High efficacy and safety of CD38 and BCMA bispecific CAR-T in relapsed or refractory multiple myeloma

Abstract

Background: B-cell maturation antigen (BCMA) chimeric antigen receptor T (CAR-T) cell therapy has obtained promising results in relapsed or refractory multiple myeloma (R/R MM), while some patients do not response, or relapse in short term after treatment. Combining with anti-CD38 might solve the problem of targeting BCMA alone. We aimed to assess the efficacy and safety of BCMA and CD38 (BCMA-CD38) bispecific CAR-T cells in R/R MM patients.

Methods: We did a single-center, single-arm clinical study at the Second Affiliated Hospital of Yangtze University in China. Patients meeting with the inclusion criteria were administered with fludarabine and cyclophosphamide before CAR-T cells infusion. Response and adverse events were assessed after infusion. This study was registered with the Chinese Clinical Trial Registration Center (ChiCTR1900026286).

Results: First, we found BCMA-CD38 CAR-T cells exhibited enhanced killing effect on BCMA+CD38+ cells in vitro, compared to BCMA CAR-T and CD38 CAR-T cells. We further demonstrated its anti-tumor activity in vivo. Then, we enrolled 16 R/R MM patients for safety and efficacy analyses. Of the 16 evaluable patients, 14 (87.5%) respond to the treatment, including 13 stringent complete response (sCR) and one partial response (PR), while two patients did not respond. At a median follow-up of 11.5 months, of the 13 patients who achieved sCR, 76.9% (10/13) did not relapse or progress during follow-up. Relapse occurred in 3 patients (Patient 2, 3 and 4) after achieving sCR. In sum, four patients died, of which one died of hemophagocytic lymphohistiocytosis syndrome secondary to severe cytokine release syndrome (CRS) and three died of disease progression or relapse. The 1-year progression-free survival rates was 68.8%. The 1-year overall survival rate was 75.0%. Extramedullary lesions were eliminated in 62.5% (5/8) patients. The most common symptoms after CAR-T infusion were cytopenia (16, 100%), fever (10, 62.5%), fatigue (8, 50.0%) and myalgias (8, 50.0%). Twelve patients (75.0%) were observed with various grades of CRS, of which five patients (31.3%) got serious CRS (Grade ≥ 3). The CAR+ cell expansion levels were associated with the severity of CRS. Transient clonal isotype switch was observed after CAR-T infusion.

Conclusion: Our results confirm that BCMA-CD38 CAR-T cells therapy is feasible in treating R/R MM patients, with high response rate, low recurrence rate and manageable CRS, which will be a promising treatment option for R/R MM.

Trial registration: ChiCTR1900026286, registered on September 29, 2019, retrospectively registered, URL: https://www.chictr.org.cn/showproj.aspx?proj=43805.

Keywords: BCMA; CAR-T; CD38; Efficacy; Multiple myeloma; Safety.

Fig. 1

BCMA-CD38 bispecific CAR-T effectively lysed BCMA+CD38+ tumor cells in vitro and in vivo studies. A Diagram of CAR cDNA plasmid and CAR-T cell structures. BCMA-CD38 CAR was composed of BCMA and CD38 targeting domains, human CD8 alpha hinge and transmembrane domain (CD8α hinge + TM), human 4-1BB cytoplasmic domain, and a human CD3 zeta cytoplasmic domain (CD3ζ). BCMA or CD38 CAR was composed of BCMA or CD38 targeting domains, human CD8 alpha hinge and transmembrane domain (CD8α hinge + TM), human 4-1BB cytoplasmic domain, and a human CD3 zeta cytoplasmic domain (CD3ζ). B Representative dot-plots of FCM analysis, detecting the CAR+ expression in T cells 6 days after CD38, BCMA and BCMA-CD38 virus transduction. C Cell indices of BCMA+CD38+ Hela cells were recorded by RTCA after treated with T cells, CD38 CAR-T cells, BCMA CAR-T cells and BCMA-CD38 CAR-T cells at E:T ratios of 0.5 and 2.5. Three replicates were done for each sample. Area under curves (AUC) of cell indices were calculated and statistically analyzed. NS: no statistically significant, *P < 0.05, **P < 0.01, ***P < 0.001. D IL-2, IL-6, IFN-γ and TNF-α levels were compared after treated with T cells, CD38 CAR-T cells, BCMA CAR-T cells and BCMA-CD38 CAR-T cells at E:T ratios of 2.5. NS: no statistically significant, *P < 0.05, **P < 0.01, ***P < 0.001. E Bioluminescence imaging (BLI) was used to assess tumor progression and regression of mice at different time after being treated with T cells and BCMA-CD38 CAR-T cells. Quantification of BLI as curves was presented. **P < 0.01, ***P < 0.001. F Representative dot-plots of FCM analysis, detecting the percentage of tumor cells in mice treated with T cells and BCMA-CD38 CAR transducing T cells on day 36. The cells were stained with GFP and anti-Human CD45. The blue populations were CAR-T cells expressing human CD45, and the red populations were MM cells expressing GFP and human CD45

