To Assess the Efficacy and Safety of RVT-1401 in the Treatment of Warm Autoimmune Hemolytic Anemia (ASCEND-WAIHA).

Inclusion Criteria: 1. Male or female ≥ 18 years of age. 2. Diagnosis of primary or secondary WAIHA as documented by a positive direct antiglobulin test (DAT) specific for anti-IgG alone or anti-IgG plus C3d. 3. Secondary WAIHA may only include Stage 0 chronic lymphocytic leukemia (CLL) in which separate treatment is not indicated, nor anticipated to require active management for the duration of the study. 4. Have failed or not tolerated at least one prior WAIHA treatment regimen as per local standards (e.g., steroids, rituximab, azathioprine, cyclophosphamide, cyclosporine, mycophenolate mofetil (MMF), danazol, or vincristine). Failure is defined as worsening or refractory disease despite steroids and or immunosuppressants. 5. Participants with splenectomy ≥3 months from Day 1 who are up to date on vaccinations (based on age and local guidance) are allowed. 6. At Screening and Baseline, subject's hemoglobin level must be \<10 g/dL and the subject must have documented symptoms related to anemia (e.g., weakness, dizziness, fatigue, shortness of breath, chest pain). 7. Subject's concurrent treatment for WAIHA may consist only of steroids (stable dose for at least two weeks prior to Day 1), immunosuppressant therapy (azathioprine, MMF, or cyclosporine) that has been at a stable dose for at least four weeks prior to Day 1, or erythropoietin (stable dose for at least 6 weeks prior to Day 1). \[Note: starting doses of WAIHA therapy must be maintained throughout the study except in the case of a rescue medication as per local standards for safety. Steroid taper down to 10 mg/day will be allowed for participants who achieve response for at least 2 weeks.\] 8. A female participant is eligible to participate if she is of: 1. Non-childbearing potential defined as pre-menopausal females with a documented bilateral tubal ligation, bilateral oophorectomy (removal of the ovaries) or hysterectomy; hysteroscopic sterilization, or postmenopausal defined as 12 months of spontaneous amenorrhea. 2. Child-bearing potential and agrees to use one of the contraception methods listed in the protocol for an appropriate period of time (as determined by the product label or Principal Investigator) prior to the start of dosing to sufficiently minimize the risk of pregnancy at that point. Female participants must agree to use contraception until 90 days after the last dose of study treatment. 9. Male participants must agree to use one of the contraception methods listed in the protocol. This criterion must be followed from the time of the first dose of study treatment until 90 days after the last dose of study treatment. 10. Willing and capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form. Other, more specific inclusion criteria are defined in the protocol. Exclusion Criteria: 1. Participants with other types of AIHA (e.g., cold antibody AIHA, cold agglutinin syndrome, mixed type AIHA, or paroxysmal cold hemoglobinuria). 2. Participants requiring more than 2 units of RBC per week in the 2 weeks prior to Screening and Baseline. 3. Use of rituximab, any monoclonal antibody for immunomodulation, or proteasome inhibitor, within the past 3 months prior to Screening. 4. Immunoglobulins given by SC, IV (IVIG), or intramuscular route, or plasmapheresis/plasma exchange (PE) within 60 days before Screening. 5. Total IgG level \<6 g/L (at Screening). 6. Absolute neutrophil count \<1000 cells/mm3(at Screening). Other, more specific exclusion criteria are defined in the protocol.