OPALESCENCE Trial Published in EJNMMI: Confirms Theranostic Potential of TLX250-CDx in Breast Cancer

Melbourne (Australia) and Indianapolis, IN (U.S.) | 12 November 2025

Telix today announces that final positive results from the Phase 2 OPALESCENCE trial[1] of TLX250-CDx (89Zr-girentuximab) in metastatic triple negative breast cancer (mTNBC) have been published in the European Journal of Nuclear Medicine and Molecular Imaging (EJNMMI)[2].

OPALESCENCE was a prospective, single-center Phase 2 investigator-initiated trial (IIT) conducted at the Institut de Cancérologie de l’Ouest (ICO) in St Herblain, France. The trial evaluated the safety, sensitivity, and diagnostic utility of TLX250-CDx PET/CT[3] imaging in women with mTNBC.

The pilot prospective study of twelve (12) patients demonstrated the expression of carbonic anhydrase IX (CAIX) in TNBC and effective tumor targeting with TLX250-CDx:

  • Overall sensitivity was 87.5% with 100% sensitivity for breast, skin, and adrenal gland;
  • Expression in nodes and bone lesions was 88.0% and 91.9%, respectively;
  • TLX250-CDx PET/CT detected all brain metastases, confirmed by MRI, whereas FDG PET/CT detected only one-third of brain lesions;
  • Tumor burden analyzed using total tumor volume (TTV) was equivalent between both PET/CT methods; and
  • No safety issues were reported after TLX250-CDx administration.

The authors conclude that TLX250-CDx immuno-PET “is a sensitive imaging method and offers promise for novel theranostics for mTNBC patients”.

The first peer-reviewed publication about the trial builds on preliminary results presented at the European Association of Nuclear Medicine Annual Congress in 2022[4] and at the San Antonio Breast Cancer Symposium in 2023[5], further substantiating the potential of CAIX-targeted PET imaging in this aggressive cancer subtype.

Principal Investigator for the OPALESCENCE study, Dr. Caroline Rousseau stated, “TLX250-CDx has already shown high sensitivity and specificity in clinical trials for the detection of clear cell renal cell carcinoma[6]. Now it has also exhibited potential utility in metastatic triple negative breast cancer, an aggressive form of breast cancer. These results demonstrate the ability of TLX250-CDx to identify lesions that may be resistant to treatment due to their aggressive profile resulting from hypoxia, in patients with limited options for therapeutic management.”

Dr. David N. Cade, Group Chief Medical Officer at Telix, added, “We are encouraged by this data in triple negative breast cancer, which remains an area of significant unmet need. Proof of concept for CAIX-targeted imaging supports the expansion of this potential pan-tumor program into new indications beyond renal cancer, including future applications for lutetium-177 (177Lu) and actinium-225 (225Ac) based therapies.” 

The full paper can be found at: https://link.springer.com/article/10.1007/s00259-025-07619-y

Telix supplied and authorized ICO to use TLX250-CDx during the clinical study. TLX250-CDx has not received a marketing authorization in any jurisdiction.

[1] ClinicalTrials.gov ID: NCT04758780.

[2] Rousseau et al. Eur J Nucl Med Mol Imaging. 2025.

[3] Positron emission tomography/computed tomography.

[4] Telix ASX disclosure 18 October 2022.

[5] Telix media release 7 December 2023.

[6] Telix ASX disclosures 7 November 2022. Shuch et al. Lancet Oncol. 2024.