Telix Pharmaceuticals (ASX:TLX) said its lutetium radio antibody-drug conjugate candidate, TLX591-Tx, demonstrated acceptable tolerability across all standard-of-care combination groups in the ProstACT global phase three study, with no new safety signals, supporting the feasibility of TLX591-Tx in combination with standard-of-care in post-ARPI metastatic castration-resistant prostate cancer, according to a Tuesday statement.

The primary endpoint was the safety and tolerability of TLX591-Tx in combination with standard-of-care, while secondary endpoints included pharmacokinetics and radiation dosimetry.

The trial enrolled prostate-specific membrane antigen-positive metastatic castration-resistant prostate cancer patients previously treated with one androgen receptor pathway inhibitor. It consisted of TLX591-Tx, administered as two doses 14 days apart, in combination with standard-of-care, which includes abiraterone, enzalutamide, or docetaxel, in comparison with standard-of-care alone. 36 patients received both doses of TLX591-Tx per protocol.

Treatment-emergent non-hematologic events were primarily fatigue, nausea, and dry mouth. Radiation exposure to key organs was below established safety limits. Lesion dosimetry confirmed uptake across tumor sites and across all cohorts, while pharmacokinetics demonstrated sustained activity at Day 15.

The firm initiated the second part of the study, a randomized treatment expansion, where it obtained regulatory approvals. It is engaging with the US Food and Drug Administration (FDA) to discuss the data from the first part and seek an Investigational New Drug (IND) amendment to advance the second part in the US.