Background Tumour necrosis factor inhibitor (TNFi) therapy is often needed for long periods of time to treat Ankylosing Spondylitis (AS) as attempts to withdraw therapy often leads to disease relapse. However, dose reduction may be possible whilst maintaining good disease control.
Objectives To determine the feasibility of TNFi dose reduction for patients with severe AS in a real world setting.
Methods 125 AS patients were identified from a Biologics Therapy Clinic database. Severe AS was defined as BASDAI>4 on two occasions and poor response to non-steroidal anti-inflammatory drugs (NSAIDs). Using standardised questionnaires, rheumatologists recorded demographics, laboratory results, disease activity, clinical outcomes and biological therapy. Criteria for dose reduction of TNFi was BASDAI <4 (low disease activity) for ≥6 months and patient agreement. TNFi dose was reduced by one-third (Adalimumab 40mg 3 weekly; Etanercept 50mg every 10 days; Infliximab 5mg/kg 3 monthly; Certolizumab 200mg 3 weekly; Golimumab 50mg 6 weekly). Patients were seen 12 weeks after starting therapy, then 24 weekly. Failure of dose reduction was defined as BASDAI >4 or patient-defined disease recurrence. Patients who flared were reviewed urgently and re-escalated to standard treatment dose.
Results All 125 patients had a clinical diagnosis of AS by a consultant rheumatologist; 90% satisfied modified New York criteria for AS, 96% satisfied ASAS criteria for axial spondyloarthritis. 83% were males. 89% were Caucasian. Mean age was 46.4±13.0 years. Mean age of diagnosis was 32.1±11.3 years. Patients were diagnosed with AS for mean of 13.7±11.1 years. 97 of 125 patients had been HLA-B27 tested with 93% (90/97) HLA-B27 positive. 66% were current or ex-smokers. 69%, 19%, 5%, 5% were on their 1st, 2nd, 3rd and 4th biologic respectively. Mean BASDAI prior to TNFi therapy was 7.2±1.5. Biologics used in order of frequency were: adalimumab (56%), etanercept (15%), infliximab (13%), golimumab (10%) and certolizumab (3%). 26% (33/125) fulfilled criteria and had TNFi dose reduction. 58% (19/33) of these maintained TNFi dose reduction for mean of 1.4±0.9 years. Re-instating standard dose TNFi therapy re-captured low disease activity in all patients who failed dose reduction (14/33) within 12 weeks, with no significant difference in mean BASDAI compared to those maintaining TNFi dose reduction (mean BASDAI 2.7±1.3 vs 2.0±2.1 respectively (p=0.238)). Smoking, HLA-B27 status, sex, sacroilitis, age of diagnosis, BASDAI prior to 1st biologic and time from diagnosis to initiation of TNFi were not associated with successful dose reduction.
Conclusions In a real world setting, about 60% of individuals with severe AS who achieve low disease activity, can successfully reduce the dose of TNFi therapy by a third for a mean of 1.4 years. Re-instating standard dose of TNFi therapy in those who fail dose reduction rapidly controls disease activity again.
Disclosure of Interest None declared
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