A participant was considered to have a response if the Hgb level increased greater than or equal to (>=) 1.5 gram per deciliter (g/dL) from baseline and this increase was maintained from Week 16 through Week 24 in absence of blood transfusion from Week 5 through Week 24.

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange) Mean change from Baseline to Week 24 in Hemoglobin (Hgb) level.

Percentage of patients who did not receive a blood transfusion between Week 5 and Week 24 was assessed

Number of Patients Achieving Transfusion Avoidance at Week 24

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

FACT-An is used to measure quality of life (QoL) in patients with anemia. Each item is rated on a 5-point Likert scale:0=Not at all, 1=A little bit ,2=Somewhat, 3=Quite a bit, 4=Very much. Some items are reverse scored. Higher scores in this scale denote a better QoL with less impact of anemia.The total FACT-An scale score ranges from 0 to 160. The total score gives a comprehensive view of a patient's well-being. It combines the FACT-G with an Anemia subscale. FACT-G (27 items):Physical Well-Being (PWB) and Social/Family Well-Being (SWB) 14 items in total, Emotional Well-Being (EWB)-6 items,Functional Well-Being (FWB)-7 items, Anemia Subscale (AnS): 13 items. Total FACT-An score=FACT-G + Anemia Subscale=40 item

Part A

Number of blood transfusions received between Week 5 and Week 24 were assessed.

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange) Mean change from baseline to Week 24 in Lactate dehydrogenase (LDH) levels

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from baseline to Week 24 in Haptoglobin level

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from baseline to Week 24 in Indirect bilirubin level

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from baseline to Week 24 in Absolute reticulocyte counts (ARC).

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange) change from baseline to Week 24 in D-dimer levels.

Percentage of patients with LDH level within normal ranges and with an abnormal value at baseline.

Percentage of patients with Indirect Bilirubin level within normal ranges and with an abnormal value at baseline.

Percentage of patients with ARC level within normal ranges and with an abnormal value at baseline.

Percentage of patients with haptoglobin level within normal ranges and with an abnormal value at baseline.

Percentage of patients with haptoglobin level normalization during the initial 24 weeks of the study

Percentage of patients with Hemoglobin level normalization during the initial 24 weeks of the study

Percentage of patients with LDH level normalization during the initial 24 weeks of the study

Percentage of patients with Indirect Bilirubin level normalization during the initial 24 weeks of the study

Percentage of patients with ARC level normalization during the initial 24 weeks of the study

Number of PRBC units transfused from Week 5 and Week 24 was assessed

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

The FACIT-F subscale is used to measure fatigue and its impact upon daily activities and function in patients with chronic illnesses and contains 20 items related to the impact of fatigue. Each item is scored on a 0-4 scale, with some items reverse-scored. Total scores range from 0 to 52, where higher scores indicate less fatigue and better outcomes, and lower scores reflect greater fatigue. It can be used alone or with other FACIT subscales as part of broader quality of life assessments.

Part A

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange.

SF-12 is a 12-item health survey assessing physical and mental health. Higher scores mean better health with scores above 50 indicating better than average health. It produces two summary scores: the Physical Component Summary (PCS) and Mental Component Summary (MCS), both norm-based (mean=50, SD=10), with ranges of ~5-80 (PCS) and ~-3.3-80 (MCS). Higher scores=better health. It also covers 8 subscales-Physical Functioning (PF), Role-Physical (RP), Bodily Pain (BP), General Health (GH), Vitality (VT), Social Functioning (SF), Role-Emotional (RE), and Mental Health (MH), each scored between 0-100, where higher=better functioning. Scores are computed using weighted formulas from item responses (not simple averages).

The EQ-5D-5L measures total health across 5 dimensions: Mobility, Self-care, Usual Activities, Pain/Discomfort, and Anxiety/Depression-each scored from 1 (no problems) to 5 (extreme problems). Scores form a 5-digit health profile (e.g., 12345). Each individual score plus a VAS for perceived health status today are separately reported. Higher scores reflect better total health. The EQ VAS is a patient-rated score from 0 (worst) to 100 (best health).

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from Baseline to Week 48 in Hemoglobin (Hgb) level.

Part B

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from Baseline to Week 48 in LDH level.

Part B

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from Baseline to Week 48 in Haptoglobin level

Part B

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from Baseline to Week 48 in Indirect Bilirubin level.

Part B

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from baseline to Week 48 in Absolute reticulocyte counts (ARC).

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

Mean change from baseline to Week 48 in D-dimer levels.

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug and plasma exchange.

The FACT-An is used to measure quality of life (QoL) in patients with anemia. Each item is rated on a 5-point Likert scale:0=Not at all, 1=A little bit ,2=Somewhat, 3=Quite a bit, 4=Very much.Some items are reverse scored. Higher scores in this scale denote a better QoL with less impact of anemia. The total FACT-An scale score ranges from 0 to 160. The total score gives a comprehensive view of a patient's well-being. It combines the FACT-G with an Anemia subscale.FACT-G (27 items):Physical Well-Being (PWB) and Social/Family Well-Being (SWB) 14 items in total, Emotional Well-Being (EWB)-6 items, Functional Well-Being (FWB)-7 items, Anemia Subscale (AnS): 13 items. Total FACT-An score=FACT-G + Anemia Subscale=40 items

Part B

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

The FACIT-F subscale is used to measure fatigue and its impact upon daily activities and function in patients with chronic illnesses and contains 20 items related to the impact of fatigue. Each item is scored on a 0-4 scale, with some items reverse-scored. Total scores range from 0 to 52, where higher scores indicate less fatigue and better outcomes, and lower scores reflect greater fatigue. It can be used alone or with other FACIT subscales as part of broader quality of life assessments.

Part B

The EQ-5D-5L measures total health across 5 dimensions: Mobility, Self-care, Usual Activities, Pain/Discomfort, and Anxiety/Depression-each scored from 1 (no problems) to 5 (extreme problems). Scores form a 5-digit health profile (e.g., 12345). Each individual score plus a VAS for perceived health status today are separately reported. Higher scores reflect better total health. The EQ VAS is a patient-rated score from 0 (worst) to 100 (best health).

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange).

The ICEs of interest were :

• Withdrawal from treatment or lost to follow-up before the end of the double-blind period
• Use of prohibited medications (rituximab alone or in combination, any other complement inhibitor, any other investigational drug, and plasma exchange SF-12 is a 12-item health survey assessing physical and mental health. Higher scores mean better health with scores above 50 indicating better than average health. It produces two summary scores: the Physical Component Summary (PCS) and Mental Component Summary (MCS), both norm-based (mean = 50, SD =10), with ranges of ~5-80 (PCS) and ~-3.3-80 (MCS). Higher scores = better health. It also covers 8 subscales-Physical Functioning (PF), Role-Physical (RP), Bodily Pain (BP), General Health (GH), Vitality (VT), Social Functioning (SF), Role-Emotional (RE), and Mental Health (MH), each scored between 0-100, where higher=better functioning. Scores are computed using weighted formulas from item responses (not simple averages).