P053 Sub-optimal response to first biologic in axial spondyloarthritis: real world data showing clinician decisions in a tertiary centre
Authors: Gates Emer , Ho May , Cavill Charlotte , Sengupta Raj 
Published: April 2024

Abstract

Background/Aims
Up to 50% of patients respond inadequately to their first biologic treatment for axial spondyloarthritis (axSpA). Whilst NICE advises that if the BASDAI improves by ≤ 2 or ≤ 50% in 12 weeks the treatment should be discontinued, we were interested to assess the real-world application of this, and particularly how clinicians manage sub-optimal response: namely patients whose BASDAI decreases by two points but remains moderately raised above four.

Methods
We retrospectively assessed clinical records of axSpA patients attending the Royal National Hospital for Rheumatic Diseases, Bath who started a biologic for axSpA between 2016 and 2018. Based on their post-biologic BASDAI, patients were divided into excellent-, sub-optimal- (drop of ≥ 2 in the BASDAI but the score remained ≥4) and non-responders.

Results
93 patients were included, of which 55% of patients were male with a mean age of 42 at the time of starting their first biologic. There was a 65:35 split in diagnosis between radiographic and non-radiographic axial spondyloarthritis.
50/93 (54%) patients had an excellent response. 31/93 (33%) patients were non-responders, with post-biologic BASDAI dropping &lt;2 from baseline. Of the non-responders, 13/31 (42%) patients switched or stopped biologic due to primary inefficacy at the first review after an average of 6.4 months, while the remaining 18/31 (58%) patients were kept under review for another 6-12 weeks. 9/18 (50%) improved on average 8.1 months after baseline and met NICE criteria to continue treatment; and 9/18 (50%) switched on average 29.9 months later with primary or secondary inefficacy, almost five times longer than those switched immediately (p=0.0009). 7/13 (54%) who switched due to primary inefficacy switched between anti-TNF and anti-IL-17 classes, whereas all five patients with secondary inefficacy switched between biologic classes. Notably, 19% of poor responders were current smokers compared to 8% of excellent responders (p=0.0004).
The remaining 12/93 (13%) patients were classified as sub-optimal responders. Of these, 5/12 (42%) patients switched to a second anti-TNF after an average 12.4 months. 7/12 (58%) patients continued with their first biologic. Pre-biologic, four patients had high CRPs (≥5mg/L) and eight had normal CRPs (&lt;5mg/L). There was no change between these categories for seven patients who had CRP checked during their sub-optimal response.

Conclusion
Our research shows that clinicians’ decisions with sub-optimal biologic response vary, with a 42:58 split between patients switching or persevering with their biologic treatment. It appears that if patients are going to respond, they should do so within eight months and non-responders should be switched at that point to avoid poor outcomes. Smoking is a known poor prognostic factor which might suggest we should switch sooner with sub-optimal response, but we have been unable to show any benefit of the CRP in guiding management of sub-optimal responders.

Disclosure
E. Gates: None. M. Ho: None. C. Cavill: Honoraria; Abbvie, Eli Lilly, Novartis, Pfizer. R. Sengupta: Honoraria; Abbvie, Biogen, BMS, Eli Lilly, MSD, Novartis, Pfizer, Roche, UCB.