Etrolizumab-s fails to control E-Cadherin-dependent co-stimulation of highly activated cytotoxic T cells.

Despite promising preclinical and earlier clinical data, a recent phase III trial on the anti-ß7 integrin antibody etrolizumab in Crohn's disease (CD) did not reach its primary endpoint. The mechanisms leading to this outcome are not well understood. Here we characterize the ß7+ T cell compartment from patients with CD in comparison to cells from individuals without inflammatory bowel disease. By flow cytometric, transcriptomic and functional profiling of circulating T cells, we find that triple-integrin-expressing (α4+ß7+ß1hi) T cells have the potential to home to the gut despite α4ß7 blockade and have a specific cytotoxic signature. A subset of triple-integrin-expressing cells readily acquires αE expression and could be co-stimulated via E-Cadherin-αEß7 interactions in vitro. Etrolizumab-s fails to block such αEß7 signalling at high levels of T cell stimulation. Consistently, in CD patients treated with etrolizumab, T cell activation correlates with cytotoxic signatures. Collectively, our findings might add one important piece to the puzzle to explain phase III trial results with etrolizumab, while they also highlight that αEß7 remains an interesting target for future therapeutic approaches in inflammatory bowel disease.

Etrolizumab-s Does Not Induce Residual Trafficking of Regulatory T Cells.

BACKGROUND: Blocking immune cell gut homing via α4ß7 integrin with the monoclonal antibody vedolizumab is an established therapeutic strategy in inflammatory bowel disease. However, despite promising preclinical and phase 2 clinical data, the anti-ß7 antibody etrolizumab yielded disappointing results in a large phase 3 trial program in UC. Mechanistic explanations are still lacking. We have recently shown that vedolizumab is associated with residual homing of regulatory T (Treg) cells in a certain exposure range and aimed to investigate whether a similar mechanism applies for etrolizumab. METHODS: We used flow cytometry, competitive dynamic adhesion, and transmigration assays to assess binding of the etrolizumab surrogate (etrolizumab-s) antibody FIB504 to Treg and effector T cells (Teff) and to explore the impact on cell trafficking. RESULTS: We observed only minimal differences in the binding of etrolizumab-s to Treg and Teff cells. Dynamic adhesion and transmigration of Treg and Teff cells was not substantially differentially affected at relevant concentrations. The ß1+ and PI16+ Treg cells were only resistant to etrolizumab-s at low concentrations. CONCLUSIONS: Etrolizumab does not seem to induce notable residual trafficking of Treg cells. Thus, the Teff overweight in the inflamed gut might persist despite reduced overall T cell recruitment. This might be one piece of the puzzle to explain recent clinical results in phase 3.

The efficacy of etrolizumab in phase 3 was disappointing. Our data suggest that, unlike vedolizumab, etrolizumab does not induce relevant residual trafficking of regulatory T cells. This might be one part of the explanation for recent observations in clinical trials.

Limited Dose-Dependent Effects of Vedolizumab on Various Leukocyte Subsets.

OBJECTIVES: The anti-α4ß7 integrin antibody vedolizumab (VDZ) is successfully used for the treatment of inflammatory bowel diseases. However, only a subgroup of patients respond to therapy. VDZ is administered at a fixed dose, leading to a wide range of serum concentrations in patients. Previous work from our group showed a dose-dependent preferential binding of VDZ to effector compared with regulatory CD4 + T cells. Therefore, we aimed to determine the dose-dependent binding profile of VDZ to other leukocyte subsets. METHODS: We characterized α4ß7 integrin expression on CD8 + T cells, CD19 + B cells, CD14 + monocytes, natural killer cells, and eosinophils from patients with inflammatory bowel disease and healthy controls. We studied the binding of VDZ to these cells at different concentrations and investigated the functional consequences for dynamic adhesion and transmigration in vitro . RESULTS: The expression of α4ß7 differed between the analyzed leukocyte subsets and was significantly higher on eosinophils from inflammatory bowel disease patients compared with controls. Almost all α4ß7-expressing cells from these subsets were bound by VDZ at a concentration of 10 µg/mL. Dynamic cell adhesion was significantly impaired in all subsets, but there were no dose-dependent differences in the inhibition of adhesion. DISCUSSION: Our data suggest that α4ß7-expressing CD8 + T cells, CD19 + B cells, CD14 + monocytes, natural killer cells, and eosinophils are a target of VDZ. However, there do not seem to be concentration-dependent differences, regarding the effects on these cells in the clinically relevant range. Thus, the reported exposure-efficacy characteristic of VDZ can probably mainly be attributed to CD4 + T-cell subsets.

Residual homing of α4ß7-expressing ß1+PI16+ regulatory T cells with potent suppressive activity correlates with exposure-efficacy of vedolizumab.

OBJECTIVE: The anti-α4ß7 integrin antibody vedolizumab is administered at a fixed dose for the treatment of IBDs. This leads to a wide range of serum concentrations in patients and previous studies had suggested that highest exposure levels are associated with suboptimal clinical response. We aimed to determine the mechanisms underlying these non-linear exposure-efficacy characteristics of vedolizumab. DESIGN: We characterised over 500 samples from more than 300 subjects. We studied the binding of vedolizumab to T cells and investigated the functional consequences for dynamic adhesion, transmigration, gut homing and free binding sites in vivo. Employing single-cell RNA sequencing, we characterised α4ß7 integrin-expressing T cell populations 'resistant' to vedolizumab and validated our findings in vitro and in samples from vedolizumab-treated patients with IBD. We also correlated our findings with a post-hoc analysis of the Gemini II and III studies. RESULTS: Regulatory T (TReg) cells exhibited a right-shifted vedolizumab binding profile compared with effector T (TEff) cells. Consistently, in a certain concentration range, the residual adhesion, transmigration, homing of and availability of functional α4ß7 on TReg cells in vivo was higher than that of/on TEff cells. We identified a vedolizumab-'resistant' α4ß7-expressing ß1+PI16+ TReg cell subset with pronounced regulatory properties as the substrate for this effect. Our observations correlated with exposure-efficacy data from Gemini II and III trials. CONCLUSION: Completely blocking TEff cell trafficking with vedolizumab, while simultaneously permitting residual homing of powerful TReg cells in an optimal 'therapeutic window' based on target exposure levels might be a strategy to optimise treatment outcomes in patients with IBD.