Overall RFS by number of RTX courses. Overall RFS was defined as a composite of time to CR, ADAMTS13 relapse, or treatment with preemptive RTX. In the combined Johns Hopkins and University of Minnesota prospective registries, overall RFS was longest after the first RTX-treated episode (median, 2.8 years) followed by the second episode (median, 2.0 years), and third and subsequent episodes episode (median, 1.0 year; P = .0001). The shortening of overall RFS was driven mostly by a loss of response durability in Black patients and was not significant in White patients with iTTP. RTX indicates RTX. Survival curves are adjusted for age, sex, race, institution, and participant.