Background/Purpose: In patients with axial SpA who have achieved partial remission, it is unclear whether continuous treatment with NSAIDs is superior to stopping treatment.

Objectives: To investigate whether continued treatment with naproxen (NPX) was superior to discontinuing all treatment in order to maintain disease control for 6 months in early, active axial SpA patients who were in partial remission after 28 weeks of therapy with either infliximab (IFX)+NPX or placebo (PBO)+NPX.

Methods: Part I of the INFAST study was a double-blind, randomized controlled trial of IFX in biologic-naïve patients 18–48 years of age with early, active axial SpA. Patients were randomized (2:1) to receive 28 weeks of treatment with either IV IFX 5 mg/kg (weeks 0, 2, 6, 12, 18, and 24)+NPX 1000 mg/d or IV PBO+NPX 1000 mg/d. In Part II of INFAST, patients who had achieved ASAS partial remission at week 28 continued in Part II of the study with no IFX treatment. These patients were randomized in a 1:1 ratio to continue on NPX or to stop NPX until week 52. Patients from the 2 treatment arms in Part I were equally balanced over the 2 groups in Part II. The main outcome was the proportion of subjects who maintained ASAS partial remission at week 52. Treatment group differences were analyzed using Fisher exact tests or ANCOVA. Predictors of remission were explored using Cox regression models. A flare was defined as BASDAI ≥30 mm (on a 100 mm VAS) during 2 consecutive visits within 1–3 weeks.

Results: 41 patients were randomized to NPX and 41 to no treatment in Part II of INFAST. 78% of patients in Part II had been in the IFX+NPX arm in Part I. At week 52, similar numbers of patients in the NPX group (19/40, 47.5%) and the no-treatment group (16/40, 40.0%) met the ASAS partial remission criteria, P=0.6525. In regression analyses, patients who received NPX in Part II stayed in remission longer than those who stopped all treatment (HR=0.21, 95% CI: 0.08, 0.52). Initial therapy with IFX+NPX was a significant predictor of the duration of partial remission and sustained remission to week 52. Overall, the group data reflected low disease activity status through week 52 (BASDAI and ASDAS results in Table 1) with a slight, nonsignificant advantage for the NPX group over the no treatment group. The overall low disease activity status was consistent with the low flare rates in both groups (NPX, 1/40, 2.5% vs no treatment, 3/40, 7.5%; P=0.6153).

Table 1. Efficacy Outcomes by Treatment Group

During the follow-up period, 1 serious adverse event was reported in the no-treatment group. No deaths occurred.

Conclusion: In patients with axial SpA who reached partial remission after treatment with either IFX+NPX or NPX alone, disease activity remained low during 6 months in which NPX was maintained or all treatment was discontinued. About half of patients remained in clinical remission for 6 months. A slight advantage may occur for patients continuing NPX treatment vs no treatment at all.