FDA Grants Priority Review to TLX250-CDx in Clear Cell RCC Imaging

The agency has set a Prescription Drug User Fee Act date of August 27, 2025, for its decision on approving the imaging agent in this indication.

The FDA has granted priority review to a biologics license application (BLA) for TLX-250CDx (Zircaix; ⁸⁹Zr-girentuximab), an investigational PET imaging agent, in the noninvasive diagnosis and characterization of clear cell renal cell carcinoma (RCC), according to a press release from the developer, Telix Pharmaceuticals Limited.¹

The agency has set a Prescription Drug User Fee Act date of August 27, 2025, for its decision on approving the imaging agent in this indication.

Developers previously submitted the BLA for TLX250-CDx in December 2024.²

“We are delighted that the FDA has accepted this BLA as it moves us one step closer to bringing our breakthrough product to patients,” Kevin Richardson, chief executive officer of Precision Medicine at Telix, stated in the press release.¹ “By providing a more definitive clinical diagnosis for renal masses, we believe that [TLX250-CDx] 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.”

Supporting data for the BLA came from the phase 3 ZIRCON study (NCT03849118), in which investigators assessed the ability of TLX250-CDx to detect and characterize clear cell RCC. Investigators previously published findings from the ZIRCON study in The Lancet Oncology.³

Among 284 evaluable patients in the primary analysis, analysis from 3 independent readers yielded a mean sensitivity of 85.5% (95% CI, 81.5%-89.6%), a mean specificity of 87.0% (95% CI, 81.0%-93.1%), and a mean positive predictive value (PPV) of 92.9% (95% CI, 90.2%-95.7%). Of those with indeterminate renal masses of 4 cm or smaller (n = 145), use of TLX250-CDx elicited a mean sensitivity of 85.0% (95% CI, 81.8%-88.1%), a mean specificity of 89.5% (95% CI, 84.2%-94.8%), and a mean PPV of 93.2% (95% CI, 90.1%-96.3%).

“[TLX250-CDx] PET-CT imaging accurately identified clear cell [RCC] in patients with a cT1 indeterminate renal masses [of 7 cm or less], with a favorable safety profile,” Brian M. Shuch, MD, director of the Kidney Cancer Program and the Alvin & Carrie Meinhardt Endowed Chair in Kidney Cancer Research at the University of California, Los Angeles Health, wrote with study coauthors.³ “These results establish the value of [TLX250-CDx] PET-CT imaging as a new standard, non-invasive tool for the diagnosis and detection, characterization, and differentiation of clear cell [RCC] from other renal and extrarenal lesions in clinical practice, minimizing the risk of unnecessary invasive interventions.”

In the open-label, multicenter phase 3 ZIRCON trial, patients received a single dose of TLX-250CDx over a minimum of 3 minutes on day 0 followed by PET-CET imaging on day 5 ± 2 days. Additionally, patients underwent partial or radical nephrectomy per surgeon’s preference within 90 days of receiving TLX-250CDx. Three blinded independent reviewers conducted central and independent PET-CT imaging analysis to evaluate disease histology from surgical samples.

The trial’s coprimary end points were the sensitivity and specificity of TLX-250CDx in the noninvasive detection of clear cell RCC among patients with cT1 indeterminate renal masses of 7 cm or smaller. Key secondary end points included the sensitivity and specificity of the imaging agent in a subgroup of patients with cT1a indeterminate renal masses of 4 cm or smaller.

Patients 18 years and older with evidence of a single, localized indeterminate renal mass of 7 cm or smaller in largest diameter that was suspicious for RCC were eligible for enrollment on the trial. Those with a renal mass associated with a metastasis of another primary tumor or prior chemotherapy, radiotherapy, or immunotherapy within 4 weeks of receiving TLX-250CDx were ineligible for enrollment.

References

1. FDA accepts BLA for TLX250-CDx (Zircaix®) for kidney cancer imaging, grants priority review. News release. Telix Pharmaceuticals Limited. February 26, 2025. Accessed February 26, 2025. https://tinyurl.com/357x76uw
2. Telix files TLX250-CDx (Zircaix®) BLA for kidney cancer imaging. News release. Telix Pharmaceuticals Limited. December 30, 2024. Accessed February 26, 2025. https://tinyurl.com/mtdcuncb
3. Shuch B, Pantuck AJ, Bernhard JC, et al. [⁸⁹Zr]Zr-girentuximab for PET-CT imaging of clear-cell renal cell carcinoma: a prospective, open-label, multicentre, phase 3 trial. Lancet Oncol. 2024;25(10):1277-1287. doi:10.1016/S1470-2045(24)00402-9