en.Wedoany.com Reported - Telix Pharmaceuticals Limited presented safety, dosimetry, and pharmacokinetic data from the first part of the ProstACT Global Phase 3 study of its prostate cancer therapeutic candidate TLX591-Tx (lutetium-177 (177Lu) rosopatamab tetraxetan) in an oral presentation at the 2026 American Society of Clinical Oncology Annual Meeting. The results indicate that the drug, when combined with standard of care for metastatic castration-resistant prostate cancer, demonstrates an acceptable safety and tolerability profile, with no new safety signals observed.
ProstACT Global is an international, multicenter, randomized Phase 3 trial in PSMA-positive mCRPC patients who have received prior treatment with one androgen receptor pathway inhibitor. The trial compares TLX591-Tx (administered twice, 14 days apart) combined with standard of care (abiraterone, enzalutamide, or docetaxel) versus standard of care alone, aiming to reflect real-world clinical practice. The study enrolled 36 patients across three cohorts: Cohort 1 (11 patients), TLX591-Tx combined with abiraterone; Cohort 2 (11 patients), TLX591-Tx combined with enzalutamide; Cohort 3 (14 patients), TLX591-Tx followed by docetaxel. All patients completed two doses of TLX591-Tx as per protocol.
Safety data showed that treatment-emergent non-hematologic events were primarily Grade 1-2, including fatigue (53%), nausea (28%), and dry mouth (25%). Hematologic events were transient and manageable, with Grade 3 thrombocytopenia occurring at 14% and Grade 3 neutropenia at 22%; Grade 4 thrombocytopenia was 31%, and Grade 4 neutropenia was 25%. These events are consistent with the expected characteristics of this class of therapy and disease severity.
Dosimetry and pharmacokinetic results indicated that radiation exposure to key organs was well below established safety limits. The highest absorbed dose was in the liver, ranging from 1.62 to 5.08 mGy/MBq, kidney doses ranged from 0.336 to 0.961 mGy/MBq, and salivary gland doses ranged from 0.001 to 0.104 mGy/MBq. Lesion dosimetry confirmed tumor uptake, consistent across all cohorts. Pharmacokinetics showed sustained activity at Day 15, with imaging confirming prolonged tumor retention, and no evidence of drug-drug interactions affecting TLX591-Tx targeting, distribution, or clearance.
Pedro C. Barata, MD, MSc, medical oncologist at University Hospitals Seidman Cancer Center and Associate Professor of Medicine at Case Western Reserve University School of Medicine, and the study's principal investigator, stated that these results support the feasibility of combining TLX591-Tx with current mCRPC standard of care. David N. Cade, MD, PhD, Chief Medical Officer of Telix Group, added that these data build on previous clinical findings and support the drug's combination with contemporary standard of care, potentially offering a new treatment option for this disease.
Telix has initiated the second part of the study, a 2:1 randomized treatment expansion, in jurisdictions with regulatory approval, and is in communication with the U.S. Food and Drug Administration regarding an investigational new drug amendment to advance Part 2 in the United States. The ProstACT Global trial aims to enroll approximately 490 patients in total. TLX591-Tx, as an antibody-based approach, demonstrates targeting and pharmacological properties distinct from other PSMA-targeted small molecule radioligand therapies, primarily clearing through the liver with very low uptake in the salivary and lacrimal glands. TLX591-Tx has not received marketing authorization in any jurisdiction.
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