A Clinical Trial to Investigate 18F-AzaFol in the Diagnosis of Large Vessel Vasculitis

Giant cell arteritis (GCA) is the most common systemic vasculitis in the elderly population. 2-[18F]Fluor-2-desoxy-D-glucose (2-[18F]FDG) positron emission tomography (PET)/ computed tomography (CT) is performed to diagnose GCA (standard of care, SOC) but unable to reliably distinguish atherosclerosis from vasculitis. Activated macrophages express folate receptor (FR)-β and are enriched in inflamed vascular tissue in GCA. 3'-Aza-2'-[18F]Fluoro-Folic Acid (AzaFol) is a nuclear tracer targeting FRβ. The investigators hypothesize that AzaFol is a specific and reliable tracer to visualize activated macrophages in GCA and therefore might improve the discrimination of vasculitic and atherosclerotic lesions as compared to 2-[18F]FDG-PET/CT.

Inclusion criteria

• Individuals ≥ 50 years with clinical suspicion of GCA
• Women of childbearing potential must not have a positive serum pregnancy test at the Screening Visit
• Subjects must be able to understand and adhere to all protocol requirements and must voluntarily sign and date an informed consent, approved by an independent ethics committee (IEC)/institutional review board (IRB), prior to the initiation of any screening or study-specific procedures.
• Are willing and able to comply with procedures required in this protocol.

Exclusion criteria

• Folate deficiency
• Female subjects who are pregnant, breastfeeding, or considering becoming pregnant during the study or within 30 days after the last dose of study drug
• Concomitant treatment with medications that lead to a significant impairment of folic acid levels (methotrexate, pemetrexed, raltitrexed)
• Concomitant glucose-containing infusion or parental nutrition within 6 hours prior to 2-[18F]FDG tracer application
• Glucose level > 10 mmol/l at the timepoint of 2-[18F]FDG PET/CT
• Unable to remain in the PET/CT for the duration of the examination
• Unable to lie still for the duration of the examination (45 min)
• Unable not to eat or drink (except water) for 6 hours prior to 2-[18F]FDG tracer application
• Prior PET-imaging within 60 days before baseline
• Intake of vitamin supplements containing > 1mg/day folic acid within 48 h prior to the PET/CT with AzaFol
• Known hypersensitivity or allergy to folic acid
• Enrolment of the investigator, his/her family members, employees and other dependent persons
• Participation in another study with investigational drug within the 7 days preceding and during the present study.