Objective: Patients may cease therapy with anti-tumour necrosis factor (TNF) agents due to inefficacy at 12 weeks (termed primary non-response) or later. Until now, the extent of this later secondary non-response has not been clearly defined. We followed-up a substantial single-centre cohort to determine kinetics of this secondary loss of response. The licensed dose of 3 mg/kg was used throughout.

Methods: Prospective data collection since anti-TNF therapy introduction in 1999 formed the basis of the analysis. Patients with rheumatoid arthritis who received infliximab as their first biologic agent, with at least 2 yrs follow-up were included. All relevant clinical data to calculate DAS-28 score and EULAR response were collected at 3, 6, 9, 12, 18 and 24 months. Reasons for cessation in those patients achieving a EULAR response at 3 months (secondary failures) were determined.

Results: Of a total of 309 patients commenced on infliximab, 290 received this as their first biologic agent.; 195 commenced > or = 2 yrs ago. Efficacy data to identify EULAR responders at 3 months was available in 174 patients. Sixty-seven per cent achieved a 'moderate' or 'good' EULAR response; 25% failed to achieve a response, 8% developed toxicity within the first 12 weeks. Of the primary responders, over 55% subsequently ceased therapy in the first year, the predominant reason was a secondary loss of response; other reasons included high disease activity despite achieving a definable response, toxicity, and intercurrent illness. Subsequent loss of response in the second year was less pronounced.

Conclusions: This study of patients treated in clinical practice with infliximab demonstrated that secondary non-response occurred in around half the patients in the first year. The data highlight the need to continue development of other therapies as well as investigation of the underlying causes of this loss of response.