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First in man study of [18F]fluoro-PEG-folate PET: a novel macrophage imaging technique to visualize rheumatoid
Nicki J F Verweij1, Maqsood Yaqub2, Stefan T G Bruijnen1
1Amsterdam Rheumatology and immunology Center (ARC), Amsterdam UMC| location VUmc, Amsterdam, the Netherlands.
Abstract:
Non-invasive imaging of arthritis activity in rheumatoid arthritis (RA) patients using macrophage PET holds promise for early diagnosis and therapeutic response monitoring. Previously obtained results with macrophage tracer (R)-[11C]PK11195 were encouraging, but the imaging signal could be further improved by reduction of background uptake. Recently, the novel macrophage tracer [18F]fluoro-PEG-folate was developed. This tracer showed excellent targeting of the folate receptor β on activated macrophages in synovial tissue in a preclinical arthritic rat model. We performed three substudies to investigate the biodistribution, potential for imaging arthritis and kinetic properties of [18F]fluoro-PEG-folate in RA patients. Firstly, biodistribution demonstrated fast clearance of [18F]fluoro-PEG-folate from heart and blood vessels and no dose limiting uptake in organs. Secondly, [18F]fluoro-PEG-folate showed uptake in arthritic joints with significantly lower background and hence significantly higher target-to-background ratios as compared to reference macrophage tracer (R)-[11C]PK11195. Lastly, dynamic scanning demonstrated fast tracer uptake in affected joints, reaching a plateau after 1 minute, co-existing with a rapid blood clearance. In conclusion, this first in man study demonstrates the potential of [18F]fluoro-PEG-folate to image arthritis activity in RA with favourable imaging characteristics of rapid clearance and low background uptake, that allow for detection of inflammatory activity in the whole body.
Insights
A new tracer, [18F]fluoro-PEG-folate, shows promise for imaging rheumatoid arthritis (RA) activity. This novel agent offers improved imaging of joint inflammation with low background uptake in patients.
Area of Science:
- Nuclear Medicine
- Radiochemistry
- Rheumatology
Background:
- Macrophage positron emission tomography (PET) imaging is crucial for monitoring rheumatoid arthritis (RA) activity.
- Previous tracers like (R)-[11C]PK11195 showed potential but suffered from high background uptake.
- A novel tracer, [18F]fluoro-PEG-folate, targets folate receptor β on activated macrophages.
Purpose of the Study:
- To investigate the biodistribution, imaging potential, and kinetics of [18F]fluoro-PEG-folate in RA patients.
- To evaluate [18F]fluoro-PEG-folate as a non-invasive tool for assessing arthritis activity.
- To compare the imaging characteristics of [18F]fluoro-PEG-folate with existing macrophage tracers.
Main Methods:
- Three substudies were conducted in RA patients to assess [18F]fluoro-PEG-folate.
- Biodistribution and organ uptake were evaluated.
- Arthritis imaging potential and kinetic properties, including target-to-background ratios, were analyzed using dynamic PET scans.
Main Results:
- [18F]fluoro-PEG-folate demonstrated rapid clearance from the body with no dose-limiting organ uptake.
- The tracer showed significant uptake in arthritic joints.
- Compared to (R)-[11C]PK11195, [18F]fluoro-PEG-folate exhibited lower background uptake and higher target-to-background ratios.
- Dynamic scans revealed fast tracer uptake in affected joints, reaching a plateau within one minute.
Conclusions:
- This first-in-human study confirms the potential of [18F]fluoro-PEG-folate for imaging RA activity.
- Favorable imaging characteristics, including rapid clearance and low background, enable whole-body detection of inflammatory activity.
- [18F]fluoro-PEG-folate offers a promising non-invasive imaging approach for RA diagnosis and treatment monitoring.
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