B-cell Maturation Antigen CAR Research Articles

Patient perspectives on BCMA-targeted therapies for multiple myeloma: a survey conducted in a patient advocacy group.

Advances in multiple myeloma (MM) treatment have shifted the therapeutic landscape. Understanding patients' perspectives can assist physicians in helping patients make informed decisions. This study aimed to understand the patient decision-making process and gain insights into patient perspectives on B-cell maturation antigen (BCMA)-targeted therapies for MM. An 18-question survey was completed by patients with MM enrolled in HealthTree® Cure Hub, an online portal helping patients with plasma cell dyscrasias navigate their disease. From October 28, 2022, to January 12, 2023, 325 patients with MM participated in the survey. The mean age (standard deviation) of the respondents was 66 (8) years; 54% were female and 90% were White. Among 218 patients with complete clinical records in the database, the median (min, max) lines of therapy (LOT) was 2 (1,16). Among 61 (28%) patients who had received ≥4 LOTs, 55 (90%) were triple-class exposed. Of the 290 patients who responded to the question about openness to new therapies, 76 (26%) were open to trying a new therapy immediately and 125 (43%) wanted more information on safety and efficacy. Most respondents reported likely or very likely to try a BCMA CAR T-cell therapy (60%) or a bispecific antibody (74%) and some needed more information to decide (16% for CAR T-cell therapy and 13% for bispecific antibody). The most requested information included efficacy, side effects (SEs), eligibility, and administration process for both CAR T-cell and bispecific therapies. When 2 therapies with the same efficacy and duration of response were offered, 69% of respondents would prefer the therapy with a lower risk of severe SEs but requires continuous dosing with no treatment-free interval, and 31% preferred a therapy given once followed by a treatment-free interval but with a potentially higher risk of severe SEs. To receive an effective therapy, the top acceptable trade-offs included frequent monitoring of SEs and initiating a new therapy in a hospital setting, and the least acceptable compromise was caregiver burden. This study found a high level of openness in patients with MM to try BCMA-targeted therapies. Information on efficacy, safety, availability, and eligibility may assist patients on decision-making.

Pre-Lymphodepletion Endothelial Activation and Stress Index As a Predictor of Clinical Outcomes in B-Cell Maturation Antigen CAR T Therapy for Multiple Myeloma

Pre-Lymphodepletion Endothelial Activation and Stress Index As a Predictor of Clinical Outcomes in B-Cell Maturation Antigen CAR T Therapy for Multiple Myeloma

BCMA CAR-T-Cell Therapy in Combination with Long-Term Pomalidomide Is a Safe and Effective Treatment for Relapsed/Refractory Multiple Myeloma

Background: B-cell maturation antigen (BCMA)-targeted chimeric antigen receptor T-cell (CAR-T-cell) therapy has exhibited remarkable efficacy in refractory or relapsed multiple myeloma (R/R MM), but recurrence and rapid progression of disease are still observed in some cases within a short time after treatment. Long-term pomalidomide therapy, which potentiates T-cell functionality and has direct antimyeloma effects, might enhance the efficacy of BCMA CAR-T-cell therapy. Here, we present the efficacy of this combination regimen for R/R MM. Methods: We performed a single-center prospective clinical study that was registered with the Chinese Clinical Trial Registration Center (ChiCTR2000036350). Patients with relpased or refractory multiple myeloma receiving BCMA CAR-T cell infusion were randomized to receive long-term pomalidomide treatment (4 mg/day) one month after infusion. The primary endpoint is overall survival (OS) in R/R MM with long-term pomalidomide administration compared to those without pomalidomide therapy after CAR T-cell infusion. The secondary endpoints include time to progression (TTP) and therapeutic response. Also, the copy numbers of CAR were assessed after infusion. Results: A total of 14 R/R MM patients who received BCMA CAT T-cell therapy, were included in this study. The median age of the enrolled R/R MM patients was 59.5 years (44-71). Five patients had high-risk cytogenetic abnormalities (IGH rearrangement, 1q21 amplification, and P53 deletion) at the time of initial diagnosis. In addition, high-risk genetic alterations were newly detected in patient 2 during first-line therapy. All patients had previously received 3 to 6 lines of treatment with proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), or anti-CD38 monoclonal antibodies. As shown in Figure 1, all patients had demonstrated progressive disease prior to CAR T-cell infusion. The objective response rate (ORR) of BCMA-CART was 100%. Three months following CAR-T-cell infusion, of the 6 patients receiving pomalidomide, all patients (6/6) achieved VGPR (very good partial response) or CR (complete response）, while only 5 patients (5/8) who did not receive pomalidomide treatment achieved VGPR or better. At a median follow-up of 19.7 months, for the 8 patients who did not receive pomalidomide administration, the median TTP (time to progression) was 4.5 (1-14) months, while the TTP was not reached in patients who received long-term pomalidomide treatment. Moreover, the dynamic abundance of circulating BCMA CAR-T cells was monitored as shown in Figure 2. In patients who received pomalidomide treatment after CAR-T-cell therapy, the CAR copy numbers of circulating CAR-T cells peaked 8 to 10 days after CAR-T-cell infusion, with a peak copy number of up to 10 6. In addition, BCMA CAR-T cells persisted (>1*10 3 copies/µg DNA) for 3 months in vivo. Without pomalidomide administration, BCMA CAR-T cells persisted for up to 2.5 months in the peripheral circulation (results not shown). Conclusion: Our results confirm the efficacy of the long-term oral pomalidomide administration (4 mg/day) after BCMA CAR T-cell infusion in patients with R/R MM. Notably, this combination regieme reduced the recurrence rate and prolonged progression-free survival for R/R MM patients, providing a promising option for treating R/R MM. In addition, oral administration of pomalidomide did not significantly prolong the persistence of BCMA CAR T-cells in vivo. However, data from studies with larger sample sizes are required to draw valid conclusions.

