131I-RPS-001 (131I-MIP-1095) is a small radiolabeled molecule, a glutamate-urea-lysine analogue, for therapeutic application in prostate cancer. 131I-RPS-001 is targeting the prostate-specific membrane antigen (PSMA) receptor. PSMA is a membrane-bound glycoprotein expressed mainly in the prostate epithelium. This antigen is considered as a cancer marker and is a good target for imaging agents and therapeutics because of its overexpression in primary, metastatic or hormone-refractory prostate cancers. Some other solid cancers also overexpress this antigen.
After a seven-year break, a clinical study was initiated in January 2017 with this molecule. The study completed in April 2019. This drug was considered on hold for a time, but has been reactivated and entered Phase II clinical trial in June 2019. This new study explores the potential of 131I-RPS-001 in combination with Enzalutamide in patients with mCRPC. PSMA-avidity will be determined by assessment of 18F-DCFPyL PET/CT imaging. The study is supposed to recruit 175 patients and completion is expected by end of 2022. Another Phase II study involving 200 patients was initiated in September 2019 and is expected to be completed by December 2024.