Effects of prophylactic high and low doses of corticosteroid on the efficacy of immune checkpoint blockade in murine hepatocellular carcinoma models.

Abstract

e14596 Background: Immune-related adverse events (irAEs) are major hurdle to immune checkpoint blockade (ICB). Corticosteroid (CS) is effective in controlling the majority of irAEs. Although recent studies suggested CS use does not jeopardize the anti-tumor efficacy of ICB, prophylactic use of CS remains prohibited with the concerns of attenuating efficacy of ICB. This study aimed to investigate the effects of CS premedication on the efficacy of ICB in murine hepatocellular carcinoma models. Methods: Anti-mCTLA-4 (9D9C, BMS) and anti-mPD-1 antibodies (4H2, ONO) were intraperitoneally (ip) administered to tumor-bearing mice (subcutaneous Hepa 1-6 model and orthotopic BNL 1MEA.7R.1 model) with or without dexamethasone (DEXA) premedication (10 and 200 μg, equivalent to minimal anti-inflammatory dosage and pulse therapy in human, respectively). Efficacy of ICB was evaluated as tumor shrinkage. Tumor-infiltrating lymphocytes (TILs) were isolated for single cell RNA-sequencing and effector function analysis through flow cytometry. Results: In the subcutaneous model, all tumors treated with ICB alone (N=7) or ICB plus DEXA 10 μg (N=5) completely regressed, but 1 out of 7 tumors treated with ICB plus DEXA 200 μg escaped. However, the tumor growth was not significantly different between groups ( P-value >0.05, multiple Mann-Whitney test). In the orthotopic model (N=5/group), the mean (± standard error) tumor weights on day 21 after tumor implantation for isotype control, ICB, ICB plus DEXA 10 μg and ICB plus DEXA 200 μg were 2.45 (± 0.54), 0.73 (± 0.18), 0.98 (± 0.65), and 0.69 (± 0.17) grams, respectively ( P-value >0.05, comparing ICB plus DEXA 10 or 200 μg with ICB). At transcriptomic level, premedication with either dosage of DEXA significantly reduced the percentage of effector memory cells and increased the percentage of exhausted effector cells in the CD8 TIL population, which appeared to counterbalance the effects of ICB. However, at protein level, premedication of DEXA 10 or 200 μg did not reduce the interferon-γ or granzyme B production of CD8 TILs in both models (Table). Conclusions: CS premedication did not attenuate the efficacy of ICB. Our study provides the scientific basis to evaluate the potential of prophylactic CS in preventing ICB-induced irAEs in clinical studies.[Table: see text]