Correlation between the expression of BCMA/soluble BCMA and the efficacy of BCMA CAR-T cell therapy in relapsed/refractory multiple myeloma

doi:10.21203/rs.3.rs-5034798/v1

Anti-B cell maturation antigen (anti-BCMA) CAR T cell therapy has led to prolonged survival and response rates of 64-85% in patients with relapsed/refractory multiple myeloma (R/R MM). In a study of 29 R/R MM patients receiving anti-BCMA CAR T cell therapy, we aimed to identify predictors of pre-treatment efficacy and side effects. We observed multiple myeloma (MM) cells in bone marrow (BM), BCMA expression in MM cells, and soluble BCMA (sBCMA) levels in BM before and after therapy. Clinical response, CAR-T cell proportions, cytokine levels, and adverse events (AEs) were monitored during therapy. Twenty patients (68.97%) experienced an objective response rate (ORR) to the therapy. Before CAR-T cell therapy, there were no differences in the proportions of MM cells or BCMA expression between the ORR group and the MR+SD group, but sBCMA levels were higher in the MR+SD group compared to the ORR group. After therapy, BCMA and sBCMA expressions were lower in the ORR group than in the MR+SD group. In patients who achieved ORR, the peak levels of CAR-T cells correlated with the proportion of MM cells. IL-6 levels were correlated with the proportion of MM cells and sBCMA expressions. There were no differences in the proportion of MM cells, BCMA expressions, or sBCMA expressions between the grade 0-1 cytokine release syndrome (CRS) group and the grade 2-4 CRS group. The proportion of MM cells and BCMA expressions were lower in the grade 0 immune effector cell-associated neurotoxic syndrome (ICANS) group compared to the grade 1-3 ICANS group. There was no correlation between BCMA expression in MM cells and sBCMA levels in BM. Interestingly, high sBCMA levels in BM impacted efficacy, while the proportions of MM cells in BM and BCMA expression in MM cells did not. Therefore, we suggest that sBCMA levels in BM could be used as a predictor of the efficacy of anti-BCMA CAR T cell therapy, but further clinical verification is needed (ChiCTR2000033925).

Anti-BCMA CAR-T

Multiple myeloma

BCMA expression

Soluble BCMA expression

Efficacy

Side effects

In the past two decades, the availability of new drugs has significantly improved the survival of multiple myeloma (MM) patients^[1]. Despite these advancements, MM remains incurable and has developed resistance to existing treatments^[2]. The prognosis for patients with relapsed/refractory (R/R) MM is very poor ^[3,4]. Chimeric antigen receptor (CAR) T cell therapy is transforming treatment for patients with hematologic malignancies^[5-7]. Anti-B cell maturation antigen (anti-BCMA) is specifically expressed in almost all MM patients ^[8]. BCMA, a transmembrane glycoprotein, is part of the tumor necrosis factor receptor superfamily (TNFRSF17) and is found on normal plasma cells and malignant MM cells. It is being studied as a target for CAR T cell therapy in R/R MM patients ^[9-11]. Anti-BCMA CAR T cell therapy has resulted in prolonged survival and response rates of 64-85% in R/R MM patients ^[12-15].

Before R/R MM patients receive anti-BCMA CAR T cell therapy, are there indicators that could predict the efficacy and side effects? Does BCMA expression in MM cells or soluble BCMA (sBCMA) levels in bone marrow (BM) affect the efficacy of anti-BCMA CAR T cell therapy? This is worthy of clinical exploration. sBCMA is cleaved by γ-secretase (GS) from the extracellular portion of BCMA ^[16]. Therefore, cleavage of BCMA by GS might theoretically limit the efficacy of anti-BCMA CAR T cell therapy by reducing the density of the target antigen ^[17]. A study showed that cleavage of BCMA could interfere with anti-BCMA CAR T cell recognition of MM cells by lowering target density on the MM cells and allowing sBCMA to bind to the BCMA CAR ^[18]. In a phase I clinical trial, it was reported that sBCMA levels declined more significantly after anti-BCMA CAR T cell therapy in the PR/VGPR/CR/sCR group than in the MR/SD/PD group^[12].

In our study, we explored the relationship between BCMA expression in MM cells and soluble BCMA expression in BM with the efficacy and side effects of anti-BCMA CAR T cell therapy. We aimed to identify indicators that could predict the efficacy before anti-BCMA CAR T cell therapy.

Clinical data of the patients before anti-BCMA CAR-T cell therapy

Twenty-nine R/R MM patients were admitted to our hospital to receive anti-BCMA CAR T cell therapy between January 2019 and August 2021. All patients had MM cells in BM that were detectable by flow cytometry (FCM). Follow-up was conducted from the date of anti-BCMA CAR T cell infusion to the cutoff date or the date of death. The cutoff date was December 31, 2022.

