4-1BB Chimeric Antigen Receptor Research Articles

Lisocabtagene maraleucel in follicular lymphoma: the phase 2 TRANSCEND FL study.

An unmet need exists for patients with relapsed/refractory (R/R) follicular lymphoma (FL) and high-risk disease features, such as progression of disease within 24 months (POD24) from first-line immunochemotherapy or disease refractory to both CD20-targeting agent and alkylator (double refractory), due to no established standard of care and poor outcomes. Chimeric antigen receptor (CAR) T cell therapy is an option in R/R FL after two or more lines of prior systemic therapy, but there is no consensus on its optimal timing in the disease course of FL, and there are no data in second-line (2L) treatment of patients with high-risk features. Lisocabtagene maraleucel (liso-cel) is an autologous, CD19-directed, 4-1BB CAR T cell product. The phase 2 TRANSCEND FL study evaluated liso-cel in patients with R/R FL, including 2L patients who all had POD24 from diagnosis after treatment with anti-CD20 antibody and alkylator ≤6 months of FL diagnosis and/or met modified Groupe d'Etude des Lymphomes Folliculaires criteria. Primary/key secondary endpoints were independent review committee-assessed overall response rate (ORR)/complete response (CR) rate. At data cutoff, 130 patients had received liso-cel (median follow-up, 18.9 months). Primary/key secondary endpoints were met. In third-line or later FL (n = 101), ORR was 97% (95% confidence interval (CI): 91.6‒99.4), and CR rate was 94% (95% CI: 87.5‒97.8). In 2L FL (n = 23), ORR was 96% (95% CI: 78.1‒99.9); all responders achieved CR. Cytokine release syndrome occurred in 58% of patients (grade ≥3, 1%); neurological events occurred in 15% of patients (grade ≥3, 2%). Liso-cel demonstrated efficacy and safety in patients with R/R FL, including high-risk 2L FL. ClinicalTrials.gov identifier: NCT04245839 .

Abstract 882: Harnessing single cell multi-omics data to identify predictors of clinical outcome in CD19 CAR T cell therapy

Abstract Background: Chimeric antigen receptor (CAR) T cell therapy is effective in treating B-cell malignancies, but factors influencing the persistence of functional CAR+ T cells, such as product composition, patients’ lymphodepletion, and immune reconstitution, are not well understood. To shed light on this issue, we conducted single-cell multi-omics analysis of transcriptional, clonal, and phenotypic profiles from pre- to 1-month post-infusion of CAR+ and CAR− T cells from patients who received a donor-derived 4-1BB CAR product targeting CD19. Methods: Longitudinal blood samples and infusion products were obtained from 10 individuals with large B cell lymphoma or B-cell acute lymphoblastic leukemia (CARTELL cohort in Sydney Australia1). CD45+ cells and enriched CAR+ T cells were single cell sorted for simultaneous scRNA-seq, 41 barcoded proteins (N=41) and T cell receptors, n= 115,000 cells across 21 samples. Machine learning methods were used to identify subsets of immune cells associated with clinically relevant parameters. Results: Following infusion, CAR+ and CAR− T cells showed similar differentiation profiles with clonally expanded populations across heterogeneous phenotypes, demonstrating clonal lineages and phenotypic plasticity. These findings were validated by performing the same analysis on two publicly available scRNA-seq data sets from two cohorts 2, 3 of paediatric (N=18) and adult (N=32) individual with large B cell lymphoma who received CAR19 T cells. Analysis of mass-cytometry data from our cohort and from 28 patients with B cell lymphoma treated with commercial CAR19 T cells (axi-cel)4, identified an association of CAR− and also CAR+ T cells, both expressing an 2B4− CD11b+ CD8+ phenotype, with complete remission or progressive disease at 3 and 6 months post-infusion. Finally, we report additional analysis on the immunogenomics of circulating CAR T cells in two patients who developed CAR T cell induced lymphoma and compared it with ascites and CAR-Lymphoma cells. Discussion: These results suggest that CAR+ and CAR− CD8+ T cells share a differentiation trajectory terminating in an NK-like phenotype that is associated with clinical outcome, and that non-CAR-derived signals may influence patients’ immune recovery and outcomes.

