Thrombotic thrombocytopenic purpura (TTP) is a condition where blood clots form in small blood vessels, which can cause serious health problems by blocking oxygen-rich blood from reaching organs. It also uses up platelets, which help blood clot, leading to bleeding and purple bruises (purpura). TTP can cause anemia, where red blood cells break apart faster than they are replaced. The lack of a protein called ADAMTS13, which helps control clotting, causes TTP.

This study tests a medicine called TAK-755 that replaces ADAMTS13 to prevent or control TTP flare-ups. The study checks for side effects of long-term TAK-755 treatment, given either weekly or when a flare-up happens. Participants will be in the study for up to 3 years, receiving treatment at home or a clinic.

Three key points:

• The study lasts up to 3 years with regular clinic visits.
• Treatment can be at home or in a clinic, depending on the group.
• The study checks for side effects of TAK-755 in long-term use.