Preparation of anti-BCMA CAR T cells

Peripheral blood mononuclear cells (PBMCs) were collected from all R/R MM patients. CD3+ T cells were isolated using Ficoll density gradient centrifugation and selected using CD3 microbeads (MiltenyiBiotec, Inc., Cambridge, MA, USA). These cells were then stimulated using anti-CD3/anti-CD28 mAb-coated Human T-Expander beads (Cat. no. 11141D, Thermo Fisher Scientific, Inc., Waltham, MA, USA) and cultured in X-Vivo 15 culture medium (Lonza Group, Ltd., Basel, Switzerland) supplemented with 250 IU/mL interleukin-2 (IL-2) (Proleukin, Novartis International AG, Basel, Switzerland). CD3+ T cells (3 × 10^6) were transduced with lentiviral supernatant from 293T cells transfected with an anti-BCMA CAR plasmid (20 µg, lenti-BCMA-2rd-CAR, Shanghai Genbase Biotechnology Co., Ltd., Shanghai, China). On the 12th to 15th days of cultivation, transduction efficiencies of anti-BCMA CAR were detected by FCM (BD Biosciences, San Jose, CA, USA).

Anti-BCMA-CAR T cell therapy

All twenty-nine R/R MM patients were enrolled in a clinical trial of anti-BCMA CAR T cell therapy (ChiCTR1800017051 and ChiCTR2000033925) at our hospital. From day -4 to day -2, the patients received lymphodepleting chemotherapy with fludarabine (30 mg/m²) and cyclophosphamide (400 mg/m²). The target dose of 2×10⁶ cells/kg autologous anti-BCMA CAR T cells was infused on day 0.

Evaluation criteria for diagnostic and therapeutic efficacy

The clinical response and disease progression after anti-BCMA CAR T cell therapy were assessed according to the International Myeloma Working Group (IMWG) Uniform Response Criteria for Multiple Myeloma two months after CAR T cell infusion ^[19]. Clinical responses included stringent complete response (sCR), complete response (CR), very good partial response (VGPR), partial response (PR), minimal response (MR), stable disease (SD), and progression of disease (PD). The overall response rate (ORR), overall survival (OS), and progression-free survival (PFS) were observed. ORR was defined as the proportion of patients who achieved sCR, CR, VGPR, or PR.

Detection of BCMA expression in MM cells and soluble BCMA (sBCMA) expression in BM

BCMA (CD269) expression in MM cells in BM, pleural effusion, and cerebrospinal fluid was detected by FCM (MACS MiltenyiBiotec, Inc., 5200206336) before and two months after the anti-BCMA CAR T cell infusion. Serum from BM was extracted and sBCMA expression was detected by FCM (QuantoBioBiotec, Inc., B113377) before and two months after the infusion.

The proportions of anti-BCMA-CAR T cell in peripheral blood

In our study, the proportions of anti-BCMA CAR T cells in CD3+ T cells in peripheral blood were observed on days 0, 7, 14, 28, and 60 post-infusion by FCM. Proportions of anti-BCMA CAR T cells in pleural effusion and cerebrospinal fluid were also observed by FCM.

Adverse events (AEs) observation in therapy

Cytokines, including interleukin-6 (IL-6), IL-2R, and tumor necrosis factor-α (TNF-α), were measured on days 0, 7, 14, 28, and 60 using enzyme-linked immunosorbent assay (ELISA). AEs were monitored during anti-BCMA CAR T cell therapy. The cytokine release syndrome (CRS) grade was determined according to the National Cancer Institute Common Terminology Criteria for AEs v4.03 ^[20]. Neurotoxicity syndrome was assessed according to the Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS) ^[21].

Statistical analysis

All statistical analyses were performed using GraphPad Prism 8 and SPSS 17.0 software. Data were expressed as mean ± SE. OS was defined as the time from the start of treatment to the date of death from any cause or the last follow-up day. PFS was defined as the time from treatment to disease progression or death from any cause. The probabilities of PFS and OS were analyzed using the Kaplan-Meier method. Data comparisons between groups were conducted using Fisher’s exact test. Correlations between variables with a normal distribution were assessed using Pearson’s correlation test, while those with abnormal distributions were assessed using Spearman’s rho test. All reported P-values are two-sided, and a P-value < 0.05 was considered statistically significant.

Patient characteristics

Table 1 shows the characteristics of all twenty-nine R/R MM patients enrolled in our clinical trial. The median follow-up time was 12.1 months (range: 3-33 months) after receiving anti-BCMA CAR T cell therapy.

BCMA expression in MM cells and sBCMA expression in BM

BCMA expression in MM cells and sBCMA expression in BM, as measured by FCM, are listed in Table 1. The median BCMA expression was 58.2% (IQR 29.1-83.2), and the median sBCMA expression was 31,712 pg/mL (IQR 19,441-40,801). There was no correlation between BCMA expression in MM cells and sBCMA expression in BM (R² = 0.0506, P = 0.2405).

Transduction efficiency, amplification efficiency and infusion dose of anti-BCMA CAR-T cells

The median anti-BCMA CAR transduction efficiency in the final product for these R/R MM patients was 41.06 ± 8.36%. Patients received an infusion dose of (2.09 ± 0.16) × 10⁶ cells/kg autologous anti-BCMA CAR T cells on day 0 after lymphodepleting chemotherapy.

