Comparison between human pharmacokinetics and imaging properties of two conjugation methods for 99mTc-annexin A5.

Annexin A5 (AnxA5) is a protein with high affinity for phosphatidyl serine, a phospholipid exposed on the cell surface during apoptosis. This phenomenon has been used for determination of cell death after myocardial infarction. To evaluate the potential of 99mTc-AnxA5 for in vivo scintigraphy of apoptotic cells, the pharmacokinetics and imaging properties of two radiopharmaceuticals, 99mTc-(n-1-imino-4-mercaptobutyl)-AnxA5 (I-AnxA5) and 99mTc-(4,5-bis(thioacetamido)pentanoyl)-AnxA5 (B-AnxA5), were studied. I-AnxA5 was administered intravenously to seven patients and one healthy volunteer, and B-AnxA5 was administered to 12 patients. All patients in the pharmacokinetic study had myocardial disease. Additionally, imaging was performed in a patient with acute myocardial infarction, as well as in three patients with different malignancies. The plasma concentration, excretion and biodistribution of 99mTc-AnxA5 were measured, as well as levels of AnxA5 antigen. The kinetic data of both radiopharmaceuticals in p...