Telix Pharmaceuticals Limited announced the publication of a new independent analysis of Phase 3 ZIRCON trial data in European Urology, demonstrating that TLX250-Px (Zircaix, 89Zr-girentuximab) PET/CT imaging may be highly predictive of renal malignancy across all subtypes, not limited to clear cell renal cell carcinoma (ccRCC). Recognizing that carbonic anhydrase IX (CAIX) expression is also observed in other renal cancer subtypes, this subsequent analysis conducted by international investigators who participated in ZIRCON Phase 3 trial evaluated centrally reviewed imaging and pathology data to explore whether tracer uptake in renal masses correlated with malignancy beyond ccRCC. The analysis demonstrated that positive PET findings were highly predictive of malignancy overall, including in non-clear cell renal cell carcinoma (nccRCC), with a reported positive predictive value (PPV) of 98% (95% CI, 96?99), sensitivity of 82% (95% CI, 82?90), and specificity of 87% (95% CI, 81?93).

These exploratory scientific findings suggest TLX250-Px has applications beyond the detection of ccRCC in primary renal masses and may have implications to management of nccRCC. These findings are based on exploratory analyses and were not the basis of Telix?s Biologics License Application (BLA) submission for TLX250-Px, which focuses exclusively on detection of ccRCC in primary renal masses. TLX250-Px is a PET imaging candidate under development for the diagnosis and characterization of ccRCC, and included in international guidelines for renal imaging.

It works by specifically binding to carbonic anhydrase IX (CAIX), a validated target protein expressed on >95% of ccRCC cells, to produce images with high tumor-to-background ratio and high intra- and inter-reader consistency. Telix's pivotal Phase 3 ZIRCON trial evaluating TLX250-Px in 300 patients, of whom 284 were evaluable, met all primary and secondary endpoints, including showing 86% sensitivity and 87% specificity and a 93% positive predictive value (PPV) for ccRCC across three independent radiology readers. ZIRCON-X, a noninterventional, prospective, post hoc study using imaging data from ZIRCON, found that almost half of all patients (48.6%) would have undergone a change in clinical management if imaged with TLX250-Px, compared with baseline standard-of-care (SOC) imaging, and that more than 20% could potentially have avoided an invasive biopsy.

TLX250-Px has not received a marketing authorization in any jurisdiction.