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Background Immune checkpoint inhibitors (ICIs) have significantly improved outcomes for patients with cancer. However, these therapies are associated with adverse events including de novo immune-related adverse events or flare of pre-exiting autoimmune disorders. Up to 80% of patients with cancer and pre-existing psoriasis (PsO) or psoriatic arthritis (PsA) experience PsO/PsA flare after initiating ICIs. Targeting the interleukin (IL)-17/IL-23 axis is a mainstream of the PsO/PsA treatment. However, whether this treatment can effectively control PsO/PsA with ICI exposure while preserving anti-tumour efficacy remains unknown.Case reports We report three patients with PsA and cancer, who received ICIs for their cancer treatment. All patients were male. Two patients had clear cell renal cell carcinoma, and one had melanoma. Two patients received anti-PD-1 antibody monotherapy, while one patient received combined anti-CTLA-4 and PD-1 antibody therapy. One patient had been receiving anti-IL-17A antibody (secukinumab), while the other two patients started anti-IL-17A antibody (ixekizumab) and anti-IL-23 antibody (guselkumab) after their PsA flared up during ICI treatment. Of note, with the anti-IL-17A or anti-IL-23 antibody treatment, their PsA remained in remission, and they well tolerated the ICI therapy. Importantly, all three patients showed persistent tumour responses to ICI therapy, including two complete remissions and one stable disease, respectively.Conclusions These three cases suggest that targeting the IL-17/23 axis may be an effective and safe approach for patients with cancer and pre-existing PsA being considered for ICI therapy.

With durable cancer responses, genetically modified cell therapies are being implemented in various cancers. However, these immune effector cell therapies can cause toxicities, including cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Pseudogout arthritis is an inflammatory arthritis induced by deposition of calcium pyrophosphate dihydrate crystals. Here, we report a case of pseudogout arthritis in a patient treated with MAGE-A4 directed T cell receptor T cells, for fallopian tube cancer. The patient developed CRS and ICANS 7 days after infusion of the T cells. Concurrently, the patient newly developed sudden onset of left knee arthritis. Synovial fluid analyses revealed the presence of calcium pyrophosphate dihydrate crystal. Notably, the pseudogout arthritis was resolved with tocilizumab, which was administered for the treatment of CRS and ICANS. Immunoprofiling of the synovial fluid showed that the proportion of inflammatory interleukin 17 (IL-17)-producing CD4+ T (Th17) cells and amount of IL-6 were notably increased, suggesting a potential role of Th17 cells in pseudogout arthritis after T-cell therapy. To the best of our knowledge, this is the first reported case of pseudogout arthritis after cell therapy. Clinicians, especially hematologists, oncologists and rheumatologists, should be aware that pseudogout arthritis can be associated with CRS/ICANS.