Telix Pharmaceuticals Completes Enrolment in IPAX-2 Phase 1 Study of TLX101-Tx for First-Line Glioblastoma

As Telix Pharmaceuticals closes enrolment in its IPAX-2 Phase 1 dose-finding study, the radiopharmaceutical sector faces a concrete signal: iodine-131-labelled therapies targeting glioblastoma are advancing toward pivotal-stage manufacturing volumes, and the GMP infrastructure required to support them remains a live operational challenge for CDMOs and plant heads.

IPAX-2 enrolled twelve patients across three dose-escalating cohorts at four sites in Australia, Austria, and the Netherlands. The study evaluated TLX101-Tx (¹³¹I-iodofalan) in combination with standard-of-care external beam radiation therapy and temozolomide in newly diagnosed glioblastoma. No dose-limiting toxicities were observed at any cohort level, including at the maximum administered dose of two 5 GBq cycles, totalling 10 GBq. Patients remain on standard-of-care treatment pending confirmation of the maximum tolerated dose primary endpoint.

The manufacturing and logistics profile of TLX101-Tx warrants close attention from quality and supply-chain leads. As a systemically administered iodine-131 agent designed to cross the blood-brain barrier via LAT1 transporter targeting, the compound requires short-lived isotope handling under radiation safety protocols, qualified cold-chain management, and site-level radiation protection infrastructure, requirements that sit outside the standard aseptic fill-finish envelope covered by 21 CFR Part 211 and demand purpose-built radiopharmaceutical GMP frameworks.

The parallel IPAX BrIGHT pivotal trial, the first Phase 3 study of a radiopharmaceutical in glioblastoma, is actively dosing patients in Australia and the Netherlands, with approvals secured in Austria and Belgium and enrolment pending. That trial assesses TLX101-Tx against lomustine monotherapy in recurrent glioblastoma. Patient selection across the IPAX programme relies on the companion PET imaging agent TLX101-Px (floretyrosine F 18) to confirm LAT1 overexpression, adding a diagnostic manufacturing dependency to the supply chain equation. TLX101-Tx holds orphan drug designation in both the U.S. and Europe; neither agent has received marketing authorisation in any jurisdiction.

Historical data from the earlier IPAX-1 study reported a median overall survival of 13 months from treatment initiation and 23 months from initial diagnosis in recurrent glioblastoma, with the investigator-initiated IPAX-Linz trial returning consistent results. An early access programme in Europe has dosed 18 patients at first recurrence or later, providing additional real-world tolerability data outside the controlled trial setting.

Confirmation of the MTD primary endpoint in IPAX-2, expected following study completion, will set the dose parameters that Phase 3 manufacturing processes and batch release specifications must be designed around.

Source: Telix Pharmaceuticals via company press release, 19 May 2026.