Allogenic hematopoietic stem cell transplantation for prolonged bone marrow aplasia after chimeric antigen receptor (CAR) T‐cell therapy for relapsed diffuse large B‐cell lymphoma
Authors: Ayman Qasrawi, Ranjana Arora, Reshma Ramlal, Reinhold Munker, Gerhard C. Hildebrandt
Journal: American Journal of Hematology (2020)

To the Editor: Chimeric antigen receptor, or CAR T-cell therapy, is a new immune therapy that is potentially curative for relapsed and refractory diffuse large B-cell lymphoma (DLBCL) and acute lymphoblastic leukemia (ALL). The main toxicities of CAR T-cell therapy are cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Other side effects include temporary cytopenias, infections, elevated liver enzymes and hypogammaglobulinemia.1 Prolonged and persistent cytopenias have been also reported.1, 2 We report a case of severe and persistent bone marrow aplasia after CAR T-cell therapy for relapsed diffuse large B-cell lymphoma, which necessitated an allogeneic hematopoietic stem cell transplantation (allo-HSCT). A 58-year-old male with relapsed DLBCL presented to our center for evaluation of CAR T-cell therapy. He was originally diagnosed with stage IIIB DLBCL, completed six cycles of rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) and achieved a complete response (CR). Six months later, a new abdominal mass was identified and biopsy confirmed recurrent DLBCL. Of note, fluorescence in situ hybridization (FISH) testing was positive for IGH/BCL2 gene rearrangement without BCL6 or c-MYC rearrangements. He was treated with three cycles of rituximab, dexamethasone, cytarabine and cisplatin (R-DHAP), and achieved a partial response (PR) to therapy. Subsequently, the patient was treated with high-dose chemotherapy with carmustine, etoposide, cytarabine and melphalan (BEAM) followed by autologous stem cell (SC) infusion. Unfortunately, positron emission tomography/computed tomography scan (PET/CT 60 days after autologous HSCT showed progressive disease. He was deemed appropriate for CAR T-cell therapy and underwent T-cell apheresis followed by bridging chemotherapy with gemcitabine and oxaliplatin. Pre-CAR-T cell therapy bone marrow biopsy (BMBx) revealed normal cellularity for age (40%) and trilineage hematopoiesis without evidence for lymphoma. He subsequently underwent lymphodepleting chemotherapy with fludarabine and cyclophosphamide (FC), and was treated with axicabtagene ciloleucel (axi-cel) with a cell dose of 2 × 106 anti-CD19 CAR-T cells/kg. The treatment was complicated by transient grade II CRS and grade III ICANS which responded to tocilizumab and steroids. The PET/CT on day 30 after CAR-T cell therapy showed near complete metabolic resolution of activity, consistent with Lugano III response. However, the patient had persistent pancytopenia with hemoglobin ranging between 6 and 9 g/dL and platelets <50 × 109/L and he required intermittent blood and platelet transfusions. Absolute neutrophil count (ANC) fluctuated and filgrastim was given for severe and very severe neutropenia. BMBx on day 80 after CAR-T showed severely hypocellular marrow (<5% cellularity), markedly decreased hematopoietic elements and no evidence of lymphoma. Cytogenetics were normal and next generation sequencing (NGS) showed the presence of ASXL1 Gln780Ter nonsense mutation with <1% allele frequency. No cryopreserved autologous SCs were available for rescue.3 Trial of eltrombopag failed to improve platelet counts and he ultimately needed iron chelation. He continued to be in remission from his lymphoma and a repeat BMBx on day 315 showed identical findings. Neutrophils response to filgrastim was only marginal and the patient developed pulmonary Nocardiosis, which was successfully treated. Furthermore, his transfusion dependency worsened and his responses to both platelet and red blood cell transfusions progressively shortened. A 10/10 matched unrelated donor was identified. His pre-transplant imaging showed no evidence of lymphoma; BMBx on day 416, again, revealed severe trilineage hypoplasia (<5% cellularity) and cytogenetics were normal. Interestingly, NGS identified the presence of ASXL1 Gln780Ter nonsense mutation, which expanded rapidly from an allelic ratio of less than 1% on day 80 to 24.5% on day 416 BMBx post-CAR-T cell therapy. Given his history of high transfusion needs due to persistent bone marrow aplasia and the possibility of evolving myelodysplasia (MDS), it was decided to proceed with allo-HSCT. Conditioning chemotherapy consisted of fludarabine, total dose of 90 mg/m2, and total body irradiation (TBI) 300 cGy. A total of 6.12 × 106 CD34+ cells/kg were given to the patient