GQ-203 is a helper-dependent adenoviral gene therapy vector expressing interleukin-1 receptor antagonist, which is being developed for treatment of knee osteoarthritis. After intraarticular injection into the affected joint, GQ-203 enters the joint cells and turns them into factories for production of the therapeutic protein interleukin-1 receptor antagonist. GQ-203 has demonstrated symptomatic and disease-modifying efficacy in several osteoarthritis animal models.

In December 2017, GQ-203 was acquired by Flexion Therapeutics, Inc. and is now designated FX201. FX201 is currently being tested in a Phase I clinical trial.