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Molecular analysis of immune checkpoint inhibitor associated erythema nodosum-like toxicity
Xiaopeng Sun1, Margaret L Axelrod2, Paula I Gonzalez-Ericsson3
1Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, United States.
Purpose:
Immune checkpoint inhibitors (ICIs) are increasingly used to treat advanced malignancy but can induce immune-related adverse events (irAE). The mechanisms behind these sporadic and sometimes life-threatening irAEs remain largely unexplored. Here, we present a case report and in-depth molecular analysis of an erythema nodosum (EN) like irAE occurring in a melanoma patient with isolated brain metastasis, aiming to explore the potential mechanism of this irAE.
Methods:
We performed RNA and T cell receptor (TCR) sequencing on the patient's resected brain metastasis and biopsy of EN-like irAE. Single cell RNA/TCR sequencing was conducted on the patient's peripheral blood mononuclear cells (PBMC) at baseline, 3 weeks after ipilimumab and nivolumab combination therapy, during EN toxicity and after resolution.
Results:
The site of EN-like irAE showed a distinct accumulation of pro-inflammatory immune cells, accompanied by the upregulation of inflammatory and interferon response signatures. In addition, clonal expansion and activation of irAE-associated CD8 T cells and upregulation of monocyte-specific interferon signatures occurred concurrently with irAE onset.
Conclusion:
The unique immune landscape at the EN-like irAE could indicate that this irAE is distinct from anti-tumor immune and analogous non-ICI autoimmune milieus. Our data also suggests that systemic immune activation induced by ICI treatment, as reflected in PBMC, may help monitor the patient's treatment response and access irAE risk.
