CAR-T Cell Therapy for Acquired Hemophilia A
Authors: Schultze-Florey Christian R , Thol Felicitas R , Stoyanov Kalin , Dobbelstein Christiane , Chill Matthias , Pietzka Sophie , Willerding Jonas , Kharazipour Daniel , Halling Tim , Sikora Ruth , Brüder Nicole , Poll Piroska , Goudeva Lilia , Ivanyi Philipp , Panagiota Victoria , Beutel Gernot , Eder Matthias , Aleksandrova Krasimira , Leise Jana , Klöß Stephan , Arseniev Lubomir , Heidel Florian H. , Tiede Andreas 
Published: December 2024

Anti-CD19 chimeric antigen receptor (CAR)-T cell therapy, initially developed for treatment of B cell malignancies, has shown promise in treating autoimmune diseases by targeting and depleting autoreactive immune cells with subsequent reduction of pathological immune responses. Clinical studies have demonstrated its potential in entities like systemic lupus erythematosus, myasthenia gravis, myositis, systemic sclerosis, multiple sclerosis, and rheumatoid arthritis. Acquired hemophilia A (AHA) is an autoimmune bleeding disorder caused by neutralizing antibodies against coagulation factor VIII (FVIII). Immunosuppressive therapy (IST) is standard of care to eradicate autoantibodies and induce remission of disease. Therapy resistance in AHA presents a significant clinical challenge, characterized by the persistence of bleeding symptoms despite standard treatment protocols. In case of IST failure, patients suffer from chronic AHA with a life-threatening risk of bleeding. CAR-T cell therapy has not been used for the treatment of bleeding disorders so far and none of the available CAR-T products are approved for the use in AHA.

Here, we report to the best of our knowledge the first use of autologous anti-CD19 CAR-T cell therapy in AHA with intractable bleeding that achieved complete remission. AHA had been diagnosed in a 39-year-old male patient following referral from a community hospital in hemorrhagic shock due to massive muscular hemorrhage (iliopsoas). A FVIII inhibitor was detected at 34.6 Bethesda units (BU)/ml that increased during the first days to 534 BU/ml. Sequential lines of IST including the use of dexamethasone, cyclophosphamide, rituximab, mycophenolate mofetil, ciclosporin A, and daratumumab did not result in induction of remission over a period of 10 months. Remarkably, life-threatening bleeding events including subarachnoid and subdural hemorrhage continued to occur despite prophylaxis with the FVIII-mimetic antibody emicizumab, repeatedly necessitating emergency interventions such as transfusions and hemostatic treatment with bypassing agents. Autologous anti-CD19 CAR-T cells were generated on site in our Cellular Therapy Center GMP-Unit using the CliniMACS Prodigy system (Miltenyi Biotec, Germany). Cells were transduced with a self-inactivating lentiviral vector for expression of a second generation (4-1BB co-stimulatory domain) anti-human CD19 CAR. Following lymphodepletion with fludarabine and cyclophosphamide, autologous anti-CD19 CAR-T cells were infused at a dose of 1x106 / kg body weight. IST was stopped prior to CAR-T infusion, while emicizumab was continued. Monitoring was performed on a daily basis for bleeding events, symptoms of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Coagulation tests were performed at least weekly. CAR+ T cells could be detected in peripheral blood with a peak expansion on day 15, followed by a decline over time, persisting at low frequency. Three months post infusion, 0.4/µl CAR+ T cells were detected. Following lymphodepletion, a general drop of leukocytes with rapid recovery by day +22 was observed. Importantly, ANC never dropped below 500/µl. ALC had recovered above &gt;1000/µl by day +63 post CAR-T. Depletion of circulating B cells was persisting with absence of reconstitution at three months follow-up. Following day +41 no further bleeding event occurred. The inhibitor was at 200 BU/ml prior to CAR-T infusion and turned negative on day +63. Complete remission (CR), defined as recovery of FVIII activity to &gt;50 IU/dl, no bleeding, undetectable inhibitor, and cessation FVIII-mimetics, was achieved on day +73 post infusion. At three months follow-up, CR was ongoing with no detectable inhibitor, stable FVIII levels and no new bleeding events since discharge. With regard to safety, the patient did not develop any CRS or ICANS. Moreover, no infections occurred.

In summary, anti-CD19CAR-T cell therapy for treatment of therapy resistant AHA was safe and effective to eradicate autoantibodies against FVIII. On site production facilitated by an experienced GMP-unit and cellular therapy team is a prerequisite for timely intervention to induce remission in an otherwise fatal autoimmune disease.