Background/Purpose:  Tumor necrosis factor-alpha (TNF-α) blocking agents are very effective in controlling inflammation and improving clinical assessments in patients with ankylosing spondylitis (AS). In view of the high costs and possible side effects, our aim was to investigate whether dose reduction of TNF-α blocking agents is possible without loss of effectiveness in AS patients in daily clinical practice.

Methods:  Patients included in the Groningen Leeuwarden AS (GLAS) cohort, fulfilling the modified New York criteria for AS, with active disease (Bath AS disease activity index (BASDAI)≥4) before start of anti-TNF-α treatment and stable (≥6 months) low disease activity (BASDAI<4) on conventional dose regime, who started with dose reduction were studied. The dose reduction was patient-tailored and consisted of either lowering the dose or extending the interval between doses. For each specific TNF-α blocking agent, a fixed dose reduction schedule was used and evaluated at each follow up visit and, if necessary, adjusted in response to disease activity, side effects and co-morbidity, Data concerning medication dose, reasons for changing medication dose, and disease activity were collected after 6, 12, 18, and 24 months of dose reduction.

Results:  Between November 2005 and January 2011, 49 AS patients with stable low disease activity started with dose reduction of infliximab (n=8), etanercept (n=35), or adalimumab (n=6). 88% of these patients were male, mean age was 46 years (SD±12), and mean duration of symptoms was 20 years (SD±10). Mean BASDAI was 1.8 (SD±1.1) at start of dose reduction, coming from 6.2 (SD±1.2) just before start of anti-TNF-α treatment.

In total, 71%, 54%, 47%, and 42% of the patients maintained on dose reduction after 6, 12, 18 and 24 months, respectively. The mean dose reduction was 37% (SD±11). Disease activity remained low (BASDAI<4) in 86% of the patients who continued dose reduction at 24 months (Table 1).

Of all 25 patients who did not continue dose reduction, 23 (92%) returned to the conventional dose regime and 2 (8%) patients stopped TNF-α blocking therapy (1 adverse events, 1 inefficacy due to antibody formation).

Conclusion:  In this observational cohort, long-term dose reduction of TNF-α blocking agents was successful preserving stable low disease activity in a substantial number of AS patients.

Table 1. Disease activity in AS patients who maintained dose reduction

	6 months	12 months	18 months	24 months
Patients still on dose reduction	35/49 71%	25/46 54%	21/45 47%	18/43 42%
BASDAI <4	88%	83%	89%	86%

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/patient-tailored-dose-reduction-of-tumor-necrosis-factor-alpha-blocking-agents-in-ankylosing-spondylitis-patients-with-stable-low-disease-activity/