ASCO 2026 | ProstACT Global part 1: 177Lu-rosopatamab and standard of care in mCRPC

So, you know, so the study, the part one of the study, as I said, is the safety dosimetry lead-in. Initially planned to enroll 30 patients, end up, you know, getting a total of 36 patients who were eligible and ended up enrolling in one of the three cohorts, which is really the design of this part one. The combination of TLX-591 with Abiraterone, 11 patients. The combination of TLX-591 with Enzalutamide, another 11 patients. And finally, the sequence of TLX-591 followed by Docetaxel, 14 patients. So overall, we presented results on the 36 patients that were eligible and were, you know, were assigned to these three cohorts. You know, all the patients were able to receive the two doses of TLX-591. At the time of cutoff, which was earlier, 2024, the median time on treatment on these, you know, was around, was shy from six months, a little bit over five months. And, you know, patients were able to receive ABI with TLX, Enzo with Telix 591, and 57% received two or more cycles of chemo. Nine of the 14 patients received chemo with more than half receiving two or more cycles at the time of data cutoff as well. So the population that we enrolled, basically 77, median age. Most patients received an ARPI in MCRPC setting. We saw more liver metastases in this cohort, you know, around a third of the patients or so. And then we go through the safety and dosimetry data as well. So we reported frequent non-hematologic events, fatigue, nausea, dry mouth, for the most part, minor. And then hematologic events were frequent, you know, thrombocytopenia, neutropenia, lymphopenia, they were frequent, but transient. The supportive interventions needed with blood transfusions or platelet transfusions or, you know, growth factors were needed in single digits or up to 14%. And then, you know, there were no toxic deaths. There were no bleeding events. And there was one episode of febrile neutropenia. And then, you know, we do a deep dive into the platelet kinetics. You see kind of the nadir around 43 days and then a recovery approximately 15 days later, which, you know, basically gives us the feasibility of incorporating, you know, TLX-591 with the standard of care in this setting. We also showed the organ radiation exposure breakdown, where we’ll see low exposure to kidneys and salivary glands, and the profile really compatible or aligned with what we’ve seen from prior clinical studies with TLX-591 as monotherapy, like the, you know, prior phase one trial data. And then finally, we also showed SPECT data from two patients showing the tumor retention, you know, through the 15 days following administration of TLX-591. So bottom line, you know, this is the data that would leverage continuing the investigation of Telix-591 into the part two, which is a larger portion of the trial, about 490 patients planned to be enrolled in a randomized fashion of 2-1 to, you know, ABI, ENZA, or Docetaxel without TLX-591. So that’s really what we presented. And, you know, and so with unique characteristics around this compound, it will be interesting to see what happens in a larger randomized prospective study.

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