P1002 Changes in circulating lymphocyte subsets and CCR9 transcripts as mechanistic biomarkers of the small molecule α4β7 inhibitor MORF-057 in patients with Ulcerative Colitis
Authors: Hussain A , Singhal P , Wong J , Goodwin B , Abhyankar B , Soo C , Rogers B , Mangada M 
Published: January 2025

Abstract

Background
MORF-057 is an orally administered, selective, and potent small molecule inhibitor of the cell surface receptor integrin a4b7. Upon binding to the a4b7 heterodimer, MORF-057 blocks the interaction of this integrin with the endothelial ligand mucosal vascular addressin cell adhesion molecule 1 (MAdCAM-1) which, in turn, prevents the extravasation of circulating lymphocytes into the intestinal mucosa. In this study, the pharmacodynamic effects of MORF-057 on immune cell trafficking were evaluated in UC patients using a flow cytometry-based assay and by assessing the expression of CCR9 gene in blood.

Methods
As part of the induction phase of an open-label, single-arm, Phase 2a study (NCT05291689) the efficacy, safety, and tolerability of MORF-057 in 35 patients with moderately to severely active UC disease were evaluated. Patients were treated with MORF-057 at a dose of 100 mg BID orally for an induction period of 12 weeks followed by a 40-week maintenance period. Blood was collected for peripheral blood mononuclear cell (PBMC) isolation and RNA extraction at baseline and post-treatment at Week 2, 6, 12, 20, 28, 36, 44, and 52. Using flow cytometry, levels of CD4+β7+ naïve, CD4+β7+ central memory (TCM), CD4+β7 Hi effector memory (TEM) T cells, and CD19+β7+ switched memory B cells (BSM) subpopulations were quantified as a percentage of the parent populations CD4 naive, TCM, TEM and BSM, respectively, then normalized to pre-treatment baseline. Expression of CCR9 mRNA in the blood was quantified as a fold ratio relative to baseline for the same timepoints. Statistical analyses were performed using the Wilcoxon Signed Rank test.

Results
The percentages of circulating lymphocyte subsets CD4+β7 Hi TEM cells, CD4+β7+ TCM and CD19+β7+ BSM were significantly elevated relative to baseline as early as Week 2 and up to Week 52 (Table 1). These changes were not observed in the overall lymphocyte counts nor in the CD4+β7+Naïve T cells (except at Week 52). The baseline-normalized expression levels of CCR9 at Weeks 12 and 52 were 1.6 [0.6] (mean [SD]) and 1.7 [0.8], respectively (Figure 1).

Conclusion
Patients receiving MORF-057 for a period of up to 52 weeks achieved statistically significant increases in specific β7+ lymphocyte subsets expressing ITGβ7. Elevated levels of the CCR9 transcript were observed in blood over the course of treatment. Effects observed were consistent with those reported for patients receiving biologic inhibitors of the same pathway as well as in healthy volunteers receiving MORF-0571,2. These changes in circulating lymphocyte populations and CCR9 transcript levels may be used as mechanistic biomarkers for MORF-057 in UC patients.

References
1.Hussain A, et al. Increase in circulating T and B lymphocyte subsets after treatment with the potent, selective, oral small molecule α4β7 inhibitor MORF-057 in healthy subjects. UEG Week; 2022 Oct 8-11; Vienna, Austria.
2.Ray A, et al. MORF-057, an oral selective α4β7 integrin inhibitor for inflammatory bowel disease, leads to specific target engagement in a single and multiple ascending dose study in healthy subjects. ECCO Congress; 2021 July 7-10; Virtual. ePoster 306.