Enbrel Treatment Leads to Early Reparative Response in Patients with Non-Radiographic Axial Spondyloarthritis

Patients with non-radiographic axial spondyloarthritis (nr-axSpA) treated with Amgen‘s Enbrel (etanercept), which blocks tumor necrosis factor (TNF), experience a very early reparative response to therapy, new research shows.

The study, “Modification of structural lesions on MRI of the sacroiliac joints by etanercept in the EMBARK trial: a 12-week randomised placebo-controlled trial in patients with non-radiographic axial spondyloarthritis,” was published in Annals of Rheumatic Diseases.

Sacroiliitis, an inflammation of one or both of the sacroiliac joints, which are at the connection between the lower spine and the pelvis, is a clinical feature of axSpA that is detected through MRI of the sacroiliac joint (SIJ).

Sacroiliitis leads to structural changes that result from inflammation. It’s characterized by bone erosion in early disease, and sclerosis and ankyloses in later stages. MRIs are able to detect inflammation of this joint soon after the onset of disease and are able to identify structural lesions.

Until now, changes in structural lesions of the SIJ by treatment with anti-TNF have not been shown in any clinical trials of spondyloarthritis patients.

Therefore, researchers analyzed data from EMBARK (NCT01258738), a Phase 3b randomized, double-blind clinical trial to evaluate the safety and efficacy of Enbrel in patients with nr-axSpA.

Patients received either 50 mg a week of Enbrel or placebo for 12 weeks and underwent MRI scans at baseline and after 12 weeks. Researchers analyzed MRIs of the sacroiliac joint and the spine to determine if there were any structural differences.

MRI scans from the 185 study patients studied showed that at the study’s start, there were no significant differences between the mean SPARCC SSS score (a measure of structural lesions) in the placebo group (97 patients) and the group taking Enbrel (88 patients).

After 12 weeks after treatment, however, the mean SPARCC SSS score was significantly higher for the Enbrel group regarding bone erosion and backfill compared to placebo. This indicates that erosion of the bone was significantly reduced in the Enbrel group and backfill (refilling the cavity of the erosion) was significantly higher.

There was also a treatment-dependent difference in patients with SIJ inflammation on the MRI regarding both erosion and backfill. The reduction in erosion and increase in backfill correlated with improved clinical outcomes for patients in the Enbrel group compared to patients receiving the placebo.

“Treatment with [Enbrel] was associated with significantly greater reduction in erosions and increase in backfill at 12 weeks compared with placebo, consistent with a very early reparative response to anti-tumor necrosis factor therapy,” the researchers concluded.

“Understanding the effect of [Enbrel] treatment on new bone formation and maintenance of clinical response beyond two years in this population with early disease requires further study,” they added.