Patients with rheumatoid arthritis receiving abatacept showed an increasing magnitude of clinical response between months 6 and 12, Dr. Michael Schiff reported.
In RA, it's important to evaluate efficacy not only at the group level—mean changes that occur in a group as a whole over time—but also at the individual level, and to measure changes in a patient's response over time, Dr. Schiff said in a press conference at the annual European Congress of Rheumatology.
In a post-hoc analysis of ATTEST (Abatacept or infliximab versus placebo, a Trial for Tolerability, Efficacy and Safety in Treating RA), patients who achieved an ACR 20 at 6 months were reevaluated at 12 months to determine whether they further improved, retained, or lost their response.
The larger ATTEST trial, sponsored by Bristol-Myers Squibb Co., included 431 patients who had an inadequate response to methotrexate, and randomized them to abatacept, approximately 10 mg/kg every 4 weeks; infliximab, 3 mg/kg every 8 weeks; or placebo. They also were on background methotrexate, 10-30 mg/week.
At baseline, patients' mean age was 49 years and mean disease duration was 8 years. The majority were women. Mean number of swollen joints was 20, mean number of tender joints was 30, and mean disease activity score (DAS) 28 was 6.4.
At month 6, a total of 32 patients receiving abatacept and 27 patients receiving infliximab had achieved an ACR 20 response, though not ACR 50 or ARC 70 responses. The responses in this subgroup of patients were then analyzed at 12 months.
A similar percentage of patients receiving abatacept and infliximab achieved at least an ACR 50 response at 1 year. A total of 28.1% of patients on abatacept and 29.6% of patients on infliximab continued to improve to this degree, a clinically significant response, said Dr. Schiff, a clinical professor of medicine in the rheumatology division, University of Colorado, Denver.
The proportion of patients who maintained an ACR 20 response at 1 year was 59.4% for abatacept and 44.4% for infliximab, while the proportions who lost their ACR 20 response at 1 year were 12.5% and 25.9%, respectively.
Among the 24 patients treated with abatacept who achieved a low disease activity score (DAS28 below 3.2) at 6 months, 41.7% went on to clinical remission (DAS28 below 2.6) at 1 year. Among the 25 patients treated with infliximab who achieved a low disease activity score at 6 months, 28% went on to remission at 1 year.
A total of 12.5% and 16% of the abatacept- and infliximab-treated patients retained their low disease activity score at 1 year, while 45.8% and 56% lost this response by 1 year.
“These findings highlight the importance of examining clinical benefits at the level of the individual patient,” Dr. Schiff wrote in a poster. “Abatacept has the potential to provide clinical benefits to patients that increase in magnitude over time.”
Dr. Schiff has received research grants and consulting fees from Bristol-Myers Squibb and Centocor.