CAR+ and CAR− T cells share a differentiation trajectory into an NK-like subset after CD19 CAR T cell infusion in patients with B cell malignancies

Chimeric antigen receptor (CAR) T cell therapy is effective in treating B cell malignancies, but factors influencing the persistence of functional CAR+ T cells, such as product composition, patients’ lymphodepletion, and immune reconstitution, are not well understood. To shed light on this issue, here we conduct a single-cell multi-omics analysis of transcriptional, clonal, and phenotypic profiles from pre- to 1-month post-infusion of CAR+ and CAR− T cells from patients from a CARTELL study (ACTRN12617001579381) who received a donor-derived 4-1BB CAR product targeting CD19. Following infusion, CAR+ T cells and CAR− T cells shows similar differentiation profiles with clonally expanded populations across heterogeneous phenotypes, demonstrating clonal lineages and phenotypic plasticity. We validate these findings in 31 patients with large B cell lymphoma treated with CD19 CAR T therapy. For these patients, we identify using longitudinal mass-cytometry data an association between NK-like subsets and clinical outcomes at 6 months with both CAR+ and CAR− T cells. These results suggest that non-CAR-derived signals can provide information about patients’ immune recovery and be used as correlate of clinically relevant parameters.

Matching-Adjusted Indirect Comparison (MAIC) of Efficacy and Safety of Lisocabtagene Maraleucel (liso-cel) and Mosunetuzumab for the Treatment (Tx) of Third Line or Later (3L+) Relapsed or Refractory (R/R) Follicular Lymphoma (FL)

Background:The tx landscape of R/R FL is evolving with the availability of anti-CD19 chimeric antigen receptor (CAR) T cell therapies and CD20xCD3 bispecific T-cell-engaging monoclonal antibodies (mAb). Liso-cel is an autologous, CD19-directed, 4-1BB CAR T cell therapy which recently reported a positive benefit-risk tx profile for the 3L+ tx of patients with R/R FL (Morschhauser F, et al. ICML 2023; LBA4). Mosunetuzumab, a CD20xCD3 bispecific T-cell-engaging mAb, is approved for the tx of R/R FL after 2 or more lines of therapy (LOT). In the absence of head-to-head data, we conducted an unanchored MAIC to compare the efficacy and safety of liso-cel and mosunetuzumab for the 3L+ tx of patients with R/R FL. Methods: Unanchored MAICs were used to estimate population-adjusted relative tx effects between individual patient-level data from TRANSCEND FL (NCT04245839; data as of January 27, 2023; median follow-up of 19.3 months) and aggregate data from GO29781 (NCT02500407; data as of August 27, 2021; median follow-up of 18.3 months; N = 90). For TRANSCEND FL, the leukapheresed (intention to treat [ITT]) set (N = 114) was used for primary comparisons of efficacy endpoints: Progression-free survival (PFS), objective response rate, and complete response rate (all per independent review committee assessment). Overall survival was not analyzed due to the low rate of events. The treated efficacy set (n = 101) was used for a sensitivity analysis of efficacy comparisons. The treated set (n = 107) was used for comparisons of safety endpoints: cytokine release syndrome (CRS), neurological events (NEs), serious infections, and use of corticosteroids or tocilizumab for CRS. Baseline characteristics and outcome measures in TRANSCEND FL were redefined to align with those reported in GO29781. Data from TRANSCEND FL were weighted using a method-of-moments propensity score model to match the marginal distribution (ie, mean, variance) of clinical factors among patients from GO29781. A panel of expert clinicians selected and ranked tx effect modifiers separately for efficacy and safety endpoints. For efficacy, factors adjusted for included number of prior systemic LOTs, progression of disease ≤ 24 months from initiation of immunochemotherapy, bulky disease at screening, FL International Prognostic Index risk factor, refractory to last therapy, double refractory to an anti-CD20 antibody and alkylating agent, ECOG PS at screening, sex, and prior autologous HSCT. For safety, factors adjusted for included age, bulky disease at screening, refractory to last therapy, number of prior systemic LOTs, ECOG PS at screening, Ann Arbor stage, and sex. Hazard ratios (HR) were used to compare PFS, and odds ratios (OR) were used for response rates and safety outcomes. Results: After adjusting for all available factors, when compared with mosunetuzumab, liso-cel was associated with higher objective response rate (OR, 3.78 [95% CI, 1.48‒9.67]), and complete response rate (OR, 6.46 [2.85‒14.65]), and improved PFS (HR, 0.28 [0.16‒0.49]) based on an effective sample size (ESS) of 71.4 (Figure). Results were consistent across all scenario analyses, including unadjusted comparisons and sensitivity analyses using the treated efficacy set for TRANSCEND FL. Although liso-cel was associated with higher incidence of any-grade CRS (OR, 1.86 [1.01‒3.43]) and any-grade NEs (OR, 2.16 [0.72‒6.44]), it demonstrated a lower incidence of grade ≥ 3 CRS (OR, 0.45 [0.04‒5.13]) and grade 3-4 serious infections (OR, 0.35 [0.12‒1.03]) based on an ESS of 81.9 compared with mosunetuzumab. Furthermore, liso-cel was associated with reduced use of corticosteroids for CRS management (OR, 0.14 [0.03‒0.65]), while the use of tocilizumab was higher in patients treated with liso-cel (OR, 2.27 [0.86‒5.99]). Conclusions: In this MAIC, liso-cel was associated with improved efficacy compared with mosunetuzumab. Liso-cel had a lower incidence of grade ≥ 3 CRS, grade 3-4 serious infections, and steroid use for management of CRS; however, liso-cel exhibited higher incidence of any-grade CRS, any-grade NEs, and tocilizumab use for CRS management. Safety comparisons were confounded by preventative use of corticosteroids in all patients in GO29781 and definition differences, most notably for NEs. These findings highlight a potential positive benefit-risk profile of liso-cel over mosunetuzumab as a 3L+ tx option for R/R FL.

