Flexion Therapeutics, Inc., a biopharmaceutical company, focuses on the discovery, development, and commercialization of therapies for the treatment of patients with musculoskeletal conditions. It offers ZILRETTA, an intra-articular injection for the management of osteoarthritis (OA) pain of the knee in the United States. The company also develops FX201, a gene therapy product candidate designed to stimulate the production of an anti-inflammatory protein, interleukin-1 receptor antagonist for pain relief from OA of the knee; and FX301, an administered NaV1.7 inhibitor for the management of post-operative pain. Flexion Therapeutics, Inc. was founded in 2007 and is headquartered in Burlington, Massachusetts.