Background/Purpose: Few studies have evaluated changes in active inflammation of spine and sacroiliac (SI) joints by MRI during long-term treatment for axial SpA, and no data are available comparing TNF-blockers with NSAIDs.

Objectives: To determine whether combination infliximab (IFX)+NSAID therapy is superior to NSAID monotherapy for improvement in inflammatory lesions in patients with early, active axial SpA who were naïve to NSAIDs or treated with a submaximal dose of NSAIDs and  to measure changes in lesions during follow-up with either NPX or no treatment in patients who achieved ASAS partial remission.

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 (<3 years symptom duration), active axial SpA with signs of active sacroiliitis on MRI. 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 with no IFX treatment and were randomized (1:1 ratio) to continue on NPX or to stop NPX until week 52. MRIs of spine and SI joints at baseline, week 28, and week 52 were used to assess active, inflammatory lesions. Group differences were analyzed descriptively or using Fisher exact tests.

Results: ASAS partial remission at week 28, the primary outcome, was achieved by more patients treated with IFX+NPX (61.9%) than PBO+NPX (35.3%), P=0.0021. At week 52, similar percentages of patients in the NPX and no-treatment groups maintained partial remission (47.5 vs 40%). 88% of patients had readable MRIs showing active SI lesions at baseline; 59% had spine lesions. A change from presence at baseline to complete absence of lesions at week 28 occurred more often with IFX+NPX than PBO+NPX for the SI joint (21.9% vs 3.9%, P=0.0043) and spine plus SI joints (16.2% vs 0%, P=0.0016), but not for spine alone (29.5% vs 15.7%, P=0.0764). In Part II, no treatment group differences were observed on these measures. Scores from Part I and II are shown in Table 1 and Table 2, respectively.

Table 1. MRI Scores in Part I

Table 2. MRI Scores in Part II (Patients in ASAS Partial Remission at Week 28)

The safety profile was consistent with that of other anti-TNF biologics.

Conclusion: Patients with early, active axial SpA who were treated with IFX+NPX had greater MRI improvement and a greater percentage achieved MRI remission than patients treated with NPX alone. During follow-up, no differences were observed in MRI measures for patients who received NPX vs no treatment.