Pb2499: blinatumomab sequential anti-cd22 car-t cells and hematopoietic stem cell transplantation for successful treatment of b lymphoblastic leukemia extramedullary recurrence: a case report

Topic: 25. Gene therapy, cellular immunotherapy and vaccination - Clinical Background: Extramedullary recurrence is an important cause of treatment failure in patients with B lymphoblastic leukemia(B-ALL). The recurrence is mainly observed in the central nervous system, while cutaneous lymph nodes are rare. Blinatumomab is a prescription medicine used to treat B-ALL in patients who still have detectable traces of cancer after chemotherapy. Chimeric antigen T(CAR-T) cells targeting CD22 has shown to be beneficial treatment effect on refractory/relapsed. Yet, few studies have reported data in the treatment of B-ALL extramedullary recurrence, especially in the skin, with blinatumomab sequential CAR-T cells. Aims: To investigate B-ALL patients with skin recurrence who received sequential allogeneic hematopoietic stem cell transplantation after blinatumomab and anti CD22 CAR-T cell therapy and achieved cytological remission. Methods: A patients with B-ALL who has extramedullary recurrence received sequential allogeneic hematopoietic stem cell transplantation after blinatumomab and anti CD22 CAR-T cell therapy were retrospectively analyzed. Results: The patient of B-ALL with skin recurrence who received sequential allogeneic hematopoietic stem cell transplantation after blinatumomab and anti CD22 CAR-T cell therapy and achieved cytological remission. A 51 old man with co-expression of CD19 and CD22, who used blinatumomab for three consecutive weeks before being transferred to our department. Skin biopsy and flow cytometry showed that CD19 (partially) and CD22 (dim+) were still expressed, which was considered to be involved in B-lymphoblastic lymphoma. After receiving anti-CD22 CAR-T cell therapy and sequential allogeneic hematopoietic stem cell transplantation, no abnormal B lineage primitive cells were found in bone marrow. Summary/Conclusion: Blinatumomab has a good clinical therapeutic effect on CD19 positive T cells in bone marrow, while it cannot remove the extramedullary recurrent leukemia cells which infiltrated in the skin. After sequential anti-CD22 CAR-T cell therapy and bridging hematopoietic stem cell transplantation, which can further remove leukemia cells and improving the patient’s outcome. Trial registration: ChicTr.org.cn number, ChiCTR2200059816, Registered 12 May 2022. Keywords: Allogeneic hematopoietic stem cell transplant, B cell acute lymphoblastic leukemia, CD19, CAR-T