Antibody Cliramitug Clears Heart Amyloid Deposits Over 29 Months
Long-term follow-up shows cliramitug safely depletes cardiac amyloid with improving heart structure, function, and quality of life.
Summary
Transthyretin amyloid cardiomyopathy (ATTR-CM) causes stiff, thickened hearts as misfolded protein deposits accumulate over time. Current treatments slow progression but do not remove existing amyloid. Cliramitug, a monoclonal antibody that targets misfolded transthyretin, was tested in an extended open-label follow-up involving 23 men with ATTR-CM, most on background tafamidis therapy. Over nearly 2.5 years, continued dosing and up-titration to 30 mg/kg reduced cardiac amyloid burden on MRI and bone scintigraphy, lowered heart-stress biomarkers NT-proBNP and troponin T, improved heart wall thickness and filling pressures, and raised patient quality-of-life scores. No serious treatment-related adverse events occurred. These findings suggest that actively clearing amyloid deposits — rather than just stabilizing the protein — may offer meaningful cardiac benefit.
Detailed Summary
Transthyretin amyloid cardiomyopathy (ATTR-CM) is an increasingly recognized cause of heart failure, particularly in older men, in which misfolded transthyretin protein accumulates as amyloid fibrils within the heart muscle. Existing approved therapies like tafamidis stabilize the transthyretin protein to slow further deposition but do not remove amyloid already present. Cliramitug is a monoclonal antibody designed to bind misfolded transthyretin and promote clearance of existing cardiac deposits — a fundamentally different and potentially more restorative approach.
This study reports long-term follow-up data from a subgroup of 23 participants in the NI006-101 first-in-human trial who continued into a second open-label extension (OLE2). All were male, 20 were on background tafamidis, and they received a median of 10 additional cliramitug infusions, bringing maximum total exposure to 24 infusions and median follow-up to 29.3 months. Thirteen participants originally treated at lower doses were up-titrated to 30 mg/kg during OLE2.
Key results were consistent and encouraging. Cardiac extracellular volume on MRI and tracer uptake on bone scintigraphy — both direct markers of amyloid burden — continued to decline with ongoing treatment and up-titration. Heart-stress biomarkers NT-proBNP and troponin T improved, as did left ventricular wall thickness, filling pressures, and relaxation indices. Kansas City Cardiomyopathy Questionnaire scores, reflecting patient-reported quality of life, also rose. Treatment adherence was 98% with no treatment-related serious adverse events or discontinuations.
These findings carry significant clinical implications. They suggest that amyloid depletion therapy may achieve structural and functional cardiac recovery beyond what stabilization alone offers, potentially reversing rather than merely halting disease progression.
Important caveats apply. This is a small, single-arm, open-label extension without a placebo control, making causal attribution difficult. The all-male cohort limits generalizability. The full-text paper was not available; this summary is based on the abstract only. Larger randomized trials are needed to confirm efficacy and long-term outcomes.
Key Findings
- Cliramitug reduced cardiac amyloid burden on MRI and bone scintigraphy over 29 months with no serious treatment-related adverse events.
- Up-titration to 30 mg/kg produced further amyloid depletion in patients previously on lower doses.
- NT-proBNP and troponin T levels improved, indicating reduced cardiac stress alongside structural changes.
- Left ventricular wall thickness, filling pressures, and relaxation all improved — suggesting partial structural reversal.
- Patient-reported quality of life (KCCQ scores) increased, supporting real-world functional benefit.
Methodology
This is a long-term open-label extension (OLE2) of the NI006-101 first-in-human phase 1 trial (NCT04360434), enrolling 23 male ATTR-CM patients who received a median of 10 additional cliramitug infusions beyond the original 12-month period. Endpoints included cardiac MRI-derived extracellular volume, bone scintigraphy tracer uptake, biomarkers (NT-proBNP, troponin T), echocardiographic indices, and KCCQ quality-of-life scores. No placebo control arm was included.
Study Limitations
The study is small (n=23), uncontrolled, and all-male, limiting generalizability and making it impossible to rule out confounding or placebo effects. Without a randomized comparator arm, the degree to which improvements exceed natural disease trajectory or tafamidis background therapy alone cannot be determined. This summary is based on the abstract only, as the full text was not available.
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