This clinical trial is focused on studying a condition called Thrombotic Microangiopathy (TMA), which can occur after a Hematopoietic Stem Cell Transplant (HSCT). TMA is a serious condition that affects the small blood vessels and can lead to complications such as low platelet counts, anemia, and organ damage. The study is testing a treatment called Ravulizumab, which is given as an infusion into a vein. This treatment is being compared to a placebo to see how effective it is in treating TMA in adults and adolescents who have undergone HSCT.

The purpose of the study is to assess how well Ravulizumab works in treating TMA. Participants in the study will receive either Ravulizumab or a placebo. The study will last for several months, during which participants will receive regular infusions and have their health monitored closely. The study aims to see if Ravulizumab can help improve symptoms of TMA and prevent further complications.

Throughout the study, participants will be monitored for changes in their health, including any improvements in organ function and overall survival. The study will also track how quickly participants respond to the treatment and if there are any relapses of TMA. This research is important for finding better ways to treat TMA in patients who have had a stem cell transplant.