Safety and Efficacy of Fully Human BCMA CAR T Cells in Combination with a Gamma Secretase Inhibitor to Increase BCMA Surface Expression in Patients with Relapsed or Refractory Multiple Myeloma

Safety and Efficacy of Fully Human BCMA CAR T Cells in Combination with a Gamma Secretase Inhibitor to Increase BCMA Surface Expression in Patients with Relapsed or Refractory Multiple Myeloma

Identification and Development of PHE885: A Novel and Highly Potent Fully Human Anti-BCMA CAR-T Manufactured with a Novel T-Charge TM Platform for the Treatment of Multiple Myeloma

Identification and Development of PHE885: A Novel and Highly Potent Fully Human Anti-BCMA CAR-T Manufactured with a Novel T-Charge TM Platform for the Treatment of Multiple Myeloma

Development of JCARH125: Optimization of a Fully Human Anti-Bcma CAR for Use in the Treatment of Multiple Myeloma

Development of JCARH125: Optimization of a Fully Human Anti-Bcma CAR for Use in the Treatment of Multiple Myeloma

ROR1-Directed Chimeric Antigen Receptor T Cell Recognition of Self-Antigen Is Associated with Acute Toxicity, T Cell Dysfunction, and Poor Tumor Control.

Chimeric antigen receptor T cells (CAR T) have demonstrated robust clinical efficacy in B cell and plasma cell malignancies. In contrast to success in these hematological malignancies, the application of CAR T cells as a treatment for solid tumors has yielded limited efficacy. While there are multiple mechanisms whereby CAR T cells targeting solid tumors could be hindered in their efficacy, of primary concern is the specificity of recognition. Ideally, investigators desire to select target tumor antigens that are uniquely expressed by the neoplasm to avoid normal tissue (“on-target/off-tumor”) toxicity, which can have serious clinical compilations, including death. We investigated the consequences of on-target/off-tumor CAR T cell recognition of the Receptor Tyrosine Kinase Like Orphan Receptor 1 (ROR1) gene, which has been proposed as a clinical target for CAR T cells. The potential for CAR T-mediated toxicity can be informed by the preclinical application of rigorous bioinformatics, and direct expression analysis using in situ hybridization (ISH), immunohistochemistry, (IHC), and flow cytometry. Using these approaches, we found that in humans and mice, ROR1 was expressed in the lungs and other normal tissues. As a specificity control, we used B-cell maturation antigen (BCMA) and confirmed that BCMA expression was limited to plasma cell-containing lymphoid tissues. Next, we generated anti-ROR1 CAR T cells (cross reactive with both human and mouse ROR1) and human-specific anti-BCMA CAR T cells. Using in vitro culture models, we demonstrated that both the ROR1 and BCMA CAR T cells robustly recognized and killed antigen expressing tumor cell lines. To follow the fate of CAR T cells in vivo, we applied ISH and IHC to study T cell activation and trafficking of anti-ROR1 and control anti-BCMA CAR T cells. ROR1-expressing multiple myeloma cells (ROR1+/BCMA+-RPMI-8226) were injected into the flanks of immune deficient NSG mice, and after tumor establishment, CAR T cells were administered by IV injections. Immediately following administration, CAR T cells traffic to the lung before release and subsequent trafficking to tumor. We observed markedly different behavior of the two CAR T cell populations. The anti-ROR1 CAR T cells accumulated in lung where they caused vasculitis and interstitial pneumonia, whereas anti-BCMA CAR T cells did not. Mice receiving anti-ROR1 CAR T cells lost weight and appeared ill. Within the lung, anti-ROR1 CAR T cells expressed the T cell activation / exhaustion marker PD-1. Lung accumulation and activation required a functional CAR molecule, as no pathology was observed with T cells expressing a CAR containing ROR1 binding elements in which the T cells signaling domains were deleted. Anti-ROR1 CAR T cell trafficking to the tumor was delayed and, compared to anti-BCMA CAR T cells, T cell infiltration of xenografts was sparse and tumor growth inhibition was not observed. By contrast, mice receiving anti-BCMA CAR T cells had robust T cell infiltration of xenografts and tumor clearance within 12 days. These findings raise concern about the effectiveness and safety of anti-ROR1 CAR T cells in humans and demonstrate that this type of preclinical safety assessment paradigm may be useful to de-risk potential CAR targets and for modeling CAR T cell toxicity and efficacy. DisclosuresRottman:bluebird bio: Employment, Equity Ownership. Ganley:bluebird bio: Employment, Equity Ownership. Horton:bluebird bio: Employment, Equity Ownership. Friedman:bluebird bio: Employment, Equity Ownership. Perkins:bluebird bio: Employment, Equity Ownership. Grande:bluebird bio: Employment, Equity Ownership. Rhodes:bluebird bio: Employment, Equity Ownership. Morgan:bluebird bio: Employment, Equity Ownership, Patents & Royalties. Horvath:bluebird bio: Employment, Equity Ownership.

