The Gastrin-Releasing Peptide Receptor Antagonist [99MTc]Tc-Rm26 is a Novel Radiopharmaceutical for Prostate Cancer Imaging

Gastrin releasing peptide receptor (GRPR) is overexpressed in prostate cancer (PC). Currently, radiopharmaceuticals (RP) for visualization of GPRP based on bombesin antagonists are developed. The aim of the present work was to conduct a phase I clinical trial of the GRPR antagonist [99mTc]Tc-RM26 and to study the possibility of its use for PC SPECT imaging. Thirteen patients diagnosed with PC were included in the study. Patients received [99mTc]Tc-RM26 intravenous bolus at a dose of 640±165 MBq (40 μg/injection). Six patients underwent whole-body planar imaging and SPECT/CT at 2, 4, 6, and 24 h after injection. Seven patients had SPECT/CT alone performed 2 h after RFP injection. The study showed that a single intravenous injection of [99mTc]Tc-RM26 is safe and well tolerated. Critical organs for RFP are the gallbladder, small intestine, upper colon and kidney. The dose burden per patient associated with the administration of [99mTc]Tc-RM26 RFP is 3–6 mSv per study. The studied RP allows to visualize primary prostate malignant tumors, as well as its metastases to lymph nodes and bones. It is reasonable to conduct further clinical studies of [99mTc]Tc-RM26 to evaluate the sensitivity and specificity of SPECT/CT with this RP for diagnostics and staging of prostate cancer.