Placebo administered as intravenous infusion

The FACIT-Fatigue is a self-administered 13-item questionnaire that assess patient-reported fatigue associated with chronic illness therapy. It assesses both the physical and functional consequences of fatigue. Each question is answered on a 5-point scale, where 0 means "not at all," and 4 means "very much." The FACIT-Fatigue scale score ranges from 0 to 52, with higher scores denoting lower levels of fatigue. A positive change from baseline score indicates an improvement.

Change from baseline in average daily dose of prednisone or equivalent at week 24 among participants on prednisone or equivalent at baseline will be reported.

Percentage of participants who achieve the durable response in improvement of Hgb during the double-blind period and maintain that response for up to 24 weeks, without the need of rescue therapy will be reported.

The FACIT-Fatigue scale is a 13-item self-administered questionnaire that assesses both the physical and functional consequences of fatigue. Each question is answered on a 5-point scale, where 0 means "not at all," and 4 means "very much." The FACIT-Fatigue scale score ranges from 0 to 52, with higher scores denoting lower levels of fatigue. A positive change from baseline score indicates an improvement.

The EQ-5D-5L quality of life questionnaire will be used to assess health related quality of life status. The 5 dimensions are mobility, self-care, usual activities, pain/discomfort, and anxiety/depression; each dimension is rated by the patient on a 5 level scale (no problems, slight problems, moderate problems, severe problems, extreme problems).

The SF-36v2 will be used to assess general quality of life. The 36 items on the SF-36 health survey encompass the following 8 domains: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. The 8 domains can be aggregated into 2 summary scales that reflect physical and mental health: a physical component summary (PCS) and a mental component summary (MCS). Responses to all items are rated on a 3-, 5- or 6-point Likert scale. Higher scores indicate a higher level of functioning. A positive change from baseline score indicates an improvement.

The PGIS will be used to assess the severity of warm autoimmune hemolytic anemia (wAIHA) fatigue symptoms. The PGIS is a 5-point response scale. Participant will be asked to rate their fatigue over the past 7 days using the following 5-point scale: 1 = None, 2 = Mild, 3 = Moderate, 4 = Severe, and 5 = Very severe.

The PGIC will assess if there has been an improvement or decline in patient-reported status since the beginning of the treatment. The PGIC is a 7-point response scale. Participants will be asked to rate their current fatigue as compared to when they started the study, using the following 7-point scale: 1 = Much better, 2 = Moderately better, 3 = A little better, 4 = No change, 5 = A little worse, 6 = Moderately worse, and 7 = Much worse.

It will be estimated using a model-based longitudinal analysis of Hgb/hemolysis parameters in relationship to IgG level and dose regimen.

Absolute change from baseline in average daily dose of prednisone or equivalent at Week 24 among all participants will be reported.

Percentage of participants who achieve corticosteroid reduction to <= 7.5 mg/day of oral prednisone (or equivalent) at Week 24 of the double-blind period, among participants with prednisone or equivalent >7.5 mg/day at baseline will be reported.