Safety and Adverse Reactions of CAR T Therapy for the Treatment of Multiple Myeloma: A Systematic Review

Introduction: Despite multiple treatment options, multiple myeloma (MM) remains an incurable disease. Chimeric antigen receptor T-cell (CAR T) therapy, a form of adoptive immunotherapy, has shown favorable outcomes in the treatment of hematological malignancies. The B cell maturation antigen (BCMA) which is present on myeloma cells, serves as a valid target site for CAR T cells. Early studies have shown promising outcomes in patients (pts) with relapsed and refractory MM (RRMM). However, CAR T therapy is also associated with multiple adverse effects. The main objective of this review is to evaluate the all grades of CRS and other commonly occurring adverse events (AE) associated with CAR T therapy in pts with RRMM. Methods: A systematic search of databases (following PRISMA guidelines) PubMed, Cochrane, Embase and, clinicaltrials.gov was performed with no restrictions of language and time period. A total of 249 articles were identified initially and after a detailed screening, we finalized 16 studies including 12 phase I and 3 phase Ib/II clinical trials and 1 retrospective analysis for data extraction. Results: Total included trials were 15 and trial-level data collected from 392 pts is summarized in Table 1 and Table 2. Commonly used CAR T regimens for the treatment of MM were bb2121 BCMA, P BCMA 101 CAR, LCAR B38 M, and anti CD19 CAR. Single Target; Anti BCMA CAR T (Table 1) BCMA CAR T, LCAR-B38M: In a phase I trial, Cohen et al. (2019) reported G1&2 CRS in 56% pts (n=25) and G3 CRS in 32% pts when treated with BCMA specific CAR T. Leukopenia, neutropenia, and lymphopenia were seen in 44%, 44% and 36% of pts, respectively. In a phase I trial, Wang et al. (2019) reported G1 & G2 CRS in 47% and 35% pts (n=57), respectively and G3 CRS in 7% pts when treated with LCAR-B38M CAR T. Pyrexia, thrombocytopenia, and leukopenia were seen in 90%, 49% and 30% pts, respectively. In a phase I trial, Chen et al. (2019) reported G1/2 CRS in 58% pts (n=17) and G3 and G5 CRS in 35% and 5% pts respectively when treated with LCAR-B38M. Hepatotoxicity and cytopenia were seen in 100% and 82% pts, respectively. In a phase 1 trial, Brudno et al. (2018) reported G1/2 in 56% pts (n=16) and G3 in 37% pts when treated with BCMA CAR T. Anemia, leukopenia and thrombocytopenia were observed in 68%, 62% and 43% pts, respectively. JNJ-4528, bb2121 In a phase Ib/II trial, Berdeja et al. (2020) reported G1/2 CRS in 86% pts (n=29), G3 and G4 CRS in 3.5% pts each when treated with JNJ-4528 (an LCAR-B38M) CAR T. Neutropenia, thrombocytopenia and leukopenia were seen in 100%, 69% and 59% pts, respectively. In a phase I trial, Berdeja et al. (2019) reported G1, G2 and G3 CRS in 22%, 32% and 5% pts (n=22), respectively when treated with bb2121 CAR T. Neurotoxicity was observed in 22% pts. In a phase I trial, Raje et al. (2017) reported CRS of any grade in 76% pts (n=33) and G3 CRS in 6% pts when treated with bb2121 CAR T. Neurotoxicity, hypotension and hyponatremia were observed in 42%, 15% and 15% pts, respectively. Dual Target CAR T (Table 2) Anti-CD19/BCMA, PF-3135, Dual Target BM38: In a phase Ib trial, Shi et al. (2019) reported G1/2 CRS in 97% pts (n=32) while G3/4 CRS in 3% pts when treated with anti-CD19/BCMA CAR T. Other AE were slight and reversible. In a phase I/II trial, Yan et al. (2019) reported G1/G2 CRS in 86% pts (n=21) and G3/4 CRS in 5% pts when treated with humanized anti-CD19/BCMA CAR T. Neutropenia, Anemia and thrombocytopenia were observed in 86%, 62% and 62% pts, respectively. In a phase I trial, Raje et al. (2019) reported G1/2 CRS in 24% pts (n=17) and G3 CRS in 5% pts when treated with PF-3515 (anti-CD3-BCMA) CAR T. Hepatotoxicity, thrombocytopenia, Neutropenia and pyrexia were observed in 18%, 24%, 18% and 18% pts, respectively. In a phase I trial, Li et al. (2019) reported G1/2 CRS in 62% pts (n=16) and G3 CRS in 25% pts when treated with Dual-target BM38 CAR T. No dose-limiting (>/G3) toxicities were observed at a median follow up of 36 months. Conclusion: CAR T therapy is emerging as a treatment modality for RRMM. With promising initial results, there is evidence for multiple side effects, the most concerning and common one is CRS. The most frequently occurring CRS grade is G 1&2 (requiring symptomatic treatment), but G3 CRS is also reported which can be dose-limiting and life-threatening. Neurotoxicity, hematological abnormalities, hepatotoxicity and pyrexia are the other common side effects Disclosures Anwer: Incyte, Seattle Genetics, Acetylon Pharmaceuticals, AbbVie Pharma, Astellas Pharma, Celegene, Millennium Pharmaceuticals.: Honoraria, Research Funding, Speakers Bureau.

