An Improved Kit Formulation for the Preparation of 99mTc-EC0652

1165 Objectives 99mTc-EC0652 is a prostate specific membrane antigen (PSMA)-targeted imaging agent that is being developed to identify tumors that express PSMA receptors. It has been evaluated in clinical trials for patients with advanced prostate cancer. The current EC0652 formulation kit has two challenges: (1) the kit requires heating for labeling with 99mTc, which is not convenient in the nuclear pharmacy; (2) the kit contains sodium glucoheptonate as the transchelating agent, which is not an FDA approved excipient and requires production as a cGMP product. The purpose of this study is to develop a robust formulation kit that contains only FDA approved excipients and to prepare 99mTc-EC0652 using a simpler method with good labeling efficiency. Methods A variety of formulation kits containing different excipients were prepared. Labeling with 99mTc was conducted by adding ≤ 50 mCi (1-2 mL) of 99mTc pertechnetate and incubating at room temperature (17°C - 27°C) for 15 - 25 minutes. The radiochemical purities were determined by radio-HPLC and TLC. The effect of each excipient and pH on radiochemical purity and stability of 99mTc-EC0652 was investigated. Results The current EC0652 formulation kit contains EC0652, sodium glucoheptonate dihydrate and tin (II) chloride dihydrate. Labeling using this formulation kit by heating at 100 °C for 10 min gave radiochemical purities of 95-98%. However, labeling at room temperature gave a lower radiochemical purity of about 84%. We evaluated the effects of different excipients on the labeling yield and developed a new kit formulation. Preparation of 99mTc-EC0652 using the new formulation kits was easily conducted at room temperature. High radiochemical purities of 95-98% were obtained by adding 50 mCi of 99mTc peretchnetate to a kit vial and incubating at room temperature for 15 minutes. The 99mTc-EC0652 solutions were stable at room temperature for at least 6 hours. Conclusions The new EC0652 formulation kit provided efficient labeling at room temperature and exhibited good stability of 99mTc-EC0652 suitable for clinical use.