An Open-label Study of Povetacicept (ALPN-303) in Subjects With Autoimmune Cytopenias (RUBY-4)

Summary of Key Inclusion Criteria: Indication-specific Criteria Immune Thrombocytopenia (ITP) Documented primary ITP of at least 12 weeks duration 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 ≤9 g/dL At least one of the following: (i) haptoglobin <LLN (ii) indirect bilirubin >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 ≤9 g/dL At least one of the following: (i) haptoglobin <LLN (ii) indirect bilirubin >ULN (iii) lactate dehydrogenase>ULN History of failure or relapse to at least 2 treatment regimens for CAD (All indications) If receiving standard-of-care medications, doses must be stable for protocol-specified durations Summary of 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, sutimlimab, other marketed biologic therapeutics: 8 weeks 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 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