Development and manufacture of novel locally produced anti-BCMA CAR T cells for the treatment of relapsed/refractory multiple myeloma: results from a phase I clinical trial

Abstract

Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor T-cell (CAR T) therapy shows remarkable efficacy in patients with relapsed and/or refractory (R/R) multiple myeloma (MM). HBI0101, a novel second generation optimized anti- BCMA CAR T-cell therapy, was developed in an academic setting. We conducted a phase I dose-escalation study of HBI0101 (cohort 1: 150x106 CAR T cells, n=6; cohort 2: 450x106 CAR T cells, n=7; cohort 3: 800x106 CAR T cells, n=7) in 20 heavily pre-treated R/R MM patients. Grade 1-2 cytokine release syndrome (CRS) was reported in 18 patients (90%). Neither grade 3-4 CRS nor neurotoxicity of any grade were observed. No dose-limiting toxicities were observed in any cohort. The overall response rate (ORR), (stringent) complete response (CR/sCR), and very good partial response rates were 75%, 50%, and 25%, respectively. Response rates were dose-dependent with 85% ORR, 71% CR, and 57% minimal residual disease negativity in the high-dose cohort 3. Across all cohorts, the median overall survival (OS) was 308 days (range 25-466+), with an estimated OS of 55% as of June 27th (data cut-off). The median progression-free survival was 160 days, with 6 subjects remaining progression free at the time of data cut-off. Our findings demonstrate the manageable safety profile and efficacy of HBI0101. These encouraging data support the decentralization of CAR T production in an academic setting, ensuring sufficient CAR T supply to satisfy the increasing local demand. Clinicaltrials.gov NCT04720313.

Figures

Figure 1.

Objective responses in patients treated with HBI0101 CAR T cells. (A) Overall response rate (ORR). The best responses for each patient are shown according to dose (150-, 450- and 800x106 CAR+ cells/dose). Disease response was determined according to the International Myeloma Working Group (IMWG) consensus criteria. Minimal residual disease (MRD) is defined as the number of multiple myeloma (MM) plasma cells detected in the bone marrow per 1x105 total nucleated cells. An MRD of 1x10-5 or less is considered MRD-negative (MRD-). (B) Response to HBI0101 treatment. Swimmer's plot of best responses among individual MM patients are shown according to cell dose (150- to 800x106 CAR+). Response assessment according to IMWG criteria. Grey: progressive disease (PD) / stable disease (SD); green: very good partial response (VGPR); light blue: stringent complete response/complete response with MRD positive (sCR/CR [MRD+]); blue: stringent complete response/complete response with MRD negative (sCR/CR [MRD-]).

Figure 2.

Survival of patients with relapsed / refractory multiple myeloma administered with HBI0101 CAR T cells. Kaplan-Meier analysis of progression-free survival (PFS) in all the patients (A) or grouped according to dose (B), overall survival (OS) in all patients (C) or grouped according to dose (D).

Figure 3.

Multiple myeloma disease monitoring. Free light chain levels were determined at the indicated time points prior to and following HBI0101 infusion in cohort 1 (N=6) (A), cohort 2 (N=6) (B), and cohort 3 (N=6) (C). Normal range for Kappa light chain: 6.7-22.4 mg/L, and Lambda light chain: 8.3-27 mg/L. (D) Soluble BCMA (sBCMA) levels prior to and following CAR T infusion were determined by ELISA in the "response" (blue squares) versus "no response" (black dots) groups.

Figure 4.

Efficacy of HBI0101 CAR T-based therapy in eliminating CD38++CD138++ malignant plasma cells. (A) Flow cytometric gating strategy for the assessment of anti-B-cell maturation antigen (BCMA) and CD56 expression on multiple myeloma plasma cells (MM-PC) (indicated by arrows). Samples were gated on CD38++CD138++. (B) Bone marrow (BM) samples prior to and one month (mth) following HBI0101-CAR T infusion were assessed for the presence of PC (as % of CD38++CD138++ cells) by flow cytometry by gating on white blood cells (WBC), as illustrated in (A). (C-E) Analysis of BCMA and CD56 expression on MM-PC, by "response" (blue squares) versus "no response" (black dots) group. (C, D) BCMA expression levels in MM patients (N=12). The mean fluorescence intensity (MFI) (C) and the percent of BCMA-positive PC (D) were determined by flow cytometry. (E) Percent of CD56-positive PC in "response" (N=9) versus "no response" (N=3) groups.

Figure 5.

Soluble anti-B-cell maturation antigen clearance and HBI0101 CAR T-cell in vivo kinetics. (A) The median number of HBI0101-CAR T cells per 1 mL blood in the "response" versus "no response" group was determined by quantification of CAR transgene levels by qRT-PCR method following CAR T infusion at the indicated times and further adjusted to the copy numbers per transduced cell at the day of CAR T infusion. The limit of quantitation (LOQ) was 500 CAR T/mL blood. (B) HBI0101 CAR T-cell overall expansion in the first month of CAR T therapy. Area under the curve (AUC) as a measure of CAR T-cell overall expansion was calculated with Prism software (GraphPad). (C) HBI0101 cells in vivo median concentration at peak (Cmax) in "response" (blue squares) versus "no response" (black dots) groups. (D) Median time to Cmax (Tmax) in "response" (blue squares) versus "no response" (black dots) groups. Upper and lower bars I represent the maximal and minimal values, respectively. (E, F) Soluble anti-B-cell maturation antigen (sBCMA) levels prior to and following HBI0101 infusion determined by ELISA and further normalized to sBCMA concentration at baseline (right y-axis; empty circles) versus HBI0101-cell expansion indicated by the CAR T/mL (left y-axis; filled circles) in the "no response" group (E), and in the "response" group (F). **P<0.01, by unpaired t test.

Figure 6.

Effect of belantamab pre-treatment on multiple myeloma patients’ response to HBI0101 therapy. Kaplan-Meier analysis of progression-free survival (PFS) (A) and overall survival (OS) (C) in "belantamab(+)" versus "belantamab(-)" group. (B, D) Effect of belantamab prior therapy on plasma cell anti-B-cell maturation antigen (BCMA) expression. Percent of BCMA-expressing bone marrow-plasma cell (BM-PC) (B) and BCMA expression mean fluorescence intensity (MFI) (D) on BM-PC were determined by flow cytometry prior to HBI0101 infusion and analyzed according to patient's pre-exposure to belantamab. Samples were gated on CD38++CD138++ cells. CR: complete response; sCR: stringent complete response; VGPR: very good partial response; MRD: minimal residual disease; ns: not significant.