Pos0151 Versatile Modulating Effect of Glucocorticoids Combined With Immune Checkpoint Inhibitors on Immune Cells Through Lag-3 Up-Regulation

Background: Cancer immunotherapy with immune checkpoint inhibitors (ICI) may cause immune-related adverse events (irAEs). Glucocorticoids (GCs) and disease-modifying anti-rheumatic drugs (DMARDs) are used for rheumatic irAEs treatment. Yet, high-dose GC may impair anti-tumor responses. In a preliminary study we found that GCs induce significant up-regulation of inhibitory molecule lymphocyte activation gene-3 (LAG-3) in peripheral blood and synovial fluid mononuclear cells (PBMCs and SFMCs, respectively). Objectives: To assess the effect of GCs and DMARDs with ICI on PBMCs proliferation and SFMCs modulation. The drugs effect on the inhibitory molecules: LAG-3 and programmed cell death-1 (PD-1) expression was tested. Methods: Healthy donors PBMCs (n=8) and psoriatic and rheumatoid arthritis (PsA and RA) SFMCs (n=6) were co-cultured with GCs, methotrexate (MTX), and biologics without and with pembrolizumab (PEM, anti-PD-1). The drugs effect on proliferation was assessed using CFSE-labeled PHA-stimulated PBMCs. LAG-3 and PD-1 expression on immune subsets in PBMCs and SFMCs was analyzed by flow cytometry. Results: Maximal proliferation rate in PHA-stimulated PBMCs (control, no drugs) was 25.9 ± 6.5%. Proliferation was significantly reduced by MTX and GCs (4.4 ± 0.9%, p<0.002 and 3.2 ± 0.6% p<0.002, respectively). Among the biologics, TNFi (infliximab, IFX) reduced the proliferation, although to a low extent (16.3 ± 0.6%), while IL-17Ai (secukinumab, SEC) and IL-6Ri (tocilizumab, TCZ) did not reduce the proliferation compared to control. PEM alone did not affect the proliferation rate compared to the control. For the drug combinations: the highest proliferation arrest was observed with MTX+PEM and GCs+PEM (4.5 ± 1.1%, p<0.002 and 3.5 ± 0.7% p<0.002, respectively) (Figure 1 A+B). In the same culture setting, the drugs effect on CD4⁺LAG-3⁺ cells was analyzed. PEM alone (0.9 ± 0.3%) did not modulate CD4⁺LAG-3⁺ cells as compared to medium (0.4 ± 1.2%). GCs induced significant up-regulation of a 15-fold increase (6.7 ± 0.9%, p<0.02), whereas MTX did not modulate this population (0.9 ± 0.3%) compared to medium. Among the biologics, TNFi led to a non-significant increase in CD4⁺LAG-3⁺ cells (1.5 ± 0.6%), but to lower level than GCs. IL-17Ai and IL-6Ri did not affect CD4⁺LAG-3⁺ cells compared to medium. The effect of anti-rheumatic drugs with PEM was similar to their effect as single drugs. GCs+PEM led to a significant increase in CD4⁺LAG-3⁺ cells (5.5 ± 1.7%, p<0.02) compared to PEM alone, MTX+PEM (0.7± 0.3%) and the biologics with PEM did not change CD4⁺LAG-3⁺ cells compared to PEM (Figure 1 C+D). CD4⁺PD-1⁺ cells were unaffected by the addition of GCs alone, PEM alone or PEM+GCs (data not shown). In SFMCs, GCs significantly up-regulated CD14⁺LAG-3⁺ cells to a 10-fold increase (12.3 ± 2.6%, p<0.04), while MTX had no effect (1.3± 0.5%), and TNFi slightly upregulated these cells (2.5± 0.4%) compared to medium (1.2± 0.3%). PEM alone (1.0 ± 0.4%) did not modulate CD14⁺LAG-3⁺ cells compared to the medium. PEM+GCs led to a significant 11-fold increase in CD14⁺LAG-3⁺ cells (13.8 ± 3.5%, p<0.04), while PEM+MTX had no effect (0.9 ± 0.4%) and PEM+ TNFi slightly increased those cells (2.2 ± 0.7%) compared to PEM alone (1.0 ± 0.4%) (Figure 1 E+F). Conclusion: In this study, circulating CD4⁺LAG-3⁺ cells and synovial CD14⁺LAG-3⁺ cells were expanded by GCs with PEM. ICI aim to suppress inhibitory molecules expression, GCs might exhibit versatile activity in both central and local environment that might directly interrupt with the ICI activity. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.