A Fully-Human Armored BCMA CAR Boosts Function of CD4+ CAR-T Cells and Resists TGF-β Suppression in Pre-Clinical Models of Multiple Myeloma

The B-cell maturation antigen (BCMA) is an immunotherapy target selectively expressed on multiple myeloma cells (MM). Despite recent success of experimental BCMA CAR-T cell therapy, clinical remissions in MM are often short, in part due to low persistence of the BCMA CAR-T cells. Additionally, immunosuppressive factors, notably TGF-β, are known to be elevated in the peripheral blood and tumor microenvironment in the bone marrow of MM patients, potentially contributing to the lack of durability of CAR-T cell therapy. We aimed to develop a fully-human BCMA CAR with long-term persistence and functional resistance to the suppressive effects of TGF-β. Initially, two fully human single chain variable fragments (scFv) specific for BCMA, derived by biopanning of a yeast display human scFv library, were characterized in a CAR format. Each of the two scFvs was cloned into a lentiviral vector CAR backbone, comprised of the CD8 hinge and transmembrane domain, 4-1BB co-stimulatory domain and CD3ζ signaling domain, and termed BCMA1 and BCMA2, respectively. BCMA2 and BCMA1 T cells, generated by lentiviral vector transduction of primary human T cells, exhibited high CAR expression at multiplicities of infection 10 to 40 (BCMA1: 64-81%; BCMA2: 84-94%), and consistently demonstrated potent cytotoxicity in an overnight co-culture with BCMA+ MM cell lines RPMI-8226 and MM1.S, but not the BCMA- 293T cells. BCMA2 CAR showed robust proliferative capacity in response to repeated, long-term exposure to MM1.S target cells, concordant with the sustained CD4 T-cell subset and high IL-2 production during the course of repeated exposure to target cells. This is in contrast to BCMA1, that showed precipitous decrease in CD4+ T-cell subset upon co-culture with MM cells, resulting in a CAR T-cell population dominated by CD8+ T-cells. Furthermore, the BCMA2 demonstrated prolonged potency in clearing tumor cells compared to BCMA1, even after continuous 20-day exposure to target cells. This was further confirmed in a mouse intradermal RPMI-8226 xenograft tumor model, in which infusion of BCMA2 T-cells resulted in the rapid and complete eradication of tumors, while BCMA1 showed a slower decline in tumor burden. To further improve the efficacy of the BCMA2, specifically within the TGF-β-rich immunosuppressive tumor microenvironment, we developed an armored BCMA2 CAR variant, which co-expresses the dominant negative TGF-β RII bicistronically via a 2A sequence (BCMA2-TbnegCAR). In a 10 day-long co-culture assay with MM1.S targets in the presence of spiked 10 ng/ml TGF-β, BCMA2-TbnegCAR retained high proliferative capacity and potent cytotoxicity, while the unarmored BCMA2 had diminished proliferation and substantially reduced cytokine and granzyme B production. Consistently, in the in vivo intradermal tumor model that utilizes RPMI-8226, which is a MM cell line that endogenously produces TGF-β, we observed that BCMA2-TbnegCAR treatment resulted in higher T-cell counts in the tumors and an earlier decrease of tumor burden compared to infusion with BCMA2, further demonstrating the increased efficacy and potency of the BCMA2-TbnegCAR. In conclusion, we have designed and characterized a new fully-human BCMA2-TbnegCAR, with a novel scFv that exhibits robust proliferative capacity and persistent cytotoxicity, and remains functionally resistant to the immunosuppressive effects of TGF-β. This novel BCMA CAR can potentially improve the effectiveness and durability of the current BCMA CAR-T cell therapy. Disclosures Alabanza: Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Vu:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Wu:Lentigen, a Miltenyi Biotec Company: Current Employment. Zhu:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Dropulic:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Schneider:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties.

