Sequential CD19 and BCMA-specific CAR T-cell treatment elicits sustained remission of relapsed and/or refractory myeloma

Abstract

The low rate of durable response against relapsed and/or refractory multiple myeloma (RRMM) in recent studies indicates that chimeric antigen receptor T-cell (CART) treatment is yet to be optimized. This study aims to investigate the safety and efficacy of sequential infusion of CD19-CART and B-cell maturation antigen (BCMA)-CARTs for RRMM with a similar 3 + 3 dose escalation combined with a toxicity sentinel design. We enrolled 10 patients, among whom 7 received autologous infusion and 3 received allogeneic infusion. The median follow-up time was 20 months. The most common grade 3/4 treatment-emergent toxicities were hematological toxicities. Cytokine-release syndrome (CRS) adverse reactions were grade 1/2 in 9 out of 10 subjects. No dose-limited toxicity (DLT) was observed for BCMA-CAR-positive T cells ≤5 × 10⁷ /kg), while two patients with dose-levels of 5-6.5 × 10⁷ /kg experienced DLTs. The overall response rate was 90% (five partial responses and four stringent complete responses). Three out of four patients with stringent complete responses to autologous CART had progression-free survival for over 2 years. The three patients with allogeneic CART experienced disease progression within 2 months. These results evidence the sequential infusion's preliminarily tolerability and efficacy in RRMM, and present a simple and safe design applicable for the establishment of multiple CART therapy.

Keywords: chimeric antigen receptor T (CAR T) cell; dose-escalation; efficacy; multiple myeloma; relapsed and/or refractory; safety.

FIGURE 1

CONSORT diagram and scheme of the clinical trial design. Following patient enrollment, autologous or allogeneic T cells were obtained via leukapheresis and transfected to generate CART‐CD19 or CARTBCMA. After administering short‐term chemotherapy for lymphodepletion (3 doses of cyclophosphamide and fludarabine), patients received one‐dose infusion of CART‐CD19 on day 0 and then a split‐dose infusion of CART‐BCMA over 2 days (40% on day 1 and 60% on day 2). Patients were admitted for 2 weeks for management of potential adverse events, followed by long‐term follow‐up for response assessment. All patients reported here were infused with CAR T cells between July 2017 and November 2017. The presented data cut‐off date was July 31, 2019.

FIGURE 2

Sequential CD19‐ and BCMA‐CART treatment induced an anti‐tumor response in MM patients. A, The swimmer's plot shows the treatment response and response duration for patients administered the autologous or allogeneic infusions. The depth of anti‐myeloma response is indicated by different colors. × indicates the time point when progression of disease occurred. → indicates clinical response persisted at the last follow‐up. B, Kaplan–Meier curve of progression‐free survival (PFS) in patients with autologous or allogeneic CART treatment. Three patients who received autologous CART treatment remained in ongoing response at the last follow‐up. C, Kaplan–Meier curve of overall survival (OS) in patients receiving autologous or allogeneic CART treatment. One patient who received allogeneic CART and all seven patients who received autologous treatment were still alive at the last follow‐up. D, The waterfall plot represents the maximum percentage change in the myeloma marker serum immunoglobulin M protein post infusion. E, Diffusion weighted magnetic resonance imaging (DW‐MRI) of patient 02's right iliac fossa a month prior to and 4 months after CART infusion. F, Immunohistochemistry staining of Patient 01's BM biopsy with CD138 indicated that BM myeloma dramatically decreased 1 month after CART infusion and remained at low levels 2 month after the infusion.

FIGURE 3

Response against myeloma by sequential CD19‐ and BCMA‐CART treatment was associated with a high dose of autologous CART infusion and decreased BCMA expression. A and B, The copies of total CAR transgene in genomic DNA extracted from peripheral blood mononuclear cells were determined by quantitative polymerase chain reaction and used to describe in vivo CART cell expansion in patients who received autologous (A) CARTs or allogeneic (B) CARTs. C, Dynamics of free BCMA in patients' serum was determined by enzyme‐linked immunosorbent assay. Serum BCMA concentration remained under normal limit in patients with durable remissions. D, The curve of free BCMA concentration in peripheral blood (PB) was similar to the change in M protein post CART cell infusion for patient 03. E, BCMA antigen expression on bone marrow (BM) plasma cells from patient 03 evaluated with multiple‐color flow cytometry. BCMA expression initially decreases with response following CART therapy, then increases at progression

FIGURE 4

Autologus and Allologous CD19‐CART/BCMA‐CART cells infusion induced a rapid immune response in MM patients. A, Serum concentrations of a panel of seven cytokines were determined within the first week after CART‐BCMA infusion using a multiplexed particle‐based flow cytometric assay. The peak serum concentrations of each of the seven cytokines in the autologous and allogeneic groups are presented (left panel). The maximum concentration of four cytokines (IL‐2, IL‐6, IL‐10, and IFNγ) increased more in patients receiving a high dose of CART‐BCMA vs. those with low dose (right panel). B and C, The time course changes in cytokine levels in the blood, temperature and serum C‐reaction protein level of Patient 01. D and E, The kinetics of mean (+SEM) monocyte count is presented compared with mean (+SEM) IFNγ(D) or IL‐6 (E) level.