Clinical responses of anti-BCMA CAR-T cell therapy

The median response time for patients to achieve the best effect was 2.07 ± 0.94 months. Twenty patients (68.97%) had an ORR, with ten achieving sCR/CR, four achieving VGPR, and six achieving PR. The other nine patients achieved MR and SD only (Figure 1A). One patient (Pt 15) who achieved VGPR received auto-HSCT two months after anti-BCMA CAR T cell therapy. Pt 22 died of CRS, Pt 18 died of cerebral hemorrhage four months after CAR T cell therapy, and Pt 5 died of infection eighteen months after CAR T cell therapy.

There was no difference in the proportion of MM cells between the ORR group and the MR+SD group (P=0.8433), nor in BCMA expression in MM cells between these groups (P=0.2948). However, sBCMA levels in BM were higher in the MR+SD group than in the ORR group (P=0.0048) (Figure 1 BCD). Among the twenty-nine patients, nine experienced disease progression again, and five of them died of MM. In these nine patients, there was no difference in the proportion of MM cells between the no progression group and the progression group (P=0.1642), nor in BCMA expression in MM cells or sBCMA levels in BM (P=0.6940 and 0.1756) (Figure 1 EFG). BCMA expression in MM cells and sBCMA levels in BM decreased significantly two months after infusion (P<0.001 and P<0.001) (Figure 1 HI). These indicators were lower in the ORR group than in the MR+SD group (P<0.001 and P<0.001) after anti-BCMA CAR T cell therapy (Figure 1JK).

As of the cutoff date, Kaplan-Meier analysis showed that PFS was 78.1% at 6 months and 64.8% at 12 months. OS was 84.7% at 6 months and 70.2% at 12 months (Figure 2).

Expressions of anti-BCMA-CAR T cells

During anti-BCMA CAR T cell therapy, the proportions of CAR T cells were measured on day 0, 4, 7, 14, 28, and 60 after infusion (Figure 3A). The median expansion peak of anti-BCMA CAR T cells in CD3+ T cells in peripheral blood was 27.3% (IQR 3.2-43.7). The average time to reach the expansion peak was 11.1 ± 3.4 days. The median expansion peak of anti-BCMA CAR T cells in CD3+ T cells in the ORR group was 33.2% (IQR 21.8-43.7), higher than in the MR+SD group (14.3% (IQR 3.2-21.7)) (P=0.0150) (Figure 3B).

There was no correlation between the peaks of CAR T cells and the proportion of MM cells (P=0.1050), BCMA expression in MM cells (P=0.3400), or sBCMA levels in BM (P=0.7100) (Figure 3CDE). However, in patients who achieved ORR, the peaks of CAR T cells correlated with the proportion of MM cells (P=0.0045). There was no correlation between the peaks of CAR T cells and BCMA expression in MM cells (P=0.1067) or sBCMA levels in BM (P=0.1956) (Figure 3FGH).

Serum levels of cytokines

In the humanized anti-BCMA CAR T cell therapy, serum levels of IL-2R, IL-6, and TNF-α peaked 7 to 14 days after infusion and declined 12 to 21 days after infusion. In patients who achieved ORR, IL-6 levels correlated with the proportion of MM cells in BM (P=0.0016) and with sBCMA levels in BM (P=0.0265), but not with BCMA expression in MM cells (P=0.0921) (Figure 4A-C). There was no correlation between IL-2R levels and the proportion of MM cells (P=0.0567), BCMA expression in MM cells (P=0.1083), or sBCMA levels in BM (P=0.0937) (Figure 4D-F). TNF-α levels correlated with the proportion of MM cells in BM (P=0.0115), but not with BCMA expression in MM cells (P=0.2327) or sBCMA levels in BM (P=0.1740) (Figure 4G-I).

The AEs in anti-BCMA-CAR T cell therapy

In anti-BCMA CAR T cell therapy, except for Pt 9, 22 patients were diagnosed with grade 4 CRS, Pt 13 and 18 were diagnosed with grade 3 CRS, and the remaining patients were diagnosed with grade 0-2 CRS. In this study, except for Pt 18, who was diagnosed with grade 3 ICANS, and Pt 22, who was diagnosed with grade 2 ICANS, the remaining patients were diagnosed with grade 0-1 ICANS. There was no difference in the proportion of MM cells in BM, BCMA expression in MM cells, or sBCMA levels in BM between the grade 0-1 CRS group and the grade 2-4 CRS group. Similar results were found between the grade 0 ICANS group and the grade 1-3 ICANS group. There was no difference in CRS levels or ICANS levels between patients with and without extramedullary disease (Figure 5A-H).

In all R/R MM patients who achieved ORR, there was no difference in the proportion of MM cells in BM, BCMA expression in MM cells, or sBCMA levels in BM between the grade 0-1 CRS group and the grade 2-4 CRS group (Figure 5 I, K, M). The proportion of MM cells in BM and BCMA expression in MM cells were lower in the grade 0 ICANS group than in the grade 1-3 ICANS group (Figure 5 J, L). However, there was no significant difference in sBCMA levels in BM between the grade 0 ICANS group and the grade 1-3 ICANS group, although levels were higher in the grade 1-3 ICANS group (Figure 5 N). CRS levels were higher in patients with extramedullary disease compared to those without it (Figure 5 O), but there was no difference in ICANS levels between patients with and without extramedullary disease (Figure 5 P).