Dual Targeting to Overcome Current Challenges in Multiple Myeloma CAR T-Cell Treatment.

In the era of highly promising novel targeted-immunotherapy strategies for multiple myeloma (MM), the first series of clinical trials with CAR T-cells targeting the plasma cell-specific B-cell maturation antigen (BCMA) have shown excellent response rates. In the long-term, however, MM appears to escape the therapy likely due to initial low and heterogeneous expression or downregulation of BCMA expression. Several other molecules targeted by CAR T-cells in MM are expressed at high levels on MM cells, but many of these attractive targets are also expressed on various, sometimes vital non-malignant cells, posing major risks for on-target, off-tumor side effects. CAR T-cell therapy for MM therefore faces two urgent challenges: (i) improving the efficacy of BCMA CAR T-cells and (ii) establishing a MM-selectivity even when CAR T-cells are directed against not entirely MM-specific target antigens. In this review, we will outline the current attempts to tackle these challenges, with a specific focus on how dual CAR targeting might be applied to tackle both issues.

Efficacy and Safety of Fully Human Bcma CAR T Cells in Combination with a Gamma Secretase Inhibitor to Increase Bcma Surface Expression in Patients with Relapsed or Refractory Multiple Myeloma

Efficacy and Safety of Fully Human Bcma CAR T Cells in Combination with a Gamma Secretase Inhibitor to Increase Bcma Surface Expression in Patients with Relapsed or Refractory Multiple Myeloma

Translational Analysis from CARTITUDE-1, an Ongoing Phase 1b/2 Study of JNJ-4528 BCMA-targeted CAR-T Cell Therapy in Relapsed and/or Refractory Multiple Myeloma (R/R MM), Indicates Preferential Expansion of CD8+ T Cell Central Memory Cell Subset

Translational Analysis from CARTITUDE-1, an Ongoing Phase 1b/2 Study of JNJ-4528 BCMA-targeted CAR-T Cell Therapy in Relapsed and/or Refractory Multiple Myeloma (R/R MM), Indicates Preferential Expansion of CD8+ T Cell Central Memory Cell Subset

Identifying Factors in Multiple Myeloma Controlling Response to B-Cell Maturation Antigen (BCMA)-Targeted Immunotherapy Using CRISPR-Based Functional Genomics

