Telix Pharmaceuticals has announced that Part 1 of its ProstACT Phase 3 trial for TLX591-Tx met its primary safety and dosimetry objectives, with no new safety concerns. The study’s success supports ongoing global enrolment in Part 2 and regulatory engagement in the US.
- Part 1 of ProstACT Phase 3 met primary safety and dosimetry goals
- TLX591-Tx showed acceptable tolerability combined with standard prostate cancer therapies
- No new safety signals or drug interactions observed across three patient cohorts
- Part 2 trial underway in multiple countries with regulatory approvals secured
- Telix to present data to FDA seeking approval to progress US trial phase
ProstACT Phase 3 Part 1 Delivers on Safety Benchmarks
Telix Pharmaceuticals Limited (ASX:TLX) has reported positive results from Part 1 of its ProstACT Global Phase 3 study, evaluating TLX591-Tx, a novel lutetium-177 radio antibody-drug conjugate (rADC) therapy for metastatic castration resistant prostate cancer (mCRPC). The safety and dosimetry lead-in phase, involving 36 patients across three cohorts, demonstrated an acceptable safety profile with no new safety signals, reinforcing the drug’s tolerability when combined with standard of care treatments.
The study cohorts combined TLX591-Tx with enzalutamide, abiraterone, or docetaxel, reflecting current clinical practice for mCRPC. Importantly, the trial showed no adverse drug-drug interactions and manageable hematologic events consistent with expectations for this therapeutic class. Non-hematologic side effects were predominantly low-grade, including fatigue, nausea, and dry mouth.
Dosimetry and Biodistribution Support Safety Profile
Dosimetry analysis revealed radiation exposure to critical organs remained well below established safety limits, with limited uptake in salivary glands and kidneys, common sites of toxicity in competing PSMA-targeted therapies. The pharmacokinetic data indicated sustained activity and prolonged tumour retention of TLX591-Tx, supporting its potential efficacy. These findings align with prior clinical studies and underscore the differentiated targeting mechanism of this first-in-class rADC.
Global Expansion and Regulatory Pathway
Following the successful completion of Part 1, Telix has initiated Part 2 of the ProstACT trial, a 2:1 randomized expansion enrolling approximately 490 patients across Australia, New Zealand, Canada, China, Singapore, South Korea, Türkiye, and the United Kingdom. The company plans to present the Part 1 data to the US Food and Drug Administration (FDA) to seek an Investigational New Drug amendment, aiming to advance Part 2 enrolment in the US.
Telix’s Chief Medical Officer, Dr David N. Cade, emphasised the unmet need for improved first- and second-line therapies in advanced prostate cancer and expressed optimism that TLX591-Tx could become a new treatment option. The trial’s design, integrating TLX591-Tx with contemporary standard of care, positions it well to address this aggressive disease.
Looking Ahead
While these initial safety results are encouraging, the ultimate impact of TLX591-Tx will depend on efficacy outcomes from the ongoing Part 2 trial. Investors and clinicians alike will be watching closely as Telix navigates regulatory discussions and expands patient enrolment globally. The company’s approach to minimising common toxicities seen in other PSMA-targeted therapies could offer a meaningful clinical advantage if confirmed in later-stage data.
Bottom Line?
Telix’s ProstACT trial advances confidently, but the market awaits Part 2 efficacy data and FDA feedback.
Questions in the middle?
- Will Part 2 confirm TLX591-Tx’s efficacy alongside its established safety profile?
- How will the FDA respond to the IND amendment request based on Part 1 data?
- Can TLX591-Tx’s differentiated safety and biodistribution translate into competitive market positioning?