A Study of TAK-079 in Adults With Persistent/Chronic Primary Immune Thrombocytopenia

Primary immune thrombocytopenia (ITP) is a rare disease that results in low levels of platelets - the cells that help blood clot. The main aim of the study is to check for side effects from taking TAK-079 at three different dose levels. Another aim is to learn if TAK-079 can increase the platelet count in people with ITP. In addition to receiving stable background therapy for ITP, participants will receive an injection of either TAK-079 or a placebo once a week for 2 months. A placebo looks like TAK-079 but will not have any medicine in it. After treatment, all participants will be followed-up for another 2 months. Then, participants who received TAK-079 will continue to be followed-up for an extra 4 months. Participants who received the placebo and would like to receive TAK-079 may be able to do this in an extension period in the study.