data.

MAIN BODY

The Amyloidosis Forum is a public-private partnership between the US Food and Drug Administration Center for Drug Evaluation and Research and the nonprofit Amyloidosis Research Consortium ( www.arci.org ). This article summarizes proceedings from the 21 June 2023 Amyloidosis Forum on advancing drug development in ATTR amyloidosis in an evolving treatment landscape. The Forum focused on elements of clinical trial design to address these challenges and discussed their strengths and weaknesses from multiple stakeholder perspectives (i.e., patient, sponsor, statistician, clinician, and regulatory authorities).

CONCLUSION

Given rapid evolution of natural history in ATTR amyloidosis, the utility of historical control data is limited. Leveraging contemporary real-world data is essential for clinical trial design. Evidence generation from clinical trials should address clinically relevant questions. Key factors in successful trial design must be informed by up-to-date data on natural history, prognostic factors, clinically meaningful thresholds, and sharing available clinical trial data. The Amyloidosis Forum includes the community of patients with ATTR amyloidosis, the physicians who treat them, and the sponsors and regulators who collectively stand ready to support further studies in order to develop novel effective therapies.

Pathway for Development and Validation of Multi-domain Endpoints for Amyloid Light Chain (AL) Amyloidosis

Immunoglobin light chain (AL) amyloidosis is a rare disease in which a plasma cell dyscrasia leads to deposition of insoluble amyloid fibrils in multiple organs. To facilitate development of new therapies for this heterogenous disease, a public-private partnership was formed between the nonprofit Amyloidosis Research Consortium and the US Food and Drug Administration Center for Drug Evaluation and Research. In 2020, the Amyloidosis Forum launched an initiative to identify clinical trial endpoints and analytic strategies across affected organ systems and life impacts via specialized working groups. This review summarizes the proceedings of the Statistical Group and proposes a pathway for development and validation of multi-domain endpoints (MDEs) for potential use in AL amyloidosis clinical trials. Specifically, drawing on candidate domain-specific endpoints recommended by each organ-specific working group, different approaches to constructing MDEs were considered. Future studies were identified to assess the validity, meaningfulness and performance of MDEs through use of natural history and clinical trial data. Ultimately, for drug development, the context of use in a regulatory evaluation, the specific patient population, and the investigational therapeutic mechanism should drive selection of appropriate endpoints. MDEs for AL amyloidosis, once developed and validated, will provide important options for advancing patient-focused drug development in this multi-system disease.

Renal Response Criteria for Clinical Trials in Amyloid Light Chain Amyloidosis

Immunoglobin light chain (AL) amyloidosis is a rare disease characterized by organ deposition of amyloid fibrils, most commonly in the heart and kidney. Disease heterogeneity necessitates organ-specific assessment to determine prognosis and response or progression. To facilitate development of new therapies, the Amyloidosis Forum (a public-private partnership between the US Food and Drug Administration and the nonprofit Amyloidosis Research Consortium) held a series of meetings and formed multiple working groups to identify clinical trial end points and analytic strategies. This report summarizes the recommendations of Renal Working Group. Estimated glomerular filtration rate (eGFR) and proteinuria were selected to evaluate eligibility, response, and/or progression in the context of investigational clinical trials for patients with AL amyloidosis. Accurate response assessments at the earliest possible time point were emphasized. The context of use, specific patient population, and the investigational therapeutic mechanism should ultimately drive selection of appropriate end points to evaluate renal response/progression in AL amyloidosis clinical trials.

Outcomes of Modified Mayo Stage IIIa and IIIb Cardiac Light-Chain Amyloidosis: Real-World Experience in Clinical Characteristics and Treatment-67 Patients Multicenter Analysis

Light-chain amyloidosis (AL) is a rare multisystem disorder characterized by the deposition of misfolded amyloid fibrils derived from monoclonal immunoglobulin light chains in various organs. One of the most common organs involved in AL is the heart, with 50-70% of patients clinically symptomatic at diagnosis. We conducted a multi-center, retrospective analysis of 67 patients diagnosed between July 2012 and August 2022 with the European 2012 modification of Mayo 2004 stage III cardiac AL. The most important factors identified in the univariate Cox analysis contributing to a longer OS included Eastern Cooperative Oncology Group performance status (ECOG PS) ≤ 1, New York Heart Association functional classification (NYHA FC) ≤ 2, the use of autologous stem cell transplantation (ASCT) after induction treatment, achieving a hematological response (≥very good partial response) and cardiac (≥partial response) response after first-line treatment. The most important prognostic factors with the most significant impact on OS improvement in patients with modified Mayo stage III cardiac AL identified by multivariate Cox analysis are ECOG PS ≤ 1, NYHA FC ≤ 2, and achieving hematological response ≥ VGPR and cardiac response ≥ PR after first-line treatment.