During anti-BCMA CAR T cell therapy, patients developed symptoms such as fever with or without chills, fatigue, headache, nausea, reduced appetite, hypotension, and edema from 3-7 days after infusion. These symptoms resolved 14 to 60 days post-infusion. Hematological toxicity ranged from grade 1-4 and occurred 5 to 8 days post-infusion, resolving 18 to 60 days later. Patients received tocilizumab, methylprednisolone, antipyretic analgesics, and supportive treatment to alleviate symptoms (Table 2).

Three patients with grade 3-4 hematological toxicity and grade 1-3 CRS developed gram-negative bacterial infections during therapy, which were managed with anti-infective treatment (Table 3). Only one patient (Pt 5), who maintained PR after therapy, died of invasive fungal disease and cytomegalovirus infection 18 months post-infusion. Four patients developed renal insufficiency or failure during therapy and were treated with hemofiltration or hemodialysis. One patient (Pt 22) was diagnosed with grade 4 CRS and grade 2 ICANS and died of cerebral hemorrhage 62 days post-infusion. Her anti-BCMA CAR T cells in peripheral blood were 23.5% at 60 days post-infusion (Figure 3A). The other three patients recovered from hemodialysis or hemofiltration about 30 days post-infusion (Table 3).

Advances in treatment over the past two decades have significantly improved the survival of MM patients. However, there is still a need for more effective treatments, especially for R/R MM patients resistant to existing therapies. Anti-BCMA CAR T cell therapy has emerged as a promising treatment with potential for long-term disease control in these patients and represents a breakthrough in therapy for R/R MM ^[22-24]. Targeting BCMA in CAR T cell therapy and antibody-based approaches is currently being explored in many clinical trials ^{[25, 26]}. However, incomplete tumor eradication and subsequent disease progression remain challenges to be addressed in CAR T cell therapy ^{[27, 28]}. One factor contributing to incomplete tumor eradication and recurrent disease in anti-BCMA CAR T cell therapy is the failure to completely eliminate MM cells, as BCMA is often expressed at low levels in these cells^{[15, 29-30]}.

BCMA is a highly selective target for CAR T cell therapy in patients with R/R MM ^[31]. However, the heterogeneity of BCMA expression on MM cells poses a challenge to the efficacy of these therapies ^[15]. In our study, BCMA was significantly differentially expressed among R/R MM patients (median expression: 58.2%, IQR 29.1-83.2%). Another factor that may be associated with clinical status among MM patients is sBCMA expression ^[32]. It has been shown that sBCMA levels are higher in patients with PD than in those with CR and decrease with response to therapy. Other studies have reported that the half-life of sBCMA and changes in sBCMA levels in clinical status are much more rapid than M-protein in MM patients ^{[33, 34]}.

Our study explored whether there is a correlation between BCMA expression in MM cells or sBCMA expression in BM and the efficacy of anti-BCMA CAR T cell therapy in R/R MM patients. We found no correlation between BCMA expression in MM cells and sBCMA expression in BM. Additionally, there was no correlation between the ORR of this anti-BCMA CAR T cell therapy and the proportion of MM cells or BCMA expression in MM cells in our clinical trials. Interestingly, sBCMA expression in BM was lower in the ORR group compared to the MR+SD group. In our study, nine patients experienced disease progression after anti-BCMA CAR T cell therapy. This progression was not associated with the proportion of MM cells, BCMA expression in MM cells, or sBCMA expression in BM. A previous study ^[14] reported that the response rate to BCMA-targeting CAR T cells was similar in patients with high or low BCMA expression. The response rates were 100% for those with BCMA expression less than 50% and 91% for those with BCMA expression of 50% or more on MM cells at screening. This result is consistent with our findings. sBCMA could be a biomarker correlated with tumor burden and prognosis in MM patients ^[32,35]. High levels of sBCMA might interfere with anti-BCMA CAR T cell function ^[36]. However, no clinical evidence to date suggests that sBCMA levels negatively impact anti-BCMA CAR T cells. Our study preliminarily supports this result, but further confirmation with a larger sample size is needed.

In our previous studies ^[37,38], we found that although the grades of CRS and ICANS were higher in patients with extramedullary disease, the ORR did not differ between patients with or without extramedullary disease. However, R/R MM patients with extramedullary disease were more likely to experience disease progression. Similar results were obtained in this current study.

CAR T cell therapy can produce potentially life-threatening toxicities, such as CRS and neurotoxicity ^[39,40]. Close monitoring and attention are essential when administering anti-BCMA CAR T cell therapy ^[41-43]. In this therapy, the peaks of CAR T cells did not correlate with the proportion of MM cells, BCMA expression in MM cells, or sBCMA expression in BM. This was relevant only if R/R MM patients achieved ORR, where the peaks of CAR T cells were higher in the ORR group than in the MR+SD group. IL-6 levels were related to the proportions of MM cells in BM and the levels of sBCMA expression in BM, but not to BCMA expression in MM cells.

