The Investigators Will Evaluate the Diagnostic Performance of [18F]-AlF-FAPI-74 PET/CT in Inflammatory Disorders and Compare it With the Current Gold Standard for Inflammation, FDG PET/CT, in Three Patient Cohort: Patients Presenting With Fever of Unknown Origin, IgG4-RD and AxSpA.

April 14, 2026 updated by: Universitaire Ziekenhuizen KU Leuven

Prospective Diagnostic Performance of PET/CT Using the Novel Fibroblast Imaging Tracer [18F]-AlF-FAPI-74 Versus Standard of Care [18F]-FDG in Inflammatory Disorders

The aim of the study to evaluate the performance of new [18F]-AlF-FAPI-74 PET/CT in three inflammatory disorders (fever of unknown origin, IgG4-related disease and axial spondyloarthritis) and compare with the current stand-of-care [18F]-FDG PET/CT

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
140

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria FUO:

  • An illness of more than 3 weeks' duration,
  • Temperature exceeding 38.3°C on > 3 occasions, or elevated inflammatory markers on > 3 occasions
  • Diagnosis uncertain despite appropriate first-line investigations.

Inclusion criteria IgG4-RD:

  • High clinical suspicion of IgG4-RD by an experienced clinician of Internal Medicine, based on anamnesis, physical examination, first-line investigations and blood tests.
  • Patients with a new diagnosis of IgG4-RD on histopathology and need for further assessment of disease extent with PET/CT,
  • Relapse of diagnosed IgG4-RD on histopathology according to an experienced clinician of Internal Medicine

Inclusion criteria AxSpA:

  • High clinical suspicion of axial spondyloarthropahy according to an experienced rheumatology (based on inflammary back pain > 3 months, insidious onset, morning stifness, improvement with exercise and worsening in rest, pain worse at night, age at onset <45 years of age, imaging findings).
  • Patient has persisting inflammatory back pain after 2 different types of NSAID's (tried for over 2-4 weeks), and is therefore eligible for biological DMARDS therapy.

Exclusion Criteria:

  • Participant is mentally or legally incapacitated, doesn't understand the study design or is not willing or capable to undergo all study-specific procedures.
  • Any disorder or condition, which in the Investigator's opinion might jeopardise the participant's safety or compliance with the protocol.
  • Any prior or concomitant treatment(s) that might jeopardise the participant's safety or that would compromise the integrity of the Trial.
  • Female who is pregnant (urinary hCG test will be performed in every WOCBP), breast-feeding or intends to become pregnant or is of child-bearing potential and not using an adequate, highly effective contraceptive (with a relatively high Pearl Index: natural methods, minipill outside postpartum period, spermicides or condoms in monotherapy or no usage of contraception when sexually active are not accepted).
  • Participation in an interventional Trial with an investigational medicinal product (IMP) or device when the trial designs are not considered compatible by the study team.
  • Participation in a clinical scientific study in the last 12 months with a radiation exposure caused by the experimental procedures greater than 1 mSv.
  • Participant has a known hypersensitivity to [18F]AlF-FAPI-74 or the used excipients.
  • Active treatment has already commenced