Fig. 2

BCMA-CD38 CAR-T cells had potent activity against intramedullary lesion in MM patients. A The duration of response to BCMA-CD38 CAR-T in 16 cases was assessed according to IMWG 2016. B The best objective response (BOR) after BCMA-CD38 CAR-T infusion to the cut off data. C The PFS curves of patients after BCMA-CD38 CAR-T infusion. D The OS curves of patients after BCMA-CD38 CAR-T infusion. E Left: CD38 expression by FCM in bone marrow before and 1 month after CAR-T cell infusion was compared. Right: Serum MIg determined by SPEP before and 1 month after CAR-T cell infusion was compared. Wilcoxon matched-pairs signed rank test was used for statistical comparison. F Left: The amplification curves of CAR+ T cells in peripheral blood of patients (response ≥VGPR) assessed by FCM; Middle: The amplification curves of CAR+ T cells in peripheral blood of patients (response <VGPR) assessed by FCM; Right: Peak values of CAR+ T cells in peripheral blood of patients assessed by FCM were compared between patients whose response ≥VGPR and response <VGPR after CAR-T delivery

Fig. 3

BCMA-CD38 CAR-T cells had potent activity against extramedullary lesions in MM patients. A - D The extramedullary lesions of patient 4 (A), 8 (B), 12 (C) and 15 (D) before and 2 months after BCMA-CD38 CAR-T infusion

Fig. 4

CRS and its risk factors. A The adverse events after BCMA-CD38 CAR-T infusion. B The rates of different CRS grades. C The peak cytokine levels (IL-6, Ferritin and CRP) between CRS grade ≥ 3 and CRS grade <3 were compared. Mann-Whitney test was used for statistical comparison. D The risk factors (MIg, β2MG, doses of CAR-T infusion, light chain, and the percentages of CD38+ and BMCA+ plasma in bone marrow) at baseline were compared between CRS grade ≥ 3 and CRS grade <3. Mann-Whitney test was used for statistical comparison. E The amplification curves and peak values of CAR+ T cells in peripheral blood of patients assessed by FCM were compared between CRS grade ≥ 3 and CRS grade <3 after CAR-T cells infusion. Mann-Whitney test was used for statistical comparison

Fig. 5

One typical cases of patients treated with BCMA-CD38 CAR-T cells. SPEP (A) and FCM analysis (B) detecting CD269 and CD38 of Patient 10 before and after CAR-T infusion

Fig. 6

Severe CRS resulted in HLH in Patient 6. A CAR+ cells in PBMC of Patient 6 was tested by FCM before and after BCMA-CD38 CAR-T infusion. Curves of max value of temperature (Tmax) and CRP before and after CAR-T infusion was recorded. B Curves of inflammatory factors (Ferritin, IL-6, and D2 polymer) of Patient 6 before and after BCMA-CD38 CAR-T infusion. C Morphology and FCM analysis detecting CD269 and CD38 staining of BMC of Patient 6 before, 1 and 2 months after BCMA-CD38 CAR-T infusion. D The extramedullary lesion images of Patient 6 before and 2 months after BCMA-CD38 CAR-T infusion. E White blood cells (WBC), hemoglobin (HGB) and platelet (PLT) levels of Patient 6 before and after BCMA-CD38 CAR-T infusion