Clinical RFS by number of RTX courses. In the USTMA retrospective iTTP registry, clinical RFS, defined as time from first RTX dose in the treatment course to CR was longest for the first RTX treatment than subsequent treatment courses (median clinical RFS, 6.0 vs 2.1 years; P = .04). When analyzed separately by race, clinical RFS was shorter with second or subsequent for Black patients but not for White patents with iTTP. RTX indicates RTX. Survival curves are adjusted for age, sex, race, institution, and participant.