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Abatacept and infliximab improve clinical response over time in methotrexate-refractory RA patients

June 16, 2008

Results from the ATTEST Trial

New data presented today at EULAR 2008, the Annual Congress of the European League Against Rheumatism in Paris, France, show that over half of rheumatoid arthritis patients resistant to methotrexate monotherapy improved when either abatacept or infliximab were added to their methotrexate treatment regimen, with positive results sustained up to one year later.

The ATTEST (Abatacept or infliximab versus placebo, a Trial for Tolerability, Efficacy and Safety in Treating RA) trial compared abatacept (~10mg/kg), a selective T cell co-stimulation modulator, with infliximab (3mg/kg), a monoclonal antibody, plus methotrexate (as per each patient's usual dosage, mean dose 16.3-16.6mg) in 431 methotrexate-refractory patients, in a randomised, double-blind, placebo-controlled, 12-month study. Data analyses evaluated the proportion of patients who achieved a 20% improvement in symptoms (as defined by the American College of Rheumatology scale as an ACR20 response) at six months and went on to either improve, maintain or lose this score at twelve months. A similar analysis was conducted in relation to Low Disease Activity Score (LDAS) (DAS28 [CRP] ≤3.2).

ACR Response

Of those patients who achieved an ACR20 response at six months (32 abatacept [ABA] and 27 infliximab [IFX] patients), over a quarter of ABA and IFX patients went on to achieve a 50% improvement (ACR50) at one year (ABA 28.1%, IFX 29.6%). These ACR20 scores were maintained to one year in more ABA than INF patients (95% confidence interval, CI) with over half ABA patients sustained (ABA 59.4%, IFX 44.4%). Furthermore, half as many ABA patients lost their ACR20 score between six months and one year compared to IFX patients (ABA 12.5%, IFX 25.9%).

Low Disease Activity Score

In the LDAS analysis, it was shown that 24 ABA and 23 IFX patients achieved LDAS (but not remission) at six months. Of these patients, over a third ABA (41.7% [22.8, 63.1]) and a quarter IFX patients (28% [12.9, 49.6]) achieved remission at one year. A similar number of ABA (12.5% [3.3, 33.5]) and IFX patients (16% [5.3, 36.9]) retained LDAS to one year, whilst fewer ABA patients (45.8% [26.2, 66.9]) than IFX patients (56% [35.3, 75.0]) lost their LDAS score between six months and one year.

Lead researcher Dr Michael Schiff, of the University of Colorado, USA, commented: "Since RA is a chronic disease, long term treatment efficacy is crucial. Clinical rheumatologists and patients alike need to know the options for maintaining or even increasing treatment responses over time, especially with the growing problem of RA patients becoming refractory, or resistant, to existing treatments. Our study offers significant promise in showing that, where treatment with methotrexate as monotherapy is inadequate, both abatacept and infliximab provide an increasing magnitude of response in measures of RA disease activity, with abatacept yielding slightly higher results across some key ACR and LDAS scores."

European League Against Rheumatism