IL20 and rheumatoid arthritis: Similarly, the IL-20 family of cytokines such as IL-20 and IL-22 play a significant role in the process of immune cell activation and bone destruction, and although an early phase trial with the IL-20 inhibitor fletikumab was well tolerated and effective, particularly in patients with seropositive RA, further studies with fletikumab and also IL-22 inhibitor fezakinumab were completed several years ago with negative or no final results released51,52.