This letter describes the potential effect of B cell depletion on immune related adverse events associated with immune checkpoint inhibition. B cell depleting agents such as rituximab reduce B cell to plasma cell differentiation and antibody production. This treatment strategy is used in several immune mediated inflammatory diseases such as rheumatoid arthritis and small vessel vasculitis. The immune related adverse events associated with immune checkpoint inhibition resemble immune mediated inflammatory diseases. Here, we report a lower incidence of hypothyroidism in a trial of combined B cell depletion and immune checkpoint inhibitor treatment compared with studies of immune checkpoint inhibitor monotherapy. This letter aims to increase awareness of the immune related adverse events associated with immune checkpoint inhibition in future clinical trials of immune checkpoint inhibition together with B cell depletion (primarily trials of B cell lymphomas). Hopefully, observations from these clinical trials can guide future treatment strategies to treat or prevent immune related adverse events associated with immune checkpoint inhibition.

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Objective During treatment with immune checkpoint inhibitors (ICI) such as the anti-PD-1 antibody pembrolizumab, half of patients with pre-existing inflammatory arthritis experience disease flares. The underlying immunological mechanisms have not been characterized. Here, we investigate the effect of pembrolizumab on cells involved in inflammation and destruction in the synovial joint and how immunosuppressive treatments affect the pembrolizumab-induced immune reactions. Methods We included synovial fluid mononuclear cells (SFMCs, n = 28) and peripheral blood mononuclear cells (PBMCs, n = 6) from patients with rheumatoid arthritis and peripheral spondyloarthritis and PBMCs from healthy controls (n = 6). Fibroblast-like synovial cells (FLSs) were grown from SFMCs. The in vitro effect of pembrolizumab was tested in SFMCs cultured for 48 h, FLS-PBMC co-cultures and in SFMCs cultured for 21 days (inflammatory osteoclastogenesis). Cells and supernatants were analyzed by ELISA, flow cytometry, and pro-inflammatory multiplex assay. Finally, the effect of the disease-modifying anti-rheumatic drugs (DMARDs) adalimumab (TNFα inhibitor), tocilizumab (IL-6R inhibitor), tofacitinib (JAK1/JAK3 inhibitor), and baricitinib (JAK1/JAK2 inhibitor) on pembrolizumab-induced immune reactions was tested. Results Pembrolizumab significantly increased monocyte chemoattractant protein-1 (MCP-1) production by arthritis SFMCs (P = 0.0031) but not by PBMCs from patients or healthy controls (P = 0.77 and P = 0.43). Pembrolizumab did not alter MMP-3 production in FLS-PBMC co-cultures (P = 0.76) or TRAP secretion in the inflammatory osteoclastogenesis model (P = 0.28). In SFMCs, pembrolizumab further increased the production of TNFα (P = 0.0110), IFNγ (P = 0.0125), IL-12p70 (P = 0.0014), IL-10 (P = 0.0100), IL-13 (P = 0.0044), IL-2 (P = 0.0066), and IL-4 (P = 0.0008) but did not change the production of IL-6 (P = 0.1938) and IL-1 (P = 0.1022). The SFMCs treated with pembrolizumab showed an increased frequency of intermediate monocytes (P = 0.044), and the MCP-1 production increased only within the intermediate monocyte subset (P = 0.028). Lastly, adalimumab, baricitinib, and tofacitinib treatment were able to attenuate the pembrolizumab-induced MCP-1 production (P = 0.0004, P = 0.033, and P = 0.025, respectively), while this was not seen with tocilizumab treatment (P = 0.75). Conclusion Pembrolizumab specifically activated intermediate monocytes and induced the production of several cytokines including TNFα but not IL-6. These findings indicate that flares in patients with pre-existing inflammatory arthritis involve monocyte activation and could be managed with TNFα neutralization.