on day 428 after his CAR-T cell therapy. His post-transplant course was uncomplicated, and he engrafted neutrophils and platelets on day T+ 20. Peripheral blood unsorted chimerism studies on T+ 32 revealed 100% donor engraftment. Figure 1 shows the trend of ANC platelets after CAR-T cell therapy. Figure S1 (supplementary material) shows the core bone marrow biopsies obtained 38 days before and 416 days after CAR-T cell therapy. In the landmark ZUMA-1 trial, 17% of patients who were treated with axi-cel had grade III or worse cytopenias at 3 months or later; including 11% neutropenia, 3% anemia and 7% thrombocytopenia. None of these patients had major bleeding or needed an allogenic transplantation.1 In the phase I/II trial utilizing tisagenlecleucel in ALL, 37% of patients had persistent cytopenias by day 28, including 16% grade IV. However, there was only one patient who had persistent neutropenia >8 weeks after infusion.4 Outside clinical trials, persistent neutropenia, anemia and thrombocytopenia for at least 28 days after CAR-T cell therapy was seen in 9%, 72% and 65%, respectively. Median time to neutrophil, hemoglobin and platelets recovery were 11, 76 and 60 days, respectively.2 Similar findings were reported in another study.5 In addition, bone marrow failure developing after CAR-T cell therapy for multiple myeloma that was successfully treated with cryopreserved autologous stem cells 35 days post-CAR cells was reported.3 The pathophysiology underlying prolonged cytopenias is unclear.1 Low platelet count at the first day of lymphodepleting chemotherapy has been suggested as an indicator of low stem cell reserve and a predictor for persistent cytopenias after axi-cel.5 Our patient was cytopenic at the time of FC administration, but that could be explained by recent bridging chemotherapy rather than low stem cell reserve, as he had a normal BMBx prior to his last line of chemotherapy. The FC combination is known to cause cytopenias that could persist for months after treatment. However, cytopenias after CAR T-cell infusion have been reported even without lymphodepleting chemotherapy; which suggests that CAR-T cells may cause myelosuppression, possibly because of a cytokine mediated or another immune-mediated mechanism.6 Finally, it is well known that FC has been associated with the later development of MDS. Early onset MDS is one possibility in our patient, given the emergence and expansion of ASXL1 mutation in his post-CAR-T cell therapy bone marrow biopsies. Given severe hypoplasia, morphologic assessment for dysplasia was impossible. It is noted from Figure 1 that his neutropenia worsened in the last weeks prior to his transplant. This coincides with the expansion of ASXL1 mutation. Therefore, a new clonal evolution is also a possibility and its significance would become clear in further follow up molecular studies. Our patient engrafted after allogenic transplantation with resolution of his cytopenias. To our knowledge, this is the first reported case of bone marrow failure after CAR-T cell therapy which necessitated an allogenic transplantation. Long-term follow-up and further research are needed to study the risk factors and incidence of bone marrow failure after CAR-T cell therapy and the role of allogenic transplantation in its management. AQ, RA, RR, RM have nothing to disclose and declare no conflicts of interest. GCH reports equity ownership from Sangamo Bioscience, Celgene/Juno, Kite Pharmaceuticals, Novartis, Insys Therapeutics, AbbVie, GW Pharmaceuticals, Cardinal Health, Immunomedics, Endocyte, Clovis Oncology, Cellectis, Aetna, CVS Health, Celgene, Bluebird Bio, Bristol-Myers Squibb/Medarex, Crispr Therapeutics, IDEXX Laboratories, Johnson & Johnson, Pfizer, Procter & Gamble, Vertex, and Jazz Pharmaceuticals, consultancy from Pfizer, Kite Pharmaceuticals, Incyte, and Jazz Pharmaceuticals, research funding from Takeda, Jazz Pharmaceuticals, and Pharmacyclin, travel, accommodations, or expenses from Kite Pharmaceuticals, Incyte, Pfizer, Falk Foundation, Jazz Pharmaceuticals, and Astellas. AQ wrote and edited the manuscript and designed the images. RA provided the pathology images, wrote the pathology findings, revised and edited the manuscript. RR, RM and GCH revised and edited the manuscript. All the authors have read final version of the manuscript and have approved this submission. Figure S1. A and B, Core bone marrow biopsy (BMBx) obtained 38 days prior to CAR-T cell therapy showing normocellular marrow. C and D, Core BMBx obtained 416 days after CAR-T cell therapy showing extremely hypocellular marrow. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.