Cardiac Toxicity in the Treatment of Light Chain Amyloidosis: Systematic Review of Clinical Studies

BACKGROUND

Light chain amyloidosis (AL) is a progressive and a fatal disease that primarily affects cardiac tissue. Although the current approach to anti-amyloidosis treatments has managed to reduce amyloidosis morbimortality, the dynamics of cardiac adverse events are unknown.

OBJECTIVE

to provide evidence about reported cardiac toxicity during treatment of AL amyloidosis through a systematic review of the literature.

METHODS

A search was performed for registered clinical trials on ClinicalTrials.gov filtered for AL amyloidosis up to December 31, 2022. Studies were filtered by those that reported intervention in patients with AL amyloidosis and that had reported adverse events. The type of study, the intervention performed, and the frequency of reported cardiac adverse events were discriminated from each trial.

RESULTS

25 clinical trials were analyzed, representing a population of 1,542 patients, among whom 576 (38.95%) adverse events were reported, 326 being serious (SAE) and 242 nonserious (nSAE). The most frequent SAEs were cardiac failure, atrial fibrillation, and cardiac arrest, while the most frequent nSAEs were palpitations, atrial fibrillation, and sinus tachycardia.

CONCLUSION

cardiac toxicity during treatment for amyloidosis seems common, and it is important to evaluate the relationship of therapies with its occurrence.

Peripheral Nervous, Hepatic, and Gastrointestinal Endpoints for AL Amyloidosis Clinical Trials: Report from the Amyloidosis Forum Multi-organ System Working Group

Systemic immunoglobulin light chain (AL) amyloidosis is a heterogeneous rare disease driven by a destructive monoclonal gammopathy and typified by misfolded immunoglobulin light and/or heavy chains which aggregate and deposit in organs as insoluble amyloid fibrils. Disease heterogeneity is driven by the degree of multi-systemic involvement; cardiac, renal, neurological, and gastrointestinal (GI) systems are affected to varying degrees in different patients. While prognosis is primarily driven by hematologic response to treatment and outcomes associated with cardiac events and overall survival, the involvement of the peripheral nervous, hepatic, and GI systems can also have a significant impact on patients. The Amyloidosis Forum ( https://amyloidosisforum.org ) is a public-private partnership between the nonprofit Amyloidosis Research Consortium ( www.arci.org ) and the US Food and Drug Administration (FDA) Center for Drug Evaluation and Research formed to advance drug development for the treatment of systemic amyloid disorders. A series of virtual workshops focused on the development of novel, patient-relevant endpoint components and analytical strategies for clinical trials in AL amyloidosis. This review summarizes the proceedings and recommendations of the Multi-Systemic Working Group which identified, reviewed, and prioritized endpoints relevant to the impacts of AL amyloidosis on the peripheral nervous, hepatic, and GI systems. The Working Group comprised amyloidosis experts, patient representatives, statisticians, and representatives from the FDA, Medicines and Healthcare products Regulatory Agency (MHRA), and pharmaceutical companies. Prioritized neuropathy/autonomic endpoints included a modified form of the Neuropathy Impairment Score (NIS + 7) and the Composite Autonomic Symptom Score (COMPASS-31), respectively. Alkaline phosphatase was identified as the most relevant indicator of liver involvement and disease progression. Following extensive review of potential GI endpoints, the Working Group identified multiple exploratory endpoints. These recommended components will be further explored through evaluation of clinical trial datasets and possible integration into composite endpoint analysis.

