Clinical Research Directory

Key Inclusion Criteria (Part 1 and Part 2) 1. Participant must provide a signed informed consent form. A fully recognized proxy may be used per local laws for participants unable to provide consent. 2. Participant is 18 years or older at time of screening. 3. Participant has been diagnosed with de novo or relapsed iTTP. 4. Participant must be willing to fully comply with study procedures and requirements. 5. Female participants of childbearing potential must present with a negative pregnancy test and agree to employ highly effective birth control measures for duration of study. Sexually active male participants must agree to use an effective method of contraception for the duration of the study. Key Exclusion Criteria (Part 1 and Part 2) 1. Participant has received more than 2 pre-study PEX prior to randomization in Part 1 or first dose of investigational product in Part 2. 2. Participant has been diagnosed with cTTP or another cause of thrombotic microangiopathy (TMA). 3. Participant has been exposed to another investigational product within 30 days prior to enrollment or is scheduled to participate in another clinical study involving investigational product or investigational device during the course of the study. 4. Participant has received caplacizumab within 30 days prior to study enrollment. 5. Participant has had a previous iTTP event within the past 30 days. 6. Participant is positive for human immunodeficiency virus (HIV) with unstable disease or cluster of differentiation (CD)4+ count ≤200 cells/mm\^3 within 3 months of screening. 7. Participant has condition of severe immunodeficiency. 8. Participant has a severe systemic acute infection. 9. Participant has another underlying progressive fatal disease and/or life expectancy \<3 months. 10. Participant is identified by the investigator as being unable or unwilling to cooperate with study procedures. 11. Participant is pregnant or lactating. 12. Participant has any condition in which methylprednisolone or other steroid equivalent is contraindicated as per prescribing information. 13. Participant has known life-threatening hypersensitivity reaction, including anaphylaxis, to the parent molecule ADAMTS13, Chinese hamster ovary (CHO) cell proteins, or other constituents of TAK-755.