Hydroxychloroquine is a safe and effective steroid-sparing agent for immune checkpoint inhibitor-induced inflammatory arthritis.

Immunotherapy for cancer treatment continues to evolve, and immune checkpoints have proven successful therapeutic targets. With success has come the challenge of managing the commonly associated immune-related toxicities. Arthralgias and arthritis are a common immune-related adverse event (IrAE), well described in the literature (Pardoll Nat Rev Cancer 12:252-264, 2012; Diesendruck and Benhar Drug Resist Updat 30:39-47, 2017; Cappelli et al. Arthritis Care Res 69:1751-1763, 2017; Brahmer et al. J Clin Oncol 36:1714-1768, 2018; Smith and Bass (2017). The optimal management of immune checkpoint inhibitor (ICI)-induced arthritis remains unclear. We describe the first series using hydroxychloroquine as a first-line disease-modifying antirheumatic drug (DMARD) for patients without pre-existing autoimmune disease, who developed arthritis secondary to ICI's. This was a single-center retrospective observational study reporting all patients evaluated by rheumatologists affiliated with the University of Alberta, a large tertiary health care center in Northern Alberta, Canada, deemed to have inflammatory arthritis (IA) following ICIs. We identified 11 patients, without pre-existing autoimmune disease, who developed IA following ICIs. Most patients presented with a symmetrical polyarthritis with both large and small joint involvement. All patients were treated according to the outlined treatment protocol with hydroxychloroquine as a first-line steroid-sparing agent: either as monotherapy or in combination with tapering doses of systemic corticosteroids (3) or intra-articular steroid injections (6). One patient required the addition of methotrexate to control symptoms and none required biologic therapy. There were no reported adverse effects from hydroxychloroquine. Inflammatory arthritis is an important complication of ICIs leading to significant impact on patient quality of life. In our experience, in patients without pre-existing autoimmune disease, hydroxychloroquine is an effective first-line therapy for IA secondary to ICI therapy.