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.

Inclusion criteria

• Diagnosed with ITP that has persisted for ≥3 months, diagnosed in accordance to The American Society of Hematology 2011 Evidence-based Practice Guideline for Immune Thrombocytopenia or the International Consensus Report on The Investigation and Management of Primary Immune Thrombocytopenia as locally applicable.
• Has a mean platelet count of <30,000/μL (and individually ≤35,000/μL) on at least 2 measurements at least 1 week apart during screening.
• Diagnosis of ITP supported by a prior response to an ITP therapy (other than a thrombopoietin receptor agonists [TPO-RA]) that achieved a platelet count of ≥50,000/μL.
• If receiving standard background treatment for ITP, treatment should be stable in dose and frequency for at least 4 weeks before dosing.

• Permitted standard background treatments may include: 1 oral corticosteroid; ±1 immunosuppressant from the following list: azathioprine, danazol, dapsone, cyclosporine, mycophenolate mofetil, mycophenolate sodium; ±1 TPO-RA (romiplostim, eltrombopag, avatrombopag); ±fostamatinib. Corticosteroids, including dexamethasone, must be given as oral, daily or every-other-day therapy as opposed to pulse therapy.
• The dose of any permitted standard background therapy must be expected to remain stable through the study, unless dose reduction is required because of toxicities.

Exclusion criteria

• Use of anticoagulants or any drug with antiplatelet effect (such as aspirin) within 3 weeks before screening.
• Has a history of any thrombotic or embolic event within 12 months before screening.
• Has a history of splenectomy within 3 months before screening.
• Use of intravenous immunoglobulin (IVIg), subcutaneous immunoglobulin or anti-D immunoglobulin treatment within 4 weeks of screening, or an expectation that any therapy besides the participant's standard background therapies may be used for treatment of thrombocytopenia (e.g., a rescue therapy) between screening and dosing.
• Diagnosed with chronic obstructive pulmonary disease (COPD) or asthma, and a prebronchodilatory forced expiratory volume in 1 second (FEV1) <50% of predicted normal.
• Use of rituximab or any monoclonal antibody (mAb) for immunomodulation within 4 months before first dosing. Note: Participants with prior exposure to rituximab must have cluster of differentiation (CD) 19 counts within the normal range at screening.
• Use of immunosuppressants (such as cyclophosphamide, vincristine) other than permitted oral immunosuppressants within 6 months before first dosing.
• Has been diagnosed with myelodysplastic syndrome.
• Has received a live vaccine within 4 weeks before screening or has any live vaccine planned during the study.

10 Has had an opportunistic infection ≤12 weeks before initial study dosing or is currently undergoing treatment for a chronic opportunistic infection, such as tuberculosis (TB), pneumocystis pneumonia, cytomegalovirus, herpes simplex virus, herpes zoster, or atypical mycobacteria.