To explore the factors related to the efficacy of anti-BCMA CAR T cell therapy in R/R MM, we summarized the predictive results of different indicators for its efficacy. We found no correlation between BCMA expression in MM cells and sBCMA expression in BM. Interestingly, high sBCMA expression in BM affected the therapy's efficacy, while the proportions of MM cells in BM and BCMA expression in MM cells did not. Therefore, could sBCMA expression in BM be a predictor of the efficacy of anti-BCMA CAR T cell therapy? Further clinical verification is needed to confirm this.

Acknowledgements

We thank all our patients for their participation in our clinical trials.

We also thank Shanghai Genbase Biotechnology Co., Ltd. for providing the anti-BCMA CAR T cells.

Author contributions

Concept and design: DQ Manuscript drafting or revision: FMW and LZ Data acquisition: GSQ, YT, AG, and CR Data analysis and interpretation: FMW and MJ Manuscript writing, review, and/or revision: FMW, LZ, and DQ Study supervision: DQ

Funding

This work was supported by the Tianjin Health Research Project (TJWJ2023ZD003), the Chinese Society of Clinical Oncology Beijing Xisike Clinical Oncology Research Foundation (Y-NCJH202201-0027, and Y-2022YMJN/MS-0001) .

Ethics approvalThis study was approved by the Medical Ethics Committee of the Department of Hematology, Tianjin First Center Hospital (Tianjin, China), with approval numbers2020N028KY. The clinical trial in our study was registered at http://www.chictr.org.cn/index.aspx as ChiCTR2000033925.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Competing interests

The authors declare no competing interests.

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ORCID: Qi Denghttps://orcid.org/0000-0002-3646-4953

