Adoptive cellular therapy using chimeric antigen receptor (CAR) T cell therapies have produced significant objective responses in patients with CD19+ hematological malignancies, including durable complete responses. Although the majority of clinical trials to date have used autologous patient cells as the starting material to generate CAR T cells, this strategy poses significant manufacturing challenges and, for some patients, may not be feasible because of their advanced disease state or difficulty with manufacturing suitable numbers of CAR T cells. Alternatively, T cells from a healthy donor can be used to produce an allogeneic CAR T therapy, provided the cells are rendered incapable of eliciting graft versus host disease (GvHD). One approach to the production of these cells is gene editing to eliminate expression of the endogenous T cell receptor (TCR). Here we report a streamlined strategy for generating allogeneic CAR T cells by targeting the insertion of a CAR transgene directly into the native TCR locus using an engineered homing endonuclease and an AAV donor template. We demonstrate that anti-CD19 CAR T cells produced in this manner do not express the endogenous TCR, exhibit potent effector functions in vitro, and mediate clearance of CD19+ tumors in an in vivo mouse model.

Reduced intensity conditioning (RIC) regimens have the potential to decrease transplant-related morbidity and mortality. However, engraftment failure has been prohibitively high after RIC unrelated umbilical cord blood transplantation (UCBT) in chemotherapy-naïve children with non-malignant diseases (NMD). Twenty-two children with a median age of 2.8 years, many with severe comorbidities and prior viral infections were enrolled in a novel RIC protocol consisting of hydroxyurea, alemtuzumab, fludarabine, melphalan and thiotepa followed by single UCBT. Patients were transplanted for inherited metabolic disorders (N=8), primary immunodeficiencies (N=9), hemoglobinopathies (N=4) and Diamond Blackfan anemia (N=1). Most UCB units were HLA-mismatched with median infused total nucleated cell dose of 7.9 × 107/kg. No serious organ toxicities were attributable to the regimen. The cumulative incidence of neutrophil engraftment was 86.4% (95% confidence interval [CI], 65%–100%) in a median of 20 days, with the majority sustaining >95% donor chimerism at 1 year. Cumulative incidence of acute graft-versus-host disease (GVHD) grades II–IV and III–IV by day 180 was 27.3% (95% CI, 8.7%–45.9%) and 13.6% (95 CI, 0%–27.6%), respectively. Cumulative incidence of extensive chronic GVHD was 9.1% (95% CI, 0%–20.8%). The primary causes of death were viral infections (N=3), acute GVHD (N=1) and transfusion reaction (N=1). One-year overall and event-free survivals were 77.3% (95% CI, 53.7%–89.8%) and 68.2% (95% CI, 44.6%–83.4%) with 31 months median follow-up. This is the first RIC protocol demonstrating durable UCB engraftment in children with NMD. Future risk-based modifications of this regimen could decrease the incidence of viral infections. (www.clinicaltrials.gov/NCT00744692)

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Expanding on our prior studies with cord blood T-cells, we hypothesized that primary AML-reactive autologous T-cells could be generated ex vivo under immunomodulatory conditions. We purified AML and T-cells from 8 newly diagnosed high-risk patients. After 2 weeks expansion, T-cells were stimulated with IFN-γ treated autologous AML weekly X 3, IL-15 and agonistic anti-CD28 antibody. CTL and ELISpot assays tested functionality; RT-qPCR tested AML and T-cell gene expression profiles. Based on combined positive ELIspot and CTL assays, T-cells reactive against AML were generated in 5/8 patients. Treg proportion declined post-co-cultures in reactive T-cell samples. AML-reactive T-cells displayed an activated gene expression profile. “Resistant” AML blasts displayed genes associated with immunosuppressive MDSC. We discuss our approach to creating primary AML-reactive autologous T-cell and limitations that require further work. Our study provides a platform for future research targeting on generating autologous leukemia reactive T-cells.