The "Department of Error" article provides a correction in Rubin DT et al. in Lancet 2025; 405: 33–49 on the QUASAR study of guselkumab in patients with moderate to severe active ulcerative colitis.[1] In Figure 2D, the time points on the x-axis were originally labeled "I-0", "I-1", "I-2", "I-4", "I-8", and "I-12".[1] The arrows in both charts have been adjusted to correctly point to weeks I-0, I-4, and I-8.[1] This correction was made to the online version of the article as of 12 February 2026.[1] The QUASAR trial included phase 3 double-blind, randomized, placebo-controlled induction and maintenance trials.[1][2] Guselkumab was administered intravenously at 200 mg at weeks 0, 4, and 8 in the induction phase.[2] In the maintenance phase, 50% of patients achieved clinical remission on 200 mg s.c. every 4 weeks (95/190) and 45% on 100 mg every 8 weeks (85/188) versus 19% on placebo (36/190).[2] No cases of active tuberculosis, anaphylaxis, serum sickness, or clinically significant liver disorders have been reported.[2]