Telix Pharmaceuticals has dosed the first patient in a phase II trial investigating the use of an imaging agent to target carbonic anhydrase (CAIX) expression in a broad range of cancer indications.

The STARBURST study (NCT05563272) is investigating TLX250-CDx (⁸⁹Zr-DFO-girentuximab), a positron emission tomography (PET) and computed tomography (CT) imaging agent that targets CAIX expression across a range of solid tumours, including breast, cervix, colorectal, gastric, oesophageal, head and neck, lung, ovarian, pancreatic and vulval cancers.

Telix hopes the agent, which is administered intravenously, can be used for both imaging and therapeutic purposes. This study follows the success of the same agent in the Phase III ZIRCON trial targeting clear cell renal cell carcinoma (ccRCC).

Chief medical officer Dr Colin Hayward said: “Building on the success of ZIRCON and positive preliminary results in investigator-initiated studies of TLX250-CDx in bladder and breast cancer, dosing a first patient in the STARBURST study is a strategically important milestone for Telix.

“This study will add value and clinical insight to the platform and enable Telix to assess the potential of CAIX as a biomarker as we continue to scout the theranostic potential of targeting CAIX beyond renal cancer.”

How the agent identifies tumours

CAIX is a protein expressed to varying degrees in many advanced-stage solid tumours with poor prognosis. Tumours that express CAIX are typically hypoxic, more aggressive, and feature a tumour microenvironment (TME) that can pose resistance to therapy, particularly immunotherapies.

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By GlobalData

The open-label study explores these tumour types in the refractory setting to assess whether tumour sites can be targeted. The half-life of ⁸⁹Zr indicates that imaging tumours with TLX250-CDx will enable predictive dosimetry for therapeutic radionuclides, effectively serving as a theranostic “scouting” study for future studies harnessing therapeutic radionuclides.

Telix aims to enrol 100 participants in the open-label study and is still recruiting in Virginia and Washington in the US. The primary outcome is the uptake of TLX250-CDx in individual tumour deposits, which will be evaluated using PET and CT imaging over an average of 18 months.

What else is Telix Pharmaceuticals investigating?

In other trials, Telix is evaluating TLX591, an antibody-based therapeutic radiopharmaceutical to treat prostate cancer. In addition, the TLX101 drug for the treatment of glioblastoma (GBM) and TLX66-CDx and TLX66 programmes for bone marrow conditioning are other trials they are involved with.

Telix utilises molecularly-targeted radiation (MTR) technology, where a radionuclide is attached to a targeted small molecule or antibody that binds to tumour cells and destroys them.