Dual CD19 and CD123 targeting prevents antigen-loss relapses after CD19-directed immunotherapies

Abstract

Potent CD19-directed immunotherapies, such as chimeric antigen receptor T cells (CART) and blinatumomab, have drastically changed the outcome of patients with relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL). However, CD19-negative relapses have emerged as a major problem that is observed in approximately 30% of treated patients. Developing approaches to preventing and treating antigen-loss escapes would therefore represent a vertical advance in the field. Here, we found that in primary patient samples, the IL-3 receptor α chain CD123 was highly expressed on leukemia-initiating cells and CD19-negative blasts in bulk B-ALL at baseline and at relapse after CART19 administration. Using intravital imaging in an antigen-loss CD19-negative relapse xenograft model, we determined that CART123, but not CART19, recognized leukemic blasts, established protracted synapses, and eradicated CD19-negative leukemia, leading to prolonged survival. Furthermore, combining CART19 and CART123 prevented antigen-loss relapses in xenograft models. Finally, we devised a dual CAR-expressing construct that combined CD19- and CD123-mediated T cell activation and demonstrated that it provides superior in vivo activity against B-ALL compared with single-expressing CART or pooled combination CART. In conclusion, these findings indicate that targeting CD19 and CD123 on leukemic blasts represents an effective strategy for treating and preventing antigen-loss relapses occurring after CD19-directed therapies.

A quantitative method for measuring the transfection efficiency of CD19-directed chimeric antigen receptor in target cells

“…The main mechanism of the toxicity and side effects could be attributed to cytokine release, tumor cell lysis, B-cell aplasia, and macrophage-activation syndrome. 26,27 Although most mild toxicity and side effects are reversible, some severe toxicities need medical treatment. A low dose of engineered cells may not trigger a response of antitumor activity, and an extra dose of immunotherapeutic cells may lead to severe toxicity and side effects.…”

Cellular Immunotherapy in B-Cell Malignancy

“…Rearrangement in the mixed lineage leukemia (MLL) gene has also been described to contribute to the switch to a CD19-negative lineage following CAR T-cell therapy [57]. Strategies to overcome this include using 2 CAR constructs with different antigen specificity, for example CD19/CD123 [58]. Zah et al [59] recently reported on the development of a bispecific CD19/CD20 CAR construct with increased anti-tumor effect and prevention of CD19-negative ALL outgrowth.…”

Specific Adoptive Cellular Immunotherapy in Allogeneic Stem Cell Transplantation

“…A different kind of relapse was reported by clonal expansion of CD19-negative B cells after treatment with CD19-CARtransduced autologous T cells after allogeneic umbilical cord blood transplantation [71]. In fact, a high number of relapsed patients after CD19-CAR therapy show a CD19-negative phenotype of the blasts [72] indicating that mono-targeting approaches will have limitations in a significant proportion of patients. Preclinical data indicate superior tumor reactivity using a dual-expressing CAR construct comprising a CD19-and a CD123-CAR targeting the interleukin-3 receptor α chain [72].…”

“…In fact, a high number of relapsed patients after CD19-CAR therapy show a CD19-negative phenotype of the blasts [72] indicating that mono-targeting approaches will have limitations in a significant proportion of patients. Preclinical data indicate superior tumor reactivity using a dual-expressing CAR construct comprising a CD19-and a CD123-CAR targeting the interleukin-3 receptor α chain [72]. CD123 is characteristically expressed also in a variety of other hematological malignancies [73].…”