Abstract 4098: Chimeric antigen receptor (CAR) T cells overexpressing Bcl-xL increase proliferation and antitumor activity alone and in combination with BH3 mimetics

Abstract Background: Chimeric antigen receptor (CAR) T cells have become a well-established treatment option for patients, with six products approved for different hematologic diseases and new approvals allowing for their therapeutic use as early as second line. However, relapse rates of around 50% have been observed in all patient subsets, with one major mechanism associated with CAR T failure being cancer cell resistance to apoptosis. A form of cancer therapeutic named BH3-mimetics has been designed to inhibit members of the anti-apoptotic B cell lymphoma-2 (Bcl-2) family and, therefore, directly activate the apoptotic machinery in malignant cells. We hypothesized that integration of these anti-apoptotic molecules into CAR T cells would induce resistance towards the BH3 mimetics and allow combinational therapeutic approaches. Methods: 4-1BB and CD28 CAR constructs were designed to overexpress one of four anti-apoptotic proteins: wildtype Bcl-2, a Venetoclax-resistant Bcl-2 variant (G101V), B cell extra-large (Bcl-xL), or myeloid cell leukemia-1 (Mcl-1). CAR T cells made from these constructs were tested against leukemia (Nalm6) and lymphoma (JeKo-1) cell lines in combination with three different BH-3 mimetics: Venetoclax (ABT-199, an FDA-approved Bcl-2 inhibitor), Navitoclax (ABT-263, a Bcl-2/Bcl-xL inhibitor), and AZD5991 (an Mcl-1 inhibitor). Results: CAR T cells with a 4-1BB costimulatory domain tended to have increased killing over CARs with CD28 and were less susceptible to apoptosis; therefore, 4-1BB CARs were used for all further testing. Integration of Bcl-2 family proteins into CAR T cells didn’t impair or even increase tumor cell clearance in vitro; however, in combination with Venetoclax, Navitoclax, or AZD5991, killing capacity significantly increased compared to control CAR T cells. Even without combination with drugs, CAR T cells overexpressing Bcl-xL and Bcl-2 (both wildtype and mutant) provided higher anti-tumor activity and prolonged survival against JeKo-1 cells in vivo, whereas only Bcl-xL overexpression showed increased tumor control compared to regular 4-1BB CARs against Nalm6 cells. Conclusion: Of the tested antiapoptotic proteins, Bcl-xL overexpressing CAR T cells proved superior, having higher proliferation and increased anti-tumor activity in combination with or without BH3 mimetics, providing a new strategy to optimize CAR T cell function for the treatment of leukemia and lymphoma. Citation Format: Felix Korell, Michael Olson, Diego Salas-Benito, Mark B. Leick, Rebecca C. Larson, Harrison Silva, Alessandro Gasparetto, Trisha R. Berger, Amanda Bouffard, Michael C. Kann, Markus Mergen, Tamina Kienka, Marc Wehrli, Stefanie R. Bailey, Anthony Letai, Marcela V. Maus. Chimeric antigen receptor (CAR) T cells overexpressing Bcl-xL increase proliferation and antitumor activity alone and in combination with BH3 mimetics. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4098.

