Autoimmune hemolytic anemia (AIHA) is a rare and heterogeneous disorder characterized by the destruction of red blood cells through warm or cold antibodies. Glucocorticoid (combined with rituximab) is the first-line treatment.

However, the recurrence rate is very high and some patients may not respond to steroids. Second-line therapies include cyclosporine A (CsA), cyclophosphamide, rituximab, azathioprine, and even splenectomy.

Bruton's tyrosine kinase (BTK) plays a crucial role in the signaling pathway of B-cell receptor (BCR), and has been found to be a major source of pathogenic signal transduction for various lymphoproliferative malignancies. The activity of BTK is related to the occurrence and progression of various B-cell lymphomas. Currently, BTK inhibitors are widely used in the treatment of B-cell lymphomas, including chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), Waldenstrom's macroglobulinemia (WM), and other B-cell lymphomas, showing significant efficacy. BTK affects the production of messenger molecules and regulates the BCR signaling pathway, causing B cells to transform into self-reactive B cells, which can trigger autoimmune diseases. Current research has shown that BTK activity increases in several autoimmune diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) . Therefore, BTK inhibitors (BTKi) are important for the treatment of autoimmune diseases.

Ibrutinib, one kind of BTKi, has been proven to treat secondary autoimmune hemolytic anemia (AIHA) in CLL and control CLL progression, and is an effective drug for treating lymphoma-associated AIHA . One kind of second-generation selective BTKi, acalabrutinib, can also reduce the incidence of AIHA in relapsed or refractory CLL patients. Currently, phase-II clinical studies exploring the treatment of AIHA using Ibrutinib, acalabrutinib, and rilzabrutinib, another BTKi, are underway.

Zanubrutinib (BGB-3111, Brukinsa®, BeiGene) is a second-generation irreversible BTKi developed by Chinese company BeiGene. Compared to Ibrutinib, zanubrutinib has shown stronger effective activity and higher selectivity towards BTK, and weaker effects on other targets such as TEC, EGFR, and Src families, with low off-target side effects. Its efficacy, durability, oral absorption, and targeting are better than those of Ibrutinib. Zanubrutinib is approved for the treatment of various B-cell lymphomas, and clinical trials have shown excellent efficacy and tolerability in CLL and WM patients. In previously treated CLL patients, zanubrutinib exhibits better efficacy and safety than Ibrutinib. Currently, phase II clinical studies of zanubrutinib in ITP, antiphospholipid syndrome, IgG4-related immune diseases, and active proliferative lupus nephritis are underway. The therapeutic effect of zanubrutinib on refractory warm autoimmune hemolytic anemia, is worth exploring through exploratory research.

Inclusion Criteria:

1. Age ≥18 years.
2. Confirmed diagnosis of wAIHA or Evans syndrome, primary or secondary to connective tissue disease. If it is secondary, there are no other treatment indications for systemic involvement of primary connective tissue disease.
3. No response or relapse after glucocorticoid treatment.
4. Baseline liver and kidney function (ALT, AST, Cr) is less than 2 times the normal range.
5. Consent to sign the informed consent form.

Exclusion Criteria:

1. Other important organ involvement in connective tissue disease.
2. Uncontrolled infection or bleeding with standard treatment.
3. Active HIV, HCV or HBV infection uncontrolled with standard treatment.
4. Concurrent uncontrolled advanced malignant tumors or lymphoma.
5. The subject is receiving any of the following drugs and has not met the following conditions of stable drug treatment duration at a fixed dose during screening: corticosteroids for at least 4 weeks; iron, vitamin B12 or folic acid for at least 4 weeks;
6. Liver cirrhosis or portal hypertension.
7. Pregnant or lactating women.
8. Participation in other clinical trials within the last 3 months.