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Diagnostic
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Axial Spondyloarthritis
Diagnostic test: [18F]AlF-FAPI-74 PET/CT
A [18F]AlF-FAPI-74 PET/CT will be performed at the same site of the screening visit (UZ Leuven). The patient will get an IV line, through which the [18F]AlF-FAPI-74 will be injected in one bolus (3,5 MBq/kg). After 60 minutes, the acquisition on the PET/CT scan will take place. The CT will be a low dose CT with oral contrast. After the scan, participants will be observed at the department in case of adverse events. If the patient receives therapy (for IgG4-RD and AxSpA), a second [18F]AlF-FAPI-74 PET/CT will be performed three months later.
Experimental: FUO/IUO
Diagnostic test: [18F]AlF-FAPI-74 PET/CT
A [18F]AlF-FAPI-74 PET/CT will be performed at the same site of the screening visit (UZ Leuven). The patient will get an IV line, through which the [18F]AlF-FAPI-74 will be injected in one bolus (3,5 MBq/kg). After 60 minutes, the acquisition on the PET/CT scan will take place. The CT will be a low dose CT with oral contrast. After the scan, participants will be observed at the department in case of adverse events. If the patient receives therapy (for IgG4-RD and AxSpA), a second [18F]AlF-FAPI-74 PET/CT will be performed three months later.
Experimental: IgG4-related disease
Diagnostic test: [18F]AlF-FAPI-74 PET/CT
A [18F]AlF-FAPI-74 PET/CT will be performed at the same site of the screening visit (UZ Leuven). The patient will get an IV line, through which the [18F]AlF-FAPI-74 will be injected in one bolus (3,5 MBq/kg). After 60 minutes, the acquisition on the PET/CT scan will take place. The CT will be a low dose CT with oral contrast. After the scan, participants will be observed at the department in case of adverse events. If the patient receives therapy (for IgG4-RD and AxSpA), a second [18F]AlF-FAPI-74 PET/CT will be performed three months later.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
FUO/IUO: Demonstrate that the diagnostic performance of [18F]AlF-FAPI-74 PET/CT is equivalent or superior to the current gold standard, [18F] FDG PET/CT, in contributing to the final diagnosis (non-inferiority study with non-inferiority limit (10%)
Time Frame: 6 months after completion of both PET/CT scans
6 months after completion of both PET/CT scans
IgG4-RD: Demonstrate that the diagnostic performance of [18F]AlF-FAPI-74 PET/CT is superior to [18F]FDG PET/CT, in patients with suspicion of IgG4-RD and assessment of disease extent in patients with confirmed or relapsed IgG4-RD.
Time Frame: After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
Axial Spondyloarthritis: evaluate the diagnostic accuracy of [18F]AlF-FAPI-74 PET/CT in differentiating inflammatory back pain in patients with axSpA from patients with mechanical back pain, and evaluate the ability to assess treatment response
Time Frame: After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment
After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
FUO/IUO: Determine the distribution of the four major causal group in FUO/IUO (infectious, inflammatory, malignant, and miscellaneous) of both tracers and evaluate for which causal groups [18F]AlF-FAPI-74 PET/CT is superior to [18F]FDG PET/CT.
Time Frame: 6 months after completion of all PET/CT scans
6 months after completion of all PET/CT scans
FUO/IUO: Evaluate for which entities [18F]AlF-FAPI-74 has the potential to outperform [18F]FDG PET/CT in lager patient cohorts.
Time Frame: 6 months after completion of all PET/CT scans
6 months after completion of all PET/CT scans
FUO/IUO: Determine the ratio of true positives, true negatives, false positives, false negative, positive predictive value, and negative predictive value.
Time Frame: 6 months after completion of all PET/CT scans
6 months after completion of all PET/CT scans
IgG4-RD: Semi-quantitative uptake measurements (maximal standardized uptake value (SUVmax), average SUV (SUVmean), peak SUV (SUVpeak) of lesions on [18F]AlF-FAPI-74 PET/CT and [18F]FDG PET/CT.
Time Frame: After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
IgG4-RD: Evaluate the organ detection ratio for every organ, defined as the percentage of patients with pathological uptake in that specific organ by each tracer for the total of number of patients with pathological uptake in that organ
Time Frame: After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
IgG4-RD: 4) Evaluate the total number of affected organs per patient for each tracer and calculate the difference for both tracers. Determine the total difference of affected organs between both tracers for all patients.
Time Frame: After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
IgG4-RD: Evaluate the treatment response of FAPI and FDG lesions by quantifying the change in SUVmax between baseline and post-therapy PET/CT scans.
Time Frame: After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
After completion of both PET/CT scans before initiation of treatment and after completion of both PET/CT scans 3 months completion of treatment.
AxSpA: Semi-quantitative uptake measurements (maximal standardized uptake value (SUVmax), target-to-background (TBR)) of lesions in the spine and the sacro-iliac joints will be computed on [18F]AlF-FAPI-74 PET/CT in all patients
Time Frame: After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment
After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment
AxSpA: Determine if there is a significant statistical difference (p<0.05) in semi-quantitative uptake measurements (SUVmax, TBR) between the two cohorts, and determine the optimal cut-off value.
Time Frame: After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment
After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment
AxSPa: Assess treatment response by evaluating changes in semi-quantitative measurements (SUVmax, TBR) in patients with axSpA following 3 month treatment with bDMARDs.
Time Frame: After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment
After completion of first PET/CT scan and after completion of PET/CT scan performed 3 months after treatment

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Universitaire Ziekenhuizen KU Leuven

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
September 17, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
March 31, 2029

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
March 31, 2030

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 20, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 14, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
April 17, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
April 17, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 14, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
March 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • S69207 - 2024-516464-28

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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