Pragmatic, open-label, multicentre, randomised controlled trial to guide initial therapy for immune checkpoint inhibitor-induced inflammatory arthritis comparing standard of care (prednisolone) to adalimumab without glucocorticoids: REACT trial protocol.

introductionImmune checkpoint inhibitors (ICIs) have revolutionised cancer treatment through targeted disruption of the physiological pathways that maintain tissue tolerance, but which are co-opted by cancers to evade immunosurveillance. Thus, the resultant T-cell activity often causes immune-related adverse events including immune checkpoint inhibitor-induced inflammatory arthritis (ICI-IA). ICI-IA results in functional impairment that frequently persists, even after ICI discontinuation, with substantial quality-of-life impacts for cancer survivors.A high-quality body of evidence to guide ICI-IA management remains an unmet need. Pharmacological treatment may be prolonged, typically begins with non-specific immunosuppression, including systemic steroids, and is usually only rationalised to more targeted therapy in resistant cases. Moreover, retrospective data suggest the high dose glucocorticoids sometimes used in new-onset ICI-IA may be associated with worse cancer outcomes.Tumour necrosis factor (TNF) inhibition strategies are well established with excellent efficacy and safety profiles in 'spontaneous' inflammatory arthritides including rheumatoid and psoriatic arthritis. Mechanistic evidence from ex vivo and murine studies also supports the utility of anti-TNF therapy for steroid-refractory cases of ICI-IA. Although good clinical responses have been reported in this setting, the REACT trial (REmission induction of Arthritis caused by Cancer ImmunoTherapy) aims to provide randomised and robust clinical evidence for deploying targeted therapy earlier in ICI-IA management. It will test whether up-front anti-TNF therapy can more effectively and quickly control symptoms, reduce glucocorticoid exposure, prevent early ICI discontinuation and increase the frequency of drug-free ICI-IA remission. METHODS AND ANALYSIS: REACT is a prospective, multicentre, open-label, superiority, two-arm, randomised controlled clinical trial to guide initial therapy for patients with ICI-IA. The trial will compare the current standard of care (initial prednisolone; Arm A) with the anti-TNF drug, adalimumab without glucocorticoids (Arm B).The primary outcome is glucocorticoid-free arthritis remission rate at 24 weeks where remission is defined as: (i) No use of systemic or intra-articular glucocorticoids (except when used for adrenal insufficiency) within 4 weeks prior to assessment at 24 weeks; and (ii) absence of synovitis on clinical examination. ETHICS AND DISSEMINATION: The protocol was approved by East Midlands-Leicester South Research Ethics Committee on 31-Oct-2024 (Ref: 24/EM/0202). Participants are required to provide written informed consent. The results of this trial will be disseminated through national and international presentations and peer-reviewed publications. TRIAL REGISTRATION NUMBER: ISRCTN18217497.