by Dr. David Borenstein M.D. updated 6/2020

Ankylosing spondylitis (AS) is an inflammatory spinal disease which is associated with damage to the axial skeleton including the sacroiliac joints, the lumbar, thoracic, and cervical spine. Inflammation in these areas of the spine results in changes in the tissues that is identifiable with ordinary xray studies. For example, plain radiographs of the sacroiliac joints in AS patients may show whitening of the bone (sclerosis), joint erosion, or in its final stages, joint fusion. In the very earliest stages of the illness, inflammation is present, but has not caused enough damage to be noticeable with regular radiographs. At this early stage of disease, joint inflammation is characterized by swelling in the bone marrow located near the edges of the joint. These changes can be identified with magnetic resonance imaging (MR). Nonradiographic spondyloarthritis is characterized by these early changes seen with MR that are not identifiable with plain radiographs. Debate remains on whether NR-SPA is an early form of AS or an entirely separate illness.

In case these illnesses are different, clinical trials that demonstrate efficacy have been completed in AS and NR-SPA in order to be considered effective therapy. Secukinumab (Cosentyx) is an interleukin-17 inhibitor (Il-17). Secukinumab is already approved for the treatment of AS. Based upon the results of the phase 3 PREVENT trial, the Food and Drug Administration approved secukinumab for the treatment of NR-SPA. In the trial, 40% of NR-SPA patients who received 150 mg monthly subcutaneously versus 28% with placebo had a clinical significant improvement by a number of parameters particular to spondyloarthritis including morning stiffness and range of spinal motion. Improved was noted at 16 and 52 weeks. No significant safety concerns appeared during the course of the trial.

Currently, secukinumab is the third biologic agent approved for the treatment of NR-SPA. The first was the anti-tumor necrosis factor (TNF) inhibitor, certolizumab (Cimzia). The second was ixekizumab which is another anti-Il-17 inhibitor allows physicians to choose between biologics with different mechanisms of action if one form of therapy is ineffective.