Health-Related Quality of Life Instruments for Clinical Trials in AL Amyloidosis: Report from the Amyloidosis Forum HRQOL Working Group

Systemic AL (light chain) amyloidosis is a rare protein misfolding disorder associated with plasma cell dyscrasia affecting various organs leading to organ dysfunction and failure. The Amyloidosis Forum is a public-private partnership between the Amyloidosis Research Consortium and the US Food and Drug Administration Center for Drug Evaluation and Research with the goal of accelerating the development of effective treatments for AL amyloidosis. In recognition of this goal, 6 individual working groups were formed to identify and/or provide recommendations related to various aspects of patient-relevant clinical trial endpoints. This review summarizes the methods, findings, and recommendations of the Health-Related Quality of Life (HRQOL) Working Group. The HRQOL Working Group sought to identify existing patient-reported outcome (PRO) assessments of HRQOL for use in clinical trials and practice deemed relevant across a broad spectrum of patients with AL amyloidosis. A systematic review of the AL amyloidosis literature identified 1) additional signs/symptoms not currently part of an existing conceptual model, and 2) relevant PRO instruments used to measure HRQOL. The Working Group mapped content from each identified instrument to areas of impact in the conceptual model to determine which instrument(s) provide coverage of relevant concepts. The SF-36v2^® Health Survey (SF-36v2; QualityMetric Incorporated, LLC) and Patient-Reported Outcomes Measurement Information System-29 Profile (PROMIS-29; HealthMeasures) were identified as instruments relevant to patients with AL amyloidosis. Existing evidence of reliability and validity was evaluated with a recommendation for future work focused on estimating clinically meaningful within-patient change thresholds for these instruments. For sponsors, the context of use-including specific research objectives, trial population, and investigational product under study-should inherently drive selection of the appropriate PRO instrument and endpoint definitions to detect meaningful change and enable patient-focused drug development.

Machine Learning Approaches in Diagnosis, Prognosis and Treatment Selection of Cardiac Amyloidosis

Cardiac amyloidosis is an uncommon restrictive cardiomyopathy featuring an unregulated amyloid protein deposition that impairs organic function. Early cardiac amyloidosis diagnosis is generally delayed by indistinguishable clinical findings of more frequent hypertrophic diseases. Furthermore, amyloidosis is divided into various groups, according to a generally accepted taxonomy, based on the proteins that make up the amyloid deposits; a careful differentiation between the various forms of amyloidosis is necessary to undertake an adequate therapeutic treatment. Thus, cardiac amyloidosis is thought to be underdiagnosed, which delays necessary therapeutic procedures, diminishing quality of life and impairing clinical prognosis. The diagnostic work-up for cardiac amyloidosis begins with the identification of clinical features, electrocardiographic and imaging findings suggestive or compatible with cardiac amyloidosis, and often requires the histological demonstration of amyloid deposition. One approach to overcome the difficulty of an early diagnosis is the use of automated diagnostic algorithms. Machine learning enables the automatic extraction of salient information from “raw data” without the need for pre-processing methods based on the a priori knowledge of the human operator. This review attempts to assess the various diagnostic approaches and artificial intelligence computational techniques in the detection of cardiac amyloidosis.

AL Amyloidosis for Cardiologists: Awareness, Diagnosis, and Future Prospects: JACC: CardioOncology State-of-the-Art Review

Amyloid light chain (AL) amyloidosis is a rare, debilitating, often fatal disease. Symptoms of cardiomyopathy are common presenting features, and patients often are referred to cardiologists. Cardiac amyloid infiltration is the leading predictor of death. However, the variable presentation and perceived rarity of the disease frequently lead to delay in suspecting amyloidosis as a cause of heart failure, leading to misdiagnoses and a marked delay in diagnosis, with devastating consequences for the patient. A median time from symptom onset to correct diagnosis of about 2 years is often too long when median survival from diagnosis for patients with AL amyloidosis and cardiomyopathy is 4 months to 2 years. The authors highlight the challenges to diagnosis, identify gaps in the current knowledge, and summarize novel treatments on the horizon to raise awareness about the critical need for early recognition of symptoms and diagnosis of AL amyloidosis aimed at accelerating treatment and improving outcomes for patients.

