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.