To the Editors:

The SLE Responder Index (SRI) was originally devised to comport with the Food and Drug Administration Guidance Document published for lupus clinical trials, and regulatory authorities accepted it as the primary outcome of 2 large phase III belimumab trials. We agree that more results than just the SRI need to be provided to understand the full impact of the intervention(s). Although we are not suggesting that the SRI be adopted as a universal metric for all SLE therapeutics, the subsequent successes of the 2 phase III studies, which collectively enrolled 1,684 patients, support consideration of its use in similarly designed studies.

Daniel J. Wallace MD*, Richard A. Furie MD†, William W. Freimuth MD, PhD‡, * Cedars-Sinai Medical Center, University of California, Los Angeles, CA, † North Shore-Long Island Jewish Health System, Lake Success, NY, ‡ Human Genome Sciences, Rockville, MD.