FDA Accepts BLA for TLX250-CDx (Zircaix®2) for Kidney Cancer Imaging, Grants Priority Review

The U.S. Food and Drug Administration (FDA) has accepted the Biologics License Application (BLA) for Telix Pharmaceuticals Limited's (ASX: TLX, Nasdaq: TLX) investigational kidney cancer PET imaging agent TLX250-CDx (Zircaix®2, 89Zr-DFO-girentuximab). The FDA granted a Priority Review designation, indicating the potential significance of the drug in addressing an unmet medical need. A Prescription Drug User Fee Act (PDUFA) date of 27 August 2025 has been set, paving the way for a potential U.S. commercial launch in 2025.

TLX250-CDx is a targeted radiopharmaceutical imaging agent designed to accurately and non-invasively diagnose and characterize clear cell renal cell carcinoma (ccRCC), the most common and aggressive subtype of kidney cancer. It works by specifically binding to carbonic anhydrase IX (CAIX), a validated target protein expressed on 95% of ccRCC cells, producing images with high tumor-to-background ratio and high intra- and inter-reader consistency.

The BLA is based on Telix's successful global Phase 3 ZIRCON trial, which demonstrated a sensitivity of 86%, specificity of 87%, and a positive predictive value (PPV) of 93% for ccRCC, including in very small, difficult-to-detect lesions. The results of this study were published in The Lancet Oncology in September 2024, highlighting the critical unmet need for a new, non-invasive technique that can accurately detect and differentiate ccRCC from other renal masses in patients.

Kevin Richardson, Chief Executive Officer, Precision Medicine at Telix, commented, "We are delighted that the FDA has accepted this BLA as it moves us one step closer to bringing our breakthrough product to patients. We are aiming to revolutionize the management of kidney cancer, just as PSMA-PET/CT scanning has changed the management of prostate cancer. By providing a more definitive clinical diagnosis for renal masses, we believe that Zircaix2 will help physicians make more timely and confident patient management decisions and more quickly provide patients with a clear understanding of their disease and treatment options. Building further on Telix’s successful urology franchise, we are preparing to bring this powerful precision medicine product to market in 2025."

TLX250-CDx is currently available through expanded access programs (EAP) in the U.S., named patient programs (NPPs) in Europe, and a special access scheme (SAS) in Australia, allowing continued access to the drug outside of clinical trials for patients with no comparable or satisfactory alternate options. If approved, TLX250-CDx would be the first commercially available targeted radiopharmaceutical imaging agent specifically for kidney cancer in the United States.



The FDA's initial concerns were related to sterility assurance, not the agent's safety or efficacy data. Telix can confirm that all Process Performance Qualification (PPQ) batches submitted as part of the BLA application passed the sterility requirements of product release. The FDA did not identify any issues regarding the clinical and nonclinical safety and efficacy data for the agent.

Data on TLX250-CDx
The BLA submission for TLX250-CDx is supported by findings from the phase 3 ZIRCON trial (NCT03849118), which met all co-primary and secondary end points by demonstrating high specificity and sensitivity of the agent for PET/CT imaging of ccRCC. Overall, data from the trial showed that the agent had an average sensitivity of 86% and an average specificity of 87% across three independent readers in detecting ccRCC in patients with an indeterminate renal mass. Further, the agent demonstrated a positive predictive value of 93% for ccRCC, including in small and difficult to detect lesions. A secondary outcome analysis of patients with small masses (defined as 4 cm or less; cT1a) showed an average sensitivity of 85.5% and an average specificity of 89.5% with the agent. For both primary and secondary end points, the lower bounds of the 95% confidence intervals exceeded 75% across all readers.

Regarding safety, there were 263 adverse events (AEs) experienced among 124 patients. Of those, 2 AEs of mild intensity were determined to be related to treatment.

In total, the open-label, multi-center ZIRCON study enrolled 300 adult patients with ccRCC who were scheduled for partial or total nephrectomy. Of those, 284 evaluable patients were included in the primary analysis. The mean age of patients in the trial was 62. All patients included in the study were given a single dose of TLX250-CDx IV (10 mg girentuximab) on day 0 and underwent PET/CT imaging on day 5 (± 2 days). The co-primary outcome measures were sensitivity and specificity of TLX250-CDx in detecting ccRCC in patients with an indeterminate renal mass.



If approved, TLX250-CDx would address a major unmet medical need for patients with suspected ccRCC, providing a more definitive clinical diagnosis for renal masses and helping physicians make more timely and confident patient management decisions. The drug's potential market opportunities and revenue streams are significant, with a substantial U.S. market for kidney cancer imaging and potential global expansion. TLX250-CDx complements Telix's broader urology franchise, which includes products like TLX591-CDx (IllumiX®) for prostate cancer imaging and TLX101 (Rucaparib) for metastatic castration-resistant prostate cancer treatment.