Durable Molecular Remissions in Chronic Lymphocytic Leukemia Treated With CD19-Specific Chimeric Antigen Receptor-Modified T Cells After Failure of Ibrutinib

Abstract

Purpose We evaluated the safety and feasibility of anti-CD19 chimeric antigen receptor-modified T (CAR-T) cell therapy in patients with chronic lymphocytic leukemia (CLL) who had previously received ibrutinib. Methods Twenty-four patients with CLL received lymphodepleting chemotherapy and anti-CD19 CAR-T cells at one of three dose levels (2 × 10⁵, 2 × 10⁶, or 2 × 10⁷ CAR-T cells/kg). Nineteen patients experienced disease progression while receiving ibrutinib, three were ibrutinib intolerant, and two did not experience progression while receiving ibrutinib. Six patients were venetoclax refractory, and 23 had a complex karyotype and/or 17p deletion. Results Four weeks after CAR-T cell infusion, the overall response rate (complete response [CR] and/or partial response [PR]) by International Workshop on Chronic Lymphocytic Leukemia (IWCLL) criteria was 71% (17 of 24). Twenty patients (83%) developed cytokine release syndrome, and eight (33%) developed neurotoxicity, which was reversible in all but one patient with a fatal outcome. Twenty of 24 patients received cyclophosphamide and fludarabine lymphodepletion and CD19 CAR-T cells at or below the maximum tolerated dose (≤ 2 × 10⁶ CAR-T cells/kg). In 19 of these patients who were restaged, the overall response rate by IWCLL imaging criteria 4 weeks after infusion was 74% (CR, 4/19, 21%; PR, 10/19, 53%), and 15/17 patients (88%) with marrow disease before CAR-T cells had no disease by flow cytometry after CAR-T cells. Twelve of these patients underwent deep IGH sequencing, and seven (58%) had no malignant IGH sequences detected in marrow. Absence of the malignant IGH clone in marrow of patients with CLL who responded by IWCLL criteria was associated with 100% progression-free survival and overall survival (median 6.6 months follow-up) after CAR-T cell immunotherapy. The progression-free survival was similar in patients with lymph node PR or CR by IWCLL criteria. Conclusion CD19 CAR-T cells are highly effective in high-risk patients with CLL after they experience treatment failure with ibrutinib therapy.

Fig 1.

The peak of chimeric antigen receptor-modified T (CAR-T) cells in blood correlates with tumor burden before commencing lymphodepletion chemotherapy. The peak of CAR-T cells in blood (vector copies/μg DNA) is plotted against (A) the absolute abnormal B cell count in blood; (B) the percentage of abnormal B cells in bone marrow; (C) the tumor cross-sectional area; and (D) the maximum standardized uptake value (SUV) on positron emission tomography imaging. Graphs depict data from all patients treated with cyclophosphamide plus fludarabine and 2 × 10⁶ CAR-T cells/kg, with the exception of one patient who died before the peak of CAR-T cell expansion and is not shown. FlapEF1α, flap elongation factor-1 alpha.

Fig 2.

Factors correlating with cytokine release syndrome (CRS) and neurotoxicity. (A) Peak CD4⁺/truncated human epidermal growth factor receptor (EGFRt⁺) and CD8⁺/EGFRt⁺ chimeric antigen receptor-modified T (CAR-T) cells (cells/μL) in blood after CAR-T cell infusion are shown in patients with grade 0 versus 1 to 3 versus 4 to 5 CRS. (B) Peak CD4⁺/EGFRt⁺ and CD8⁺/EGFRt⁺ CAR-T cells (cells/μL) in blood after CAR-T cell infusion are shown in patients with grade 0 versus 1 to 3 versus 4 to 5 neurotoxicity. (C) Peak serum cytokine, C-reactive protein (CRP) and ferritin concentrations in patients with grade 0 to 1 compared with grade 2 to 5 CRS. (D) Peak serum cytokine, CRP, and ferritin concentrations in patients with grade 0 to 1 compared with grade 2 to 5 neurotoxicity. (E) Serum cytokine concentrations 0 to 48 hours after CAR-T cell infusion in patients who subsequently developed grade 0 to 1 compared with grade 2 to 5 neurotoxicity. CRP units are mg/L. Ferritin units are ng/mL. FlapEF1α, flap elongation factor-1 alpha; IFNγ, interferon-gamma; IL, interleukin; MCP1, monocyte chemotactic protein-1; sIL6R, soluble IL-6 receptor; sIL2Rα, soluble IL-2 receptor alpha; TGFβ, transforming growth factor-beta; TIM3, T cell immunoglobulin and mucin domain containing 3; TNFα, tumor necrosis factor-alpha; TNFβ, tumor necrosis factor-beta; TNFRp55, tumor necrosis factor receptor p55; TNFRp75, tumor necrosis factor receptor p75. (*) P < .05, (**) P < .01, Wilcoxon two-sample test.

Fig 3.

Factors correlating with the response to chimeric antigen receptor-modified T (CAR-T) cell therapy. (A) progression-free survival (PFS) and (B) overall survival (OS) in patients with complete remission (CR), partial remission (PR), or no response (stable disease [SD] and/or progressive disease [PD]) by International Workshop on Chronic Lymphocytic Leukemia (IWCLL; 2008) after cyclophosphamide plus fludarabine lymphodepletion and CAR-T cell infusion at or below the maximum tolerated dose (dose level 1 or dose level 2). The median PFS and OS follow-up for patients in CR/PR was 12.3 and 12.4 months, respectively. (C) The peak CD4⁺/truncated human epidermal growth factor receptor (EGFRt⁺; left) and CD8⁺/EGFRt⁺ (right) CAR-T cell counts in blood are shown in patients who did or did not clear disease from the bone marrow (BM) by high-resolution flow cytometry. (D) The peak CD4⁺/EGFRt⁺ (left) and CD8⁺/EGFRt⁺ (right) CAR-T cell counts in blood are shown in patients who cleared disease from BM by high-resolution flow cytometry and did or did not have detectable malignant IGH sequences in marrow. Curves depict the probability estimated by logistic regression of clinical outcomes associated with (E) peak CD4⁺/EGFRt⁺ and (F) CD8⁺/EGFRt⁺ CAR-T cell counts in blood. (G) Waterfall plot showing the change in cross-sectional area of the six largest lymph nodes on computed tomography scan by IWCLL (2008) imaging criteria at best response in high-risk patients with CLL after CAR-T cell immunotherapy. Four patients (two CR, one SD, one died) without high-resolution imaging to enable tumor measurement are not shown. (H) CD19-negative progression in a patient with robust CAR-T cell expansion in blood. BM, bone marrow; CRS, cytokine release syndrome; flow-neg, flow-negative; gr, grade; mOS, median OS; mPFS, median PFS; NR, not reached; NT, neurotoxicity.

Fig 4.

(A) Progression-free survival and (B) overall survival in patients who cleared disease from bone marrow 4 weeks after CAR-T cell infusion by flow cytometry and had no detectable malignant IGH copies (IGHseq-negative) compared with those who had detectable malignant IGH copies (IGHseq-positive). mOS, median OS; mPFS, median PFS; NR, not reached.

Fig A1.

Progression-free survival (PFS) and overall survival (OS) for all patients with CLL. CAR-T, chimeric antigen receptor-modified T; mOS, median OS; mPFS, median PFS; NR, not reached.