Telix Pharmaceuticals NASDAQ: TLX hosted an educational webinar outlining its next-generation prostate-specific membrane antigen (PSMA) radiopharmaceutical strategy, with management and a clinical investigator emphasizing the need for more patient-centric dosing and improved tolerability as PSMA-targeted therapy moves earlier in prostate cancer care.
The session was moderated by Stewart Holmstrom, Telix’s Director of Corporate Communications, and featured Dr. David Cade, Telix Group Chief Medical Officer, alongside guest speaker Professor Louise Emmett, Director of Theranostics and Nuclear Medicine at St Vincent’s Hospital Sydney and Principal Investigator of the OPTIMAL-PSMA trial.
Positioning radioligand therapy and Telix’s portfolio approach
Dr. Cade reviewed how radioligand therapy has established itself in advanced metastatic castration-resistant prostate cancer (mCRPC), pointing to the role of PSMA-617 (Novartis’ Pluvicto) and its VISION trial results, which he said showed a four-month overall survival extension compared with conventional standard of care.
He also described growing interest in deploying radioligand therapy earlier, in metastatic hormone-sensitive prostate cancer (mHSPC), while highlighting challenges observed with first-generation small-molecule radioligands in fitter patients. Dr. Cade said emerging concerns include salivary gland radiation exposure leading to dry mouth and quality-of-life impacts, as well as kidney radiation exposure that could contribute to long-term renal injury.
Against that backdrop, Dr. Cade outlined Telix’s portfolio strategy using “very distinct mechanisms of action,” including:
- TLX591, a radioantibody-drug conjugate being studied in advanced mCRPC in the ongoing Phase 3 ProstACT Global trial.
- TLX597-Tx, a second-generation small-molecule radioligand therapy that Dr. Cade said has shown “very minimal salivary gland and kidney dose” alongside a high tumor dose, which he said could make it suitable for earlier use in mHSPC and for dose intensification strategies.
OPTIMAL-PSMA: testing dose intensification and optimization
Professor Emmett presented the rationale and early experience from OPTIMAL-PSMA, a randomized Phase 2 trial comparing dose intensification versus standard dosing. She framed the trial as an effort to address what she described as frustration that common Lutetium-177 PSMA schedules were built around external beam kidney constraints rather than efficacy, while overall survival gains have been difficult to demonstrate.
Professor Emmett said the trial is designed to evaluate whether short, intensified dosing early can “attack the cancer cells when they're most vulnerable,” followed by later “maintenance.” She described the underlying biological thesis as combining (1) PSMA upregulation following radiation-induced DNA damage and (2) timing doses before DNA repair has fully resolved, potentially producing a “deeper hit” by treating already damaged cells.
In the trial, patients have mCRPC and must have failed an androgen receptor pathway inhibitor (ARPI) and failed docetaxel or be docetaxel-ineligible; she noted many enrolled patients have failed one or two lines of chemotherapy. She described the cohort as high-volume and heavily pre-treated, noting the trial’s broad inclusion criteria were partly driven by limited access to Lutetium-177 PSMA therapy in Australia.
Dosimetry and early tolerability observations
Professor Emmett highlighted dosimetry findings from the safety lead-in cohort (the first 12 patients), comparing TLX597-Tx with prior publications for PSMA-617 and PSMA I&T. She reported a kidney dose of 0.28 gray per gigabecquerel, compared with 0.58 and 0.71 in the referenced comparators, and said lacrimal and salivary gland activity was “significantly lower” while tumoral activity was maintained.
She also described serial SPECT/CT imaging timepoints after a 7.5 gigabecquerel dose of TLX597-Tx, noting that by 120 hours post-injection, tumor signal remained bright while salivary glands and kidneys were difficult to visualize, attributing part of the profile to bowel excretion.
On safety, Professor Emmett said toxicity to date has been low, including a data safety monitoring board review (after 10 weeks) of the first 10 patients treated with a dose-intensified regimen. She reported five grade 1 anemias, two grade 1 thrombocythemias, one grade 1 xerostomia, and two grade 3 lymphopenias. She added that in high-volume disease, pain can worsen in the first couple of weeks, and her team uses pain planning and dexamethasone to mitigate fatigue.
Enrollment update and plans for earlier disease (OPTIMAL-E)
Professor Emmett said OPTIMAL-PSMA was approaching completion of enrollment, with roughly 90 of 120 patients randomized, largely at a single site at St Vincent’s Hospital Sydney. She added that the median number of doses received was four because progression commonly occurred around that time, and she said about 45% of patients had progressed by dose three—calling that “the thing to beat” in future efforts to keep patients on therapy longer.
Looking to earlier mHSPC, Professor Emmett described OPTIMAL-E, a concept using intensive dosing up front combined with ARPI and androgen deprivation therapy (ADT), followed by PSMA PET-guided adaptive dosing. If disease is absent on a 12-week PSMA PET scan, Lutetium-177 PSMA therapy would stop while ARPI and ADT continue, with retreatment triggered at first confirmed PSA rise. She said she would like to see a high proportion of patients reaching a PSA below 0.2 and no residual disease on PSMA PET at key timepoints, while maintaining quality of life and avoiding overtreatment.
During Q&A, Dr. Cade responded to questions on hematologic toxicity and gastrointestinal effects, saying the early dosimetry profile suggests low off-target dose in organs including bone marrow and that the observed adverse-event profile reported to the independent monitoring committee included relatively low constitutional side effects compared with other small molecules.
The webinar concluded with Telix reiterating its emphasis on aligning mechanism, dosing strategy, and tolerability with disease stage, and with Professor Emmett acknowledging the trial’s role in expanding treatment access for patients across New South Wales.
About Telix Pharmaceuticals NASDAQ: TLX
Telix Pharmaceuticals NASDAQ: TLX is a clinical-stage biopharmaceutical company focused on the development and commercialization of molecularly targeted radiopharmaceuticals for the diagnosis and treatment of cancer. Leveraging expertise in radiochemistry, nuclear medicine and oncology, Telix aims to address unmet clinical needs across a range of tumor types by pairing diagnostic imaging agents with therapeutic radionuclides.
The company’s pipeline spans both imaging and therapeutic candidates.
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