A single-step kit formulation for the 99mTc-labeling of HYNIC-Duramycin

Abstract

Introduction 99mTc-Duramycin is a unique radiopharmaceutical that binds specifically to phosphatidylethanolamine (PE). The current effort is to develop a single-step kit formulation for the 99mTc labeling of HYNIC-Duramycin. Methods A titration series of Tricine/TPPTS coligand systems were tested for an optimal formulation to produce 99mTc-Duramycin with high radiochemical purity and specific activity. The radiopharmaceutical prepared using the kit formulation was tested for PE binding specificity using polystyrene microbeads coated with different phospholipid species. Radiochemical performance of the kits was assessed after storage at –20 °C, room temperature and 37 °C. Biodistribution profile of kit-prepared 99mTc-Duramycin was characterized in healthy rats at 3, 10, 20, 60 and 180 min after intravenous injection. Binding studies were performed using the rat aortic arch and a rat model of myocardial ischemia/reperfusion, which represent scenarios of physiological and pathological PE externalization. Results A Tricine/TPPTS ratio of 10:1 led to a consistent production of 99mTc-Duramycin with high radiochemical purity (N 90%), whereas a higher ratio at 40:1 produced radiopharmaceuticals with incomplete substitution of Tricine coligand. 99mTc-Duramycin prepared using the single-step kit formulation retained PE-binding specificity. The kits are stable over long-term storage. The biodistribution profile of kit-prepared 99mTc-Duramycin is consistent with HPLC purified radiopharmaceutical from prior studies. Binding studies on a tissue level indicate that the radiopharmaceutical is suitable for studying biological processes that involve PE distribution and redistribution in various physiological and pathological conditions. Conclusion A single-step kit formulation is developed for 99mTc-labeling of HYNIC-Duramycin. The radiopharmaceutical has high radiochemical purity and specific activity, retained PE binding activities, amiable to long-term storage, and is injection-ready for in vivo applications.

The feasibility of imaging myocardial ischemic/reperfusion injury using 99mTc-labeled duramycin in a porcine model

“…The radiopharmaceutical was prepared using a single-step kit formulation, where 740∼925 MBq (20∼25mCi) technetium-99m was injected into duramycin kit vial and heated for 20 min at 80°C. Quality control steps, including radioHPLC and stability tests, were carried out as described before (11,14). …”

Duramycin-porphyrin conjugates for targeting of tumour cells using photodynamic therapy

“…Also it has been recently shown that PE was present in much higher abundance in xenografts formed from a number of different tumour types (lung, colon, pancreatic and glioblastoma) than in their normal tissue counterparts [54]. It is well established that duramycin binds to PE when exposed on the sur-face of cells and on the luminal surface of the endothelium [1,15,47,49,55]. Duramycin was used in conjunction with bavituximab to image the co-localisation of exposed PE and phosphatidylserine on irradiated endothelial cells [56].…”

“…Fluorescent duramycin conjugates have been used to successfully target and image the lymphoma cancer cell line U937 [4], cancer derived microparticles [17], prostate tumour endothelium in rats [1] and the endothelium of aortic flow dividers [47]. Duramycin has been radiolabelled with gadolinium [3] and tech-netium-99 m where it was used to image cell death in a rat model of acute myocardial infarction [47][48][49]. The radiolabelled duramycin conjugate quickly accumulated in the PE expressing myocardium.…”

Imaging Cell Death

“…Duramycin, a 19-aminoacid peptide with antimicrobial properties, has nanomolar affinity for phosphatidylethanolamine, which, like phosphatidylserine, is also externalized during apoptosis and repre- sents 20%-40% of total cell phospholipid (1). A single-step kit for 99m Tc labeling of duramycin has been proposed recently for SPECT imaging of apoptosis (12).…”