Telix Reports Positive rPFS Data from ProstACT SELECT Trial of TLX591 rADC in Prostate Cancer

Telix Pharmaceuticals Limited, based in Melbourne, Australia, has released promising new data from its ProstACT SELECT trial evaluating TLX591 (177Lu rosopatamab tetraxetan), a lutetium-labelled radio-antibody-drug conjugate (rADC) therapy intended for the treatment of metastatic castrate-resistant prostate cancer (mCRPC). The study seeks to validate PET imaging for patient selection and determine TLX591's efficacy, with reported median radiographic progression-free survival (rPFS) of 8.8 months in a heavily pre-treated patient cohort.

The ProstACT SELECT trial aims to assess lesion concordance between 68Ga-based PSMA-PET imaging and TLX591 dosimetry, thereby substantiating PET imaging for patient selection in rADC therapy. The study's focus included patients with various levels of disease burden, most of whom had undergone at least two prior lines of therapy. TLX591 was administered in two 76 mCi intravenous infusions spaced 14 days apart to 23 patients with progressive mCRPC.

Dr. Nat Lenzo, a Nuclear Oncologist and the lead recruiter for the SELECT trial, highlighted the significance of the 8.8-month median rPFS. He noted that this compares favorably with initial findings from Phase I and II studies of small molecule radioligand therapies, indicating TLX591's potential efficacy in a significantly pre-treated patient group. The results also suggest that TLX591 could be promising for earlier-stage mCRPC patients, supporting its further development in the Phase III ProstACT GLOBAL trial, which is soon to enroll patients at its first U.S. sites.

Dr. David N. Cade, Group Chief Medical Officer at Telix, emphasized TLX591's considerable advantages over small molecule radiopharmaceuticals due to its lower cumulative radiation exposure and patient-friendly dosing regimen. This latest signal of efficacy builds on previous studies, which have shown TLX591's potential for improving quality of life and providing durable tumor control in advanced mCRPC patients.

The Phase III ProstACT GLOBAL trial, designed for first and second-line mCRPC, offers physicians a choice between androgen receptor inhibition or docetaxel chemotherapy, aligning with real-world treatment standards. This trial reflects Telix's ongoing commitment to advancing prostate cancer care and improving patient outcomes.

TLX591 is Telix’s leading investigational rADC therapy for mCRPC, featuring a high-specificity PSMA-targeting antibody, a chelator linker, and a cytotoxic lutetium (177Lu) payload. Administered intravenously in a two-dose fractionated regimen, TLX591 aims to deliver a potent, targeted dose while minimizing off-target radiation exposure. The monoclonal antibody-based approach of TLX591 presents distinct advantages in terms of selectivity, internalization, and retention time over small molecule radioligand therapies.

To date, 242 patients have been treated with TLX591 across multiple Phase I and II trials, including a previously published Phase II trial that reported a median overall survival of 42.3 months in 17 advanced mCRPC patients treated with fractionated dosing.

The SELECT trial also evaluates the utility of PSMA-PET imaging with Illuccix® for selecting patients for TLX591 therapy, with primary objectives including the assessment of whole-body biodistribution, organ radiation dosimetry, and safety. Previously reported data from the SELECT trial confirmed favorable biodistribution, safety, internalization, and retention, alongside lower rates of hematologic toxicity compared to later-line studies.

Telix Pharmaceuticals Limited is a biopharmaceutical company specializing in diagnostic and therapeutic radiopharmaceuticals, with headquarters in Melbourne and operations in the United States, Europe, and Japan. Telix’s lead imaging product, Illuccix®, has received regulatory approval in the U.S., Australia, and Canada. The company continues to innovate in oncology and rare disease treatments to address unmet medical needs.