Dual targeting heterodimer PET tracer [<sup>18</sup>F]AlF‑FAPI‑RGD in patients with rheumatoid arthritis: a pilot exploratory study
Hao Wang, Wei Su, Limeng He, Dongze Wu, Nan Liu, Jing Zhu, Jingjing Zhang, Wei Zhang
Abstract
Purpose: Fibroblast-like synoviocytes and angiogenesis play crucial roles in the advancement of rheumatoid arthritis (RA).This prospective study aimed to assess the efficacy of [ 18 F]AlF-FAPI-RGD, a dual-targeting heterodimer tracer that focuses on fibroblast activation protein (FAP) and integrin v3, through PET/CT imaging for evaluating disease activity and response to treatment in RA.Methods: Twenty-eight participants with active RA (12 males and 16 females; mean age, 55 9 years) underwent clinical evaluation of disease activity and [ 18 F]AlF-FAPI-RGD PET/CT imaging at enrollment.Subsequently, after a 3-month period, a follow-up scan and clinical assessments were conducted on these participants.Imaging parameters such as PET-positive joint count (PJC), PET-positive articular index (PAI), average SUVmax (aSUVmax), and highest SUVmax (hSUVmax) in affected joints were compared with clinical and laboratory findings, as well as traditional imaging modalities.Results: [ 18 F]AlF-FAPI-RGD PET/CT imaging produced high-quality images, revealing notable tracer uptake in the synovium of affected joints.[ 18 F]AlF-FAPI-RGD demonstrated a higher positivity rate in detecting affected joints compared to the tender or swollen joint counts during clinical assessment (82.4% [342 of 415] vs 68.4% [284 of 415], respectively).Additionally, this imaging method successfully identified lung lesions with atypical respiratory symptoms in participants with RA.Following treatment, PJC, PAI, aSUVmax, and hSUVmax values significantly decreased in responders (P < 0.001), while no significant changes were observed in non-responders (P > 0.05).Furthermore, a notable association was found between the percentage change in certain PET parameters and modifications in specific clinical parameters.Conclusion: [ 18 F]AlF-FAPI-RGD PET/CT represents a promising tool for the objective assessment of disease activity and treatment response in patients with RA.Furthermore, it may offer a novel imaging method for the early detection of subclinical RA and interstitial lung disease present with atypical respiratory symptoms.