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Telix Pharmaceuticals Begins Phase III Radiopharmaceutical Trial in PSMA-Positive mCRPC

NEW YORK – Telix Pharmaceuticals said on Sunday that it has treated the first metastatic castration-resistant prostate cancer patient in a Phase III trial of its radiopharmaceutical TLX591.

In the ProstACT GLOBAL trial, Melbourne, Australia-based Telix is evaluating TLX591 as a second-line treatment for mCRPC patients whose tumors express prostate-specific membrane antigen (PSMA), as determined by the gallium-labeled PSMA PET/CT imaging agent Illuccix (68Ga-PSMA-11). The firm aims to enroll 387 patients in the trial and randomly assign them to receive either TLX591 plus the standard-of-care treatment — consisting of physician's choice of chemotherapy or androgen receptor pathway inhibitors — or to just the standard of care. Researchers are tracking patients' radiographic progression-free survival as the primary endpoint; secondary endpoints are overall survival and objective response rates, among other outcomes. 

TLX591 is a radio-antibody drug conjugate comprising the therapeutic isotope lutetium-177 and a PSMA-targeting antibody joined by a chelator linker. The firm claims TLX591 offers a different targeting approach and a dosing advantage compared to other PSMA-directed radiopharmaceuticals. Patients on TLX591 get two infusions two weeks apart, whereas patients receive six doses of Novartis' PSMA-directed prostate cancer treatment Pluvicto (lutetium vipivotide tetraxetan), one every six weeks.

Telix has begun the ProstACT GLOBAL study in Australia but expects to open the trial globally, including in Europe and the US. According to the firm, it is on track to file an investigational new drug application for TLX591 with the US Food and Drug Administration in the fourth quarter of this year. Telix hopes to test a new commercial-scale manufacturing process for TLX591 at US trial sites.

In addition to testing TLX591 in prostate cancer, Telix is also evaluating its radiopharmaceuticals in certain patients with brain cancers and in select tumor-agnostic indications.