Abramson H N. The Multiple Myeloma Drug Pipeline-2018: A Review of Small Molecules and Their Therapeutic Targets.Clinical Lymphoma Myeloma & Leukemia 2018;18:611-627
Kazandjian D. Multiple myeloma epidemiology and survival: A unique malignancy.Seminars in Oncology 2016;43:676-681
Moreau P. How I treat myeloma with new agents.Blood 2017;130:1507-1513
Lonial S, L H Boise, and J Kaufman. How I treat high-risk myeloma.Blood 2015;126:1536-1543
Kochenderfer J N, M E Dudley, S H Kassim,et al. Chemotherapy-Refractory Diffuse Large B-Cell Lymphoma and Indolent B-Cell Malignancies Can Be Effectively Treated With Autologous T Cells Expressing an Anti-CD19 Chimeric Antigen Receptor.Journal of Clinical Oncology 2015;33:540-U31
Maude S L, N Frey, P A Shaw,et al. Chimeric Antigen Receptor T Cells for Sustained Remissions in Leukemia.New England Journal of Medicine 2014;371:1507-1517
Turtle C J, K A Hay, L A Hanafi,et al. Durable Molecular Remissions in Chronic Lymphocytic Leukemia Treated With CD19-Specific Chimeric Antigen Receptor-Modified T Cells After Failure of Ibrutinib.Journal of Clinical Oncology 2017;35: 3010-3020
Hosen N. Chimeric Antigen Receptor T-Cell Therapy for Multiple Myeloma.Cancers 2019;11: 2024
O'Connor B P, V S Raman, L D Erickson,et al. BCMA is essential for the survival of long-lived bone marrow plasma cells.Journal of Experimental Medicine 2004;199:91-97
Seckinger A, J A Delgado, S Moser,et al. Target Expression, Generation, Preclinical Activity, and Pharmacokinetics of the BCMA-T Cell Bispecific Antibody EM801 for Multiple Myeloma Treatment.Cancer Cell 2017;31:396-410
Friedman K M, T E Garrett, J W Evans,et al. Effective Targeting of Multiple B-Cell Maturation Antigen-Expressing Hematological Malignances by Anti-B-Cell Maturation Antigen Chimeric Antigen Receptor T Cells.Human Gene Therapy 2018;29:585-601
Cohen A D, A L Garfall, E A Stadtmauer,et al. B cell maturation antigen-specific CAR T cells are clinically active in multiple myeloma.Journal of Clinical Investigation 2019;129:2210-2221
Ali S A, V Shi, I Maric,et al. T cells expressing an anti-B-cell maturation antigen chimeric antigen receptor cause remissions of multiple myeloma.Blood 2016;128:1688-1700
Raje N, J Berdeja, Y Lin,et al. Anti-BCMA CAR T-Cell Therapy bb2121 in Relapsed or Refractory Multiple Myeloma.New England Journal of Medicine 2019;380:1726-1737
Brudno J N, I Maric, S D Hartman,et al. T Cells Genetically Modified to Express an Anti-B-Cell Maturation Antigen Chimeric Antigen Receptor Cause Remissions of Poor-Prognosis Relapsed Multiple Myeloma.Journal of Clinical Oncology 2018;36: 2267-2280
Laurent S A, F S Hoffmann, P H Kuhn,et al. γ-Secretase directly sheds the survival receptor BCMA from plasma cells.Nature Communications 2015; 6:7333
Chen H, Li M, Xu N, et al. Serum B-cell maturation antigen (BCMA) reduces binding of anti-BCMA antibody to multiple myeloma cells.Leukemia research2019; 81:62-66.
Pont M J, T Hill, G O Cole,et al. gamma-Secretase inhibition increases efficacy of BCMA-specific chimeric antigen receptor T cells in multiple myeloma.Blood 2019;134:1585-1597
Rajkumar S V, M A Dimopoulos, A Palumbo,et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma.Lancet Oncology 2014;15:E538-E548
Lee DW, Santomasso BD, Locke FL.et al.ASTCT consensus grading for cytokine release syndrome and neurologic toxicity associated with immune effector cells.Biol Blood Marrow Transplant2019; 25: 625-638
Lee D W, B D Santomasso, F L Locke,et al. ASTCT Consensus Grading for Cytokine Release Syndrome and Neurologic Toxicity Associated with Immune Effector Cells.Biology of Blood and Marrow Transplantation 2019;25:625-638
Adaniya S P S, A D Cohen, and A L Garfall. Chimeric antigen receptor T cell immunotherapy for multiple myeloma: A review of current data and potential clinical applications.American Journal of Hematology2019;94:S28-S33
Wu C, L N Zhang, Q R Brockman,et al. Chimeric antigen receptor T cell therapies for multiple myeloma.Journal of Hematology & Oncology 2019;12:120
Timmers M, G Roex, Y D Wang,et al. Chimeric Antigen Receptor-Modified T Cell Therapy in Multiple Myeloma: Beyond B Cell Maturation Antigen.Frontiers in Immunology 2019;10:1613
Varga C, J P Laubach, K C Anderson,et al. Investigational agents in immunotherapy: a new horizon for the treatment of multiple myeloma.BritishJournal of Haematology 2018;181:433-446
Lyu M A, L H Cheung, W N Hittelman,et al. The rGel/BLyS fusion toxin specifically targets malignant B cells expressing the BLyS receptors BAFF-R, TACI, and BCMA.Molecular Cancer Therapeutics 2007;6:460-470
O'Rourke D M, M P Nasrallah, A Desai,et al. A single dose of peripherally infused EGFRvIII-directed CAR T cells mediates antigen loss and induces adaptive resistance in patients with recurrent glioblastoma.ScienceTranslational Medicine 2017;9: eaaa0984
Grupp S A, M Kalos, D Barrett,et al. Chimeric Antigen Receptor-Modified T Cells for Acute Lymphoid Leukemia.New England Journal of Medicine 2013;368:1509-1518
Watanabe K, S Terakura, A C Martens,et al. Target Antigen Density Governs the Efficacy of Anti-CD20-CD28-CD3 zeta Chimeric Antigen Receptor-Modified Effector CD8(+) T Cells.Journal of Immunology 2015;194:911-920
Walker A J, R G Majzner, L Zhang,et al. Tumor Antigen and Receptor Densities Regulate Efficacy of a Chimeric Antigen Receptor Targeting Anaplastic Lymphoma Kinase.Molecular Therapy 2017;25:2189-2201
Tai Y T and K C Anderson. Targeting B-cell maturation antigen in multiple myeloma.Immunotherapy 2015;7:1187-1199
Sanchez E, M J Li, A Kitto,et al. Serum B-cell maturation antigen is elevated in multiple myeloma and correlates with disease status and survival.British Journal of Haematology 2012;158:727-738
Sanchez E, A Gillespie, G Tang,et al. Soluble B-Cell Maturation Antigen Mediates Tumor-Induced Immune Deficiency in Multiple Myeloma.Clinical Cancer Research 2016;22:3383-3397
Anderson C L, C Chaudhury, J Kim,et al. Perspective - FcRn transports albumin: relevance to immunology and medicine.Trends in Immunology 2006;27:343-348
Ghermezi M, M J Li, S Vardanyan,et al. Serum B-cell maturation antigen: a novel biomarker to predict outcomes for multiple myeloma patients.Haematologica 2017;102:785-795
Ying Shen, Jie Liu, Baiyan Wang, et al. Serum soluble BCMA can be used to monitor relapse of multiple myeloma patients after chimeric antigen receptor T-cell immunotherapy.Current research in translational medicine 2023; 71:103378
Deng H B, M J Liu, T Yuan,et al. Efficacy of Humanized Anti-BCMA CAR T Cell Therapy in Relapsed/Refractory Multiple Myeloma Patients With and Without Extramedullary Disease.Frontiers in Immunology 2021;12: 720571
Li W, M J Liu, T Yuan,et al. Efficacy and follow-up of humanized anti-BCMA CAR-T cell therapy in relapsed/refractory multiple myeloma patients with extramedullary-extraosseous, extramedullary-bone related, and without extramedullary disease.Hematological Oncology 2022; 40: 223-232
Brudno J N and J N Kochenderfer. Toxicities of chimeric antigen receptor T cells: recognition and management.Blood 2016;127:3321-3330
Liu D L and J J Zhao. Cytokine release syndrome: grading, modeling, and new therapy.Journal of Hematology & Oncology 2018;11: 121
Neelapu S S, S Tummala, P Kebriaei,et al. Chimeric antigen receptor T-cell therapy - assessment and management of toxicities.Nature Reviews Clinical Oncology 2018;15:47-62
Mei H, H W Jiang, Y H Wu,et al. Neurological toxicities and coagulation disorders in the cytokine release syndrome during CAR-T therapy.British Journal of Haematology 2018;181:689-692
Brudno J N and J N Kochenderfer. Recent advances in CAR T-cell toxicity: Mechanisms, manifestations and management.BloodReviews 2019;34:45-55

