230P - Deciphering the mechanism of immunosuppressive activity of acetaminophen in the context of cancer immunotherapy

Background

Our prior research demonstrated that the presence of detectable plasma levels of acetaminophen (APAP) at the initiation of treatment was associated to a poor clinical outcome in cancer patients receiving immune checkpoint inhibitors (ICIs), independent of other known prognostic factors (Bessede et al. Ann Oncol 2022). This observation raised concerns about the potential immunomodulatory effects of APAP. Consequently, we aimed to elucidate the mechanistic basis of APAP’s immunosuppressive action.

Methods

We established an in vitro model using peripheral blood mononuclear cells (PBMCs) activated with anti-CD3 in the presence of APAP. Cellular responses were assessed at 3 and 6 days post-treatment using live-cell imaging and immunophenotyping via flow cytometry. Cytokine production was quantified through Homogeneous Time-Resolved Fluorescence assays, and key analytes were measured using ELISA.

Results

Our findings revealed that APAP significantly reduced the production of interferon-gamma (IFNγ) and suppressed PBMC proliferation in a dose-dependent manner, independent of cell death pathways. Notably, serotonin and kynurenine pathways did not appear to contribute to the impaired IFNγ response. In the presence of APAP, a distinct subset of CD4+ T cells emerged, characterized by low IFNγ production and expression of exhaustion markers such as Tim-3 and LAG-3, although PD-1 expression remained low. These results suggest that APAP selectively affects a subpopulation of immune cells, driving their exhaustion. Additionally, we identified tramadol and nefopam as viable alternatives to APAP, as neither PBMC cluster formation nor IFNγ production were impaired in our model.

Conclusions

APAP exerts a potent immunosuppressive effect on PBMC activation, promoting the expansion of an exhausted CD4+ T cell subset. Ongoing investigations using single-cell RNA sequencing will provide deeper insights into the phenotypic and functional characteristics of these cells. These findings may have critical implications for the use of APAP in cancer patients undergoing immunotherapy and highlight the potential of alternative analgesics with limited immunomodulatory activity.

Legal entity responsible for the study

The authors.

Funding

Fondation ARC pour la recherche sur le cancer.

Disclosure

All authors have declared no conflicts of interest.