Abstract 186P
Background
Immune checkpoint inhibitor (ICI) pneumonitis is the most common fatal immune-related adverse event (irAE) from PD-1/PD-L1 blockade, and a diagnosis of exclusion. Based on single-cell transcriptomics, we identified pathogenic T-helper 17.1 cells in ICI-pneumonitis bronchoalveolar lavage fluid (BALF), putatively engaging with pro-inflammatory “M1-like” monocytes, as a key pathophysiologic mechanism. Herein, we present the cytokine profile of ICI-pneumonitis BALF, aiming to identify further mechanistic insights and diagnostic biomarkers.
Methods
Levels of 22 cytokines (GM-CSF, Granzyme B, IFN-γ, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-13, IL-15, IL-17A, IP-10, MCP-1, MIP-1α, MIP-1β, Perforin, sCD137, TNF-α, TNF-β) were measured in BALF supernatant of 17 ICI-pneumonitis and 6 controls from 23 independent patients at UZ Leuven (discovery), using Isoplexis’ CodePlex platform. Validation was performed in a published cohort of 13 ICI-pneumonitis and 6 controls from independent patients at Johns Hopkins University. Mann-Whitney U test (Benjamini-Hochberg corrected) was used to compare cytokine levels between groups.
Results
In the discovery cohort, we observed significantly lower levels of IL-8, IL-9, IL-10, IL-17A, CCL2, and sCD137 in ICI-pneumonitis BALF vs. controls. There was a trend towards higher levels of TNF-α and CXCL10 (p = 0.11; p = 0.16 respectively). Next, we investigated the biomarker potential of ratios of differentially abundant proteins, arguing that disbalance rather than absolute cytokine values provides a more meaningful readout for inflammation, while correcting for technical variability in BALF-derived data. We identified that a high CXCL10: IL-8 ratio distinguishes ICI-pneumonitis from control patients in the discovery cohort (ROC AUC 0.92) and in the validation cohort (ROC AUC 0.82).
Conclusions
Bulk cytokine profiling identifies a high CXCL10: IL-8 ratio as a reproducible characteristic of ICI-pneumonitis BALF, in line with immunophenotypic data suggesting an interferon-γ driven immune response and absence of neutrophilic inflammation, respectively. The diagnostic utility of the CXCL10: IL-8 ratio in BALF to identify ICI-pneumonitis should be further investigated.
Clinical trial identification
NCT04807127.
Legal entity responsible for the study
University Hospitals Leuven.
Funding
This work was supported by internal KU Leuven (Belgium) and UZ Leuven (Belgium) funding. This project has received funding from Foundation against Cancer, Flemish Fund for Scientific Research (FWO; projects G0B6120N and G065615N). A.F. is supported by a Stand up to Cancer research fund. P.V.M. is supported by an FWO PhD fellowship (1S66020N). R.V. and J.W. are supported by an FWO Fundamental Clinical Mandate (1803521N and 1833317N, respectively). E.W. is supported by the Belgian Foundation against Cancer (Mandate for basic & clinical oncology research). P.V.M., J.V. and E.W. acknowledge the patronage of the KU Leuven M.D. Davidse Research Chair for Immuno-oncological Research.
Disclosure
All authors have declared no conflicts of interest.