Introduction: Multiple myeloma (MM) is the second most common blood cancer in the United States. Recent breakthroughs in immunotherapy have the potential to transform MM treatment. An immunotherapy target that shows considerable promise in myeloma is the B-cell maturation antigen (BCMA). BCMA is specifically expressed in myeloma cells and plasma cells, making it an ideal target in myeloma. Results from two early-phase clinical trials using anti-BCMA therapy, showed remarkable response in most patients. Although immunotherapy has been promising, recent findings suggest that patients can develop resistance to such therapies by lowering the levels of the target. Here we employ our innovative CRISPR-interference/activation (CRISPRi/a)-based functional genomics platform to identify mechanisms that regulate BCMA expression, which would enable us to design strategies to improve the efficacy of available BCMA immunotherapy agents.Methods: The CRISPRi/a platform utilizes a catalytically dead Cas9 (dCas9) fused to a transcriptional repressor domain to silence genes (CRISPRi) or to activator domains to activate transcription (CRISPRa). The CRISPR machinery is targeted to specific genes using single guide-RNAs (sgRNA). We have engineered a panel of myeloma cell lines to express components of the CRISPRi system. Here we transduced CRISPRi-AMO1 cell line with sgRNAs targeting the human genome. The sgRNA expressing cells were stained with a fluorescent-tagged BCMA antibody and FACS sorted into cells expressing high and low levels of BCMA. The cells were processed for next generation sequencing to determine the frequency of sgRNA in each of these populations. To develop BCMA chimeric antigen receptor-T (CAR-T) cells, CD8+ T cells were transduced with BCMA CAR construct specifically recognizing BCMA. To examine the anti-myeloma activity of the BCMA CAR-T cells, CAR-T cells were co-cultured with MM cell lines at a ratio of 1:2 (Effector:Target) for 24hrs. The cells were analyzed by flow cytometry for expression of CD69, an activation marker on T cells and for apoptosis of cancer cells using propidium iodide.Results: Our FACS-based genome-wide CRISPRi screen identified several genes and pathways regulating BCMA cell surface expression. In addition to previously reported gamma-secretase complex and transcription factor POU2AF1 we identified genes involved in peroxisome biogenesis, subunits of the proteasome, transcription factors and a few druggable targets regulating cell surface expression of BCMA. We are currently validating the novel genes identified from our primary genome-wide screen in a panel of MM cell lines and developing MM cell lines expressing CRISPRa machinery to perform gain-of-function screens that will complement our CRISPRi screen. Furthermore, we have developed active CAR-T cells targeting BCMA and demonstrated its efficacy in MM cell lines expressing different levels of BCMA. We are currently testing the novel genes identified from our CRISPRi screen in combination with BCMA CAR-T cells to identify genes that alter sensitivity to BCMA immunotherapy.Conclusions: Our studies have identified several novel genes and pathways regulating BCMA expression including some druggable targets. Through these studies, we expect to uncover mechanisms regulating expression of BCMA and its impact on sensitivity to BCMA immunotherapy, and pinpoint potential combination therapy targets that pre-empt resistance to BCMA immunotherapy. DisclosuresWiita:Sutro Biopharma: Research Funding; TeneoBio: Research Funding.

JCARH125, Anti-BCMA CAR T-cell Therapy for Relapsed/Refractory Multiple Myeloma: Initial Proof of Concept Results from a Phase 1/2 Multicenter Study (EVOLVE)

JCARH125, Anti-BCMA CAR T-cell Therapy for Relapsed/Refractory Multiple Myeloma: Initial Proof of Concept Results from a Phase 1/2 Multicenter Study (EVOLVE)

Updated Analysis of a Phase 1, Open-Label Study of LCAR-B38M, a Chimeric Antigen Receptor T Cell Therapy Directed Against B-Cell Maturation Antigen, in Patients with Relapsed/Refractory Multiple Myeloma

LCAR-B38M is a bispecific chimeric antigen receptor T cell (CAR T) therapy directed against B-cell maturation antigen (BCMA). The bi-epitope BCMA binding moieties confer high avidity binding and distinguish LCAR-B38M from other BCMA CAR constructs. Preliminary results of LCAR-B38M in patients (pts) with relapsed/refractory (R/R) multiple myeloma (MM) showed encouraging efficacy and manageable safety (Fan et al.JCO 2017;35:18_suppl LBA3001). Here we present updated safety and efficacy results of the trial.LEGEND-2 (NCT03090659) is an ongoing phase 1, single-arm, open-label multicenter study evaluating LCAR-B38M in pts (18-80 years) with R/R MM. Lymphodepletion was performed using 3 doses of cyclophosphamide 300 mg/m2 on days -5, -4, and -3. Five days after lymphodepletion, LCAR-B38M CAR T cells (median CAR+ cell dose = 0.5x106 cells/kg, [range, 0.07-2x106]) were given in 3 infusions (20, 30, and 50% of total dose). The primary objective is to evaluate the safety of LCAR-B38M CAR T cells; the secondary objective is to evaluate the anti-myeloma response of the treatment. Adverse events (AEs) were graded using the Common Terminology Criteria for AE, v.4.03, and cytokine release syndrome (CRS) was assessed according to Lee et al. (Blood 2014;124:188-95). Response was evaluated using International Myeloma Working Group criteria. This analysis presents data from a single institution.As of June 25, 2018, 57 pts have been infused with LCAR-B38M CAR T cells. The median age was 54 years (range, 27-72), median number of prior therapies was 3 (range, 1-9), and 74% of pts had stage III disease by Durie-Salmon staging. The median duration of follow-up for all pts was 12 months (range, 0.7-25).AEs were reported by all pts; most common were pyrexia (91%), CRS (90%), thrombocytopenia (49%), and leukopenia (47%). Grade ≥3 AEs were reported by 65% of pts; most common were leukopenia (30%), thrombocytopenia (23%), and increased aspartate aminotransferase (21%).CRS was mostly grade 1 (47%) and 2 (35%); 4 pts (7%) had grade 3 cases. Liver function abnormalities were the most common signs of end organ injury among pts with CRS. The median time to onset of CRS was 9 days (range, 1-19). All but 1 CRS events resolved, with a median duration of 9 days (range, 3-57). No clear relationship was demonstrated between dose and CRS; there may be some effect at higher doses, but conclusions are limited by the small number of pts in the grade 3 CRS group (n=4; Figure 1A). Neurotoxicity was observed in 1 pt who had grade 1 aphasia, agitation, and seizure-like activity.The overall response rate (partial response [PR] or better) was 88% (95% confidence interval [CI], 76-95). Complete response (CR) was achieved by 42 pts (74%; 95% CI, 60-85), very good partial response was achieved by 2 pts (4%; 95% CI, 0.4-12), and PR was achieved by 6 pts (11%; 95% CI, 4-22; Figure 1B). Among pts with CR, 39/42 were minimal residual disease (MRD) negative by 8-color flow cytometry. The median time to initial response was 1 month (range, 0.4-4). No clear relationship between LCAR-B38M CAR T cell dose and response was observed (Figure 1C). BCMA expression did not correlate with clinical response.The median duration of response (DOR) was 16 months (95% CI, 12-not reached [NR]). The median DOR for pts who achieved a CR was 22 months (95% CI, 14-NR). At data cutoff, 18 pts (36%) who achieved PR or better progressed. The median progression-free survival (PFS) for all treated pts was 15 months (95% CI, 11-NR); median PFS for pts who achieved CR was 24 months (95% CI, 15-NR). The median overall survival was not reached. Overall, 17 pts died during the study and follow-up period; causes of death were progressive disease (PD; n=14), suicide after PD (n=1), esophagitis (n=1), and pulmonary embolism and acute coronary syndrome (n=1).Peak levels of LCAR-B38M (≥1x104 copies/µg genomic DNA) were observed in a majority of pts with blood samples for analysis (n=32). LCAR-B38M CAR T cells were not detectable in peripheral blood in 71% of pts at 4 months; 5 pts showed CAR T cell persistence up to 10 months.This ongoing first-in-human study has provided initial proof-of-concept that bispecific LCAR-B38M CAR T cells may be a highly effective therapy for R/R MM. LCAR-B38M CAR T cell therapy displayed a manageable safety profile consistent with its known mechanism of action and demonstrated deep and durable responses in pts with R/R MM. A phase 1/2 study of LCAR-B38M in R/R MM has been initiated in the US (NCT03548207). DisclosuresZhuang:Nanjing Legend Biotech: Employment. Fan:Nanjing Legend Biotech: Employment.

