Flexion is developing a gene therapy (named FX201) for the treatment of osteoarthritis. FX201 is a locally administered helper-dependent adenovirus whose gene product is the anti-inflammatory protein interleukin-1 receptor antagonist (IL-1Ra). By persistently suppressing inflammation, FX201 may both reduce pain and modify disease progression of osteoarthritis. Based on strong preclinical data, a single injection of FX201 could enable expression of IL-1Ra in an osteoarthritic joint for a long period of time, and it may hold the potential to be disease-modifying. Flexion aims to initiate a Phase 1 clinical trial with FX201 in 2019.