The Use of Anti-CD4 Monoclonal Antibody (mAb)-Fragment for the Imaging of Chronic Inflammation in Patients With Active Rheumatoid Arthritis

Overview

Rheumatoid arthritis (RA) is a disease with a large economic impact due to the long lasting disabling nature of the disease. Furthermore, diagnosis of the disease is difficult and only a scheme with different symptoms is used to diagnose rheumatoid arthritis, often only by probability. Due to the fact that effective disease modifying pharmacological treatment is available and should be started early in established cases of RA, in combination with the adverse effect potential of these substances (e.g. methotrexate), a fast reliable diagnostic tool to diagnose rheumatoid arthritis would be highly appreciated by the medical community and the patients. Furthermore, for invasive treatments (surgery, puncture), an imaging method to display the activity pattern in different joints would be a major advantage. For the evaluation of the effectiveness of pharmacological therapy in rheumatoid arthritis, up to now, radiological measurements of the destruction process of the joints are used. This method has the disadvantage that it is time consuming insofar as changes in the radiological images must occur. It allows only an evaluation if the joints are destructed (which should be excluded by the new therapy regimen). Again, a quantifiable method for the determination of the effects of new therapeutic approaches would be highly appreciated.

The substance will be used as iv injection due to the protein nature of the antibody and, to ensure a fast distribution within the body. The study will be performed as an open clinical trial due to the fact that the applied radiation has to be documented; the use of "placebo" radiation would be unethical. It is expected, that the new antibody fragment with its radioactive linkage will display an image of the activity distribution of the disease. Due to the fact that only patients with active disease have to be imaged and, to allow for comparison of the activity and the clinical distribution of the disease, this proof of concept study (phase I study) will be performed in patients with active disease. Healthy volunteers could not display an activity pattern of the disease. Furthermore, it seems to be unethical to use volunteers for studies with radioactivity with such a risk/benefit ratio (radiation risks vs. missing chance of display of tissue distribution) in a proof of concept study.