FDA Issues Response Letter for Mirikizumab

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The FDA cited manufacturing concerns in their letter for the potential ulcerative colitis treatment.

The US Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) for mirikizumab, a potential treatment for ulcerative colitis, citing issues related to the proposed manufacturing of the treatment.1

The CRL, which was issued for the Biologic License Application (BLA) by Eli Lilly and Company, did not cite any concerns about the clinical data package, safety, or label for the medicine.

"We remain confident in mirikizumab's pivotal Phase 3 clinical data and its potential to help people with ulcerative colitis," said Patrik Jonsson, Lilly executive vice president, president of Lilly Immunology and Lilly USA, and chief customer officer, in a statement. "We are working diligently with the FDA and hope to launch mirikizumab in the U.S. as soon as possible."

Mirikizumab is a p19-directed IL-23 antibody that has shown promise in treating patients with moderately to severely active ulcerative colitis in the phase 3, randomized, double-blind, placebo-controlled LUCENT-1 and LUCENT-2 trials.

As recent as March, there was new data presented during the European Crohn’s and Colitis Organization 2023 Meeting in Copenhagen showing the success of mirikizumab treating patients with inflammatory bowel disease (IBD).2

Patients treated with mirikizumab saw statistically significant reductions in certain inflammatory biomarkers such as fecal calprotectin (fCal) and C-reactive protein (CRP).

The results show a higher percentage of patients treated with mirikizumab achieved HEMI (n = 235) had normalized fCal (76.2%) and CRP values (88.5%), compared to patients treated with mirikizumab who did not achieve HEMI (n = 633) (21.8% and 72.7%; both P <0.001).

There was also a higher proportion of patients achieving HEMR (n = 193) with normalized fCal (76.6%) and CRP values (88%) compared to patients not achieving HEMR (n = 207) (33.8% and 63.3%; both P <0.001).


1. U.S. Food and Drug Administration Issues Complete Response Letter for mirikizumab. Eli Lilly and Company. (2023, April 13). Retrieved April 13, 2023, from

2. R Panaccione, C Sapin, F W Chan-Diehl, R E Moses, B Siegmund, A Walsh, T Kobayashi, D S Parambir, S Travis, DOP90 The association of endoscopic and histologic endpoints with fecal calprotectin and C-reactive protein in patients with moderately to severely active ulcerative colitis treated with mirikizumab, Journal of Crohn's and Colitis, Volume 17, Issue Supplement_1, February 2023, Pages i167–i169,