Biologics and biosimilars in axial spondyloarthritis: Lots of kids on the block

The management of axial spondyloarthritis (axSpA) has been completely transformed since the introduction of biologic therapies. Tumor necrosis factor inhibitors (TNFis) were the first effective drug therapies in people affected with axSpA who had previously failed to respond to nonsteroidal anti-inflammatory drugs. Currently, there are five TNFis licensed for the treatment of established axSpA, traditionally known as ankylosing spondylitis or radiographic axSpA, with four of them also available for use in the nonradiographic axSpA disease group. More recent developments comprise new drugs designed to block the interleukin-17 or JAK inflammatory pathways. The high cost associated to these drugs has been the main limiting factor for their use and availability at global level, a problem that will, in part, be addressed with the recent introduction of biosimilars, with comparable efficacy and safety profile at lower cost. The fast arrival of so many "kids on the block" poses many challenges for the clinician in order to choose the right drug for each patient and brings the need for feasible, well-validated biomarkers of treatment response to the forefront of research in axSpA.