Ozanimod-exposed Patients with Ulcerative Colitis Undergoing Total Colectomy Exhibit Unique Lymph Node Histological Changes Free

Abstract

Introduction

Ozanimod regulates lymphocyte egress from the spleen and lymph nodes into the systemic circulation. The histological changes which occur in the lymph nodes of patients on ozanimod is unknown.

Materials and Methods

This retrospective study included patients with ulcerative colitis [UC] undergoing total colectomy for treatment-refractory disease who received ozanimod, and a cohort of patients with UC undergoing colectomy who did not have ozanimod exposure. Histology of the lymph nodes from the mesentery of colectomy specimens was reviewed and multiple features were scored by experienced pathologists.

Results

Six [13%] ozanimod-treated patients with UC required surgery for treatment-refractory disease. Colectomy specimen data were available for five patients [one patient had surgery at an outside centre]. Lymph node specimens from six control patients with UC who had colectomy were examined. Histological examination of lymph nodes showed that patients treated with ozanimod had significantly greater extent of dilated sinuses [p = 0.03] and greater degrees of sinus histiocytosis [p = 0.03] compared with control patients. In addition, there was a trend towards more Castleman-like angiotrophic hyperplasia, plasma cell infiltration, and subcortical interfollicular expansion in ozanimod-treated patients.

Conclusion

This study identifies unique histological changes in the lymph nodes of patients with UC treated with ozanimod. The presence of sinus histiocytosis and dilated sinuses is in keeping with the known mechanism of action of ozanimod, and suggests that blocking lymphocyte egression from lymph nodes was insufficient to ameliorate disease severity in these patients. The possibility of Castleman-like features, identified in several of the cases, needs to be further investigated.

1. Introduction

Ulcerative colitis [UC] is a chronic inflammatory condition affecting the colon and rectum. It is characterised by a relapsing and remitting course and generally requires the use of long-term therapy in order to achieve and maintain disease control.¹ Untreated and persistent inflammation can result in complications including impaired quality of life, hospitalisations, colorectal cancer, and need for surgery.^2,3

Sphingosine-1-phosphate [S1P] receptor modulation is a relatively new therapeutic target in patients with UC. In May 2021, the US Food and Drug Administration [FDA] approved the use of the first-in-class selective S1P1 and S1P5 receptor modulator, ozanimod, in patients with moderately to severely active UC.

S1P is a membrane-derived lysophospholipid signalling molecule that primarily functions through the activation of five cell-surface G protein-coupled receptors [S1P1-S1P5] and regulates lymphocyte egress from the spleen and lymph nodes into the systemic circulation.^4,5 This results in the sequestration of lymphocytes in the lymphoid organs.^6,7 In mouse models, exposure to S1P receptor modulators has been shown to increase lymphocyte numbers in peripheral lymph nodes.⁸ Furthermore, there appears to be a specific pattern of lymph node sequestration with a relative disappearance of lymphocytes from the subcapsular and medullary sinuses and conversely increased lymphocyte presence of the abluminal side of sinus lining endothelium.⁶

Data regarding the effects of ozanimod on mesenteric lymph nodes in patients with ulcerative colitis are lacking. The aim of this study was to compare histopathological findings in lymph nodes removed during total abdominal colectomy with those from patients with UC on other therapies.

2. Materials and Methods

This retrospective study was conducted at the University of Chicago Medicine Inflammatory Bowel Disease Center, and included patients with UC treated with ozanimod who underwent total abdominal colectomy, and a control group of patients with UC on other advanced therapies also undergoing total abdominal colectomy. All patients underwent colectomy for treatment of refractory UC. All patients were receiving corticosteroids at the time of surgery. All patients treated with ozanimod underwent colectomy within 2 months of their last treatment dose. This study received institutional board review approval [#IRB21-1355]. All demographic and clinical data were recorded.

2.1. Histopathological assessment

We retrospectively analysed haematoxylin and eosin [H&E]-stained slides from formalin-fixed and paraffin-embedded lymph nodes from the pathology archives at the University of Chicago. The lymph nodes had been collected and processed as part of routine surgical pathology assessment following total abdominal colectomy. Only lymph nodes that were deemed adequately preserved were included in the study. The following histological parameters were blindly scored by a gastrointestinal [GI] pathologist [CRW] and a haematopathologist [JXC] based on previously described scoring systems^9–11: Castleman-like angiotrophic hyperplasia [0–3], monomorphic lymphoid cells [0-3], plasma cell infiltration [0-4], sinus dilatation [0-6], follicular hyperplasia [0–3], subcortical interfollicular expansion[0–2], vascular proliferation[0–2], and sinus histiocytosis [0–3].

2.2. Statistical analysis

Student’s unpaired two-tailed t test was used to determine significance between pathological scores between groups. Parametric continuous variables are shown as mean ± standard deviation [SD] and non-parametric variables as median ± interquartile range [IQR]. Categorical variables are presented as percentages of the cohort population. The SPSS software package [version 26.0] or Microsoft Excel were used for all analyses.

