P0166Afimkibart downregulates Th17, myeloid, and fibrotic pathways in ulcerative colitis: serum proteomics from the phase 2b TUSCANY-2 trial

Abstract Background The tumor necrosis factor (TNF)-like ligand 1A (TL1A)/death receptor 3 (DR3) pathway regulates pathogenic T helper subsets, innate lymphoid cells, and fibrotic responses in inflammatory bowel disease (IBD). Afimkibart (RO7790121) is a fully human monoclonal antibody that neutralizes TL1A signaling through DR3. In the phase 2a TUSCANY study, TL1A inhibition by afimkibart showed target engagement associated with downregulation of Th17- and fibrosis-related pathways, including reductions in IL-17A and MMPs1. That PD assessment did not include a placebo control group, and tested 52 proteins. High-sensitivity multiplex serum proteomics was enabled in the placebo-controlled TUSCANY-2 trial to confirm and extend these mechanistic insights. Methods Serum from patients with moderately to severely active ulcerative colitis (UC) in TUSCANY-2 (n = 135) and 30 healthy controls, was analysed using the NULISAseqTM Inflammation Panel AQ. This panel generates absolute quantification (AQ) for 156 proteins and relative quantification (as NULISA Protein Quantification units; NPQ) for all 250 proteins. Longitudinal changes were assessed at 3 timepoints from baseline to week 14, comparing afimkibart (450 mg SC Q4W) versus placebo, with false discovery rate adjustment. Results Afimkibart treatment significantly downregulated 45/250 tested proteins (Fig 1A and B) encompassing several current standard of care pathways (TNFR and IL-12RB1) and other inflammatory mediators (e.g. IL-17A/F, IL-6, G-CSF and CCL17), in addition to OSM, which has been associated with non-response to anti-TNF therapy2,3. Stromal and tissue-remodelling mediators (AREG, HGF, OSM, MMP8, MMP12) were also reduced following treatment. These results confirm previous findings from TUSCANY of downregulation in Th17, Th9 and other inflammatory pathways, and extend observations by showing broader suppression of neutrophil activation, myeloid–stromal signaling, and fibrosis-related pathways. The proteomic profile supports contraction of inflammatory and tissue remodelling networks illustrating the potential mechanisms underlying clinical efficacy. Conclusion This large-scale, placebo-controlled proteomic analysis from TUSCANY-2 confirms and extends mechanistic insights from TUSCANY, showing that afimkibart consistently downregulates proteins associated with Th17, Th9, myeloid, and fibrotic signaling pathways in UC, including markers of TNF non-response. Collectively, these findings show that afimkibart goes beyond inflammation by modulating both immunological and fibrotic pathways, provide preliminary evidence of TL1A differentiation from TNF as a therapeutic target, and underscore afimkibart’s potential as a novel disease-modifying therapy in IBD. References: 1. Hassan-Zahraee M, et al. Inflamm Bowel Dis 2022;28(3):434–46. 2. West NR, et al. Nat Med 2017;23(5):579–89. 3. Yang Y, Fu KZ, Pan G. World J Gastrointest Surg 2024;16(1):228–38. Conflict of interest: Chang, Sarah: I am a full-time employee of Genentech, Inc., a wholly owned subsidiary of Roche, and receive Roche stock/options. Nguyen, Allen: I am employed by Genentech, Inc., a subsidiary of Roche, Inc. I own Roche shares/stock. Shim, Jeongsup: I am a full-time employee of Genentech, Inc., a wholly owned subsidiary of Roche, and receive Roche stock/options. Sperinde, Gizette: Gizette Sperinde has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the abstract apart from those disclosed. Gizette Sperinde is an employee of Genentech and Roche, and stockholders of Roche. Banerjee, Anindita: Employee and stockholder of Pfizer. Chandra, Deepa E.: I am an employee at Pfizer and own stock at Pfizer. Peeva, Elena: I am a full time employee of Pfizer and hold Pfizer stock. Neelakantan, Srividya: Pfizer employee and hold Pfizer stocks. Vincent, Michael S.: MSV is an employee and shareholder of Pfizer Inc. Dr. Neighbors, Maggie: I am a full-time employee of Genentech, Inc., a wholly owned subsidiary of Roche, and receive Roche stock/options.