The Efficacy and Safety of Leflunomide in the Treatment of Giant Cell Arteritis: A Protocol for a Systematic Review

BackgroundGiant cell arteritis (GCA) is a type of large vessel vasculitis that causes inflammation, scarring and stenosis in large vessels. Clinical symptoms include headaches, visual changes and myalgias. The standard treatment for GCA consists of glucocorticoid therapy, however long-term use of glucocorticoid therapy poses important health risks. For this reason, there has been a growing interest in exploring other glucocorticoid-sparing therapies, such as leflunomide. The objective of this systematic review is to assess the efficacy and safety of leflunomide in the treatment of GCA. MethodsWe will include studies with adult patients who received leflunomide in the treatment of GCA. We will include randomized controlled trials, cohort studies, case-control studies, and case series. The intervention of interest is the use of leflunomide, which may be initiated at any time over the course of the disease. The comparator is glucocorticoid therapy alone. The primary efficacy outcome is the incidence (proportion) of patients who attain GC-free remission, as defined by the following: 1) absence of signs or symptoms of GCA, and/or 2) normalization of inflammatory markers, and/or 3) radiologic response, and 4) complete discontinuation of GC. Outcomes will be assessed after 1 year of follow-up. Quality appraisal will be performed using the respective risk of bias tools. We will perform a meta-analysis using a random-effects model if the included studies are sufficiently homogenous. For quantitative synthesis, we will employ Cochran-Mantel-Haenszel method with odds ratios as a measure of effect and 95% confidence intervals for our primary endpoint. DiscussionThe challenge in the treatment of GCA is attaining and maintaining disease remission with the least amount of glucocorticoid therapy possible. The only approved glucocorticoid-sparing agent in the treatment of large vessel vasculitis is tocilizumab. Leflunomide is a molecule with similar downstream effects on dendritic cells and cytokines as tocilizumab. Should leflunomide demonstrate similar benefits, it would be a cost-effective, safe, and user-friendly (oral route) option. Systematic review registrationOur systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO, registration number CRD42023490373).