Evaluation of the structure‐modifying effects of diacerein in hip osteoarthritis: ECHODIAH, a three‐year, placebo‐controlled trial

Objective To evaluate the ability of diacerein, an interleukin‐1β inhibitor, to slow the progressive decrease in joint space width observed in patients with hip osteoarthritis (OA). Methods In this randomized, double‐blind, placebo‐controlled 3‐year study, 507 patients with primary OA of the hip (by the American College of Rheumatology criteria) received diacerein (50 mg twice a day) or placebo. The minimal hip joint space width was measured by a central reader on yearly pelvic radiographs, using a 0.1‐mm–graduated magnifying glass. Results Baseline characteristics were comparable in the 2 treatment groups (255 patients receiving diacerein, 252 receiving placebo); 238 patients (47%) discontinued the study, mainly because of adverse events in the diacerein group (25% versus 12% with placebo) and because of inefficacy in the placebo group (14% versus 7% with diacerein). The percentage of patients with radiographic progression, defined by a joint space loss of at least 0.5 mm, was significantly lower in patients receiving diacerein than in patients receiving placebo, both in the intent‐to‐treat analysis and in the completer analysis (50.7% versus 60.4% [ P = 0.036] and 47.3% versus 62.3% [ P = 0.007], respectively). In those patients who completed 3 years of treatment, the rate of joint space narrowing was significantly lower with diacerein (mean ± SD 0.18 ± 0.25 mm/year versus 0.23 ± 0.23 mm/year with placebo; P = 0.042). Diacerein had no evident effect on the symptoms of OA in this study. However, a post hoc covariate analysis that took into account the use of analgesics and antiinflammatory drugs showed an effect of diacerein on the Lequesne functional index. Diacerein was well tolerated during the 3‐year study. The most frequent adverse events were transient changes in bowel habits. Conclusion This study confirms previous clinical findings indicating that the demonstration of a structure‐modifying effect in hip OA is feasible, and shows, for the first time, that treatment with diacerein for 3 years has a significant structure‐modifying effect as compared with placebo, coupled with a good safety profile. The clinical relevance of these findings requires further investigation.