Understanding the mechanisms underlying the lack of response to Janus kinase inhibition in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon. About one-third of UC patients failed to respond to available drugs, including tofacitinib, a broad Janus kinase (JAK) inhibitor. However, the mechanisms underlying patient response or resistance to oral JAK inhibitors remain unknown. To elucidate the molecular and cellular pathways activated by tofacitinib in responder and non-responder patients, we generated a longitudinal single-cell RNA sequence dataset profiling both immune and non-immune cell populations from colonic biopsies of UC patients. Our analysis revealed that responders exhibited higher baseline JAK-STAT activity, while non-responders had increased baseline NF-kB pathway activation. Longitudinal comparisons showed that disease progression in non-responders was associated with increased abundance and enhanced activation of macrophages and fibroblasts. Our data suggest that resistance to tofacitinib is mediated by the hyperactivation of myeloid cells, and we identified IL-10-dependent macrophages as a cellular subset contributing to this resistance.