Background/Purpose: Patients (pts) with non-radiographic axial spondyloarthritis (nr-axSpA) and active disease may have objective evidence of inflammation, either as bone marrow edema (BME) on magnetic resonance imaging (MRI) of the sacroiliac joints (SIJ) or spine, and/or an elevated CRP level. These pts may benefit from adalimumab (ADA) therapy. The objective was to determine whether untreated pts with clinically active disease but initially negative MRI or normal CRP, can develop objective evidence of inflammation and respond to ADA treatment.

Methods

ABILITY-1 was a phase 3, double blind (DB), randomized, controlled trial in pts with nr-axSpA who had an inadequate response, intolerance, or contraindication to NSAIDs. A 12-week (wk) DB period of ADA 40 mg every other wk (eow) or placebo (PBO), was followed by an open-label (OL) period, in which pts could receive ADA 40 mg eow for up to an additional 144 wks. MRI of the spine and SIJ were performed at baseline (BL) and wk 12. A positive MRI (MRI+) was defined as SPARCC MRI score ≥2 in either the SIJ or spine. C-reactive protein (CRP) levels were measured every 4 wks. This post hoc analysis evaluated 1) PBO-treated pts with negative MRI and normal CRP levels at BL, to determine if subsequent evidence of inflammation by MRI or CRP level occurs in untreated pts; and 2) if pts with a positive MRI or elevated CRP subsequent to the BL visit can achieve an ASAS40 response at wk 24, similar to that observed in ADA-treated patients at wk 12.

Results In the DB period, 9/29 (31.0%) of the PBO-treated pts with both a negative MRI of the SIJ and spine at BL, were MRI+ in either the SIJ or spine at wk 12 (table). Of the 57 PBO-treated pts with normal CRP at BL, 14 (24.6%) had elevated CRP at a timepoint between BL and wk 12. 20 PBO-treated pts had a negative MRI of the SIJ and spine and a normal CRP at BL; of these pts 10 (50.0%) had a positive MRI of either the SIJ or spine and/or an elevated CRP at ≥1 post-BL timepoint through wk 12. 5/10 (50.0%) of these pts achieved ASAS40 response at wk 24 (after 12 wks of OL ADA).  

Table. Proportion of PBO patients who had a +MRI and/ or elevated CRP through wk 12, among those who had a –MRI and/or normal CRP at Baseline*
Status at Baseline N	Status at Wk 12 n (%)
Spine MRI – : 43	Spine MRI + : 11 (25.6)
SIJ MRI – : 54	SIJ MRI+ : 5 (9.3)
Spine and SIJ MRI- : 29	Spine or SIJ MRI+: 9 (31.0)
Normal CRP : 57	Elevated CRP : 14 (24.6)
Spine and SIJ MRI- and normal CRP: 20	Spine or SIJ MRI+ and/or elevated CRP: 10 (50.0)
*MRI was repeated at wk 12, CRP was repeated every 4 wks through week 12.

Conclusion

Among PBO-treated pts who did not have objective signs of inflammation at BL, but who demonstrated either a positive MRI or elevated CRP at a later timepoint, 50.0% achieved ASAS40 response after 12 wks of OL ADA treatment (wk 24). Although the sample size is small and higher response rates are expected with OL therapy, this is similar to that observed in the MRI+/elevated CRP ADA-treated population at wk 12 (41.0%).  Thus, patients with clinically active disease but without objective inflammation at one point, may benefit from subsequent re-testing for inflammation, and if present, from initiation of ADA therapy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinically-active-non-radiographic-axial-spondyloarthritis-patients-who-initially-have-a-negative-mri-and-normal-crp-may-develop-a-positive-mri-or-elevated-crp-at-a-later-timepoint/