Phase 3 Trial of TLX591 Kicks Off in Miami

On February 25, 2025, Telix Pharmaceuticals announced a significant step forward in the fight against advanced prostate cancer with the activation of its ProstACT Global Phase 3 clinical trial at the Biogenix Molecular Research Center in Miami, Florida.

This trial centers on TLX591, a novel radiopharmaceutical designed to target prostate-specific membrane antigen (PSMA), a protein highly expressed in prostate cancer cells. TLX591 combines a potent radioactive particle, Lutetium-177, with a PSMA-targeting antibody, aiming to deliver precise radiation to cancer cells while sparing healthy tissue.

Though still in the pre-approval stage, TLX591 builds on the success of other PSMA-targeted therapies, like Lutetium-177 PSMA-617 (Pluvicto), which has shown promise in extending survival for patients with metastatic castration-resistant prostate cancer (mCRPC). Early-phase trials of TLX591 have demonstrated encouraging safety and efficacy, with patients showing tumor responses and manageable side effects, setting the stage for this pivotal Phase 3 study.

In contrast to Pluvicto, TLX591 employs a monoclonal antibody, rosopatamab (formerly J591), to carry Lutetium-177 to PSMA. This antibody binds to PSMA with higher affinity and specificity, latching onto cancer cells more tightly and persistently. This stronger binding allows TLX591 to use lower radiation doses—delivered as two injections of 76 mCi (2.8 GBq) 14 days apart in the Phase 3 trial—potentially targeting smaller, less detectable metastases.
The ProstACT Global Phase 3 trial is a multi-center, international effort to rigorously evaluate TLX591’s effectiveness and safety in men with advanced prostate cancer. In Miami, the Biogenix Molecular Research Center has already administered two doses of TLX591, given 14 days apart, to a local patient this month, marking the trial’s U.S. rollout. The study is now actively recruiting eligible patients in the Miami area, offering them a chance to participate in testing this cutting-edge therapy.

This phase aims to confirm TLX591’s ability to improve outcomes—like survival and quality of life—compared to existing treatments. It’s a randomized, controlled trial, meaning some participants will receive TLX591 while others get standard care, allowing researchers to measure its true impact. Telix, headquartered in Melbourne, Australia, with operations across the U.S., Canada, Europe, and Japan, is spearheading this effort as part of its broader mission to advance radiopharmaceuticals for both diagnosis and treatment.

Clinical trial.