This story was originally published on April 10, 2020. As part of MedPage Today's review of the past year's top stories, we are republishing it, along with an update on psoriatic arthritis, reviewing subsequent developments in 2020. The monoclonal antibody guselkumab (Tremfya), which binds the interleukin (IL)-23 p19 subunit, was effective for psoriatic arthritis in two large clinical trials, providing comprehensive benefits for this heterogeneous disorder, investigators reported in The Lancet. In one of the trials, DISCOVER-1, a 20% improvement on the response criteria established by the American College of Rheumatology (ACR20) at week 24 was achieved by 59% of patients receiving 100-mg subcutaneous guselkumab every 4 weeks and by 52% of those given the monoclonal antibody every 8 weeks compared with 22% of those randomized to placebo. These represented differences versus placebo of 37% (95% CI 26%-48%,