First Patient Receives Antibody-based Prostate Cancer Treatment TLX591

The first patient has received TLX591 (Lu-rosopatamab tetraxetan) in a phase 3 trial for patients with PSMA-positive metastatic castrate-resistant prostate cancer (mCRPC), according to an announcement from Telix Pharmaceuticals Limited, the drug’s manufacturer.

PSMA (prostate-specific membrane antigen) is a protein that is found on the surface of prostate cells, as defined by the National Cancer Institute, and is “found in higher amounts on prostate cancer cells.”

The trial, ProstACT GLOBAL, is considered the first phase 3 trial to analyze the treatment with TLX591, which is a radio-antibody drug conjugate (rADC) that is made of a high-specificity PSMA-targeting antibody. The trial’s researchers found that using a PSMA-targeted monoclonal antibody may offer different targeting for this cancer type.

ProstACT GLOBAL follows previous phase 1 and phase 2 trials, including the phase 1 ProstACT SELECT trial, which demonstrated preliminary results earlier in 2023.

There were two cohorts in the ProstACT GLOBAL trial, according to clinicaltrials.gov, which included one cohort that was administered TLX591 combined with standard of care (SoC; widely used treatment accepted by medical experts as proper treatment for specific cancer types), which was androgen receptor inhibition or taxanes (chemotherapy drugs). The second cohort received only the standard of care.

“Recent studies, including ProstACT SELECT, have further advanced the development of this antibody-based PSMA therapy for prostate cancer patients. We have been encouraged with the safety profile, tolerability and early efficacy observed in our previous and ongoing studies, in particular for symptom control. It’s an important step forward for patients to see this investigational therapy enter a Phase III study,” Dr. Nat Lenzo, clinical director for GenesisCare Group and principal investigator for the ProstACT GLOBAL trial, said in the news release.

According to the news release, previous data from a phase 2 trial evaluating TLX591 reflected 42.3 months for overall survival (OS; length of time from diagnosis or the start of treatment when a patient is still alive).

The results from the previous phase 2 trial also established an acceptable safety profile when the regimen was administered at a fractioned dose in combination with docetaxel chemotherapy.

Looking forward, Telix stated that its investigational new drug application is still on track for filing with the U.S. Food and Drug Administration during the fourth quarter of 2023. The news release also noted that an interim analysis in the ongoing trial will likely occur after the first 120 patients receive treatments.

“Dosing a first patient in the ProstACT GLOBAL study is a significant milestone for Telix and will help build on an already extensive data set for this product candidate,” Dr. Colin Hayward, group chief medical officer of Telix, said in the news release. “The current TLX591 experience underlines the potential benefits of an antibody-based approach in combination with real-world standards of care, including physician choice of ARPIor taxane. As we take this potential first-in-class rADC candidate into a large, mid-stage patient population for the first time, we would like to thank Professor Lenzo and his clinical team, as well as the patients who will contribute to the study.”

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