(UroToday.com) The European Association of Urology (EAU) 2026 Annual Congress was host to a renal cell carcinoma abstract session. Dr. Fabrizia Gelardi presented the first-in-human results of a multicentre phase I study evaluating [⁶⁸Ga]Ga-OncoCAIX PET/CT, a novel carbonic anhydrase IX (CAIX)-targeted radiotracer, for imaging in patients with clear cell renal cell carcinoma (ccRCC).
Dr. Gelardi noted that conventional imaging modalities remain the cornerstone for diagnosing and staging ccRCC; however, they provide limited insight into tumour biology and can have restricted ability to accurately characterize renal masses. Carbonic anhydrase IX (CAIX), which is strongly overexpressed in ccRCC, represents an attractive molecular imaging target and has significant theranostic potential.
[⁶⁸Ga]Ga-OncoCAIX is a novel small-molecule PET radiopharmaceutical engineered to bind selectively to CAIX-expressing tumours. Preclinical investigations have demonstrated strong affinity for CAIX, tumour-specific uptake, and favourable biodistribution characteristics. This multicentre prospective phase I trial represents the first-in-human clinical evaluation of [⁶⁸Ga]Ga-OncoCAIX PET/CT in patients with ccRCC, with primary objectives focused on safety, pharmacokinetics, and early diagnostic performance.
This ongoing multicentre, prospective phase I study plans to enrol up to 20 patients with suspected ccRCC or suspected recurrence based on conventional imaging findings.
Participants are stratified into two clinical cohorts:
- Cohort A: patients with primary renal tumours (n = 6)
- Cohort B: patients with suspected metastatic disease
All participants receive a single intravenous administration of 250 MBq of [⁶⁸Ga]Ga-OncoCAIX followed by serial PET/CT acquisitions performed at four time points: immediately following injection (0 minutes), and at 10, 60, and 120 minutes post-injection.
To evaluate pharmacokinetic characteristics, blood and urine samples are collected throughout the imaging protocol. Safety monitoring includes assessment of adverse events, which are recorded and graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.
Where available, PET imaging findings are correlated with histopathologic results to evaluate concordance between imaging and definitive tumour diagnosis.
As of October 31, a total of 16 patients had completed the imaging protocol. The study population included 13 males and 3 females with a median age of 67 years (range: 35–79 years).
Among the enrolled participants:
- Thirteen patients underwent evaluation for incidentally detected renal masses
- Three patients were assessed for suspected recurrence of ccRCC
From a safety standpoint, no drug-related adverse events were observed, suggesting an excellent safety profile for the radiotracer.
Imaging analysis demonstrated favourable biodistribution characteristics. Clearance of [⁶⁸Ga]Ga-OncoCAIX occurred through a mixed renal and hepatic pathway, while normal renal parenchyma showed minimal tracer retention. Physiologic uptake was primarily noted in the gastrointestinal tract, particularly within the stomach.
Lesions identified as PET-positive exhibited rapid and selective tumour uptake shortly after tracer administration. Importantly, signal intensity increased over time, with stronger uptake observed on the delayed scans obtained at 60- and 120-minutes post-injection.
Overall imaging findings were as follows:
- PET-positive scans: 7 of 16 patients
- PET-negative scans: 9 of 16 patients
Histopathological confirmation is currently available in five patients, with complete concordance between PET imaging and pathology:
- One PET-positive lesion confirmed as ccRCC
- Three PET-negative lesions confirmed as oncocytomas
- One PET-negative lesion confirmed as chromophobe RCC
These early findings suggest a promising ability of the radiotracer to distinguish ccRCC from other renal tumour histologies.
Dr. Gelardi concluded as follows:
- The novel CAIX-targeted radiotracer [⁶⁸Ga]Ga-OncoCAIX demonstrated an excellent safety profile and favourable pharmacokinetic characteristics in this first-in-human phase I study.
- Early imaging results indicate strong tumour-targeting properties and suggest that this tracer may serve as a non-invasive molecular imaging biomarker for detecting and characterising ccRCC.
- Ongoing enrolment and additional histopathological validation will be critical to further establish the diagnostic performance and potential clinical utility of this targeted PET imaging approach in renal cell carcinoma.
Presented by: Fabrizia Gelardi, MD, PhD, Department of Nuclear Medicine, IRCCS Ospedale San Raffaele, Milan, Italy
Written by: Rashid K. Sayyid, MD, MSc, Assistant Professor, Urologic Oncologist, Department of Urology at The University of Arizona and Banner University Medical Center, Tucson, AZ – @rksayyid on X during the 2026 European Association of Urology (EAU) Annual Meeting, London, United Kingdom, Fri, Mar 13 – Mon, Mar 16, 2026.