BACKGROUND AND AIMS: Corticosteroid is effective in alleviating immune-related adverse events (irAEs) of immune checkpoint blockade (ICB). However, prophylactic use of corticosteroid to prevent irAEs is not recommended due to a looming concern that it may attenuate anti-tumor effect of ICB. This study aims to investigate whether corticosteroid premedication may compromise anti-tumor efficacy of dual ICB, a regimen that may cause significant irAEs. METHODS: Orthotopic BNL 1MEA.7R.1 and subcutaneous Hepa1-6 syngeneic hepatocellular carcinoma (HCC) models were used. Low-dose (LD
10 µg) or high-dose (HD
200 µg) dexamethasone (Dexa) was intraperitoneally administered before each dose of anti-CTLA-4 and anti-PD-1. Tumor shrinkage, T cell priming, cytokine quantitation, as well as cytotoxicity and single-cell RNA-sequencing (scRNA-seq) of tumor-infiltrating T cells were assessed. RESULTS: In the orthotopic model, dual immune checkpoint blockade (dICB) plus phosphate buffered saline (PBS) significantly reduced the mean tumor weight (adjusted for SE) (0.73±0.18 g vs 2.45±0.54 g
p=0.03), while neither LD nor HD Dexa premedication affected dICB-induced tumor shrinkage. In the subcutaneous model, dICB plus PBS or LD Dexa yielded a complete tumor response (CR) rate of 100%, while dICB plus HD Dexa yielded a CR rate of 85.7% (p>
0.05, comparing to dICB plus PBS). ScRNA-seq analysis demonstrates that Dexa did not affect dICB-induced reduction of major clusters of exhausted CD4+ and CD8+ T cells but halved dICB-induced expansion of effector memory CD8+ T cells. Nevertheless, Dexa premedication, regardless of dosage, did not diminish dICB-induced T cell priming, cytokine production, or cytotoxicity of tumor-infiltrating CD8+ T cells. CONCLUSION: Corticosteroid premedication does not significantly compromise anti-tumor efficacy of dICB treatment in murine HCC models. These results suggest that clinical investigations of prophylactic corticosteroids to alleviate severe irAEs may be feasible.