Table 1. Baseline characteristics of the R/R multiple myeloma patients

Pt

Sex

Age

KPS

Subtype

ISS stage

MM cells in BM, %

BCMA expression

(%)

sBCMA

expression (pg/mL)

High-Risk
Cytogenetics

Extramedullary disease

Numbers of
prior therapy

BCMA CAR-T cell therapy before

(Murine CAR-T)

Auto-HSCT before

1

Female

70

100

IgG-κ

III

32.6

90.8

29415

Del(17p)，t(4;14)

Yes

10

Yes

No

2

Male

72

100

Nonsecretory

III

28.9

88.2

16007

None

4

No

3

Female

77

90

IgD-κ

III

66.8

1.5

48945

None

13

No

4

Male

57

70

k light chain

III

86.0

55.8

40801

t(4;14)，t(14;16)，Del(17p)

None

14

No

Yes

5

Male

63

80

IgG-κ

III

35.6

92.9

11751

t(14,16)

None

5

No

Yes

6

Female

52

100

IgA-λ

III

20.7

62.6

33816

None

9

No

7

Male

66

70

IgA-κ

II

19.2

49.1

33659

t(14;16)，Del(17p)

None

16

No

8

Male

44

100

IgG-κ

II

22.1

96.5

28790

t(14;16)

None

5

No

9

Female

58

90

IgG-λ

III

88.1

1.6

49623

None

Yes

30

No

10

Male

59

100

k light chain

III

41.8

77.3

21276

t(14,16)

Yes

7

Yes

No

11

Female

54

90

IgG-κ

III

17.5

16.8

11245

None

8

No

12

Male

56

70

IgG-κ

II

32.3

78.1

79448

None

Yes

10

No

13

Female

38

90

k light chain

II

20.4

69.7

41187

None

Yes

17

No

Yes

14

Male

73

90

IgD-λ

II

23.0

69.8

37856

None

Yes

12

No

15

Male

45

90

IgG-κ

II

19.4

92.5

32045

None

7

No

16

Male

46

100

IgG-κ

III

22.2

71.1

18742

None

9

No

17

Male

65

90

k light chain

III

17.0

29.1

26425

None

Yes

6

No

Yes

18

Female

79

60

λ light chain

III

79.4

12.9

37973

Del(17p)

Yes

28

No

19

Male

63

80

IgG-κ

III

32.4

30.8

26425

t(14,16)

Yes

25

No

20

Female

58

90

IgG-κ

II

16.1

87.3

27427

None

8

No

21

Female

64

80

IgA-κ

III

64.4

76.2

44437

Del(17p)

None

14

No

22

Female

65

60

k light chain

III

89.6

92.1

33816

t(14;16)，Del(17p)

None

22

No

23

Male

55

100

IgG-κ

II

22.1

82.4

17378

None

Yes

15

No

24

Male

68

60

IgD-λ

III

40.1

26.3

49826

t(4;14)

Yes

21

No

Yes

25

Female

55

90

IgG-λ

III

44.2

80.2

30731

t(14,16)

None

12

No

Yes

26

Female

59

70

λ light chain

III

60.8

0.6

47046

Del(17p)

None

27

No

27

Female

47

80

IgG-λ

III

14.8

73.1

7496

t(14;16)

