Abatacept for lupus nephritis: alternative definitions of complete response support conflicting conclusions.

OBJECTIVE Recent clinical trials in lupus nephritis have all used different criteria to assess complete response. The objective of this analysis was to compare several previously proposed criteria, using the same data set from a large trial of abatacept in lupus nephritis (IM101075). In so doing, we sought to determine which criteria are most sensitive to differences among treatment groups and to further examine the potential of abatacept in lupus nephritis. METHODS Patients in the IM101075 trial received abatacept at 1 of 2 different dose regimens or placebo, both on a background of mycophenolate mofetil and corticosteroids. Using data from this trial, we assessed rates of complete response at 12 months according to 5 sets of criteria, from 1) the trial protocol, 2) the Aspreva Lupus Management Study (ALMS) trial of mycophenolate mofetil, 3) the Lupus Nephritis Assessment with Rituximab (LUNAR) trial of rituximab, 4) an ongoing National Institutes of Health trial of abatacept (Abatacept and Cyclophosphamide Combination: Efficacy and Safety Study [ACCESS]), and 5) published recommendations of the American College of Rheumatology. RESULTS According to the complete response definition from the IM101075 study protocol, there was no difference among treatment groups in the IM101075 study. In contrast, according to the ALMS, LUNAR, and ACCESS criteria, rates of complete response among patients in the IM101075 study were higher in both treatment groups relative to control. The largest differences were obtained with use of the LUNAR criteria (complete response rate of 6% in the control group, compared to 22% and 24% in the 2 abatacept groups). CONCLUSION The choice of definition of complete response can determine whether a lupus nephritis trial is interpreted as a success or a failure. The results of this analysis provide an evidence-based rationale for choosing among alternative definitions and offer a strong rationale for conducting further studies of abatacept in lupus nephritis.