Chemically Controlled, Immunosuppression-Resistant, Anti-Bcma CAR-T Cells for Treatment of Antibody-Mediated Autoimmunity

Auto-reactive antibody production by plasma cells is the direct cause of many auto-immune diseases. In such cases elimination of plasma cells would ameliorate the disease. Chimeric antigen receptor T (CAR-T) cells with cytotoxicity toward cells expressing B-cell maturation antigen (BCMA) have shown remarkable promise for the treatment of multiple myeloma, a plasma cell neoplasm. Elimination of non-malignant plasma cells is a side-effect of anti-BCMA CAR-T treatment of multiple myeloma, suggesting the use of these anti-BCMA CAR T cells for auto-immune indications. Unfortunately, CAR-T administration requires use of lymphodepletion to achieve efficient cell engraftment, and is often accompanied by cytokine release syndrome (CRS), a potentially life-threatening side-effect.As lymphodepletion and CRS pose morbidity/mortality risks that are unacceptable for therapy of many auto-immune diseases, we have utilized CRISPR-Cas9 gene editing to develop a controllable CAR-T cell platform that provides for (1) engraftment with non-cytotoxic transient immunosuppression; and (2) small-molecule dependent CAR T-cell expansion. We have implemented this platform using a unique dual targeting approach in which a BCMA CAR transgene is integrated into the TRAC locus, and additional payloads are integrated into a second locus, thus also enabling an allogeneic manufacturing process. Transgene integration occurred in >50% of cells individually with several percent of cells targeted at two loci. TRAC-targeted, anti-BCMA CAR T cells demonstrated CAR-dependent, target-cell-BCMA-dependent cytotoxicity towards both high-BCMA- and low-BCMA-expressing cell lines and in multiple myeloma cells xenografted into NSG mice. Drug-regulation properties and immunosuppression resistance are the subject of ongoing experiments. Anti-BCMA CAR T cells that are chemically controlled, incapable of graft-versus-host disease, and insensitive to immunosuppression may be an attractive treatment option a variety of antibody-mediated auto-immune conditions. DisclosuresRajavel:Casebia Therapeutics: Employment. Ito:Casebia Therapeutics: Employment. Abe:Casebia Therapeutics: Employment. Guerrero:Casebia Therapeutics: Employment. Uenishi:Casebia Therapeutics: Employment. Scharenberg:Casebia Therapeutics: Employment; Generation Bio: Equity Ownership; Alpine Immune Sciences: Equity Ownership. Cost:Casebia Therapeutics: Employment.

