According to results of a study published in Blood, children and young adults with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL) who had minimal residual disease (MRD) prior to treatment and received high-dose preconditioning chemotherapy were most likely to respond to a second-generation CD-19 chimeric antigen receptor-T cell (CAR-T) therapy.1

Although it has been estimated that 90% or more of pediatric patients witha diagnosis of ALL will respond to multi-agent chemotherapy, the prognosis forthose with relapsed/refractory disease remains poor. One CD19-directed CAR-Ttherapy, tisagenlecleucel, is approved by the US Food and Drug Administration inpatients up to age 25 years with B-cell precursor ALL who either have refractorydisease or have experienced a second or later relapse.2

This open label, nonrandomized, phase 1 study (Clinical Trial Identifier: NCT01860937), evaluated the toxicity, feasibility, and response of 19-28z CAR-T therapy, a second-generation CD19-directed CAR-T therapy involving T cells expressing a chimeric receptor composed of an anti-CD19 antibody binding site and intracellular domains from the T-cell coactivating receptors, CD28 and the CD3-zeta chain3 in children and young adults up to 25 years of age with very high-risk ALL.1 Inclusion criteria included at least 2 relapses, early bone marrow relapse following complete response (CR), intermediate/late CR with poor response to re-induction therapy, or those with refractory disease, or ineligibility for allogeneic hematopoietic stem cell transplantation (allo-HSCT) or additional chemotherapy.1

The age range of the 25 patients treated with 19-28z CAR-T therapy onstudy was 1 to 22.5 years, with a median age of 13.5 years. Preconditioningchemotherapy involved high-dose cyclophosphamide (15 patients) and low-dosecyclophosphamide (8 patients), with 3 patients in each subgroup also receivingfludarabine.1

Regarding the feasibility of this approach, the prespecified CAR-Tcell dose was achieved for all patients for whom the 19-28z CAR-T therapyprocedure was undertaken.1

With respect to treatment toxicity,approximately one-third of patients experienced a grade 3/4 adverse event,including cytokine release syndrome (CRS) and neurotoxicity in 16% and 28% ofpatients, respectively. With the exception of 1 patient with grade 4 CRS andneurotoxicity who died following refractory Stenotrophomonas septic shock,these adverse events were reversible.1

Of the 24 patients includedin the response analysis, 75% achieved either a CR or a CR with incompletecount recovery (CRi). In the subsets of patients receiving preconditioningchemotherapy with either high- or low-dose cyclophosphamide, the CR/CRi rateswere 94% and 38%, respectively. Furthermore, treatment response was influencedby disease burden as evidenced by the considerably higher CR/CRi rate inpatients with baseline minimal residual disease (ie, less than 5% bone marrowblasts; 93%) compared with morphological evidence of disease at baseline (5% orhigher bone marrow blasts; 50%).1

The CR/CRi rate for thesubset of patients with pretreatment MRD treated with high-dose cytarabine was100%.1

Consolidation allo-HSCT was performed in 83% (15) of the patientsresponding to CAR-T therapy, with a median time from CAR-T infusion toallo-HSCT of 57 days. At a median follow-up of 28.6 months for respondingpatients, over half of these patients (8) were alive and had no evidence ofdisease.1

In their concluding remarks, the study authorscommented that thisanalysis has allowed us to determine the toxicity profile, confirm feasibility,evaluate response of this approach, and provide a direct comparison of the sameCD19-specific CAR T cell product that was previously published[3] inadult patients for the same indication.

The authors went on to highlight the findingof a reversible toxicity profile in the patients within their study as well asthe impact of preconditioning chemotherapy dose intensity and minimal pretreatmentdisease burden on response.

They further noted that within this cohort,the long-term persistence of response is encouraging, and in our primarilytransplant-naive patient population, the ability to proceed to allo-HSCT hasdemonstrated a favorable overall survival, manageable toxicity, and limitedincidence of relapse.

References

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19-28z CAR-T Therapy in Children and Young Adults With Relapsed/Refractory ALL: Promising Early Results - Cancer Therapy Advisor