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.