Assessment of disease activity in rheumatoid arthritis using a novel folate targeted radiopharmaceutical Folatescan ^TM

Development of a simple and accurate technique for detecting active inflammation in the joints and other tissues of patients with inflammatory disorders is an unmet need in rheumatic diseases. This study is a preliminary assessment of the safety and usage of a radiopharmaceutical, FolateScan ^TM (Technetium-99m EC20; ^99mTc-EC20), for detecting disease activity in patients with rheumatoid arthritis. Methods EC2O is afolate-targeted diagnostic radiopharmaceutical which binds to the folate receptor and is preferentially taken up by activated macrophages. In this open-label, cross-sectional study, a total of 40 patients with RA (26 with one or more swollen joints, 14 with clinically quiescent joint disease; 0/66 joint count) as well as 6 patients with osteoarthritis, 12 patients with other inflammatory conditions and 5 healthy subjects received 0.1 mg of EC2O labeled with 20-25mCi of technetium-99m. Disease activity was scored in each joint and other target tissues by a radiologist blinded to the clinical assessment, and results were compared to the rheumatologist physical examination, which served as the test standard. The 40 patients (78% female) with RA had a mean age of 56.9 years. Assessment of uptake of ^99mTc-EC2O in joints of patients with RA based on image analysis was compared to the clinical examination. FolateScan detected more actively involved joints in 27 patients (68%) than joints recorded as "swollen", and more actively involved joints in 25 patients (63%) than joints recorded as "painful and/or swollen". The number of swollen joints by clinical exam was correlated with ESR (r=0.43; p=O.OOi5) and C-rp (r=0.35; p =0.03). The number of actively involved joints by Folate Scan was also correlated with ESR (r=0.47; p =0.002) and C-rp (r=0.36; p =0.02). Joint uptake was also seen in patients with osteoarthritis. FolateScan is a potentially useful tool for detection of disease activity in patients with RA and may be more sensitive than the physical examination.