ProstACT Part 1: TLX591‑Tx Safety and Dosimetry Readout

Telix reports that Part 1 of the ProstACT Global Phase 3 study—the safety and dosimetry lead-in for TLX591‑Tx—achieved its primary objectives in a 36-patient cohort. The company also reported an acceptable safety and tolerability profile and stated that no new safety signals were observed. In the same update, Telix states TLX591‑Tx was administered as two doses given 14 days apart for the Part 1 evaluation. Telix’s summary frames these Part 1 findings around cohort description, safety and tolerability, dosimetry/biodistribution, and the next steps it says will follow as the trial advances.

Telix describes Part 1 as enrolling prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer (mCRPC) patients previously treated with one androgen receptor pathway inhibitor (ARPI). It allocated 36 participants across three combination cohorts, pairing TLX591‑Tx with enzalutamide, abiraterone, or docetaxel. The company characterizes this lead-in as intended to confirm the safety profile alongside biodistribution and dosimetry when TLX591‑Tx is used in combination with these standard-of-care therapies, and it presents the Part 1 dataset as supporting progression to the next stage of the Phase 3 program.

For treatment-emergent adverse events, Telix reports that almost all non-hematologic events were Grade 1–2, with fatigue (53%), nausea (28%), and dry mouth (25%) listed as the most prevalent. The company also states hematologic events were transient and manageable, reporting Grade 3 thrombocytopenia at 14% and Grade 3 neutropenia at 22%, alongside Grade 4 thrombocytopenia at 31% and Grade 4 neutropenia at 25%. Telix characterizes these hematologic findings as consistent with expectations for the therapeutic class and extent of disease, and reiterates that no new safety signals were observed in this cohort.

On dosimetry and biodistribution, Telix states that radiation exposure to key organs was well below established safety limits, and it reports limited dose to the salivary glands and kidneys. The company adds that lesion dosimetry demonstrated uptake across tumor sites and across all cohorts. Telix also says it has advanced ProstACT Global into Part 2, described as a 2:1 randomized treatment expansion enrolling in jurisdictions where the trial has received health-authority approval, and states it intends to present Part 1 data to the U.S. FDA to seek an IND amendment to progress Part 2 in the United States.

Key Takeaways:

• Telix stated ProstACT Global Part 1 achieved its primary objectives in 36 patients and reported an acceptable safety and tolerability profile with no new safety signals observed.
• The company describes mostly low-grade non-hematologic events, alongside specified Grade 3/4 hematologic rates that it reported as transient and manageable.
• Telix states organ radiation exposure was below established safety limits with limited salivary/kidney dose, and describes Part 2 enrollment and planned FDA engagement to support U.S. progression.