124Iodine Evuzamitide Positron Emission Tomography in Patients with Established or Suspected Cardiac Amyloidosis

Background 124I-evuzamitide is a pan-amyloid positron emission tomography (PET) radiotracer. Objectives We conducted an open-label study to assess the performance and safety of 124I-evuzamitide PET/magnetic resonance imaging (MRI) in patients with known or suspected cardiac amyloidosis (CA). Methods Consecutive patients with suspected or known CA, were invited to participate in the trial and underwent imaging with 124I-evuzamitide (mean administered activity 1.05±0.02 mCi), using PET/MRI preferentially, and PET/computed tomography (CT) as an alternative. A positive scan was defined visually as tracer uptake in the left ventricular (LV) myocardium greater than blood pool activity by 3 expert readers. Equivocal scans were prespecified to be classified as negative (except for inter-reader agreement). Results A total of 126 patients (mean age 71.6 ± 10.6 years, 76.2% male) completed the 124I-evuzamitide PET/MRI (n=123) or PET/CT (n=3) scan, where 87 (69%) received a diagnosis of CA. All patients with CA had a visually positive scan and all patients without CA had a visually negative scan by all 3 readers (100% sensitivity and specificity). There was disagreement on 5 patients who were graded as equivocal or negative scans (Fleiss' Kappa 0.94, none received CA diagnosis). Quantitatively, mean LV/blood pool standardized uptake value ratio (SUVRmean) was 1.89 ±0.29 and 0.91 ±0.15, in patients with and without CA, respectively (p<0.001). 124I-evuzamitide was well-tolerated without significant tracer-related adverse events. Conclusion 124I-evuzamitide PET provides excellent diagnostic accuracy in patients known or suspected to have cardiac amyloidosis, and might provide a single upstream assessment for the presence or absence of cardiac amyloidosis.