A Study of TAK-755 (rADAMTS13) With Little to No Plasma Exchange (PEX) Treatment in Adults With Immune-mediated Thrombotic Thrombocytopenic Purpura (iTTP)

Part 1: Achievement of Clinical Response Without On-Study Plasma Exchange (PEX)

Clinical response is defined as normalization of platelets and no clinical evidence of new or progressive ischemic organ injury. Normalization of platelets: First occurrence of normal platelet count (greater than or equal to \[\>=\]150,000/microliter \[mcL\]) that is followed by a confirmatory platelet count of \>=150,000/mcL and a lactate dehydrogenase (LDH) \<1.5×upper limit of normal (ULN) at 48±12 hours after the first occurrence.

Time frame: Through study completion, approximately 12 weeks

Part 2: Achievement of Platelet Response Without On-Study Plasma Exchange (PEX)

Platelet response is defined as first occurrence of normal platelet count (\>=150,000/mcL) that is followed by a confirmatory platelet count of \>=150,000/mcL at 48±12 hours after the first occurrence.

Time frame: Through study completion, approximately 12 weeks

Part 1: Achievement of Clinical Response With Zero or Minimal on-Study PEX

The number of PEX administered considered Zero when no PEX is administered and considered Minimal when 1 to 3 PEX are administered.

Time frame: Through study completion, approximately 12 weeks

Part 2: Achievement of Platelet Response With Zero or Minimal on-Study PEX

The number of PEX administered considered Zero when no PEX is administered and considered Minimal when 1 to 3 PEX are administered.

Time frame: Through study completion, approximately 12 weeks

Part 1: Achievement of Clinical Response Overall

Overall indicates clinical response regardless of whether on-study PEX is administered, or the number of PEX administered.

Time frame: Through study completion, approximately 12 weeks

Part 2: Achievement of Platelet Response Overall

Overall indicates platelet response regardless of whether on-study PEX is administered, or the number of PEX administered.

Time frame: Through study completion, approximately 12 weeks

Part 1: Time to Clinical Response (Acute Phase)

Time frame: Through study completion, approximately 12 weeks

Part 2: Time to Platelet Response (Acute Phase)

Time frame: Through study completion, approximately 12 weeks

Part 1: Occurrence of Refractoriness (Acute Phase)

Time frame: Through study completion, approximately 12 weeks

Part 1: Time to First On-Study PEX in Participants who Achieved Clinical Response

Time frame: Through study completion, approximately 12 weeks

Part 2: Time to First On-Study PEX in Participants who Achieved Platelet Response

Time frame: Through study completion, approximately 12 weeks

Part 1: Number of Days of On-study PEX in Participants to Achieve Clinical Response (Acute Phase)

Time frame: Through study completion, approximately 12 weeks

Part 2: Number of Days of On-study PEX in Participants to Achieve Platelet Response (Acute Phase)

Time frame: Through study completion, approximately 12 weeks

Part 1: Total Volume of Plasma Administered (Acute Phase) to Achieve Clinical Response

Time frame: Through study completion, approximately 12 weeks

Part 2: Total Volume of Plasma Administered (Acute Phase) to Achieve Platelet Response

Time frame: Through study completion, approximately 12 weeks

Part 1: Occurrence of Treatment Failure

Treatment failure is defined as failure to achieve clinical response, or experience iTTP recurrence.

Time frame: Through study completion, approximately 12 weeks

Part 2: Occurrence of Treatment Failure

Treatment failure is defined as failure to achieve platelet response, or experience iTTP recurrence.

