This is a parallel-group, Phase 3, double-blind, 2-arm study to investigate the efficacy, safety, PK and PD of oral rilzabrutinib in achieving durable Hb response (DHR) compared with placebo in approximately 90 male and female participants ≥ 18 years of age with a confirmed diagnosis of primary wAIHA.

Following a 4-week screening period, eligible participants will be randomized in a 2:1 ratio to receive rilzabrutinib or placebo in primary analysis period (PAP) for a duration of up to 24 weeks. All participants who completed PAP will then continue in open-label period (OLP) to receive rilzabrutinib for a duration of 28 weeks. Upon the completion of OLP, only participants who demonstrate Hb increase during the last 8 weeks of OLP per specified criteria in the protocol will be eligible to continue in long-term extension (LTE) of the study. The duration of the LTE period will be from the first-participant-in (FPI)-LTE until the last participant completes 52 weeks in LTE. The safety follow-up period of this study following treatment completion or discontinuation will be 2 weeks.

Inclusion Criteria:

• Male and female participants with a documented (confirmed) diagnosis of primary wAIHA for at least 6 months.
• Participants who have previously failed to maintain a sustained response after treatment with CS (CS-resistance [defined as failure to obtain hemoglobin response within 3 weeks on at least 1 mg/kg or 60 mg prednisone or equivalent per day], CS-dependent wAIHA [defined as need to continue on prednisone or equivalent at a dose of >10 mg/day to maintain a response]), or are intolerant or ineligible to CS (defined as with contraindications, pre-existing medical conditions or CS-related complications that may render CS intolerant or ineligible per the best clinical judgement of the investigators).
• Participants with Eastern Cooperative Oncology Group (ECOG) performance status Grade 2 or lower.
• Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

Exclusion Criteria:

• Participants with clinically significant medical history or ongoing chronic illness that would jeopardize the safety of the participant or compromise the quality of the data derived from his or her participation in the study as determined by the Investigator.
• Participants with medical history of lymphoma, leukemia, or any malignancy within the past 5 years except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for the past 3 years.
• Participants with symptomatic herpes zoster within 3 months prior to screening.
• Participants with mixed wAIHA, or secondary wAIHA from any cause including drugs, Evans Syndrome, lymphoproliferative disorders (low count monoclonal B-cell lymphocytosis is allowed), infectious or autoimmune disease, or active hematologic malignancies. Participants with positive antinuclear antibodies but without a definitive diagnosis of an autoimmune disease are allowed.
• Participants with history of myelodysplastic syndrome.
• Participants with uncontrolled or active HBV infection or Active HCV infection.
• HIV infection.
• Participants with history of solid organ transplant.
• Participants with a history of active or latent tuberculosis (TB).
• Splenectomy within 12 weeks before screening and planned surgery during the PAP.
• Concurrent treatment with other experimental/investigational drugs within 30 days or 5 half-lives, whichever is longer, prior to treatment start. Participants who previously received treatment with BTK inhibitors for wAIHA before Day 1 (randomization) are not eligible.
• Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that, in the opinion of the Investigator, contraindicates participation in the study.

The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org