Stability matters: Radiochemical stability of therapeutic radiopharmaceutical of ¹⁷⁷Lu-PSMA-I&T

Abstract

Labelling radiopharmaceuticals and testing the quality of the labelled product before injecting it into patients are standard operating procedures in the Nuclear Medicine department. There is a different shelf life for each labelled product, which determines how long a product can maintain in-vitro stability before it needs to be discarded. Lutetium-177 (¹⁷⁷Lu) is a radioactive isotope that is increasingly being accepted into the treatment paradigm for palliation of advanced-stage tumours, including metastatic castration-resistant prostate cancer (mCRPC) and neuroendocrine tumours (NET). In our institution, synthesis of ¹⁷⁷Lu with prostate-specific membrane antigen imaging and therapy (PSMA-I & T) for palliation of mCRPC is performed on Eckert & Ziegler Eurotope’s Modular-Lab Pharm Tracer® automated synthesis system. Sterile GMP-certified no-carrier-added ¹⁷⁷Lu is supplied by Australia’s Nuclear Science and Technology Organization (ANSTO). Following each synthesis, the final product quality is evaluated by High-performance liquid chromatography (HPLC) and instant thin-layer chromatography (ITLC) at three different time points: 0 hours, 24 hours, and 48 hours. Between February 2020 to October 2020, the quality of 35 batches of ¹⁷⁷Lu-PSMA-I & T was evaluated. The average radiochemical purity of ITLC-SG was found to be greater than 99 percent (99.70±05%), and HPLC was greater than 98 percent (98.60±0.05%). Our findings demonstrate that automated synthesis of ¹⁷⁷Lu-PSMA-I & T with Eckert & Ziegler Eurotope’s Modular-Lab Pharm Tracer® can remain stable for 48 hours post labelling.