Critères d'inclusion : 1.12 years of age or older, at the time of signing the informed consent form (ICF)
2.participants who received HSCT within the past 6 months at the time of Screening
3.A TMA diagnosis, based on all of the following criteria occurring simultaneously:
• De novo thrombocytopenia or platelet transfusion refractoriness
• De novo anemia or increase in transfusion requirements
• Either one of the following markers of hemolysis
− LDH > 1.5 × ULN or,
− Presence of schistocytes ≥ 2 high power field (HPF)
• Proteinuria on spot urinalysis
• Presence of hypertension
4.Participants must have HSCT-TMA that persists despite initial management of any triggering condition (persists for at least 72 hours after management of triggering agent/condition)
• Withdrawal or dose reduction of the offending agent (eg, CNIs)
• Treatment of any underlying infection
• Treatment of underlying GVHD
5.Participants must be vaccinated against meningococcal infections if clinically feasible, according to institutional guidelines for immune reconstitution after HSCT. Participants < 18 years of age must be re-vaccinated against Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae if clinically feasible, according to institutional guidelines for immune reconstitution after HSCT. All participants should be administered coverage with prophylactic antibiotics according to institutional posttransplant infection prophylaxis guidances including coverage against N. meningiditis for at least 2 weeks after meningococcal vaccination. Participants who cannot receive meningococcal vaccine should receive antibiotic prophylaxis coverage against N. meningiditis the entire Treatment Period and for 8 months following the final dose of ravulizumab
6.Male or female
Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.
7.Capable of giving signed informed consent or assent which includes compliance with the requirements and restrictions listed in the informed consent and in this protocol
Critères de non-inclusion : 1.Known familial or acquired ‘a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13’ (ADAMTS13) deficiency (activity < 5%) .
2.Known Shiga toxin-related hemolytic uremic syndrome (ST-HUS)
3.Positive direct Coombs test
4.Diagnosis or suspicion of disseminated intravascular coagulation (DIC)
5.Known bone marrow/graft failure
6.Diagnosis of veno-occlusive disease (VOD), regardless of severity
7.Human immunodeficiency virus (HIV) infection (evidenced by HIV-1 or HIV-2 antibody titer,
8.Unresolved meningococcal disease
9.Presence or suspicion of sepsis (treated or untreated) within 7 days prior to Screening
10.Pregnancy or breastfeeding
11.Hypersensitivity to murine proteins or to 1 of the excipients of ravulizumab
12.Previously or currently treated with a complement inhibitor