Clinical Study of 99mTc-3PRGD2 SPECT/CT in Diagnosis and Efficacy Evaluation of Rheumatoid Arthritis

As a critical member of adhesion molecule integrin family and an important representative angiogenesis-related molecular, integrin αvβ3 is expressed at low levels on mature endothelial cells and normal cells, but it is overexpressed on the neovasculature endothelial cells, which has a high specificity and affinity in binding to the tri-peptide sequence of arginine-glycine-aspartic acid (RGD). Angiogenesis in the synovial membrane plays an important role in the pathogenesis of rheumatoid arthritis (RA). Therefore, radiolabeled RGD peptides can be used as molecular probe in radionuclide imaging to assess angiogenesis noninvasively in vitro and investigate the progress of RA, so as to achieve the goal of early diagnosis and efficacy evaluation for RA.

Accordingly, a variety of radiolabeled RGD peptides have been used as radiotracers targeting the integrin αvβ3 expression to assess angiogenesis in vitro for noninvasive imaging via PET (positron emission tomography) or SPECT (single photon emission computed tomography). Some radiolabeled cyclic RGD peptides, such as 18F-Galacto-RGD, 18F-AH111585 and 99mTc-NC100692, have been investigated into clinical trials. The results demonstrated that both radiotracers allowed the specific imaging of various types of tumors, and the tumor uptake correlated well with the expression of integrin αvβ3 in both animal models and patients. Recently, several RGD dimeric peptides with PEG linkers have been studied. The new types of RGD peptides showed much higher in vitro integrin αvβ3-binding affinity than the single RGD tri-peptide sequence, and importantly, they exhibited significantly increased tumor uptake and improved in vivo kinetics in animal models. As a representative, 99mTc-3PRGD2 could be easily prepared and exhibited excellent in vivo behaviors in animal models. No adverse reactions are observed in animal models to date.

99mTc-3PRGD2, a novel tracer targeting integrin αvβ3 receptor, was tried to use in some tumors in recent years. However, there are few studies of 99mTc-3PRGD2 in other diseases except for tumors, especially no relevant reports in rheumatoid arthritis. Therefore, the investigators expect to further expand the applications of 99mTc-3PRGD2 in other diseases and to provide new methods and thoughts of assessing the efficacy of anti-αvβ3 or anti-angiogenesis therapy in rheumatoid arthritis. Based on the investigators previous animal study of 99mTc-3PRGD2 in RA, the investigators have strong interests in clinical trials of 99mTc-3PRGD2. An open-label SPECT/CT study has been designed to investigate 99mTc-3PRGD2 SPECT/CT in diagnosis and efficacy evaluation of RA. A single dose of nearly 11.1MBq/kg body weight 99mTc-3PRGD2 (≤20µg 3PRGD2) will be intravenously injected into the patients. Visual and semiquantitative method will be used to assess the whole-body planar and lesions section SPECT/CT images. Adverse events will also be observed in the patients.