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# Complete Response on Telix PET Imaging Agent
- URL: https://www.fdaweb.com/complete-response-on-telix-pet-imaging-agent/
- Published: 2025-08-28T12:00:00.000Z
- Updated: 2026-09-14T15:20:26.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5159772

FDA has issued Telix Pharmaceuticals a complete response letter for its BLA seeking approval of Zircaix (89Zr-DFO-girentuximab), an investigational positron emission tomography (PET) imaging agent designed to help diagnose and characterize clear cell renal cell carcinoma. The letter cited deficiencies in the drug’s chemistry, manufacturing, and controls package, specifically requesting additional data to confirm comparability between the product used in the pivotal Phase 3 ZIRCON trial and material produced through Telix’s scaled-up commercial manufacturing process, according to the company. The agency also flagged unresolved quality issues at two third-party manufacturers, noted in prior inspection findings, which must be remediated before resubmission, it adds.

Despite the setback, Telix says the issues were “readily addressable” and that it will begin remediation efforts immediately. The company plans to request a Type A meeting with FDA to discuss next steps and resubmission timelines.

The company says Zircaix “breaks new ground as a highly novel biologic-based PET imaging agent using a first-in-class isotope. Like many radiopharmaceuticals, it has a complex supply chain, and as the field advances this creates new challenges around the regulatory framework. We believe the outstanding matters are resolvable and can be addressed within a reasonable timeframe.”