4-1BB-Based CAR T Cells Effectively Reverse Exhaustion and Enhance the Anti-Tumor Immune Response through Autocrine PD-L1 scFv Antibody.

Exhaustion of chimeric antigen receptor (CAR) T cells is one of the limitations for CAR T efficacy in solid tumors and for tumor recurrence after initial CAR T treatment. Tumor treatment with a combination of programmed cell death receptor-1 (PD-1)/programmed cell death ligand-1 (PD-L1) blockage and CD28-based CAR T cells has been intensively studied. However, it remains largely unclear whether autocrine single-chain variable fragments (scFv) PD-L1 antibody can improve 4-1BB-based CAR T cell anti-tumor activity and revert CAR T cell exhaustion. Here, we studied T cells engineered with autocrine PD-L1 scFv and 4-1BB-containing CAR. The antitumor activity and exhaustion of CAR T cells were investigated in vitro and in a xenograft cancer model using NCG mice. CAR T cells with autocrine PD-L1 scFv antibody demonstrate enhanced anti-tumor activity in solid tumors and hematologic malignancies by blocking the PD-1/PD-L1 signaling. Importantly, we found that CAR T exhaustion was largely diminished by autocrine PD-L1 scFv antibody in vivo. As such, 4-1BB CAR T with autocrine PD-L1 scFv antibody combined the power of CAR T cells and the immune checkpoint inhibitor, thereby increasing the anti-tumor immune function and CAR T persistence, providing a cell therapy solution for a better clinical outcome.

Preinfusion factors impacting relapse immunophenotype following CD19 CAR T cells.

Relapse following chimeric antigen receptor (CAR) T-cell therapy directed against CD19 forrelapsed/refractory B-acute lymphoblastic leukemia (r/r B-ALL) remains a significant challenge. Three main patterns of relapse predominate: CD19 positive (CD19pos) relapse, CD19 negative (CD19neg) relapse, and lineage switch (LS). Development and validation of risk factors that predict relapse phenotype could help define potential pre- or post-CAR T-cell infusion interventions aimed at decreasing relapse. Our group sought to extensively characterize preinfusion risk factors associated with the development of each relapse pattern via a multicenter, retrospective review of children and young adults with r/r B-ALL treated with a murine-based CD19-CAR construct. Of 420 patients treated with CAR, 166 (39.5%) relapsed, including 83 (50%) CD19pos, 68 (41%) CD19neg, and 12 (7.2%) LS relapses. Agreater cumulative number of prior complete remissions was associated with CD19pos relapses, whereas high preinfusion disease burden, prior blinatumomab nonresponse, older age, and 4-1BB CAR construct were associated with CD19neg relapses. The presence of a KMT2A rearrangement was the only preinfusion risk factor associated with LS. The median overall survival following a post-CAR relapse was 11.9 months (95% CI, 9-17) and was particularly dismal in patients experiencing an LS, with no long-term survivors following this pattern of relapse. Given the poor outcomes for those with post-CAR relapse,study of relapse prevention strategies, such as consolidative hematopoietic stemcell transplantation, is critical and warrants further investigation on prospective clinical trials.

