CLR 121225

CLR 121225 is an investigational targeted alpha therapy (TAT) radiopharmaceutical developed by Cellectar Biosciences. It consists of a proprietary phospholipid ether (PLE) conjugate labeled with the alpha-emitting radioisotope actinium-225 (Ac-225). The drug is designed to selectively deliver potent alpha radiation to tumor cells, leveraging the PLE platform’s ability to target cancer cell membranes. Preclinical studies have demonstrated robust anti-tumor activity in refractory pancreatic cancer and other solid tumor models, with high tumor uptake, dose-dependent efficacy, and good tolerability. CLR 121225 is being advanced for the treatment of several solid tumors with significant unmet need, including pancreatic cancer and triple negative breast cancer. As of early 2025, it remains in preclinical development with plans for first-in-human Phase I clinical trials.