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

Key Inclusion Criteria: 1. Indication-specific Criteria 1. 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 2. 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 3. 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 2. (All indications) If receiving protocol-specified standard-of-care medications, doses must be stable for protocol-specified durations Key Exclusion Criteria: 1. Secondary AIHA, CAD, or ITP 2. Treatment with any of the following within the noted period prior to study entry 1. rituximab: \<12 weeks 2. IVIg: \<4 weeks 3. sutimlimab, any use after initiation of screening is exclusionary 4. plasmapheresis, plasma exchange, or double-filtration plasmapheresis: \<8 weeks 5. transfusions with blood, blood products or other rescue medications: \<2 weeks 6. splenectomy: \<12 weeks 7. 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 3. Recent serious or ongoing infection; risk or history of serious infection Other protocol defined Inclusion/Exclusion criteria may apply.