# CAIX theranostics: 89Zr-girentuximab PET and 177Lu/225Ac-girentuximab therapy

Source: https://onco.cc/ideas/idea-caix-theranostics/  
OnCo record `idea-caix-theranostics` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Almost every clear-cell kidney cancer carries the CAIX protein. Image it with one radioactive antibody, then treat with the same antibody carrying a therapeutic isotope.

## Summary

Nearly every clear-cell renal cell carcinoma expresses carbonic anhydrase IX as a direct consequence of VHL loss, so the antigen is near-universal and stable. This theranostic idea images it with 89Zr-girentuximab PET, validated for diagnosis in ZIRCON, and then treats with the same antibody carrying 177Lu for beta emission or 225Ac for targeted alpha therapy. The rationale combines a stable target, the PSMA precedent in prostate cancer, and radiation-induced immunogenic cell death in a cancer that already responds to immunotherapy. STARLITE-1 and STARLITE-2 are testing 177Lu-girentuximab with nivolumab or cabozantinib, and the proposed test is a randomised phase 2 of 177Lu-girentuximab plus nivolumab versus nivolumab alone; Telix Pharmaceuticals is the linked company.

## Fields

- Kind: Idea
- Last checked: 2026-09-07
- Hypothesis: 177Lu- or 225Ac-girentuximab produces objective responses in ≥25% of heavily pretreated clear-cell RCC patients selected by CAIX PET, and synergises with PD-1 blockade.
- Rationale: Stable antigen, theranostic pairing proven in prostate cancer (PSMA), and radiation-induced immunogenic cell death in an immunotherapy-responsive tumour.
- Proposed test: Randomised phase 2 of 177Lu-girentuximab + nivolumab vs nivolumab after IO-TKI progression, PET-selected.
- Maturity: early-clinical

## Sources

- Shuch et al., ZIRCON: 89Zr-girentuximab PET-CT imaging of clear-cell renal cell carcinoma (Lancet Oncology 2024): https://doi.org/10.1016/S1470-2045(24)00402-9

## Connected records

- cancers: [Renal cell carcinoma](https://onco.cc/cancers/rcc/)
- technologies: [CAIX PET (89Zr-girentuximab)](https://onco.cc/technologies/caix-pet/), [Radio-antibody & radio-ADC](https://onco.cc/technologies/radioimmunotherapy/), [Radioligand therapy (beta emitters)](https://onco.cc/technologies/radioligand-therapy/), [Targeted alpha therapy](https://onco.cc/technologies/targeted-alpha-therapy/)
- targets: [HIF-2α](https://onco.cc/targets/hif2a/)
- companies: [Telix Pharmaceuticals](https://onco.cc/companies/telix/)
- key papers: [[ 89 Zr]Zr-girentuximab for PET-CT imaging of clear-cell renal cell carcinoma: a prospective, open-label, multicentre, phase 3 trial](https://onco.cc/key-papers/paper-shuch-lancet-oncol/)

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