P034 Peripheral immune cell activity and biopsy gene expression in chronic pouchitis patients treated with tofacitinib: early induction results from the STOPit trial

Abstract

Abstract Background The Study of TOfacitinib for the treatment of chronic PouchITis (STOPit) is an investigator-initiated, open-label induction, double-blind, placebo-controlled, maintenance withdrawal study to determine the effectiveness of tofacitinib at inducing and maintaining remission in patients with chronic pouchitis. In this interim assessment, we evaluated blood samples and biopsy gene expression collected during the open-label induction period to discover biomarkers of initial clinical response. Methods We collected blood (n = 10 pairs, n = 5 non-responders) and biopsies (n = 21 pairs, n = 9 non-responders) at baseline and after 8 weeks of tofacitinib induction therapy (all participants received 10 mg twice daily induction). We classified patients as responders if they achieved a decrease of ≥ 2 in their modified pouchitis disease activity index after 8 weeks. Bulk peripheral blood mononuclear cells (PBMCs) and memory CD4+ T cells (TMEMs) were isolated from whole blood samples. Cytokines induced by stimulation in the presence or absence of tofacitinib were assessed in culture supernatants by bead array (PBMCs stimulated with PMA/Io or LPS, TMEMs stimulated with CD3/CD28 tetramer). Gene expression was measured in biopsies by qPCR in the pouch and pre-pouch ileum at both time points. Results At baseline, non-responders produced more IL-17 from both their PBMCs stimulated with PMA/Io and TMEMs stimulated with tetramer than responders, but responders secreted more IL-12p70, MCP, IL-10 and IL-8. Tofacitinib inhibited stimulation-induced IL-10 and IL-6 secretion in PBMCs in both responders and non-responders but failed to reduce IFNγ and TNF secretion selectively in non-responders only. All cytokine responses investigated in TMEMs, including IFNγ and TNF, were inhibited by tofacitinib in both responders and non-responders, suggesting the PBMC cell type refractory to inhibition with tofacitinib in non-responders is not TMEMs. Baseline biopsy ileal gene expression of IL18, HES1 and CXCL10 was decreased in responders compared to non-responders, while MMP7 was increased. Clinical response to tofacitinib led to a reduction in pouch expression of GLIS3, G0S2 and WNT5a from baseline to week 8 whereas these genes were unchanged or increased in non-responders. Conclusion Baseline functional immune cell responses and biopsy gene expression may discriminate chronic pouchitis patients' response to tofacitinib therapy and point to a mechanism underlying non-responsiveness. Recruitment for this trial is ongoing, allowing us to bolster and expand our findings with increasing sample sizes.