Bonnie Yates

CD22-targeted CAR T cells induce remission in B-ALL that is naive or resistant to CD19-targeted CAR immunotherapy

Chimeric antigen receptor (CAR) T cells targeting CD19 mediate potent effects in relapsed and/or refractory pre–B cell acute lymphoblastic leukemia (B-ALL), but antigen loss is a frequent cause of resistance to CD19-targeted immunotherapy. CD22 is also expressed in most cases of B-ALL and is usually retained following CD19 loss. We report results from a phase 1 trial testing a new CD22-targeted CAR (CD22-CAR) in 21 children and adults, including 17 who were previously treated with CD19-directed immunotherapy. Dose-dependent antileukemic activity was observed, with complete remission obtained in 73% (11/15) of patients receiving ≥1 × 106 CD22-CAR T cells per kg body weight, including 5 of 5 patients with CD19dim or CD19− B-ALL. Median remission duration was 6 months. Relapses were associated with diminished CD22 site density that likely permitted CD22+ cell escape from killing by CD22-CAR T cells. These results are the first to establish the clinical activity of a CD22-CAR in B-ALL, including leukemia resistant to anti-CD19 immunotherapy, demonstrating potency against B-ALL comparable to that of CD19-CAR at biologically active doses. Our results also highlight the critical role played by antigen density in regulating CAR function.Chimeric antigen receptor (CAR) T-cells targeting CD19 mediate potent effects in relapsed/refractory pre-B cell acute lymphoblastic leukemia (B-ALL) but antigen loss is a frequent cause of resistance to CD19-targeted immunotherapy. CD22 is also expressed on most B-ALL and usually retained following CD19 loss. We report results from a phase I trial testing a novel CD22-CAR in twenty-one children and adults, including 17 previously treated with CD19-directed immunotherapy. Dose dependent anti-leukemic activity was observed with complete remission in 73% (11/15) of patients receiving ≥ 1 × 106 CD22-CART cells/kg, including 5/5 patients with CD19dim/neg B-ALL. Median remission duration was 6 months. Relapses were associated with diminished CD22 site density that likely permitted escape from killing by CD22-CART cells. These results are the first to eastablish the clinical activity of a CD22-CAR in pre-B cell ALL, including in leukemia resistant to anti-CD19 immunotherapy, demonstrating comparable potency to CD19-CART at biologically active doses in B-ALL. They also highlight the critical role played by antigen density in regulating CAR function. (Funded by NCI Intramural Research Program)

Sequential loss of tumor surface antigens following chimeric antigen receptor T-cell therapies in diffuse large B-cell lymphoma

Chimeric antigen receptor (CAR) T cell therapy using an anti-CD19 binding domain has been shown to be effective in adults with lymphoma and may represent an alternative treatment strategy in pediatric lymphoma, although experience in this younger age group is limited. Loss of the target antigen, as a mechanism of tumor escape following immunotherapy, is an increasingly recognized phenomena which has limited the efficacy of immunotherapy in leukemia, however little is known about antigen loss in lymphoma. We present a case of a pediatric patient with multiply relapsed advanced stage DLBCL who developed sequential antigen loss disease following sequential CAR immunotherapy. This case provides a proof of concept of antigen loss as a mechanism for relapse following immunotherapy in lymphomas, and highlights the need for repeat biopsy and flow cytometric analysis in guiding sequential immunotherapeutic interventions.

Procalcitonin and cytokine profiles in engraftment syndrome in pediatric stem cell transplantation

Diagnosis of engraftment syndrome (ES) following allogeneic hematopoietic stem cell transplantation (HSCT) can be a challenge due to the systemic presentation and alternative etiologies. With a goal of establishing biomarkers to more accurately distinguish ES, we prospectively analyzed levels of cytokines during HSCT.