Effective Chimeric Antigen Receptor T Cell Therapy for Relapsed and Refractory Acute Lymphoblastic Leukemia in Children Can be Administered Safely Under the Real-Time Monitoring of Th1/Th2 Cytokine Patterns Measured By the Cytometric Bead Array Technology

Background and Objectives: Chimeric antigen receptor modified T (CAR-T) cell therapy has emerged as a promising strategy for the treatment of relapsed and refractory hematological malignancies recently. CD19 chimeric antigen receptor T (CD19CAR-T) cell therapy is a representative case showing promising results in treating relapsed and refractory B-lineage acute lymphoblastic leukemia (r/r B-ALL). However, challenges remain due to the concurrent severe side-effects such as cytokine release syndrome (CRS) or neurological toxicities which may cause death if they are not properly managed. So, how to safely use the CAR-T cell therapy in patients has drawn a lot of concern and attention worldwide. The objective of this study was to investigate the cytokine patterns to early identify and monitor the severe side-effects of cytokine release syndrome (CRS) and neurotoxicity caused by the therapy so that the therapy can be safely administered. Patients and Method: From December 2015 to March 2017, five patients with r/r B-ALL treated with CD19CAR-T cells were enrolled in this study. The Th1/Th2 cytokines including Interleukin (IL)-2, IL-4, IL6, IL-10, Tumor necrosis factor (TNF) and Interferon-gamma (IFN-γ ) in the serum and cerebral spinal fluid (CSF) were quickly measured by cytometric bead array (CBA) technology which allowed the result being available within 5 hours after the samples taken. The test were repeated more than once a day during the therapy. Results: 5 pediatric patients (2 boys and 3 girls) with r/r B-ALL aged 4 months -12 years old were treated by CD19CAR-T cell therapy. Four patients achieved complete remission (80% of CR rate) with minimal residual diseases (MRD) negative detected by flow cytometry within 2 weeks. One patient did not respond to the therapy due to the poor quality of his T cells. Five to 10 times of cytokine measurements were carried out for the five patients. Two types of cytokine patterns were identified: (1) very high levels of IL-6, IFN-γ with moderately elevated IL-10 indicated the CAR-T therapy effective pattern; (2) IL-6 slightly - severely elevated IL-6 level without concurrent elevation of IFN-γ represented a CAR-T cell therapy ineffective pattern but rather indicating a current infection. All the four responding patients presented the CAR-T therapy effective cytokine pattern, while the non-responding patient presented the CAR-T therapy ineffective cytokine pattern. We also analyzed the relationship between the cytokine levels and the severity of the side-effects and found that they were highly correlated. The cytokine levels in the CSF of two patients with seizure were also measured and we found that the elevation of the cytokine pattern in the CSF was paralleled to those in their serum but CNS-leukemia and CAR-T cells in their CSFs were not detected, indicating that the neurotoxicity concurrently presented in these two patients might be caused by the cytokines in the serum leaked into the CSF through the blood brain barrier. Extremely high level of cytokines occurred at 12 hours after CAR-T cell infusion in a patient was identified immediately and treated timely in onn-ICU setting to avoid the fatal consequence. Acute toxicities including fever, hypotension and other neurological toxicities occurred in responding patients within 2 weeks post infusion and managed properly with tocilizumab and/or steroids according to the "real-time" monitoring of this simple 6-Th1/Th2 cytokine patterns at the non-ICU setting. In conclusion, our study demonstrates that CD19CAR-T cell therapy can be administered safely for patients with relapsed and refractory leukemia under the "real-time" monitoring of a simple 6-cytokine pattern.