3. Results

3.1. Study population

In all, 45 patients with UC initiated therapy with ozanimod. Of these, five patients underwent colectomy at our centre for treatment refractory disease. Treatment with ozanimod ranged from 6–24 weeks in duration. We retrospectively analysed pathology specimens from six patients with UC who underwent colectomy for treatment-refractory UC, who had never received ozanimod in the past. There was no significant difference between cases and controls in terms of median age 34 years (interquartile range [IQR] 22–43.5] vs 33 years [IQR 29.8–52.5], p = 0.66) or median disease duration (5 years [IQR 2–15] vs 12 years [IQR 3.3–28.5], p = 0.46). Three patients [60%] treated with ozanimod and three [50%] control patients had extensive colitis. All patients were exposed to multiple advanced therapies prior to colectomy. Demographic and clinical characteristics are detailed in Table 1.

3.2. Ozanimod-treated patients have distinct histopathological changes in lymph nodes

Lymph nodes from patients treated with ozanimod had significantly greater extent of sinus dilatation than control patients [1.5 vs 0.67, p = 0.022]; they also had significantly more sinus histiocytosis [2.67 vs 1.67, p = 0.03] [Figure 1]. There was a tendency towards more Castleman-like angiotrophic hyperplasia [1.5 vs 1, p = 0.34], plasma cell infiltration [1.5 vs 0.67, p = 0.26] and subcortical interfollicular expansion [1.5 vs 0.83, p = 0.1] in ozanimod-treated patients. Patients treated with ozanimod and controls showed similar amounts of monomorphic lymphoid cells [1.3 vs 1.5, p = 0.7], follicular hyperplasia [1 vs 1.1, p = 0.8] and vascular proliferation [1.5 vs 1.5, p = 1].

4. Discussion

This study shows that patients with UC treated with ozanimod have distinct histopathological changes in lymph nodes compared with those from patients undergoing colectomy while on other therapies. Ozanimod is an S1P receptor modulator which prevents the egress of lymphocytes from lymph nodes and prevents their reaching areas of inflammation.⁶ The findings of this study, in particular the sinus dilatation and sinus histiocytosis, represent a direct histological correlate of blocked lymphocyte extrusion.

Whereas this study was not adequately powered to find significant differences in all histopathological parameters, one feature of particular interest that was observed in patients treated with ozanimod was Castleman’s-like angiotrophic hyperplasia. The significance of this finding is unclear although, if proven to be common in future studies, may have clinical relevance particularly in patients where a lymphoproliferative disorder is being considered. Furthermore, all patients in this study received ozanimod for short periods of time, and as such it is unknown whether these changes become more prominent over time.

It is of interest that these changes were observed in patients who were ozanimod treatment failures undergoing colectomy for treatmen- refractory disease. This indicates that although the therapy did prevent egress of lymphocytes from lymph nodes, this was insufficient to treat the inflammation and prevent disease progression. This observation indicates, that in these patients, other mechanisms of inflammation were predominant. It is known that for most therapies there is a primary non-response rate of around 30%. Our findings support the notion that in primary non-responders to one therapeutic mechanism or those who lose response for reasons other than immunogenicity, a different mechanism should be attempted next.¹²

The primary limitation is the small sample size of the ozanimod-treated cohort limiting the ability to find differences in less prominent histological features. Despite this limitation, this study is the first to describe histopathological features associated with ozanimod in humans, and closer inspection of lymph nodes from larger cohorts of patients undergoing colectomy while on S1P receptor modulator therapy may provide further insights as to the mechanisms of both therapy failure and success.

In conclusion, patients with UC treated with ozanimod have distinct histopathological features in lymph nodes which are in keeping with their known mechanism of action. These data are intriguing in that despite effecting these changes, this was not enough to ameliorate disease and prevent colectomy. The possibility of Castleman-like features identified in several of the cases, needs to be further investigated in larger prospective studies, but should be kept in mind while evaluating any patient treated with ozanimod for a lymphoproliferative disorder.

Data are available upon reasonable request.

Funding

Dr Nathaniel Cohen is supported by an educational grant from the Maor Foundation. The study was also supported in part by the Gastro-Intestinal Research Foundation of Chicago.

Conflict of Interest

Nathaniel A. Cohen has served as a consultant for Abbvie, Iterative Health, Rafa, Takeda, and Seres Pharmaceuticals and has received travel support from Pfizer. David T. Rubin has received grant support from Takeda and has served as a consultant for Abbvie, Abgenomics, Arena Pharmaceuticals, Bellatrix Pharmaceuticals, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Syneos, Dizal Pharmaceuticals, Genentech/Roche, Gilead Sciences, Ichnos Sciences S.A., InDex Pharmaceuticals, Iterative Scopes, Janssen Pharmaceuticals, Lilly, Pfizer, Prometheus Laboratories, Reistone, Takeda, and Techlab.

Author Contributions

Study concept and design: NAC, CRW, DTR. Acquisition of data: NAC, DC, NG, CRW, JXR. Analysis and interpretation of data: NAC, CRW, DTR, JXR. Drafting of manuscript: NAC, CRW. Critical revision of manuscript: DC, DTR.

References

Author notes