An Open-label Study of Povetacicept in Participants With Autoimmune Cytopenias (RUBY-4)

Key Inclusion Criteria:

• Indication-specific Criteria

• Immune Thrombocytopenia (ITP)

• Documented persistent or chronic primary ITP of at least 12 weeks duration from diagnosis to Cycle 1 Day 1
• History of failure or relapse to at least 2 treatment regimens for ITP
• History of exposure to a TPO-RA unless otherwise contraindicated or unavailable
• Documented history of platelets <30 × 10^9/L
• Warm Autoimmune Hemolytic Anemia (wAIHA)

• Diagnosis of primary wAIHA of at least 12 weeks duration documented with a current or prior positive direct antiglobulin test (DAT) for anti-IgG (±C3d)
• Documented history of anemia with hemoglobin ≤10 g/dL
• At least one of the following: (i) haptoglobin < lower limit of normal (LLN) (ii) indirect bilirubin > upper limit of normal (ULN) (iii) lactate dehydrogenase>ULN
• History of failure or relapse to at least 2 treatment regimens for wAIHA
• Cold Agglutinin Disease (CAD)

• Diagnosis of primary CAD of at least 12 weeks duration with all of the following: (i) chronic hemolysis (ii) polyspecific DAT positive (iii) monospecific DAT strongly positive for C3d (iv) cold agglutinin titer ≥64 at 4°C (v) IgG DAT ≤1+ (vi) no overt malignant disease
• Documented history of anemia with hemoglobin ≤10 g/dL
• Evidence of hemolysis during screening: (i) indirect bilirubin

>ULN and (ii) lactate dehydrogenase>ULN or haptoglobin <LLN

• History of failure or relapse to at least 1 treatment regimen for CAD
• (All indications) If receiving protocol-specified standard-of-care medications, doses must be stable for protocol-specified durations

Key Exclusion Criteria:

• Secondary AIHA, CAD, or ITP
• Treatment with any of the following within the noted period prior to study entry

• rituximab: <12 weeks
• IVIg: <4 weeks
• sutimlimab, any use after initiation of screening is exclusionary
• plasmapheresis, plasma exchange, or double-filtration plasmapheresis: <8 weeks
• transfusions with blood, blood products or other rescue medications: <2 weeks
• splenectomy: <12 weeks
• other immunomodulatory or investigational agents, except for investigational agents for COVID-19 that have been granted emergency use authorization or approved by the applicable national health authority: <5 half-lives and requires agreement of the Medical Monitor
• Recent serious or ongoing infection; risk or history of serious infection Other protocol defined Inclusion/Exclusion criteria may apply.