AB1079 CHECKPOINT INHIBITOR-ASSOCIATED ARTHRITIS: PHENOTYPES AND CYTOKINE ASSOCIATIONS
Authors: Karmela Kim Chan, Gregory Vitone, Sara Shanaj, Aidan Tirpack, Jackie Finik, Laura Donlin, Deepak Rao, Caroline Benson, Vivian Bykerk, Dana Orange, Michael Brenner, Susan Goodman, Anne Bass
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Immune checkpoint inhibitors (CI) have revolutionized cancer management, but can also cause immune-related adverse events. Five percent of CI-treated patients develop inflammatory arthritis, but it is poorly defined phenotypically and immunologically. <h3>Objectives</h3> To characterize phenotypes of CI-associated arthritis, and compare cytokine levels in these patients to rheumatoid arthritis (RA) and osteoarthritis (OA) controls. <h3>Methods</h3> Patients referred for CI-associated arthralgia or arthritis were prospectively enrolled in an institutional registry. Serum was collected when patients underwent phlebotomy for a clinical indication. We used a Luminex Human Magnetic Assay to measure levels of IL-1β, IL-2, IL-6, IL-8, IL-10, IL-12, IL-17, IL-22, TNF, IFN-γ, PD-L1, CCL2, CXCL2, CXCL13, OSM, CCL20, GM-CSF, CXCL-11 in CI-treated patients, and in stored serum from 7 RA patients (matched for medication, age, sex, CDAI) and 4 OA patients (age, sex matched). All comparisons were planned a priori. <h3>Results</h3> Thirty-six patients were enrolled 5/1/18-1/25/19. Median [IQR] age was 67[58-78], 18(50%) were female, 14(39%) were smokers and 13(36%) had melanoma. Twenty-two (61%) were on anti-PD1 or PD-L1 monotherapy, and the remainder were on combination CI. Phenotypes included 1. Small joint involvement in 17(47%), 2. Exclusively large joint involvement in 6(17%), 3. Arthralgia without arthritis in 9(25%), and 4. Polymyalgia rheumatica in 4(11%). In all, 7(19%) had concomitant tenosynovitis or enthesitis, mostly accompanying large joint arthritis or arthralgia (6/7). Median CDAI at entry was 11[7-23] and median ESR 29[18-44]. The majority (58%) of patients with the small joint phenotype were RF and/or CCP positive and one had erosive disease, compared to none with the large joint phenotype. ANA positivity was common (74%) and did not vary across phenotypes. Median time of symptom onset was 4[0.8-12] months after CI initiation. Median follow up was 7[3-22] months but only 5(14%) had resolution of arthritis off medication during that period. 22(61%) required CI discontinuation, 5(14%) due to arthritis. 29(81%) required steroids including 15(42%) who required &gt;20mg prednisone. 19(53%) required a synthetic DMARD and 5(14%) required a biologic DMARD. Of 33 patients with known cancer status, 15(45%) had a complete response, 5(15%) a partial response, 5(15%) "stable" disease, 6(18%) progression, and 2(6%) died. Cytokines were measured in 22 patients, who were similar to the cohort as a whole except for more CCP positivity (p=0.02). CI patients with the small joint phenotype had higher levels of IL-6 than RA controls (p=0.04) (Figure 1) and IL-6 levels trended higher in the small joint vs. exclusively large joint phenotype (Figure 2). The B cell chemoattractant CXCL13, a factor produced by T peripheral helper cells in RA synovium<sup>1</sup>, trended higher in the serum of CI patients (Figure 3). Other cytokine levels did not differ significantly in patients with the small joint vs. exclusively large joint phenotype, or in CI-arthritis patients vs. controls. <h3>Conclusion</h3> Half of patients with CI-arthritis present with an RA-like phenotype with small joint involvement and frequent seropositivity, and have elevated levels of IL-6 compared to RA patients. This small joint phenotype may represent an accelerated form of RA. <h3>References</h3> [1] Rao DA, et al. Nature 2017: 542(7639):110-114 <h3>Disclosure of Interests</h3> Karmela Kim Chan Grant/research support from: Roche: sponsored research agreement on stromal cells, Consultant for: GSK: consultant. (I am part of their immunology network, a group of about 8 immunologists who advise them regularly and broadly in the areas of inflammation and infection)., Gregory Vitone: None declared, Sara Shanaj: None declared, Aidan Tirpack: None declared, Jackie Finik: None declared, Laura Donlin: None declared, Deepak Rao Grant/research support from: Merck - Sponsored research project funding support, Consultant for: Janssen - Consultant Scipher Medicine - Consultant Amgen - Scientific advisory board Patent submitted on Tph cells, Caroline Benson: None declared, Vivian Bykerk Grant/research support from: Mallinckrodt, BMS, Crescendo Biosciences, Sanofi/Regeneron., Consultant for: Amgen, Pfizer, UCB, Scipher, Sanofi/Genzyme/Regeneron, Dana Orange Consultant for: Astra Zeneca and Pfizer., Michael Brenner Grant/research support from: Roche: sponsored research agreement on stromal cells (but has nothing to do with checkpoint related disease), Consultant for: GSK: consultant. (I am part of their immunology network, a group of about 8 immunologists who advise them regularly and broadly in the areas of inflammation and infection)., Susan Goodman Grant/research support from: Novartis: research support, Consultant for: Novartis, UCB, Pfizer: consulting, Anne Bass: None declared