The safety and pharmacokinetics in adult subjects of an intravenously administered 99mTc-labeled 17 amino acid peptide (CYT-379)

A phase I study was designed to evaluate the safety and pharmacokinetics of a novel platelet reactive peptide, peptide acetyl-SYGRGDVRGDFKCTCCA-amide (CYT-379), which binds to the fibrinogen receptor of activated platelets and also binds to 99m Tc. Eleven subjects with suspected deep venous thrombosis had 0.1, 0.5 or 1.0 mg of the peptide infused intravenously. Pharmacokinetics were determined by assaying blood samples in 6 of the 11 subjects and by urine sampling in 5 of these 6 subjects. Plasma and whole blood time-activity curves demonstrated an initial fast component with half-time clearance of 0.2 ± 0.01 and 0.2 ± 0.02 h and a slow component with half-time clearance of 2.8 ± 0.3 and 2.7 ± 0.2 h (mean ± SEM for plasma and whole blood, respectively). Urine clearance was 22.6 ± 3.3 and 10.8 ± 1.6 mL/min when normalized to body surface area. The cumulative excretion of 99m Tc-CYT-379 in the urine was 16.6 ± 3.6, 45.6 ± 16.9 and 45.6 ± 1.8% of the administered dose over 0–2, 0–12 and 0–24 h after radiopharmaceutical injection, respectively. Images obtained in 11 subjects immediately, at 1–2, and 4–6 h after injection were evaluated for abnormalities and were compared with duplex Doppler ultrasonography. 99m Tc-CYT-379 images were positive in only 3 of 7 subjects who had a positive duplex Doppler examination in at least one lower extremity. One subject with negative duplex Doppler had also negative 99m Tc-CYT-379 scintigraphy. One subject with negative scintigraphy and two other subjects with positive scintigraphy had no other imaging studies of the deep venous system performed. No adverse reactions were observed during or after the infusion of 99m Tc-CYT-379. 99m Tc-CYT-379 appears to be a safe radiopharmaceutical and demonstrates rapid clearance from plasma in human subjects.