Quantification of NC100692, a new tracer for 99mTc-imaging of angiogenesis, in human plasma using reversed-phase liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry

NC100692 is under development as a diagnostic radiopharmaceutical for targeting angiogenesis associated with diseases, such as cancer and endometriosis. NC100692 consists of a cyclic RGD-containing peptide with an ethylene glycol chain linked to the C-terminal amino acid and a (99m)Tc-binding chelator linked to the N-terminal amino acid. The present report describes a method for quantification of NC100692 in human citrated plasma. The method is based on solid-phase extraction followed by reversed-phase liquid chromatography using a gradient of water and acetonitrile with 0.1% formic acid. The chromatographic system was coupled on-line with an electrospray mass spectrometer. The analyses were performed by selective ion monitoring of the [M+2H](2+) and the [M+3H](3+) ions of NC100692 and the internal standard, which was identical to NC100692 except for containing twice the length of the ethyleneglycol chain. The limit of quantification of the method was 0.5 ng NC100692/ml plasma. The calibration curve ranged from 0.5 to 250 ng NC100692/ml plasma and was fitted to a quadratic equation with a weighing factor of 1/y and found to be highly reproducible. The total precision of the method, expressed as the relative standard error of the mean, was 11.1, 10.8 and 9.7% for the low, medium and high control samples, respectively. The accuracy of the method was 103.4, 111.1 and 107.5% for the low, medium and high control samples, respectively. NC100692 was stable in human plasma during at least 3 freeze/thaw cycles, during 48 h on dry ice and at least 8 weeks when stored in a -20 degrees C freezer.