Molecular imaging progress in RA research

Rheumatoid arthritis causes chronic pain for almost half of adults by the time they retire. It is estimated that one in five adults and almost 50 percent of those age 65 years or older have been clinically diagnosed with arthritis. However a new molecular imaging technique can visualize inflammation in the joints, giving doctors a clear read on chronic pain and possible joint destruction, according to a recent report by a group of Dutch researchers at the Society of Nuclear Medicine and Molecular Imaging’s 2014 Annual Meeting.

In order to image arthritis inside the joints, researchers used multiple molecular imaging systems, PET and SPECT, both of which image physiological processes. In this case researchers evaluated anti-fibroblast activation protein (FAP) antibodies involved in the inflammation associated with rheumatoid arthritis. This was made possible with radiotracers that combine the molecular compound 28H1, which can bind to FAP in the body, with the radionuclides In-111, used in conjunction with SPECT imaging systems, and with Zr-89, used with PET systems. “This research is novel because radiolabeled anti-FAP antibodies have never been used before in molecular imaging for rheumatoid arthritis,” remarked Dr P Lavermann from the Department of Radiology and Nuclear Medicine at Radboud University Medical Center in Nijmegen, The Netherlands. “These antibodies are used for cancer imaging, but can also be used to image FAP expressed on activated fibroblasts in arthritic joints. We found a high accumulation of radiolabeled anti-FAP antibodies in arthritic joints using SPECT and PET imaging.” This was a preclinical study using small animal scanners. Results of the research showed that both In-111 28H1 and Zr-89 28H1 showed significantly increased imaging agent uptake in inflamed joints. In fact, that uptake was three to four times higher with these agents than another antibody agent evaluated as a control. Researchers also evaluated the commonly used imaging agent, FDG, to image the inflammation, but uptake of this agent was not correlated with the severity of inflammation. This experimental model proved that 28H1 tagged with either In-111 or Zr-89 is a superior method for imaging arthritis.

“To the best of our knowledge, high-contrast images of this kind were unheard of until now,” said Laverman. He estimated that it may take two or more years to accumulate enough research to get the agents approved for arthritis imaging in mainstream clinical practice.