Murine allogeneic CAR T cells integrated before or early after posttransplant cyclophosphamide exert antitumor effects

• Published in: Blood Vol. 141; no. 6; pp. 659 - 672
• Main Authors: Patterson, Michael T., Khan, Shanzay M., Nunes, Natalia S., Fletcher, Rochelle E., Bian, Jing, Hadjis, Ashley D., Eckhaus, Michael A., Mendu, Suresh K., de Paula Pohl, Alessandra, Venzon, David J., Choo-Wosoba, Hyoyoung, Ishii, Kazusa, Qin, Haiying, Fry, Terry J., Cam, Maggie, Kanakry, Christopher G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.02.2023; The American Society of Hematology
• Subjects: Animals; CD4-Positive T-Lymphocytes - pathology; Cyclophosphamide - pharmacology; Cyclophosphamide - therapeutic use; Graft vs Host Disease; Hematopoietic Stem Cell Transplantation - adverse effects; Humans; Leukemia - drug therapy; Mice; Transplantation
• ISSN: 0006-4971; 1528-0020; 1528-0020
• DOI: 10.1182/blood.2022016660

•Murine allogeneic anti-CD19 CAR T cells integrated before or early after PTCy for allo-HCT can clear leukemia without added toxicity.•Clinical translation of this approach would combine the activity of both CAR T cells and polyclonal alloreactive T cells to reduce relapse. [Display omitted] Relapse limits the therapeutic efficacy both of chimeric antigen receptor (CAR) T cells and allogeneic hematopoietic cell transplantation (allo-HCT). Patients may undergo these therapies sequentially to prevent or treat relapsed malignancy. However, direct integration of the 2 therapies has been avoided over concerns for potential induction of graft-versus-host disease (GVHD) by allogeneic CAR T cells. We have shown in murine T-cell-replete MHC-haploidentical allo-HCT that suppressive mechanisms induced immediately after posttransplant cyclophosphamide (PTCy), given on days +3/+4, prevent GVHD induction by alloreactive T cells infused as early as day +5. Therefore, we hypothesized that allogeneic CAR T cells given in a similarly integrated manner in our murine MHC-haploidentical allo-HCT model may safely exert antitumor effects. Indeed, allogeneic anti-CD19 CAR T cells given early after (day +5) PTCy or even prior to (day 0) PTCy cleared leukemia without exacerbating the cytokine release syndrome occurring from the MHC-haploidentical allo-HCT or interfering with PTCy-mediated GVHD prevention. Meanwhile, CAR T-cell treatment on day +9 or day +14 was safe but less effective, suggesting a limited therapeutic window. CAR T cells infused before PTCy were not eliminated, but surviving CAR T cells continued to proliferate highly and expand despite PTCy. In comparison with infusion on day +5, CAR T-cell infusion on day 0 demonstrated superior clinical efficacy associated with earlier CAR T-cell expansion, higher phenotypic CAR T-cell activation, less CD4+CD25+Foxp3+ CAR T-cell recovery, and transcriptional changes suggesting increased activation of CD4+ CAR T cells and more cytotoxic CD8+ CAR T cells. This study provides mechanistic insight into PTCy’s impact on graft-versus-tumor immunity and describes novel approaches to integrate CAR T cells and allo-HCT that may compensate for deficiencies of each individual approach. Little is known about how to optimally sequence allogeneic stem cell transplants (allo-HCT) and CAR T-cell therapy. Using murine models, Patterson et al demonstrate that allo-HCT with posttransplantation cyclophosphamide can be combined effectively with allogeneic CD19 CAR T-cell treatment. The authors highlight that CAR T cells given just before or shortly after cyclophosphamide graft-versus-host disease prophylaxis exert stronger antileukemic effects than CAR T cells administered later, suggesting a strategy to leverage the complementary antileukemic effects of polyclonal alloreactive T cells and antigen-specific CAR T cells.