Noninvasive Diagnostics of Renal Amyloidosis: Current State and Perspectives

Amyloidoses is a group of diseases characterized by the accumulation of abnormal proteins (called amyloids) in different organs and tissues. For systemic amyloidoses, the disease is related to increased levels and/or abnormal synthesis of certain proteins in the organism due to pathological processes, e.g., monoclonal gammopathy and chronic inflammation in rheumatic arthritis. Treatment of amyloidoses is focused on reducing amyloidogenic protein production and inhibition of its aggregation. Therapeutic approaches critically depend on the type of amyloidosis, which underlines the importance of early differential diagnostics. In fact, the most accurate diagnostics of amyloidosis and its type requires analysis of a biopsy specimen from the disease-affected organ. However, absence of specific symptoms of amyloidosis and the invasive nature of biomaterial sampling causes the late diagnostics of these diseases, which leads to a delayed treatment, and significantly reduces its efficacy and patient survival. The establishment of noninvasive diagnostic methods and discovery of specific amyloidosis markers are essential for disease detection and identification of its type at earlier stages, which enables timely and targeted treatment. This review focuses on current approaches to the diagnostics of amyloidoses, primarily with renal involvement, and research perspectives in order to design new specific tests for early diagnosis.

Proposed Cardiac End Points for Clinical Trials in Immunoglobulin Light Chain Amyloidosis: Report From the Amyloidosis Forum Cardiac Working Group

Immunoglobulin light chain amyloidosis is a rare, multisystemic, phenotypically heterogenous disease affecting cardiovascular, renal, neurological, and gastrointestinal systems to varying degrees. Its underlying cause is a plasma cell dyscrasia characterized by misfolding of monoclonal immunoglobulin light chains which leads to aggregation and deposition of insoluble amyloid fibrils in target organs. Prognosis is primarily dependent on extent of cardiac involvement and depth of hematologic response to treatment. To facilitate development of new therapies, a public-private partnership was formed between the nonprofit Amyloidosis Research Consortium and the US Food and Drug Administration Center for Drug Evaluation and Research. In 2020, the Amyloidosis Forum launched an initiative to identify novel/composite end points and analytic strategies to expedite clinical trials for development of new therapies for the primary hematologic disorder and organ system manifestations. Specialized working groups identified organ-specific end points; additional working groups reviewed health-related quality of life measures and statistical approaches to data analysis. Each working group comprised amyloidosis experts, patient representatives, statisticians, and representatives from the Food and Drug Administration, the UK Medicines and Healthcare Products Regulatory Agency, and pharmaceutical companies. This review summarizes the proceedings and recommendations of the Cardiac Working Group. Using a modified Delphi method, the group identified, reviewed, and prioritized cardiac end points relevant to immunoglobulin light chain amyloidosis in the context of an antiplasma cell therapy. Prioritized cardiovascular end points included overall survival, hospitalization, N-terminal pro-B-type natriuretic peptide level, 6-minute walk test, Kansas City Cardiac Questionnaire, and cardiac deterioration progression-free survival. These recommended components will be further explored through evaluation of clinical trial datasets and formal guidance from regulatory authorities.

Future Perspectives

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

Diagnosis of amyloid beyond Congo red

PURPOSE OF REVIEW

Amyloidoses are a group of rare and heterogeneous diseases in which abnormally folded proteins deposit in tissues and lead to organ damage. A brief review of advances in the diagnosis of extracerebral systemic amyloidoses in the context of recent advances in their clinical management is provided.

RECENT FINDINGS

Although steady progress in the treatment of AL and AA has evolved over many years, significant advances in the treatment of ATTR, transthyretin-derived amyloidosis, have been achieved only recently. This coincides with the emergence of nontissue diagnosis of cardiac ATTR in both the hereditary and wild-type settings. The latter is emerging as possibly the most prevalent type of systemic amyloidosis.Available treatments are amyloid protein type dependent and, hence, following amyloid detection, amyloid protein typing is necessary. Although mass spectrometry has emerged as the preferred method of amyloid typing, careful application of immune methods is still clinically useful but caution and experience, as well as awareness of the limitations of each method, are necessary in their interpretation.

SUMMARY

Despite significant advances in the treatment of the systemic amyloidoses, outcomes remain poor, primarily due to delays in diagnosis. Precise diagnosis of the amyloid protein type is critical for treatment selection.