Favorable Long-Term Safety and Efficacy of Cliramitug in Transthyretin Amyloidosis Cardiomyopathy

Cliramitug, a monoclonal antibody targeting misfolded transthyretin, reduced cardiac amyloid burden and improved heart function in patients with transthyretin amyloidosis cardiomyopathy. According to a study published June 26, 2026, in Nature Medicine, an open-label extension of the NI006-101 trial showed favorable safety and biomarker improvements over a median follow-up of 29.3 months.

The trial focused on patients with transthyretin amyloidosis cardiomyopathy (ATTR-CM), a condition where proteins misfold and deposit as amyloid fibrils in the heart muscle. These deposits stiffen the heart walls, leading to restrictive cardiomyopathy and eventual heart failure.

Researchers used cliramitug to target these misfolded proteins. The long-term follow-up data indicates that the drug’s ability to deplete cardiac amyloid transthyretin persists over time, contributing to a further reduction in the overall amyloid burden within the heart.

How does cliramitug treat cardiac amyloidosis?

Cliramitug is a monoclonal antibody designed to specifically bind to and deplete misfolded transthyretin. In ATTR-CM, the liver produces transthyretin, which normally transports thyroxine and retinol. When this protein becomes unstable and misfolds, it aggregates into insoluble fibrils that infiltrate the myocardial tissue.

By targeting the misfolded form of the protein, the antibody helps clear these deposits from the heart. This process aims to stop the progression of the disease and potentially reverse some of the structural damage caused by the amyloid buildup, according to the Nature Medicine report.

What were the long-term results of the NI006-101 trial?

The open-label extension of the NI006-101 trial tracked patients for a median of 29.3 months. The data revealed three primary areas of improvement:

The study also monitored the safety of the drug over the nearly 30-month period. The researchers reported favorable safety outcomes, suggesting the monoclonal antibody was well-tolerated by the participants during long-term administration.

Why does reducing amyloid burden matter for heart failure?

Reducing the amyloid burden is critical because the accumulation of these proteins is the primary driver of heart failure in ATTR-CM patients. As fibrils build up, the heart’s ventricles can’t relax properly during diastole. This leads to increased pressure in the heart and lungs, causing shortness of breath and fluid retention.

Most existing treatments for ATTR-CM focus on stabilizing the TTR protein to prevent new fibrils from forming. Cliramitug’s approach is different because it targets the misfolded proteins themselves. By depleting existing deposits, it addresses the damage already present in the heart tissue.

The improvement in structural and functional endpoints mentioned in the NI006-101 trial suggests that clearing these deposits may allow the heart to recover some of its natural elasticity and pumping efficiency.

What happens next for cliramitug?

The results from the NI006-101 extension study provide a baseline for the long-term efficacy and safety of cliramitug. Because it’s an open-label study, the findings reflect the outcomes of patients receiving the active treatment without a blinded control group for this specific phase.

Future research will likely focus on whether these structural improvements translate into a significant increase in overall survival rates and a reduction in hospitalization for heart failure. The Nature Medicine publication establishes that the drug can effectively reduce amyloid burden over a period exceeding two years.