MELBOURNE, Australia & INDIANAPOLIS, U.S., June 2, 2026
Telix Pharmaceuticals announced positive Part 1 data from its global Phase 3 ProstACT study evaluating TLX591-Tx (lutetium-177 rosopatamab tetraxetan) in patients with PSMA-positive metastatic castration-resistant prostate cancer (mCRPC). Presented in a late-breaking oral session at the ASCO 2026 Annual Meeting, the results demonstrated acceptable safety, favorable dosimetry, and sustained tumor targeting when TLX591-Tx was combined with current standard-of-care therapies.
Phase 3 Study Confirms Feasibility of Combining TLX591-Tx with Standard Therapies
The ProstACT Global trial is evaluating TLX591-Tx administered as two doses, 14 days apart, in combination with standard-of-care treatments including abiraterone, enzalutamide, or docetaxel. The study enrolled PSMA-positive mCRPC patients who had previously received one androgen receptor pathway inhibitor (ARPI). Across all three treatment cohorts, investigators reported successful administration of both planned TLX591-Tx doses in every patient, demonstrating strong treatment compliance and feasibility.
Safety Profile Consistent with Prior Studies
TLX591-Tx demonstrated an acceptable safety and tolerability profile across all treatment combinations, with no new safety signals identified. Most non-hematologic treatment-emergent adverse events were mild to moderate (Grade 1–2), with fatigue (53%), nausea (28%), and dry mouth (25%) reported most frequently. Hematologic adverse events, including thrombocytopenia and neutropenia, were generally transient and manageable, remaining consistent with expectations for radiopharmaceutical therapies used in advanced prostate cancer.
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Dosimetry and Imaging Confirm Strong Tumor Targeting
Dosimetry analyses showed radiation exposure to critical organs remained well below established safety thresholds. The highest absorbed radiation dose was observed in the liver, while significantly lower exposure was seen in the kidneys and salivary glands. Imaging studies confirmed consistent uptake of TLX591-Tx across tumor sites in all treatment cohorts. Pharmacokinetic data further demonstrated sustained therapeutic activity through Day 15, with prolonged tumor retention supporting the drug’s targeted delivery mechanism.
Phase 3 Expansion Underway Following Positive Results
Based on the encouraging Part 1 findings, Telix has already initiated Part 2, a randomized 2:1 treatment expansion phase in regions where regulatory approvals have been obtained. The company is also engaging with the U.S. FDA to advance the program in the United States through an Investigational New Drug (IND) amendment. If future data continue to support the current findings, TLX591-Tx could emerge as a new treatment option for patients with metastatic castration-resistant prostate cancer who require additional therapies beyond existing androgen receptor-targeted treatments.
Source: Telix Pharmaceuticals press release
