Telix Pharmaceuticals has secured FDA alignment to advance the U.S. randomized Phase 3 ProstACT Global trial of TLX591-Tx in metastatic castration-resistant prostate cancer, following positive Part 1 safety and dosimetry data.
Written By: Disha Jadhao, BPharm
Reviewed By: Pharmacally Editorial Team
Telix Pharmaceuticals has reached agreement with the U.S. Food and Drug Administration on advancing Part 2 of its global Phase 3 ProstACT Global trial (NCT06520345), evaluating TLX591-Tx (lutetium-177 [¹⁷⁷Lu] rosopatamab tetraxetan) for patients with metastatic castration-resistant prostate cancer (mCRPC).
The positive outcome from a Type B meeting confirms that safety and dosimetry data from the completed Part 1 study support progression into the randomized U.S. cohort, while aligning the company and FDA on the clinical protocol, statistical analysis plan, and ongoing safety monitoring strategy.
The agreement allows Telix to submit an Investigational New Drug (IND) amendment to initiate Part 2 in the United States. The expansion is expected to harmonize study execution across international sites as patient enrollment continues in regions where regulatory approvals are already in place.
Scientific rationale for TLX591-Tx
TLX591-Tx is an investigational PSMA-targeted radiopharmaceutical therapy that combines a monoclonal antibody with the beta-emitting radioisotope lutetium-177 to selectively deliver radiation to prostate-specific membrane antigen (PSMA)-expressing tumor cells. Unlike currently approved PSMA-targeted small-molecule radioligand therapies, the antibody-based approach exhibits distinct pharmacokinetics and biodistribution.
According to Telix, long-term follow-up has not identified significant acute or delayed kidney toxicity, largely because the therapy is cleared through the liver rather than the kidneys. The agent also demonstrates minimal uptake in salivary and lacrimal glands, which may reduce treatment-related xerostomia and dry eye, two common adverse effects associated with existing PSMA-targeted radiopharmaceuticals.
Phase 3 study expands internationally
The ProstACT Global trial is an international, multicenter study conducted in two stages. Part 1 enrolled 36 patients to evaluate safety and dosimetry and has now been completed. Part 2 will randomize approximately 490 patients in a 2:1 ratio.
Eligible participants must have progressive mCRPC confirmed by gallium-68 PSMA-11 PET imaging following prior treatment with one androgen receptor pathway inhibitor (ARPI). Patients in the randomized phase receive two doses of TLX591-Tx administered 14 days apart in combination with one of three standard-of-care therapies: abiraterone, enzalutamide, or docetaxel.
The FDA also endorsed the proposed statistical framework across all three treatment cohorts, providing a consistent approach for efficacy evaluation and safety oversight throughout the global study.
Regulatory momentum supports broader development
Group Chief Medical Officer David N. Cade, MD, said the FDA alignment enables submission of the IND amendment required to launch Part 2 in the United States while international recruitment continues. He noted that patient enrollment remains strong in countries where the randomized phase has already opened.
Principal investigator Neeraj Agarwal, MD, of the Huntsman Cancer Institute, said the short treatment schedule could simplify integration of radiopharmaceutical therapy into routine clinical practice. Delivering the complete course over roughly two weeks may allow physicians to combine TLX591-Tx with existing systemic therapies while preserving future treatment options for patients with metastatic prostate cancer.
Telix also plans to align its U.S. IND amendment with a pending regulatory submission to initiate the Phase 3 study in Europe, supporting broader global expansion of the ProstACT Global program.
Reference
FDA Alignment to Advance ProstACT Global Phase 3 Trial – Telix Pharmaceuticals
About the Writer
Disha Sanjay Jadhao (LinkedIn) is a pharmacy graduate and healthcare writer with a strong interest in clinical documentation and simplifying healthcare information for better reader understanding. She is enthusiastic, adaptable, and eager to take on new challenges while contributing to clear, accurate, and engaging medical and pharmaceutical content.