Developing lisocabtagene maraleucel chimeric antigen receptor T-cell manufacturing for improved process, product quality and consistency across CD19+ hematologic indications

Background aimsAutologous chimeric antigen receptor (CAR) T-cell therapies have demonstrated substantial clinical benefit across several hematologic malignancies. However, patient-to-patient variability and heterogeneity of starting cellular material across patient populations and disease indications pose challenges to manufacturing consistency. Lisocabtagene maraleucel (liso-cel) is an autologous, CD19-directed, defined-composition, 4-1BB CAR T-cell product administered at equal target doses of CD8+ and CD4+ CAR+ T cells. Here the authors describe the optimization of the liso-cel manufacturing platform for product quality and consistency. MethodsLeukapheresis starting materials were collected from patients with large B-cell lymphoma, mantle cell lymphoma or chronic lymphocytic leukemia treated with liso-cel in clinical trials (NCT02631044 and NCT03331198). The liso-cel manufacturing process involves selection of CD8+ and CD4+ T cells from leukapheresis material followed by independent CD8+ and CD4+ T-cell activation, transduction, expansion, formulation and cryopreservation. Multivariate design of experimental approaches was utilized to optimize process conditions at both specific unit operations and across the process. Flow cytometry methods were used to assess cellular composition, memory phenotypes and cell proliferation. Antigen-specific functions, including cytokine secretion, cytolytic activity and proliferation, were assessed using endpoint assays after independent stimulation of CD8+ and CD4+ CAR+ T-cell product components. ResultsReductions in process duration time, optimization of drug product container and formulation and activation signal optimization led to significantly increased CAR+ T-cell product viability. The heterogeneity of patient-derived starting material, including low absolute lymphocyte counts in some samples, was reduced through early T-cell purification, leading to median T-cell frequencies >95% in selected materials across disease indications and limited non-T-cell impurities. These changes further increased lineage purity in CD8+ and CD4+ CAR+ T-cell drug products. CD8+ and CD4+ CAR+ T-cell component lot functional profiles demonstrated multifunctional mechanisms of action, including differential cytokine release, differential cytolytic kinetics and high frequencies of proliferating cells. Correlative analyses demonstrated strong underlying associations between starting material attributes and final CAR+ T-cell product phenotype. ConclusionsDespite substantial heterogeneity of starting leukapheresis material quality/composition between individual patients and across disease indications/histologies, the liso-cel manufacturing platform is robust and capable of generating a consistent drug product from diverse starting materials with a single manufacturing platform.

Immune Checkpoint Blockade via PD-L1 Potentiates More CD28-Based than 4-1BB-Based Anti-Carbonic Anhydrase IX Chimeric Antigen Receptor T Cells.

The complete regression of clear cell renal cell carcinoma (ccRCC) obtained pre-clinically with anti-carbonic anhydrase IX (CAIX) G36 chimeric antigen receptor (CAR) T cells in doses equivalent to ≅108 CAR T cells/kg renewed the potential of this target to treat ccRCC and other tumors in hypoxia. The immune checkpoint blockade (ICB) brought durable clinical responses in advanced ccRCC and other tumors. Here, we tested CD8α/4-1BB compared to CD28-based anti-CAIX CAR peripheral blood mononuclear cells (PBMCs) releasing anti-programmed cell death ligand-1 (PD-L1) IgG4 for human ccRCC treatment in vitro and in an orthotopic NSG mice model in vivo. Using a ≅107 CAR PBMCs cells/kg dose, anti-CAIX CD28 CAR T cells releasing anti-PD-L1 IgG highly decrease both tumor volume and weight in vivo, avoiding the occurrence of metastasis. This antitumoral superiority of CD28-based CAR PBMCs cells compared to 4-1BB occurred under ICB via PD-L1. Furthermore, the T cell exhaustion status in peripheral CD4 T cells, additionally to CD8, was critical for CAR T cells efficiency. The lack of hepatotoxicity and nephrotoxicity upon the administration of a 107 CAR PMBCs cells/kg dose is the basis for carrying out clinical trials using anti-CAIX CD28 CAR PBMCs cells releasing anti-PD-L1 antibodies or anti-CAIX 4-1BB CAR T cells, offering exciting new prospects for the treatment of refractory ccRCC and hypoxic tumors.

