AMBIGUOUS RESULTS

Telix's IPAX-2 shows no dose-limiting toxicities in newly diagnosed glioblastoma

The Phase 1 safety readout for TLX101-Tx completed enrollment at 12 patients, clearing the dose-limiting toxicity bar the trial was designed to test.

IPAX-2, a Phase 1 study of the radiotherapy TLX101-Tx in newly diagnosed glioblastoma, completed enrollment of 12 patients and Telix Pharmaceuticals reported no dose-limiting toxicities observed to date.

By AppliedXLJuly 20, 2026Trial NCT05450744

Executive Summary

A Phase 1 dose-escalation study of Telix Pharmaceuticals' radiotherapy in newly diagnosed glioblastoma completed enrollment and reported no dose-limiting toxicities, meeting the trial's core safety objective.
The design was built to characterize toxicity and identify a recommended dose, not to establish efficacy, so the disclosure speaks to tolerability rather than to tumor response or survival.
The same drug is already being tested in a larger, later-phase trial in recurrent glioblastoma against standard of care, so this earlier-line safety result feeds a broader development effort rather than standing alone.
The trial's status moved to Unknown status for roughly six months before reverting to Recruiting, and its completion date shifted by a year, but enrollment held exactly at its 12-patient target throughout.

The readout

Telix Pharmaceuticals Limited disclosed in a July 20, 2026 shareholder update that IPAX-2, its Phase 1 study of 131I-TLX-101 in newly diagnosed glioblastoma, completed patient enrollment and that no dose-limiting toxicities have been observed to date. The trial, registered as NCT05450744, enrolled 12 adults with Karnofsky Performance Status of 70 or higher who had undergone surgical resection for intracranial glioblastoma before starting chemoradiation. Its two primary endpoints are the incidence and severity of dose-limiting toxicities and the safety, tolerability, and recommended Phase 2 dose of the radiolabeled therapy delivered intravenously. Telix+1

Probability of Success

Endpoint Met4%

Completes52%

Clinical Significance9%

Regulatory54%

What the design measures

This is a dose-escalation safety study, not an efficacy trial: a single-arm, open-label design in 12 patients cannot establish whether the treatment shrinks tumors or extends survival. What it can establish is whether escalating doses of an intravenously delivered iodine-131-labeled radiotherapy can be given without triggering toxicities severe enough to cap the dose. The absence of dose-limiting toxicities across the full enrolled cohort answers that question in the affirmative for the doses tested, and supports carrying a recommended dose forward rather than halting on safety grounds. NCT05450744+1

Program context

TLX101-Tx is also being tested in a Phase 3 trial, NCT07100730, that combines the drug with standard of care against standard of care alone in patients with recurrent glioblastoma, with a primary completion date of July 2027. That later-stage, later-line trial is the registrational vehicle for the drug; IPAX-2's newly diagnosed, earlier-line safety data functions as supporting evidence for the therapy's tolerability profile rather than as a separate efficacy catalyst. TLX101-Tx has also received orphan drug designation for glioma in both the United States and Europe, a signal of the disease's small population and unmet need rather than a predictor of eventual approval.

The competitive field

Radiopharmaceutical approaches are not new to glioblastoma: 17 trials have used radiopharmaceutical modalities in the indication, including Novartis's Lu-NeoB and Plus Therapeutics' Rhenium-186 nanoliposomes, both in Phase 1 testing. No trial in the competitive set shares TLX101-Tx's specific radioisotope-antibody construct as a direct comparator, so the nearest context is this broader modality precedent rather than a head-to-head rival. Outside radiopharmaceuticals, the glioblastoma field includes NovoCure's Optune device and Nuvation Bio's small-molecule IDH1 inhibitor safusidenib in Phase 3 testing for glioma, reflecting a field with no single validated disease-modifying mechanism and multiple modality classes still in testing. [177Lu]

Operational history

The trial's registry status moved from Recruiting to Unknown status on July 1, 2025, before reverting to Recruiting on January 21, 2026, the same date its primary completion date shifted from June 2025 to June 2026. Enrollment held at its 12-patient target throughout that period, a change of 0% against target, which the trial's own operational baseline classifies as typical for a Phase 1 design. The amendment pattern otherwise remained limited, with two eligibility-criteria changes and no changes to the registered endpoints. NCT05450744

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