Telix Pharmaceuticals (ASX:TLX) has reported positive early outcomes from the first part of its global Phase 3 ProstACT study, marking an important step in the development of a new targeted treatment for advanced prostate cancer.
The company announced that the initial stage of the trial met its primary objectives, demonstrating that the investigational therapy TLX591-Tx has an acceptable safety and tolerability profile when used alongside existing standard treatments.
The study focused on men with prostate-specific membrane antigen-positive metastatic castration resistant prostate cancer, a form of the disease that progresses despite hormone therapy. Patients enrolled in the trial had previously been treated with one androgen receptor pathway inhibitor, reflecting a population that often requires additional therapeutic options once earlier treatments lose effectiveness.
Part 1 of the ProstACT Global trial served as a safety and dosimetry lead-in and involved 36 patients divided into three treatment groups. Each group received two doses of TLX591-Tx administered two weeks apart in combination with one of three widely used therapies, including enzalutamide, abiraterone or docetaxel. Researchers observed that all participants completed both treatment doses as planned and no new safety signals were identified during the study period.
Most side effects reported in the trial were mild to moderate. The most common non-hematologic symptoms included fatigue, nausea and dry mouth. Blood-related events such as thrombocytopenia and neutropenia were recorded but were transient and considered manageable within the expected profile for this class of therapy and patient population.
Imaging and pharmacokinetic data also produced encouraging findings. Radiation exposure to major organs remained well below established safety thresholds, and the therapy demonstrated consistent uptake across tumour sites. Investigators also noted sustained activity of the treatment two weeks after dosing, supported by imaging that showed prolonged retention within tumours. Importantly, the study found no evidence of drug interactions between TLX591-Tx and the standard therapies used in combination.
Researchers say these results reinforce the potential for integrating the investigational therapy into existing treatment regimens for advanced prostate cancer. The therapy is designed as a lutetium-based radio antibody drug conjugate that targets PSMA-expressing tumour cells. Unlike some other radioligand therapies that are cleared primarily through the kidneys, TLX591-Tx is largely processed through the liver, which may reduce the risk of certain toxicities seen with alternative approaches.
With the safety stage completed, the ProstACT Global trial has already moved into its second phase in several regions, including Australia, New Zealand and Canada, with approvals also secured in multiple additional countries. The next stage will expand enrollment and compare the combination treatment approach directly against standard therapies alone, with a target enrollment of approximately 490 patients worldwide.
Telix said it plans to present the Part 1 data to the United States Food and Drug Administration to seek an amendment that would allow the study's expansion stage to proceed in the United States. If the larger trial confirms the early findings, the company believes the therapy could emerge as a new first-line treatment option for men facing aggressive forms of advanced prostate cancer.