Characteristics of Post-Infusion Chimeric Antigen Receptor (CAR) T Cells and Endogenous T Cells Associated with Early and Long-Term Response in Lisocabtagene Maraleucel (liso-cel)-Treated Relapsed or Refractory (R/R) Large B-Cell Lymphoma (LBCL)

Background: Liso-cel is an autologous, CD19-directed, defined composition, 4-1BB CAR T cell product administered at equal target doses of CD8 + and CD4 + CAR + T cells. In the pivotal TRANSCEND NHL 001 study (NCT02631044) in patients (pts) with R/R LBCL after ≥ 2 prior lines of therapy, liso-cel demonstrated significant clinical activity with an objective response rate of 73%, complete response (CR) rate of 53%, and median duration of response (DOR) not reached at 12 months' median DOR follow-up, and a low incidence of severe cytokine release syndrome (2%) and neurological events (10%; Abramson et al. Lancet 2020;396:839-852). While CAR T cells have shown remarkable efficacy in treating LBCL, with a well-understood mechanism of direct CAR T cell tumor killing, the contribution of the endogenous immune system in this response is currently unclear. Previously, histologic and gene expression analysis of pre- and posttreatment tumor biopsies from pts who received liso-cel in TRANSCEND NHL 001 showed a relationship between tumor-infiltrating CAR-negative (endogenous) T cells and early and durable response [Reiss et al. Blood 2019;134(suppl 1):202].Here we examine, by gene expression and flow cytometry, post-infusion characteristics of liso-cel and peripheral endogenous T cells in pts from TRANSCEND NHL 001 with early (CR at 1 or 3 months) and long-term (CR at 9 or 12 months) response versus pts with progressive disease (PD) before or at the same time points.Methods: CAR and endogenous T cells were assayed using a novel cell-sorting and low-input RNA-seq method. CAR and endogenous T cells were isolated from peripheral blood mononuclear cell samples from 39 pts at time to maximum concentration of liso-cel (T max; Day 8-22), 1 month, and 2 months after liso-cel infusion. In addition, samples from 44 pts were assayed only at T max by RNA-seq. A subset of these samples was assessed by flow cytometry for expression of the T cell differentiation markers CD4, CD8, CD45RA, CCR7, CD27, and CD28.All RNA-seq analyses were performed in R version 4.0.2. Differential expression analysis was performed with the DESeq2 package with gene set enrichment analysis using clusterProfiler and GSVA packages with gene sets obtained from MSigDB. Comparisons of 2 groups were made with a Wilcoxon rank sum test. Association with the time-to-event outcome of progression-free survival (PFS) was assessed using Cox proportional hazards model or log rank test.Results: Characteristics consistent with less differentiated CAR T cells and endogenous T cells were significantly associated with early and long-term response. Elevated CAR T cell expression of CD27 at T max was associated with CR at 1 month and longer PFS. Expression of CCR7 by CAR T cells at 1 and 2 months was associated with CR at 9 months. Additionally, at T max, gene sets associated with T cell effector differentiation and metabolism were enriched in CAR T cells from pts with early relapse (pts with CR vs PD at 3 months).In endogenous T cells, elevated expression of CCR7 and CD28 at T max was associated with early response (CR at 1 and 3 months). Additionally, expression of CCR7 and CD28 in T cells isolated at 1 and 2 months was associated with long-term response (CR at 9 and 12 months). Furthermore, expression of the immune checkpoint receptor LAG3 by endogenous T cells was associated with PD from month 3 to month 12.Conclusions: In summary, the data from our study show the relationship between CAR T cell differentiation status and achieving response over time, and provide new evidence for the involvement of endogenous T cells in the therapeutic efficacy of CAR T cell therapy. DisclosuresThorpe: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Jiang: Bristol Myers Squibb: Ended employment in the past 24 months. Rytlewski: Adaptive Biotechnologies: Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months; Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Kostic: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Kim: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Peiser: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company.

Updated Phase 1 Results of C-CAR088, an Anti-BCMA CAR T-Cell Therapy in Relapsed or Refractory Multiple Myeloma

