P0101 Phenotyping of human UC colonic tissue reveals inflammatory pathway gene expression in PD-1+ conventional and regulatory T cells which overlap with those regulated by rosnilimab in a mouse model of colitis
Authors: Linggi B , Haines C , Ren Y , Parmley S , Dahl M , Kwon J , Soroosh P , Lizzul P , Sibley C 
Published: January 2025

Abstract

Background
PD-1 co-inhibitory receptor agonists, such as rosnilimab, are a promising class of therapeutics that leverage immune homeostatic mechanisms to regulate T cell activity for treatment of inflammatory diseases, including ulcerative colitis (UC). In UC lamina propria, multiple T cell subtypes express PD-1, including peripheral helper T cells (Tph) and effector memory T cells, and the reduction of PD-1+ Tph cells is correlated with remission.1 Also, PD-1+ Tregs may comprise a subpopulation of pro-inflammatory Tregs in the UC colon. In a mouse model of colitis (induced by transfer of CD4+CD45Rb+ T cells from human PD-1 transgenic mice), rosnilimab treatment of established disease showed reduced body weight loss, reduced inflammation of the colon, and reduced infiltration of CD4 T cells.2

Methods
A secondary analysis of active UC patient-derived colonic tissue characterized PD-1+ T cell subsets via a CD3-sorted single-cell proteomics and transcriptomics dataset.3 Pathway activity was estimated using Progeny.4 Bulk RNA-sequencing, gene expression analysis, and enrichment of human UC significant Reactome5 pathways was performed on colonic tissue from mice treated with rosnilimab in the colitis model.

Results
In human UC colonic tissue, PD-1+ CD4 conventional T (Tcon) cells and PD-1+ Tregs had increased JAK-STAT, TNF, and NF-κB estimated pathway activity compared to PD-1(-) cells. PD-1+ Tregs had increased expression of genes associated with a pro-inflammatory phenotype, including TNF, TBX21(TBET), and IL12RB2, and decreased expression of IL2RA (CD25). RNA-Seq of mouse colitis identified upregulated genes, compared to naive animals, in pathways that were also involved in human UC (“Signaling by interleukins” (e.g., Il6) and “Chemokine receptors bind chemokines” (e.g., Ccl20)). Expression levels of these genes in rosnilimab treated mice were similar to naive control animals. Additionally, the barrier gene Muc3 and fibrosis-associated Mmp9 were dysregulated in colitis but normal in rosnilimab-treated mice.

Conclusion
In UC colonic tissue, PD-1+ CD4 Tcon cells demonstrated increased inflammatory gene expression and PD-1+ Tregs exhibited a pro-inflammatory phenotype, suggesting that targeting both PD-1+ CD4 Tcon and PD-1+ Tregs may contribute to the therapeutic efficacy of rosnilimab in UC. These additional analyses support preclinical findings and suggest beneficial modulation of gene expression pathways of human UC, including reduction of pro-inflammatory cytokines and fibrosis, and upregulation of barrier function genes. These data demonstrate that PD-1 is upstream of multiple clinically validated drivers of UC and support the scientific rationale for studying rosnilimab in an ongoing Phase 2 study in UC (NCT06127043).

References
1.Long Y, et al. Immunol Letters 2021;233:2-10.
2.Parmley S, et al. United European Gastroenterol J 2024;12:482 (Abstract MP448).
3.Gupta T, et al. Cancer Cell 2024;42:797–814.
4.Schubert M, et al. Nat Commun 2018;9:20.
5.Linggi B, et al. Sci Rep 2021;11:18243.