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.

The drug being tested in this study is called TAK-079. TAK-079 is being tested to treat people who have primary immune thrombocytopenia (ITP). This study will evaluate the safety and biologic activity of TAK-079 or matching placebo in combination with stable ITP background therapy. The study will enroll approximately 36 to 54 participants. In Part A of the study, participants will be randomly assigned (by chance, like flipping a coin) to one of the three treatment groups. Those who received placebo in this period will have the choice to receive TAK-079 after a safety follow-up period and will be randomized to one of the two open-label TAK-079 treatment arms. An unblinded safety review will take place once a minimum of 24 evaluable participants are available for analysis in Part A to decide whether to open enrollment into Part B. In Part B participants will be randomly assigned to one of two treatment groups. Those who received placebo in this period will have the choice to receive study drug after a safety follow-up period in a single open-label TAK-079 treatment arm. This multi-center trial will be conducted worldwide. All participants will be followed for at least 8 weeks in a Safety Follow-up Period, and a 16-week Long-term Follow-up Period after the 8 weeks of treatment.