Stability Matters: Radiochemical Stability of Therapeutic Radiopharmaceutical<sup>177</sup>Lu-PSMA I&T
Madhusudan Vyas, Remy Lim, Jessica Fagan, Rudresh Chandrashekar
Abstract
Labeling radiopharmaceuticals and testing the quality of the labeled product before injecting it into patients are standard operating procedures in the nuclear medicine department. There is a different shelf life for each labeled product, which determines how long a product can maintain in vitro stability before it needs to be discarded. <sup>177</sup>Lu is a radioactive isotope that is increasingly being accepted into the treatment paradigm for palliation of advanced-stage tumors, including metastatic castration-resistant prostate cancer (mCRPC) and neuroendocrine tumors (NETs). In our institution, synthesis of <sup>177</sup>Lu with prostate-specific membrane antigen imaging and therapy (PSMA I&T) for palliation of mCRPC is performed on an automated synthesis system. <b>Methods:</b> After each synthesis, the final product quality was evaluated by high-performance liquid chromatography (HPLC) and instant thin-layer chromatography (ITLC) at 3 different time points: 0, 24, and 48 h. Between February 2020 and October 2020, the quality of 35 batches of <sup>177</sup>Lu-PSMA I&T was evaluated. <b>Results:</b> The average radiochemical purity of ITLC-silica gel was found to be greater than 99% (99.70% ± 0.05%), and HPLC was greater than 98% (98.60% ± 0.05%). <b>Conclusion:</b> Our findings demonstrate that synthesis of <sup>177</sup>Lu-PSMA I&T with an automated synthesis system can remain stable for 48 h after labeling.