Time frame: Through study completion, approximately 12 weeks

Part 1: Occurrence of Immune-Mediated Thrombotic Thrombocytopenic Purpura (iTTP) Recurrence (Following Clinical Response), Exacerbation, or Relapse (Post-acute Phase)

iTTP recurrence comprised of exacerbation or relapse. Clinical exacerbation: Occurs \<30 days after achieving initial clinical response (i.e., before clinical remission) and recurrent thrombocytopenia (platelet levels \<150,000/μL), with or without clinical evidence of new or progressive ischemic organ damage, requiring daily PEX or rescue therapy. Clinical relapses: Occurs \>=30 days after achieving initial clinical response (i.e., after clinical remission) and recurrent thrombocytopenia (platelet levels \<150,000/μL), with or without clinical evidence of new or progressive ischemic organ damage, requiring daily PEX or rescue therapy.

Time frame: Through study completion, approximately 12 weeks

Part 2: Occurrence of iTTP Recurrence (Following Platelet Response), Exacerbation, or Relapse (Post-acute Phase)

iTTP recurrence comprised of exacerbation or relapse. Clinical exacerbation: Occurs \<30 days after achieving initial platelet response (i.e., before clinical remission) and recurrent thrombocytopenia (platelet levels \<150,000/μL), with or without clinical evidence of new or progressive ischemic organ damage, requiring daily PEX or rescue therapy. Clinical relapses: Occurs \>=30 days after achieving initial platelet response (i.e., after clinical remission) and recurrent thrombocytopenia (platelet levels \<150,000/μL), with or without clinical evidence of new or progressive ischemic organ damage, requiring daily PEX or rescue therapy.

Time frame: Through study completion, approximately 12 weeks

Part 1: Time to iTTP Recurrence (Following Clinical Response), Exacerbation, or Relapse

Time frame: Through study completion, approximately 12 weeks

Part 2: Time to iTTP Recurrence (Following Platelet Response), Exacerbation, or Relapse

Time frame: Through study completion, approximately 12 weeks

Part 1: Occurrence of Any One of the Following Events: Clinical Recurrence (Following Clinical Response), iTTP-Related Death, or Major Thrombotic Event From Time of First IP Administration Through Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 2: Occurrence of Any One of the Following Events: Clinical Recurrence (Following Platelet Response), iTTP-Related Death, or Major Thrombotic Event From Time of First IP Administration Through Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 1: Time to Occurrence of Any One of the Following Events: Clinical Recurrence (Following Clinical Response), iTTP-Related Death, or Major Thrombotic Event From Time of First IP Administration Through Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 2: Time to Occurrence of Any One of the Following Events: Clinical Recurrence (Following Platelet Response), iTTP-Related Death, or Major Thrombotic Event From Time of First IP Administration Through Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 1: Change From Baseline in Lactate Dehydrogenase [LDH] Levels at Clinical Response and Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 2: Change From Baseline in LDH Levels at Platelet Response and Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 1: Change From Baseline in Troponin Levels at Clinical Response and Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 2: Change From Baseline in Troponin Levels at Platelet Response and Study Completion

Time frame: Through study completion, approximately 12 weeks

Part 1: Achievement of Clinical Remission

Clinical remission is defined as achieving clinical response and no recurrence for \>=30 days.

Time frame: Through study completion, approximately 12 weeks

Part 2: Achievement of Clinical Remission

Clinical remission is defined as achieving platelet response and no recurrence for \>=30 days.

Time frame: Through study completion, approximately 12 weeks

Part 1 and 2: A Disintegrin and Metalloproteinase With Thrombospondin Motifs 13 (ADAMTS13) Antigen Level Resulting From TAK-755 Administration in Acute and Post-Acute Phases

Time frame: Through study completion, approximately 12 weeks

Part 1 and 2: ADAMTS13 Activity Level Resulting From TAK-755 Administration in Acute and Post-Acute Phases

Time frame: Through study completion, approximately 12 weeks

Part 1: Von Willebrand Factor (VWF) Antigen Level Resulting From TAK-755 Administration in Acute and Post-Acute Phases

Time frame: Through study completion, approximately 12 weeks

Part 1: VWF Activity Level Resulting From TAK-755 Administration in Acute and Post-Acute Phases

Time frame: Through study completion, approximately 12 weeks