Background: Modern biologic therapies have demonstrated encouraging results in the treatment of axial spondylarthropathy (AxSpA). The benefits of interleukin-17 inhibitors (IL-17i), as first and second line therapies, are well established [1, 2]. A systematic literature review by Navarro-Compán has shown some benefit of second line therapies using both anti-tumour necrosis factor (anti-TNF) and IL-17i [3]. To our knowledge, there are currently no studies that have directly compared which pathway has a better overall outcome. This is therefore the first observational study directly comparing both treatment arms after anti-TNF had been administered as first line therapy.

Objectives: To investigate which second line therapy is superior, anti TNF or IL-17i (secukinumab), in patients with AxSpA, that have failed first line anti-TNF therapy.

Methods: Patient data was extracted from the Whipps Cross Hospital Rheumatology biologics registry database. All patients selected were required to have a diagnosis of AxSpA on magnetic resonance imaging (MRI). The patient cohort that was selected had previously been treated with anti-TNF as a first line therapy and were being considered for second line therapy with either anti-TNF or IL-17i. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores were recorded at 3, 6 and 12 months to assess treatment response. The unpaired t-test was used to assess the significance between the treatment groups and were analysed using the R statistical package.

Results: Seventy patients were identified for this study of which, 57% (46/70) were male and 37% (26/70) were female. The age ranged from 30-97 years, with an average age of 72. The HLA-B27 gene association in this cohort was 71% (50/70). Three patients out of the cohort had psoriatic spondylarthropathy and the remaining had isolated AxSpA. There were an equal number of secukinumab and anti-TNF patients. The anti-TNF patients were subdivided into their respective anti-TNF drug (listed in Table 1 ).

This study revealed that the patients experienced an average of a 52% reduction in the BASDAI score after 6 months of anti-TNF treatment compared to only a 6% reduction in patients on secukinumab (P 0.009). However, the disease activity improvement at 12 months was not sustained in the anti-TNF group and at this stage there was no difference between the groups. Overall both treatment groups showed an average reduction in the BASDAI score by more than 30% at each 3 monthly interval.

Figure 1.

BASDAI percentage reduction at 3 monthly intervals between the two second line treatment groups using anti-TNF and Secukinumab.

Conclusion: A significant difference could not be demonstrated between the anti-TNF and secukinumab groups in this observational cohort. Interestingly, at 6 months, anti-TNF demonstrated better outcomes according to BASDAI scores than Secukinumab but this efficacy was lost at 12 months. It was difficult to interpret these isolated results without further testing, as this is a small non-randomised study. We observed similar outcomes to the Navarro-Compán review where there was a low percentage change in the BASDAI improvement in patients on second line therapy when compared to first line treatment BASDAI scores. Therefore, exploring the mechanism for the reduction in the BASDAI response would be an interesting future study. Moreover, to fully understand these results, randomised controlled studies would need to be conducted.

REFERENCES:

[1]Baeten el al. NEJM 2015.

[2]van der Heijde et al. ARD 2018.

[3]Navarro-Compán et al. RMD Open 2017.

Disclosure of Interests: None declared