ProstACT Global Phase 3 Update: First Patient Dosed in Randomized Treatment Expansion, Part 1 Readout Plans Confirmed

Melbourne (Australia) and Indianapolis (United States) | 8 December 2025

Telix today announces that the first patient has been dosed in Part 2 (randomized treatment expansion) of its ProstACT Global Phase 3 study evaluating its lead prostate cancer therapy candidate TLX591 (lutetium (¹⁷⁷Lu) rosopatamab tetraxetan) in patients with metastatic castration resistant prostate cancer (mCRPC). The patient was dosed at the Australian Prostate Centre (APC) in Melbourne, Australia.

ProstACT Global is the first Phase 3 trial to combine a PSMA^[1]-targeted radio antibody-drug conjugate (rADC) therapy administered together with Standard of Care (SOC; abiraterone, enzalutamide or docetaxel) versus SOC alone. Part 2 of ProstACT Global will enroll approximately 490 patients and is currently recruiting patients in Australia, New Zealand and Canada.

As previously agreed with FDA and disclosed to the market, Telix will submit Part 1 data to the United States (U.S.) Food and Drug Administration (FDA) to enable clearance to expand Part 2 of the trial to U.S. sites. A public disclosure of preliminary results from Part 1 of the study will be aligned to engagement with the FDA.

The study is also approved to commence in China, Japan[2], Singapore, South Korea, Türkiye and the United Kingdom. As part of the further global expansion of the trial, Telix will file a clinical trial application (CTA) with the European Medicines Agency (EMA) to enable expansion into EU sites.

Dr. David N. Cade, Group Chief Medical Officer, Telix, commented, “Dosing the first patient into Part 2 of the randomized treatment expansion of ProstACT Global trial is a significant milestone for Telix’s late-stage prostate cancer therapeutics pipeline. We look forward to presenting the preliminary data from Part 1 of the study to the FDA and EMA in the coming months[3].”

About ProstACT Global

ProstACT Global (ClinicalTrials.gov ID: NCT06520345) is an international, multicenter trial in two parts: Part 1, safety and dosimetry lead-in with 30 patients (target enrollment complete); and Part 2, 2:1 randomized global expansion with an overall target enrollment of approximately 490 patients. Eligible patients must have confirmed progressive mCRPC assessed with a ⁶⁸Ga-PSMA-11 PET[4] imaging agent (such as Illuccix® or Gozellix®, kits for the preparation of gallium-68 (⁶⁸Ga) gozetotide injection) following prior treatment with an androgen receptor pathway inhibitor (ARPI).

The antibody approach demonstrates different targeting and pharmacology to that observed in other PSMA-targeted small peptide radioligand therapies (RLT). In contrast to these therapies[5], collective long-term follow-up of patients administered with TLX591 has not observed significant acute or delayed kidney toxicity, as the agent is cleared through the liver, instead of the kidneys[6]. Due to its large molecular weight, TLX591 also demonstrates minimal salivary and lacrimal gland uptake, reducing dry mouth and dry eyes, common adverse effects of existing PSMA-targeted RLTs[7].

Additional information on the Phase 3 ProstACT Global study can be found at: https://telixpharma.com/prostact/

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TLX591 has not received a marketing authorization in any jurisdiction.

[1] Prostate-specific membrane antigen.

[2] Japanese regulator Pharmaceuticals and Medical Devices Agency (PMDA) has granted approval for a Japan-specific Part 1 in nine patients, prior to commencing Part 2.

[3] Collation of available published data. Not from head-to-head studies, cross trial or product data should be interpreted with caution.

[4] Positron emission tomography.

[5] Tagawa et al. Curr Oncol Rep. 2021; Steinhelfer et al. JNM. 2024.

[6] Tagawa et al. Cancer. 2019.

[7] Pepin et al. Pract Radiat Oncol. 2025.