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

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.