Partial remission in ankylosing spondylitis and non-radiographic axial spondyloarthritis in treatment with infliximab plus naproxen or naproxen alone: associations between partial remission and baseline disease characteristics

Objectives. To evaluate partial remission during treatment with infliximab (IFX) + naproxen (NPX) vs NPX alone in patients from the two subgroups of SpA and explore baseline predictors of partial remission. Methods. Infliximab as First Line Therapy in Patients with Early Active Axial Spondyloarthritis Trial was a double-blind, randomised controlled trial of IFX in biologic-naïve patients with early, active axial SpA. Patients were randomised (2:1) to receive 28 weeks of treatment with i.v. IFX 5 mg/kg (weeks 0, 2, 6, 12, 18 and 24) + NPX 1000 mg/day or i.v. placebo (PBO) + NPX 1000 mg/day. The current post hoc analysis evaluated outcomes in patients who did or did not meet modified New York radiographic criteria for AS. Results. The analysis included 94 patients who met AS criteria and 56 with non-radiographic axial SpA (nr-axSpA). At week 28, Assessment of SpondyloArthritis international Society (ASAS) partial remission was greater with IFX + NPX than PBO + NPX for both the AS group (70.5 vs 33.3%, respectively) and the nr-axSpA group (50.0 vs 37.5%, respectively). A similar pattern occurred with several efficacy measures. Larger treatment effects occurred in the AS group than the nr-axSpA group, possibly due to baseline differences in disease characteristics. Multivariable analyses identified the type of treatment, age and HLA-B27 status as predictors of ASAS partial remission in the total study population. MRI sacroiliac joint scores were associated with partial remission during IFX + NPX treatment. Conclusion. Patients with AS had greater partial remission with IFX + NSAID than NSAID therapy alone; patients with nr-axSpA had a smaller treatment effect. Baseline disease characteristics and age were associated with partial remission with IFX therapy.