CD19-Targeted T Cells Rapidly Induce Molecular Remissions in Adults with Chemotherapy-Refractory Acute Lymphoblastic Leukemia

Five adults with chemotherapy-refractory B-ALL were induced into molecular remissions after treatment with CD19 CAR-targeted T cells. CARving a Niche for Cancer Immunotherapy Acute lymphoblastic leukemia (ALL) is a cancer of the white blood cells that fend off infection. It’s most common in children but—as with many diseases that primarily affect children—has a much worse prognosis when it affects adults. Adults with relapsed disease have a very low chance of survival, and new therapies are desperately needed. Now, Brentjens et al. test T cells engineered to target CD19, which is expressed on both healthy B lymphocytes and B-ALL cells, in five chemotherapy-refractory adult B-ALL patients. Here, the authors treat patients with the patients’ own T cells altered to express not only CD19 but also a fusion of the costimulatory molecule CD28 with CD3ζ chain—so-called “second-generation chimeric antigen receptor (CAR) T cells. ” All patients treated with these cells achieved tumor eradication and complete remission. These CAR T cells were well tolerated, although there was substantial cytokine release in some patients that correlated to tumor burden. These patients were treated with steroid therapy. Long-term follow-up in four of these patients was not possible because the CAR T cell therapy allowed these patients to be eligible for subsequent hematopoietic stem cell transplant (HSCT), which resulted in restored hematopoiesis. The remaining patient experienced a relapse of CD19+ cells that coincided with the lack of persistence of the CAR T cells from circulation. These data suggest that subsequent transfusions should be considered for patients unable to undergo HSCT. Adults with relapsed B cell acute lymphoblastic leukemia (B-ALL) have a dismal prognosis. Only those patients able to achieve a second remission with no minimal residual disease (MRD) have a hope for long-term survival in the context of a subsequent allogeneic hematopoietic stem cell transplantation (allo-HSCT). We have treated five relapsed B-ALL subjects with autologous T cells expressing a CD19-specific CD28/CD3ζ second-generation dual-signaling chimeric antigen receptor (CAR) termed 19-28z. All patients with persistent morphological disease or MRD+ disease upon T cell infusion demonstrated rapid tumor eradication and achieved MRD− complete remissions as assessed by deep sequencing polymerase chain reaction. Therapy was well tolerated, although significant cytokine elevations, specifically observed in those patients with morphologic evidence of disease at the time of treatment, required lymphotoxic steroid therapy to ameliorate cytokine-mediated toxicities. Indeed, cytokine elevations directly correlated to tumor burden at the time of CAR-modified T cell infusions. Tumor cells from one patient with relapsed disease after CAR-modified T cell therapy, who was ineligible for additional allo-HSCT or T cell therapy, exhibited persistent expression of CD19 and sensitivity to autologous 19-28z T cell–mediated cytotoxicity, which suggests potential clinical benefit of additional CAR-modified T cell infusions. These results demonstrate the marked antitumor efficacy of 19-28z CAR-modified T cells in patients with relapsed/refractory B-ALL and the reliability of this therapy to induce profound molecular remissions, forming a highly effective bridge to potentially curative therapy with subsequent allo-HSCT.