Quantification of B-cell maturation antigen, a target for novel chimeric antigen receptor T-cell therapy in Myeloma

B-cell maturation antigen (BCMA) is expressed by normal and malignant plasma cells and is targeted via anti-BCMA chimeric antigen receptor T-cell therapy (BCMA CAR T-cell therapy) in plasma cell myeloma (PCM) patients. Surface BCMA expression is required for CAR T-cell binding and killing. We determined the incidence and intensity of expression of BCMA in bone marrow PCM cells using flow cytometry (FC) and immunohistochemistry (IHC).PCM BCMA expression was assessed by FC in 70 patients and in 43 concurrent specimens by IHC. BCMA expression was detected in 94% of patients. FC could assess BCMA expression in all specimens and expression was quantifiable (QuantiBRITE system, BD Biosciences, San Jose, CA) in 89% of cases. Expression was highly variable and could be numerically classified into dim, moderate or bright levels of expression. In the 43 specimens assessed successfully by both IHC and FC, FC showed higher positivity rate (97%) than IHC (72%), indicating that FC is more useful than IHC in detection of BCMA (p = 0.002; McNemar’s test).We conclude that FC is more sensitive than IHC and can be used to objectively quantify BCMA expression by myeloma cells. IHC is primarily useful when there is significant infiltration of the bone marrow by myeloma and is less sensitive with low numbers of myeloma cells. Furthermore, the ability of FC to differentiate between normal and abnormal plasma cells and to quantify BCMA on these cells, makes it a useful and sensitive tool in screening patients for CAR T-cell therapy and for follow-up post therapy.

747. Towards the Clinical Application of BCMA CAR T Cells: The Importance of Reduced Tonic Signaling and Methods to Enhance Memory T Cells

B cell maturation antigen (BCMA) is expressed on most multiple myeloma (MM) and some lymphoma cells, yet normal tissue expression is limited to plasma and some B cells. Here we describe the development of a CAR T cell that targets BCMA. We tested 19 BCMA-specific single chain variable fragments (scFv) linked to CD137 (4-1BB) and CD3zeta T cell signaling domains. The activity of each CAR T cell candidate differed despite targeting the same antigen. One anti-BCMA CAR T cell candidate (bb2121) was selected based on strong surface CAR expression, superior biological activity to multiple BCMA+ cell lines, and low antigen-independent activity. In vitro analysis demonstrated that antigen-independent activity was associated with T cell differentiation characterized by significantly lower CD62L expression (p=0.003). To determine the impact on tumor control, CAR T cells with antigen-independent activity, or bb2121 CAR T cells, were used to treat an NSG mouse model of MM (RPMI-8226). Immunohistochemical analysis found MM-infiltrated bb2121 T cells within 5 days and mice showed complete regressions by 12 days post treatment. In contrast, mice that received CAR T cells with antigen-independent activity had delayed regressions that occurred 20 days post treatment. Robust recognition of as few as 220 BCMA molecules/cell (compared to >10,000 molecules on MM cell lines) permitted reactivity to primary chronic lymphocytic leukemia (CLL) and other CD19+ B cell tumor lines. Indeed comparable tumor regressions were observed after administration of bb2121 or anti-CD19 CAR T cells into an NSG mouse model of disseminated Burkitt's lymphoma (Daudi: 1,170 BCMA and 267,000 CD19 molecules). Prior investigators have shown improved therapeutic efficacy by enriching for memory CAR T cells, yet current antibody-based selection methods are expensive and difficult to scale. Unexpectedly, we found bb2121 manufacture in the presence of a PI3-kinase inhibitor enriched for memory-like CAR T cells without a complicated cell sorting procedure. bb2121 CAR T cells cultured with a PI3K inhibitor expressed markers associated with T cell memory including CD62L, CD127, CD197, and CD38. In a first “stress test,” of advanced disseminated lymphoma (Daudi), NSG mice were administered an amount of bb2121 CAR T cells that failed to control tumor outgrowth. Mice administered the same number of bb2121 CAR T cells cultured with a PI3K inhibitor resulted in complete tumor regressions. A defining property of memory T cells is durability despite multiple antigen encounters. In a second “stress test,” bb2121 CAR T cell durability was evaluated after initial MM (RPMI-8226) clearance. Two weeks post-tumor elimination, mice were re-challenged with tumor on the opposite flank without an additional dose of CAR T cells. None of the mice treated with bb2121 CAR T cells prevented tumor outgrowth in this model. In contrast, all mice treated with bb2121 CAR T cells cultured with a PI3K inhibitor were able to control the tumor re-challenge. These data demonstrate that a potent, antigen-dependent, memory-like BCMA CAR T cell produced with an industrially scalable manufacturing process has promise for robust tumor regressions in clinical applications.