Background/Purpose: In patients with ankylosing spondylitis (AS), TNF-α inhibitors influence the course of serum bone turnover markers (BTM), favoring an increase in mineralization during the first years¹. Little is known about the effect of IL-17 inhibitors on these serum BTM levels. Objective of this study was to evaluate serum markers of bone resorption, formation, and mineralization during 1 year of secukinumab treatment in AS patients in daily clinical practice.

Methods: Included were consecutive outpatients from the GLAS cohort with a clinical diagnosis of AS who started treatment with secukinumab between April 2016 and June 2020, and had available serum samples at ≥1 visit. Standardized follow-up visits were performed at baseline (before start of secukinumab) and after 3 or 6 months and 1 year of treatment. BTM were measured in serum: osteocalcin (OC; regulation marker), serum type 1 collagen C-telopeptide (sCTX; collagen resorption marker), procollagen type 1 N-terminal peptide (PINP; collagen formation marker) and bone-specific alkaline phosphatase (BALP; bone mineralization marker). BTM Z-scores were calculated using a healthy reference population to correct for the normal influence of age and gender. Patients using bisphosphonates were excluded from analyses. Data was coded missing if patients experienced a fracture or received systemic corticosteroids within 1 year of a study visit. Generalized estimating equations were used to analyze BTM Z-scores over time within patients.

Results: In total, data of 26 AS patients were eligible for analyses; 50% were male, mean age was 46.0±14.6 years, 81% were HLA-B27 positive, mean ASDAS at baseline was 3.7±1.0, and 50% was TNFi naïve. Before secukinumab treatment, median PINP and BALP Z-scores were +0.6 and +0.7 SD, respectively, compared to age and gender matched healthy controls, however, the large majority remained within the normal range of ±2 SD. Overall, BTM Z-scores of OC, sCTX, PINP and BALP did not change significantly compared to baseline during the 1st year of secukinumab treatment (Figure 1).

Conclusion: In daily clinical practice, serum BTM levels including mineralization corrected for the normal influence of age and gender did not change during the 1^st year of secukinumab treatment in patients with AS. Our data confirm recent findings of stable BTM levels at group level during 2 years of secukinumab treatment in posthoc analysis of MEASURE 1².

References:
1:Arends et al. Arthritis Res Ther. 2012;14(2):R98
2: Braun et al. BMC Musculoskelet Disord 22, 1037 (2021

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/no-change-in-serum-levels-of-bone-turnover-markers-corrected-for-age-and-gender-during-the-first-year-of-secukinumab-treatment-in-patients-with-ankylosing-spondylitis/