Background Inflammatory arthritis including rheumatoid arthritis (RA) and spondyloarthritis (SpA) is characterized by inflammation and destruction of the joints. Approximately one third of patients do not respond to first-line treatments. Nitro-fatty acids are bioactive lipids with anti-inflammatory properties and tissue-protective functions. The nitro-fatty acid 10-NO2-oleic acid (10-NO2-OA) is being tested in clinical trials for patients with fibrotic and inflammatory conditions. Here, we tested whether 10-NO2-OA could inhibit immune reactions involved in the inflammatory and joint destructive processes in inflammatory arthritis. Methods Synovial fluid and blood samples were obtained from 14 patients with active RA or SpA. The in vitro models consisted of synovial fluid mononuclear cells (SFMCs) cultured for 48 h, SFMCs cultured for 21 days, and fibroblast-like synovial cells (FLSs) co-cultured with peripheral blood mononuclear cells (PBMCs) for 48 h. Cells were treated with or without 10-NO2-OA or the tumor necrosis factor alpha (TNFα) inhibitor etanercept. Supernatants were analyzed for type I interferon, monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase 3 (MMP3) and tartrate resistant acid phosphatase (TRAP). Results In SFMCs cultured for 48 h, 10-NO2-OA dose-dependently decreased the secretion of bioactive type I interferons and MCP-1 but not MMP3 (P = 0.032, P = 0.0001, and P = 0.58, respectively). Both MCP-1 and MMP3 were decreased by etanercept (P = 0.0031 and P = 0.026, respectively). In SFMCs cultured for 21 days, 10-NO2-OA significantly decreased the production of MCP-1 but not TRAP (P = 0.027 and P = 0.1523, respectively). Etanercept decreased the production of TRAP but not MCP-1 (P < 0.001 and P = 0.84, respectively). In co-cultures of FLSs and PBMCs, 10-NO2-OA decreased the production of MCP-1 (P < 0.0001). This decrease in MCP-1 production was not seen with etanercept treatment (P = 0.47). Conclusion 10-NO2-OA decreased the release of MCP-1 in three models of inflammatory arthritis. Of particular interest, 10-NO2-OA inhibited type I interferon, and 10-NO2-OA was more effective in reducing MCP-1 production in cultures dominated by FLSs compared with etanercept. Our results encourage clinical investigations of 10-NO2-OA in patients with inflammatory arthritis.

Background:During cancer treatment with immune checkpoint inhibitors (ICI) such as the anti-PD-1 antibody pembrolizumab, 2-4% of patients develop inflammatory arthritis as an immune related adverse event and half of patients with pre-existing inflammatory arthritis have disease flares. This type of adverse events shows striking similarities with traditional immune mediated inflammatory arthritis. However, the underlying immunological mechanisms of inflammatory arthritis associated with ICI are not fully understood.Objectives:We aimed to develop an in vitro model of inflammatory arthritis associated with ICI, and to use this model to investigate monocyte differentiation and activation following treatment with pembrolizumab.Methods:First, synovial fluid mononuclear cells (SFMCs) and peripheral blood mononuclear cells (PBMCs) from patients with immune mediated inflammatory arthritis (rheumatoid arthritis and peripheral spondyloarthritis, n=22) and PBMCs from healthy controls were incubated with pembrolizumab and assessed for monocyte chemoattractant protein 1 (MCP-1) secretion by ELISA. Then, cytokine production in SFMCs was studied in more detail by the multiplex V-PLEX proinflammatory panel and by intracellular flow cytometry. Finally, pembrolizumab treated SFMCs were incubated with the different disease modifying anti-rheumatic drugs adalimumab, tocilizumab, tofacitinib, and baricitinib.Results:Pembrolizumab significantly increased MCP-1 production in the SFMCcultures (P=0.0031). In contrast, pembrolizumab did not change MCP-1 production by PBMCs from neither patients nor healthy controls (P=0.77 and P=0.43). Pembrolizumab also increased the production of TNFα (P=0.049), IFNγ (P=0.047), and IL-12p70 (P=0.031), but did not change the production of IL-6 (P=0.98). Among SFMCs treated with pembrolizumab there was an increased frequency of intermediate monocytes (P=0.044). Interestingly, pembrolizumab also increased the MCP-1 production within the intermediate monocytes only (P=0.028). In contrast, among SFMCs treated with LPS, only the classical monocyte subset was increased (P=0.0045) and MCP-1 production increased in both intermediate and classical monocyte subsets. Lastly, the TNFα inhibitor adalimumab and the Janus kinase inhibitors baricitinib and tofacitinib attenuated the pembrolizumab-induced MCP-1 production (P=0.0004, P=0.033, and P=0.025, respectively) while this was not seen with the IL-6 inhibitor tocilizumab (P=0.75).Conclusion:We have developed a very simple in vitro model of inflammatory arthritis associated with ICI. Using this model, we found that pembrolizumab specifically activated intermediate monocytes and induced TNFα, IFNγ, and IL-12p70 production, whereas IL-6 was unchanged. These findings were supported by effectful reduction of MCP-1 secretion with TNFα inhibition but not with IL-6 inhibition. This model could potentially be used to further study the effects of ICIs and the underlying immunological mechanisms of inflammatory arthritis associated with ICI.References:None.Disclosure of Interests:Anne Sofie Sørensen: None declared, Morten Nørgaard Andersen: None declared, Kristian Juul-Madsen: None declared, Cæcilie Skejø: None declared, Henrik Schmidt: None declared, Thomas Vorup-Jensen: None declared, Tue Wenzel Kragstrup Shareholder of: iBio Tech ApS, Consultant of: Bristol-Myers Squibb, Speakers bureau: TWK has engaged in educational activities talking about immunology in rheumatic diseases receiving speaking fees from Pfizer, Bristol-Myers Squibb, Eli Lilly, Novartis, and UCB.