Metabolism and disposition of the αv‐integrin ß3/ß5 receptor antagonist cilengitide, a cyclic polypeptide, in humans

Cilengitide (EMD 121974, manufactured by Merck KGaA, Darmstadt, Germany) is an αv-integrin receptor antagonist showing high affinity for αvβ3 and αvβ5.This study determined the mass balance of cilengitide in healthy volunteers receiving a single intravenous infusion of 2.1 MBq 14C-cilengitide spiked into 250 mL of 2000 mg of cilengitide. Blood, urine, and feces were collected up to day 15 or until excretion of radioactivity was below 1% of the administered dose. Total radioactivity derived from the administration of 14C-cilengitide and unlabeled cilengitide levels were determined and used for calculation of pharmacokinetic parameters.14C-cilengitide-related radioactivity was completely recovered (94.5%; 87.4%–100.6%) and was mainly excreted into urine (mean, 79.0%; range, 70.3%–88.2%) and to a lesser extent into feces (mean, 15.5%; range, 9.3%–20.3%). Of the administered dose, 77.5% was recovered as unchanged cilengitide in urine. The concentration profiles of cilengitide and total radioactivity in plasma were comparable. No circulating metabolites were identified in plasma and urine. Two metabolites,M606-1 and M606-2, were identified in feces considered to be formed by intestinal peptidases or by peptidases from fecal bacteria. In conclusion, the data show that following intravenous administration, 14C-cilengitide was completely recovered, was excreted mainly via renal elimination, and was not metabolized systemically.