Diagnostic Accuracy of 68Ga-FAPI-46 PET/CT in Patients with Suspected Giant Cell Arteritis–Polymyalgia Rheumatica Spectrum Disease

Primary objective: To assess the diagnostic accuracy of 68Ga-FAPI-46 PET/CT in patients with suspected giant cell arteritis‑polymyalgia rheumatica spectrum disease. This evaluation determines the ability of the imaging modality to correctly identify disease involvement, thereby supporting timely therapeutic decisions. Secondary objectives: to evaluate tracer uptake as a marker of treatment response at two intervals after initiation of standard therapy.

• Uptake measurement after 28 days of standard treatment.
• Uptake measurement after 6 months of standard treatment.

The sponsor did not provide information on the total number of participants. The trial enrolled adult patients aged ≥ 50 years, including both female and male individuals, who presented with suspected giant cell arteritis - polymyalgia rheumatica spectrum disease. Eligibility required the ability to attend scheduled study visits, comply with protocol procedures, and provide informed consent. All participants were intended to undergo imaging with 68Ga-FAPI-46 PET/CT to evaluate its diagnostic accuracy in this population. No additional lifestyle or health status criteria were specified beyond the requirement for suspected disease and general capacity to adhere to study requirements.

The study is a phase 4, single‑arm diagnostic accuracy trial evaluating the performance of giant cell arteritis – polymyalgia rheumatica spectrum disease assessment with intravenous 250 MBq [68Ga]FAPI‑46 PET/CT; recruitment is planned from March 2026 to September 2029, with each participant followed for approximately six months. After an eligibility screening visit, subjects receive a baseline PET/CT scan following administration of the investigational radiopharmaceutical; subsequent visits occur at 28 days and at six months to repeat imaging and assess treatment‑related changes in tracer uptake, serving as secondary endpoints. The final study visit includes a concluding safety assessment and collection of end‑of‑study data. Participants are required to attend all scheduled visits and comply with protocol procedures; early discontinuation may occur if a subject withdraws consent, is unable to attend visits, experiences a serious adverse event, or deviates substantially from required protocol compliance.

The investigational agent used in the study is Giant Cell Arteritis-Polymyalgia Rheumatica Spectrum Disease diagnostic imaging tracer [68Ga]FAPI-46, supplied as a sterile solution for injection. Each participant receives a single intravenous administration of 250 MBq (megabecquerels) of the radiopharmaceutical. The dose is delivered via peripheral venous access over a brief infusion period, and no repeat dosing is scheduled within the study protocol. Administration is performed under controlled conditions with documentation of the exact radioactivity, injection time, and any immediate adverse reactions. Compliance with the dosing schedule is verified by study staff through real‑time recording of administration parameters and post‑procedure checklists.

No additional therapeutic agents, placebo, or standard‑of‑care treatments are administered as part of this diagnostic trial. Participants continue their usual clinical management for the underlying condition, and any concomitant medications are recorded for safety monitoring but are not subject to study‑directed dosing adjustments.

The primary efficacy assessment focuses on the diagnostic accuracy of 68Ga‑FAPI‑46 PET/CT in patients with suspected giant cell arteritis‑polymyalgia rheumatica spectrum disease. Diagnostic performance will be quantified by calculating sensitivity, specificity, positive predictive value, and negative predictive value through comparison of PET/CT findings with the established clinical reference standard.

Secondary efficacy assessments evaluate changes in 68Ga‑FAPI‑46 uptake following standard therapy. Quantitative PET/CT scans will be performed at baseline, at 28 days, and at 6 months after treatment initiation. Uptake values will be measured using standardized imaging software and expressed as standardized uptake values (SUV) or equivalent metrics. Changes from baseline will be analyzed to determine the extent of treatment‑related modification in radiotracer accumulation.