A 4-part Phase 1/2 Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of M254 in Healthy Volunteers and in Patients With Immune Thrombocytopenic Purpura

Parts A, B, and C: Number of Participants With Clinically Significant Abnormalities in Clinical Laboratory Values

Time Frame: From Day 1 up to Day 29

Number of participants with clinically significant laboratory abnormalities (chemistry, hematology, urinalysis and coagulation) were reported. Data was planned to be collected and analyzed on pooled population of participants who received placebo in Part A.

Parts A, B, and C: Number of Participants With Treatment-emergent Adverse Events (TEAEs) by Severity

Time Frame: From Day 1 up to Day 29

An AE is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product. A TEAE was defined as any event not present prior to administration of the study drug or any event already present that worsened in either severity or frequency following exposure to the study drug. Severity was graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0. Severity scale ranges from Grade 1 (Mild) to Grade 5 (Death). Grade 1= Mild, Grade 2= Moderate, Grade 3= Severe, Grade 4= Life-threatening, and Grade 5= Death related to adverse event. Data was planned to be collected and analyzed on pooled population of participants who received placebo in Part A. For Parts B and C, treatment period wise AE data were presented.

Parts A, B, and C: Number of Participants With Clinically Significant Abnormalities in Vital Signs

Time Frame: From Day 1 up to Day 29

Number of participants with clinically significant abnormalities in vital signs (blood pressure \[systolic blood pressure {SBP} and diastolic blood pressure {DBP}\], pulse rate, respiratory rate, and body temperature) were reported. Data was planned to be collected and analyzed on pooled population of participants who received placebo in Part A.

Parts A, B, and C: Number of Participants With Clinically Significant Abnormalities in Electrocardiograms (ECGs)

Time Frame: From Day 1 up to Day 29

Number of participants with clinically significant abnormalities in ECGs were reported. Data was planned to be collected and analyzed on pooled population of participants who received placebo in Part A.

Part C: Maximum Observed Response of M254 (Rmax) on Platelet Count

Time Frame: Predose (baseline) up to Day 29 post dose

Rmax is defined as the maximum observed response of M254 on platelet count. Baseline was the pre-dose sample. Data was planned to be collected and analyzed Part C only. For Part C, data were collected and analyzed on the pooled population per the study drug (M254 120 mg/kg and IVIg 1000 mg/kg) which the participants received.

Part C: Change From Baseline in Rmax of M254 in Platelet Count

Time Frame: Predose (baseline) up to Day 29 post dose

Change from baseline in Rmax of M254 in platelet count was reported. Rmax is defined as the maximum observed response of M254. Baseline was the predose sample. Therapeutic platelet count was defined as \>=50\*10\^9 cells/L. Platelet response of \>=20\*10\^9 cells/L was considered as increase from baseline. Data was planned to be collected and analyzed for Part C only. For Part C, data were collected and analyzed on the pooled population per the study drug (M254 120 mg/kg and IVIg 1000 mg/kg) which the participants received.

Part C: Area Under Effect Curve of the Change From Baseline in Platelet Count From Day 0 to Day 28 (AUEC[0-Day 28]) of M254

Time Frame: Predose (baseline) up to Day 29 post dose

AUEC(0-Day 28) is defined as the area under effect curve of the change from baseline in platelet count from Day 0 to Day 28 of M254. Baseline was the predose sample. Data was planned to be collected and analyzed for Part C only. For Part C, data were collected and analyzed on the pooled population per the study drug (M254 120 mg/kg and IVIg 1000 mg/kg) the participants received.

Part C: Area Under Effect Curve of the Change From Baseline in Platelet Count From Day 0 to Day 14 (AUEC[0-Day 14]) of M254

Time Frame: Predose (baseline) up to Day 14 post dose

AUEC(0-Day 14) is defined as the area under effect curve of the change from baseline in platelet count from Day 0 to Day 14 of M254. Baseline was the predose sample. Data was planned to be collected and analyzed for Part C only. For Part C, data were collected and analyzed on the pooled population per the study drug (M254 120 mg/kg and IVIg 1000 mg/kg) which the participants received.