Highlights

  • Telix doses the first patient in Part 2 of the Phase 3 ProstACT Global study.
  • Randomized trial evaluates TLX591 combined with standard prostate cancer treatments.
  • Part 1 data submission planned to support expansion into U.S. trial sites.

Telix Pharmaceuticals Limited (ASX:TLX) has announced that the first patient has been treated in Part 2 of its ProstACT Global Phase 3 clinical trial. The dosing took place at the Australian Prostate Centre in Melbourne, Australia. Part 2 represents the randomized treatment expansion phase of the study and follows the completion of target enrollment in Part 1.

The ProstACT Global study is evaluating TLX591, a lutetium-177–based radio antibody drug conjugate, in patients with metastatic castration-resistant prostate cancer (mCRPC). The Phase 3 trial is designed to compare the use of TLX591 in combination with standard of care (SOC) therapies versus SOC therapy alone.

Trial design and enrollment details
ProstACT Global is the first Phase 3 study to assess a PSMA-targeted radio antibody drug conjugate given alongside approved SOC treatments, including abiraterone, enzalutamide, or docetaxel. Part 2 of the trial is structured as a 2:1 randomized global expansion and is planned to enroll approximately 490 patients.

Recruitment for Part 2 is currently ongoing in Australia, New Zealand, and Canada. Eligible patients must have confirmed progressive mCRPC, determined using 68Ga-PSMA-11 PET imaging, and must have received prior treatment with an androgen receptor pathway inhibitor.

Regulatory engagement and global rollout
As previously disclosed, Telix plans to submit data from Part 1 of the ProstACT Global study to the U.S. Food and Drug Administration. This submission is intended to support regulatory clearance to expand Part 2 of the trial into U.S. clinical sites. Public disclosure of preliminary Part 1 results is expected to align with engagement with U.S. regulators.

Beyond North America, the trial has already received approval to commence in several markets, including China, Japan, Singapore, South Korea, Türkiye, and the United Kingdom. In addition, Telix plans to file a clinical trial application with the European Medicines Agency to enable further expansion into European Union sites.

Rationale for antibody-based approach
TLX591 uses an antibody-based targeting method that differs from PSMA-targeted small peptide radioligand therapies. According to available published data, the agent is primarily cleared through the liver rather than the kidneys. Long-term follow-up data referenced by the company indicate no significant acute or delayed kidney toxicity observed to date.

The larger molecular structure of TLX591 has also been associated, in prior studies, with limited uptake in salivary and lacrimal glands. This approach is intended to reduce the occurrence of dry mouth and dry eyes, which have been reported with other PSMA-targeted radioligand treatments.

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