Baseline Eosinophils and Response to Mirikizumab in UC

February 24, 2026

Issue 04

Clinical Question

Can serum and histologic eosinophil levels predict response to mirikizumab in patients with ulcerative colitis?

Editor’s Bottom Line

Patients with ulcerative colitis and prominent eosinophilia may represent a distinct subgroup with different responses to current and emerging therapies.

Reference

Wong ECL, Dulai PS, Marshall JK, et al. Serum and Histologic Eosinophilia as a Predictive Biomarker of Response to Mirikizumab in Ulcerative Colitis. Inflamm Bowel Dis. Epub ahead of print Nov 25, 2025. https://pubmed.ncbi.nlm.nih.gov/41277684/

Synopsis

This post-hoc analysis of the randomized, double-blind LUCENT-1 trial evaluated serum and histologic eosinophils as predictive biomarkers for response to mirikizumab induction therapy in ulcerative colitis (UC). The study included 928 participants with moderate-to-severe UC who received mirikizumab 300mg intravenously every four weeks. Mean age was 42.8 years, 38.3% were female and mean disease duration was 7.2 years. At baseline, 66.5% had severe endoscopic disease, 15.7% were using corticosteroids and 17.7% were using immunomodulators.

Outcomes included clinical response, defined as a decrease of at least 2 points on the modified Mayo score with at least a 30% decrease from baseline, plus a decrease of at least 1 point in the rectal bleeding subscore or a rectal bleeding subscore of 0 or 1; clinical remission, defined as a stool frequency score of 0 or 1 with a decrease of at least 1 point from baseline, a rectal bleeding subscore of 0 and a Mayo endoscopic subscore below 2; and endoscopic improvement, defined as a Mayo endoscopic subscore below 2.

Overall, 66.6% of patients achieved clinical response at week 12. Responders had significantly higher baseline serum eosinophil counts compared to non-responders (0.23×10⁹/L vs. 0.19×10⁹/L; p=0.001). However, there were no significant baseline differences in eosinophil counts between remitters and non-remitters (0.23×10⁹/L vs. 0.21×10⁹/L; p=0.363) or between those with and without endoscopic improvement (0.21×10⁹/L for both; p=0.343).

Eosinophil counts decreased progressively during treatment across all groups. By week eight, counts were significantly lower in remitters than among non-remitters (0.15×10⁹/L vs. 0.18×10⁹/L; p=0.014) and among those with endoscopic improvement versus those without (0.16×10⁹/L vs. 0.18×10⁹/L; p=0.033). At week 12, significant differences persisted for remitters versus non-remitters (0.13×10⁹/L vs. 0.16×10⁹/L; p=0.010) and those with endoscopic improvement versus those without (0.14×10⁹/L vs. 0.16×10⁹/L; p=0.027).

Also at week 12, among 60 patients with abnormally elevated baseline eosinophils (defined as ≥0.57×10⁹/L), clinical response rates were significantly higher (80% vs. 65.7%; adjusted Odds Ratio [aOR], 2.31; 95% Confidence Interval [CI], 1.19-4.50; p=0.013), as were clinical remission rates (33.3% vs. 25.1%; aOR, 1.81; 95% CI, 1.02-3.23; p=0.044) and endoscopic improvement rates (46.7% vs. 33.8%; aOR, 2.33; 95% CI, 1.33-4.09; p=0.003), compared to those with lower baseline levels. Statistical analyses adjusted for corticosteroid use, prior biologic failure, severe modified Mayo score at baseline and albumin levels.

Patients experiencing any rise in eosinophils from baseline to week 12 had significantly lower rates of clinical response (61.8% vs. 74.9%; aOR, 0.54; 95% CI, 0.40-0.73; p<0.001), clinical remission (22.5% vs. 31.0%; aOR, 0.65; 95% CI, 0.48-0.88; p=0.005) and endoscopic improvement (31.1% vs. 40.6%; aOR, 0.63; 95% CI, 0.46-0.82; p=0.002). Patients with more than a 50% rise in eosinophils had even lower response rates.

Histologic eosinophil assessment showed that among patients with moderate/marked eosinophil elevations at baseline (16% of cohort), 62.2% of responders achieved a reduction to absent or mildly elevated levels by week 12, compared to 50.9% of non-responders (p<0.001). For endoscopic improvement, 68.1% with moderately/markedly elevated baseline eosinophils achieved a reduction at week 12, compared to 52.9% without endoscopic improvement (p<0.001).

Finally, the odds of achieving clinical remission with mirikizumab versus placebo were significantly higher in patients with moderate/marked histologic eosinophils at baseline (aOR, 3.32; 95% CI, 1.20-9.22; p=0.021), compared to those without/mildly elevated eosinophils at baseline (aOR, 1.73; 95% CI, 1.19-2.52; p=0.004). These findings remained consistent in patients not using corticosteroids.

Details

Study Design: Post-hoc analysis of randomized controlled trial
Funding: None stated
Allocation: Not applicable
Setting: Multicenter
Level of Evidence: 1b