Long-Duration Complete Remissions of Diffuse Large B Cell Lymphoma after Anti-CD19 Chimeric Antigen Receptor T Cell Therapy

Abstract

T cells expressing anti-CD19 chimeric antigen receptors (CARs) can induce complete remissions (CRs) of diffuse large B cell lymphoma (DLBCL). The long-term durability of these remissions is unknown. We administered anti-CD19 CAR T cells preceded by cyclophosphamide and fludarabine conditioning chemotherapy to patients with relapsed DLBCL. Five of the seven evaluable patients obtained CRs. Four of the five CRs had long-term durability with durations of remission of 56, 51, 44, and 38 months; to date, none of these four cases of lymphomas have relapsed. Importantly, CRs continued after recovery of non-malignant polyclonal B cells in three of four patients with long-term complete remissions. In these three patients, recovery of CD19⁺ polyclonal B cells took place 28, 38, and 28 months prior to the last follow-up, and each of these three patients remained in CR at the last follow-up. Non-malignant CD19⁺ B cell recovery with continuing CRs demonstrated that remissions of DLBCL can continue after the disappearance of functionally effective anti-CD19 CAR T cell populations. Patients had a low incidence of severe infections despite long periods of B cell depletion and hypogammaglobulinemia. Only one hospitalization for an infection occurred among the four patients with long-term CRs. Anti-CD19 CAR T cells caused long-term remissions of chemotherapy-refractory DLBCL without substantial chronic toxicities.

Keywords: adoptive T cell therapy; chimeric antigen receptors; lymphoma.

Figure 1

Complete Remissions of Long Duration and Assessment of B Cell and Immunoglobulin Recovery in Patients Receiving Anti-CD19 CAR T Cells (A) Patient 7 had chemotherapy-refractory DLBCL NOS. Patient 7’s lymphoma went into a CR that is ongoing (at the time of this report) after CAR T cell infusion as shown on positron emission tomography (PET) imaging. Examples of sites of lymphoma in this patient are indicated by the red arrows pointing to the black lesions. Note that the brain, heart, kidneys, and bladder are normally dark on these images and do not represent lymphoma in the after- treatment images. (B) Patient 8 had chemotherapy-refractory PMBCL that had undergone 10 previous lines of therapy. At the time of enrollment in the anti-CD19 CAR trial, she had extensive abdominal lymphoma, as shown by PET. The patient entered a complete remission that was ongoing 39 months after CAR T cell infusion, at which time she was diagnosed with myelodysplastic syndrome. Lymphoma is indicated by the white arrows pointing to red areas. Note that the brain, heart, kidneys, and bladder are normally red on these images and do not represent lymphoma in the after-treatment images. (C) Blood CAR⁺ cell levels were determined by qPCR. CAR⁺ cell numbers peaked in the first 2 weeks after infusion for all patients and then decreased. (D) Blood B cell levels were determined by flow cytometry for CD19 at multiple time points after CAR T cell infusion in patients who obtained long-term CRs. Blood B cell numbers recovered in three of four patients in long-term CRs. B cell and immunoglobulin recovery of patients not obtaining long-term CRs is not included in this figure because these patients developed progressive lymphoma, which was a criteria for patients to be removed from the study, so the patients were removed from the study. (D–G) The dashed line represents the lower limit of the normal range. The patient symbols used in (D) were used to represent the same patients in (E)–(G). (E) Serum IgM levels were determined for patients in long-term CRs. (F) Serum IgA levels were determined for patients in long-term CRs. (G) Serum IgG levels are shown. Note that IgG levels fluctuate because patients 2, 7, and 8 received infusions of intravenous IgG.

Figure 2

Phenotype of Recovering B Cells after Anti-CD19 CAR T Cell Therapy The phenotypes of recovering B cells in the three patients with recovery of B cells during long-term complete remissions are shown. (A) is patient 2, (B) is patient 7, and (C) is patient 15. The time from CAR T cell infusion until B cell analysis was 50 months for patient 2, 45 months for patient 7, and 43 months for patient 15. The first column of plots shows the CD19 and CD20 phenotype of B cells. The number on the plot is the percentage of cells outside the box in the left lower quadrant. This number also represents the sum of the percentages of cells that are either CD19⁺ or CD20⁺. The plot is gated on CD3⁻, CD56⁻, CD16⁻, and CD14⁻ lymphocytes. The second column of plots shows that the recovering B cells were polyclonal as shown by flow cytometry for immunoglobulin kappa and lambda. Plots are gated on all CD19⁺ and/or CD20⁺ lymphocytes. The third column of plots shows the IgD and CD27 phenotype of recovering B cells after CAR T cell infusion. Plots are gated on CD20⁺ lymphocytes. CD27 is a marker of memory B cells, and IgD expression is found on B cells that have not undergone isotype switching. Most cells had a CD27⁻, IgD⁺ phenotype, which is consistent with naive B cells.