Molecular Imaging of the Human Pulmonary Vascular Endothelium Using an Adrenomedullin Receptor Ligand

This phase I study (NCT01539889) evaluated the safety, efficacy, and dosing of PulmoBind for molecular imaging of pulmonary circulation. PulmoBind is a ligand of the adrenomedullin receptor abundantly distributed in lung capillaries. Labeled with Tc-99m, it allows single-photon emission computed tomographic (SPECT) imaging of lung perfusion. In preclinical studies, PulmoBind scans enabled detection of lung perfusion defects and quantification of microcirculatory occlusion caused by pulmonary hypertension. Healthy humans (N = 20) were included into escalating groups of 5 mCi (n = 5), 10 mCi (n = 5), or 15 mCi (n = 10) Tc-99m-PulmoBind. SPECT imaging was serially performed, and Tc-99m-PulmoBind dosimetric analysis was accomplished. The radiochemical purity of Tc-99m-PulmoBind was greater than 95%. There were no safety concerns at the three dosages studied. Imaging revealed predominant and prolonged lung uptake with a mean peak extraction of 58% +/- 7%. PulmoBind was well tolerated, with no clinically significant adverse event related to the study drug. The highest dose of 15 mCi provided a favorable dosimetric profile and excellent imaging. The postural lung perfusion gradient was detectable. Tc-99m-PulmoBind is safe and provides good quality lung perfusion imaging. The safety/efficacy of this agent can be tested in disorders of pulmonary circulation such as pulmonary arterial hypertension.