None

9

No

Yes

28

Female

58

80

λ light chain

III

31.6

0.2

16634

None

21

No

29

Female

65

80

IgG-κ

III

29.6

83.2

19441

None

9

No

Table 2. Adverse events in the anti-BCMA CAR-T cell therapy, n (%)
	Any	Grade 1	Grade 2	Grade 3	Grade 4
Any	29 (100%)	0 (0%)	16 (55.17%)	7 (24.14%)	5 (17.24%)
Pyrexia	23 (79.31%)	4 (13.79 %)	11 (3.45 %)	7 (24.14%)	1 (3.45 %)
Chills	16 (55.17%)	2 (6.9 %)	7 (24.14%)	5 (17.24%)	2 (6.9%)
Fatigue	22 (75.86%)	9 (31.03%)	5 (17.24%)	6 (20.69%)	2 (6.9%)
Hematological toxicity (Leukopenia)	21 (72.41 %)	9 (31.03 %)	7 (24.14%)	4 (13.79%)	1 (3.45 %)
Hematological toxicity (Anemia)	18 (62.07 %)	8 (27.58 %)	5 (17.24%)	3 (10.34 %)	2 (6.9%)
Hematological toxicity (Thrombocytopenia)	20 (68.97 %)	11 (37.93%)	6 (20.69%)	2 (6.9%)	1 (3.45 %)
Hypocalcaemia	7 (24.14%)	3 (10.34 %)	3 (10.34 %)	1 (3.45 %)	0 (0%)
Hyponatraemia	6 (20.69%)	4 (13.79 %)	1 (3.45 %)	1 (3.45 %)	0 (0%)
Hypokalaemia	10 (34.48%)	5 (17.24%)	2 (6.9%)	3 (10.34 %)	0 (0%)
Nausea	10 (34.48%)	5 (17.24%)	3 (10.34 %)	1 (3.45 %)	1 (3.45 %)
Vomiting	6 (20.69 %)	4 (13.79%)	1 (3.45 %)	1 (3.45 %)	0 (0%)
Decreased appetite	23 (79.31 %)	11 (37.93%)	7 (24.14%)	3 (10.34 %)	2 (6.9%)
Constipation	5 (17.24%)	4 (13.79%)	1 (3.45 %)	0 (0%)	0 (0%)
Diarrhoea	10 (34.48%)	6 (20.69%)	1 (3.45 %)	2 (6.9%)	1 (3.45 %)
Increased aminotransferase	16 (55.17%)	8 (27.58 %)	4 (13.79%)	2 (6.9%)	2 (6.9%)
Hypoxemia	6 (20.69%)	4 (13.79 %)	1 (3.45 %)	1 (3.45 %)	0 (0%)
Dyspnoea	4 (13.79%)	2 (6.9%)	1 (3.45 %)	0 (0%)	1 (3.45 %)
Cough	7 (24.14%)	4 (13.79%)	2 (6.9%)	1 (3.45 %)	0 (0%)
Pleural effusion	11 (37.93%)	4 (13.79%)	2 (6.9%)	3 (10.34 %)	2 (6.9%)
Creatinine increased	11 (37.93 %)	5 (17.24%)	1 (3.45 %)	2 (6.9%)	2 (6.9%)
Hyperkalaemia	4 (13.79%)	3 (10.34 %)	0 (0%)	1 (3.45 %)	0 (0 %)
Peripheral oedema	11 (37.93%)	7 (24.14%)	2 (6.9%)	1 (3.45 %)	1 (3.45 %)
Tachycardia	4 (13.79%)	2 (6.9%)	1 (3.45 %)	1 (3.45 %)	0 (0%)
Sinus tachycardia	15 (51.72 %)	9 (31.03 %)	4 (13.79%)	1 (3.45 %)	1 (3.45 %)
Hypertension	7 (24.14%)	5 (17.24%)	1 (3.45 %)	1 (3.45 %)	0 (0%)
Hypotension	4 (13.79%)	3 (10.34 %)	1 (3.45 %)	0 (0%)	0 (0 %)
Headache	12 (41.38 %)	8 (27.58%)	3 (10.34 %)	1(3.45%)	0 (0%)
Dizziness	8 (27.58%)	5 (17.24%)	3 (10.34 %)	0 (0 %)	0 (0%)
Confusion	6 (20.69 %)	4 (13.79%)	2 (6.9%)	0 (0 %)	0 (0%)
Tremor	4 (13.79%)	3 (10.34 %)	1 (3.45 %)	0 (0%)	0 (0 %)
Epilepsy Coagulopathy	4 (13.79%) 8 (27.58%)	2 (6.9%) 5 (17.24%)	1 (3.45 %) 2 (6.9%)	1 (3.45 %) 0 (0%)	0 (0%) 1 (3.45%)
AEs were according to the National Cancer Institute’s Common Terminology Criteria for Adverse Events (version 5.0).

Table 3. Secondary infection and renal insufficiency in anti-BCMA CAR-T cell therapy

*Infection*	Effect evaluation	Days after infusion	CRS/ICANS	Leukopenia （×10⁹/L）	Pathogen / Therapy	Outcomes	ICU admission
Pt 1	CR	16	2 / 0	0.12	E. coli sepsis / Meropenem	Healing	No
Pt 9	PR	8	4 / 2	0.02	E. coli sepsis / Meropenem	Healing	No
Pt 26	MR	18	1 / 0	0.04	Staphylococcus aureus sepsis / Vancomycin + Meropenem	Healing	No
*Renal insufficiency*	Effect evaluation	Days after infusion	CRS/ICANS	Peak of creatinine （μmol/mL）	Therapy	Outcomes	ICU admission
Pt 3	VGPR	12	2 / 1	553.2	Hemodialysis	Healing	No
Pt 4	SD	9	1 / 0	415.0	Bedside hemofiltration	Healing	Yes
Pt 18	CR	5	2 / 0	611.6	Bedside hemofiltration	Healing	No
Pt 22	PR	7	4 / 2	707.2	Bedside hemofiltration	Death from cerebral hemorrhage	No

No competing interests reported.

Correlation between the expression of BCMA/soluble BCMA and the efficacy of BCMA CAR-T cell therapy in relapsed/refractory multiple myeloma

Status:

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Abstract

Figures

Introduction

Patients and Methods

Results

Discussion

Declarations

References

Tables

Additional Declarations

Status:

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