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.

Disposition of perfluorobutane in rats after intravenous injection of Sonazoid.

The new ultrasound contrast agent Sonazoid was injected IV in rats at doses of 0.8 and 8 muL perfluorobutane (PFB)-containing microbubbles/kg body weight. Samples were obtained from blood, liver, spleen, fat, kidney, muscle, heart, lung and brain from both males and females and the PFB gas was analyzed using validated gas chromatography mass spectrometry methods. No differences were observed between genders or doses for any of the pharmacokinetic parameters. For all tissues, the highest concentrations were observed at the first time point (i.e., 5 min postinjection) (51% of injected dose in liver; total recovery of 69%). The highest concentrations of PFB in tissue were observed in spleen > liver > lung > kidney >> other tissues. At 24 h after dosing, the total amount of PFB remaining in the tissues was 1.9%. These data fit well with the finding that after a Sonazoid dose of 8 microL microbubbles/kg to male rats, more than 50% of the injected PFB was recovered in exhaled air by 20 min after dosing. During the first 24 h after administration, more than 96% of the PFB dose was recovered in exhaled air.

Nc100668, a new tracer for imaging of venous thromboembolism: disposition and metabolism in rats.

The 99mTc-complex of NC100668 [Acetyl-Asn-Gln-Glu-Gln-Val-Ser-Pro-Tyr(3-iodo)-Thr-Leu-Leu-Lys-Gly-NC100194] is being evaluated for nuclear medical imaging of venous thromboembolism. NC100668 is a 13-amino acid peptide with a Tc-binding chelator [NC100194; -NH-CH2-CH2-N(CH2-CH2-NH-C(CH3)2-C(CH3)=N-OH)2] linked to the C-terminal end. Following injection in rats of [Asn-U-14C]NC100668 (labeling of the N-terminal amino acid), approximately 70% of the radioactivity was recovered in urine within 3 days. Following injection of [Lys-U-14C]NC100668 (labeling close to the C-terminal amino acid), radioactivity was cleared more slowly, with only 8% recovered in urine and approximately 80% of the radioactivity present in the body after 3 days. The highest concentration of radioactivity in the body following injection of [Lys-U-14C]NC100668 was observed in the kidney inner cortex; this probably represents 14C-labeled Lys, which is reabsorbed in the kidney tubules and incorporated into protein metabolism. Metabolite profiling by high-performance liquid chromatography with radiochemical detection revealed that following injection of [Asn-U-14C]NC100668, there is a rapid appearance in blood of one peak containing radioactive metabolite(s) originating from the N-terminal part of the molecule. In urine samples, only this radioactive peak was observed with no intact NC100668 remaining; this very hydrophilic N-terminal metabolite was probably either the N-terminal amino acid or a very short peptide. Liquid chromatography-mass spectrometry analyses of rat urine samples obtained after injection of nonlabeled NC100668 confirmed the identity of two metabolites generated from the C-terminal end of the molecule; Gly-NC100194 was identified as the major of these metabolites and NC100194 as a minor metabolite present at approximately one-tenth the amount of Gly-NC100194. No other metabolites were identified.

A respiration-metabolism chamber system and a GC-MS method developed for studying exhalation of perfluorobutane in rats after intravenous injection of the ultrasound contrast agent Sonazoid.

Sonazoid is a new contrast agent for ultrasound imaging comprising an aqueous suspension of lipid-stabilised perfluorobutane (PFB) gas microbubbles. A respiration-metabolism chamber system was developed to collect exhaled air following intravenous administration of Sonazoid to rats. Analysis of PFB in the exhaled rat air was performed using a modified version of an earlier published method for blood samples, i.e. an automatic headspace gas chromatographic mass spectrometric (GC-MS) method using electron impact ionisation. The calibration standards were PFB diluted in air (2.5-1800 pg/ml). Perfluoropentane (PFP) was used as an internal standard and the MS detector was set to single ion monitoring of the base fragment ions of PFB (m/z 69 and 119) and PFP (m/z 69). The calibration curve, made by plotting the peak area ratios of PFB (m/z 69) to PFP (m/z 69) against the theoretical concentration of PFB, was fitted to a linear equation with weighting 1/y2 and found to be reproducible. The lower limit of quantification (LLOQ) was 2.5 pg PFB/ml. The between-day variation of the method was below 2.6% relative standard deviation (R.S.D.) and the within-day variation of the method was below 6.4% R.S.D. The accuracy of the method was evaluated and showed a relative error less than 5.2%. PFB was found to be stable for 14 days when stored in Tedlar sample bags at room temperature. An even lower detection limit may be obtained by using the more time-consuming process of solid-phase micro extraction; thus, by concentrating PFB on carboxen-PDMS fibres an LLOQ of 0.5 pg PFB/ml was obtained. When five rats were given an i.v. bolus injection of Sonazoid at a dose of 8 microl microbubbles/kg a mean recovery of 96% (range, 81-110%) was found during 24 h; more than 50% was exhaled during the first 30 min after injection.