Efficacy and toxicity management of 19-28z CAR T cell therapy in B cell acute lymphoblastic leukemia

Abstract

We report on 16 patients with relapsed or refractory B cell acute lymphoblastic leukemia (B-ALL) that we treated with autologous T cells expressing the 19-28z chimeric antigen receptor (CAR) specific to the CD19 antigen. The overall complete response rate was 88%, which allowed us to transition most of these patients to a standard-of-care allogeneic hematopoietic stem cell transplant (allo-SCT). This therapy was as effective in high-risk patients with Philadelphia chromosome-positive (Ph(+)) disease as in those with relapsed disease after previous allo-SCT. Through systematic analysis of clinical data and serum cytokine levels over the first 21 days after T cell infusion, we have defined diagnostic criteria for a severe cytokine release syndrome (sCRS), with the goal of better identifying the subset of patients who will likely require therapeutic intervention with corticosteroids or interleukin-6 receptor blockade to curb the sCRS. Additionally, we found that serum C-reactive protein, a readily available laboratory study, can serve as a reliable indicator for the severity of the CRS. Together, our data provide strong support for conducting a multicenter phase 2 study to further evaluate 19-28z CAR T cells in B-ALL and a road map for patient management at centers now contemplating the use of CAR T cell therapy.

Fig. 1. Characteristics of the CRS

(A) Average max temperatures on days 1 to 11 after CAR T cell infusion in patients with sCRS compared to nCRS patients. Error bars represent the SD. The dashed line is at 38°C to indicate the threshold for fevers. Two-way analysis of variance (ANOVA) analysis between the sCRS and nCRS groups revealed a P = 0.019 (n = 22). (B) Max fold changes of seven inflammatory cytokines selected for their consistent pattern of elevation during sCRS. Depicted are the max fold changes relative to pretreatment values over days 1 to 21 after CAR T cell infusion. The highlighted box represents changes 75-fold and above. Correlation was assessed for pretreatment tumor burden and cytokine elevations for patients diagnosed with sCRS. The Spearman rank correlation coefficient was calculated with pretreatment tumor burden, measured by deep sequencing, and cytokine concentration (pg/ml), and is listed next to each cytokine. IFN-γ, interferon-γ; GM-CSF, granulocyte-macrophage colony-stimulating factor.

Fig. 2. The effect of steroids and/or tocilizumab on the expansion of CAR T cells in patients with sCRS

The number of CAR T cells per microliter of whole blood, detected by qPCR, was measured in samples drawn before treatment and from days 1 to 22 after CAR T cell infusion. Max temperatures on days 1 to 11 are also depicted. In addition, the days when steroids or tocilizumab was administered to manage sCRS are shown. The red dashed line represents the duration of steroid treatment, and the gray dashed line is at the 38°C fever threshold.

Fig. 3. CAR T cells detected in the BM by deep sequencing

BM was isolated from patients and submitted to Adaptive Biotechnologies for deep sequencing of the IgH rearrangement associated with the 19-28z CAR. The max number of CAR T cells in the BM within 6 weeks of CAR T cell infusion is shown. The mean and SD are depicted for the patient groups stratified on the basis of CRS and its management. *P = 0.048, one-way t test between these two groups (n = 6).

Fig. 4. CRP levels in patients infused with 19-28z CAR T cells

CRP was measured before treatment and from days 1 to 18 after CAR T cell infusion. The green lines represent CRP levels from patients who met the diagnostic criteria for sCRS (n = 4) and were treated with either tocilizumab or nothing. The CRP levels of patients classified as nCRS are illustrated in blue. Error bars are the SEM. The gray dashed line is at 20 mg/dl, which indicates the threshold where patients are at high risk for clinical complications secondary to sCRS. *P < 0.05, unpaired t tests at the corresponding time point. Specific P values for the time points are as follows: day 2, P = 0.035 (n = 13); day 4, P = 0.025 (n = 12); day 5, P = 0.019 (n = 11); and day 9, P = 0.01 (n = 8).