▪Background:C-CAR088, an anti-BCMA CAR T-cell therapy, is a novel 2nd generation 4-1BB chimeric antigen receptor T (CAR-T) cell therapy targeting BCMA. Previously presented results from an ongoing study of C-CAR088 in R/R MM (NCT03751293, NCT03815383, NCT04322292, NCT04295018) included a 95.7% overall response rate (ORR) for the dose of 1.0~6.0x10 6 CAR-T cells/kg with a favorable safety profile (Lu, 2020 ASH Oral Presentation #182). Here we present the updated results of the study, with more patients and longer follow up time.Methods:Dose escalation and expansion studies were conducted at four medical centers in China to evaluate the safety and efficacy of C-CAR088 in patients with R/R MM who were previously treated with at least 2 lines of therapy, including proteasome inhibitors (PIs) and IMiDs. C-CAR088 was administered to patients as a single infusion after lymphodepletion with fludarabine (30 mg/m 2) and cyclophosphamide (300 mg/m 2) daily for 3 days. The primary endpoint was the incidence of adverse events (AEs), including dose-limiting toxicities (DLTs), and the secondary endpoints included overall response rate(ORR), duration of response (DOR), and progression-free survival (PFS) by IMWG Uniform Response Criteria.Results:As of July 2nd, 2021, 31 patients had been infused with C-CAR088. The median vein-to-vein time was 18 days. The manufacturing success rate was 100%. 4, 13 and 14 patients were infused with 1.0, 3.0 and 4.5~6.0 x10 6 CAR+ T cells/kg respectively. The median follow-up time for all patients was 8.0 months (0.1-24.2). The median age of patients was 61 years (45-74). The median number of prior lines of therapy was 4 (2-13). There were 25 (80.6%) patients with at least one high risk cytogenetic abnormality and 17 (54.8%) patients with at least two high risk cytogenetic abnormalities. 7 patients (22.6%) received bridging therapy before C-CAR088 therapy.Cytokine release syndrome (CRS) developed in 29/31 (93.5%) patients, grade 1 in 18/31 (58.1%), grade 2 in 8/31 (25.8%) and grade 3 in 3/31 (9.7%) respectively. The median time to the first onset of CRS was 6 days (1-11) and the median duration of CRS was 5 days (2-14). 9/31 (29%) patients used tocilizumab and 6/31 (19.4%) patients used corticosteroids to manage CRS. Only one patient developed a grade 1 neurotoxicity. No DLTs were observed and all adverse events were reversible. One patient died of septic shock on day 2 after receiving C-CAR088.Clinical efficacy was assessed in 28 patients with ≥ 1 month of follow up. Among the 28 patients, 3, 11 and 14 patients were infused with the dose of 1.0 x 10 6 CAR+ T cells/kg 3 x10 6 CAR+ T cells/kg, and 4.5~6x10 6 CAR+ T cells/kg respectively.The ORR was 27/28 (96.4%): 4 (14.3%) achieved CR, 12 (42.9%) achieved sCR and 9 (32.1%) achieved very good partial response (VGPR).At the dose level of 1.0 x10 6 CAR+ T cells/kg, 3(100%) patients achieved VGPR. The median DOR was 3.7 months (1.8-5.8), and the median PFS was 4.6 months (2.7-6.2).The CR rate was 54.5% (6/11) and 71.4% (10/14) in the 3.0 and 4.5~6.0 x10 6 CAR+ T cells/kg cohorts respectively. The median time to CR was 2.0 (0.5-9.5) months. Minimal residual disease (MRD) was testedbyEuroFlow-based flow cytometric analysis in 16 patients who had CR, 15/16 (93.7%) patients were MRD negative with the sensitivity of 10 -5. With a median follow-up of 9.5 months (1.9-24.2) in ≥ 3.0x10 6 CAR+ T cells/kg cohorts, the median DOR and PFS had not been reached. The Kaplan-Meier estimation of PFS at 6 and 12 months was 81.1% (95% CI:65.9% ~99.8%) and 69.5 % (95% CI:51.6 % ~93.6%) respectively.8 patients in the ≥ 3.0x10 6 CAR+ T cells/kg cohorts discontinued the study. 7 discontinued due to disease progression (PD), and 1 discontinued for other anticancer therapy. 4 progressed within 6 months, 2 progressed within 6-12 months, and 1 progressed within 12-24 months.C-CAR088 proliferated and expanded well in patients' blood. The median C max was 734,868 copies/μg gDNA. The median AUC 0~28day was 7,468,779 day·copies/μg gDNA. The median T max was 14 days. The median T last was 84 days. 71% (95% CI: 42%~92%) of patients with C max equal to or greater than the median C max achieved CR/sCR.Conclusion:C-CAR088 has a manageable safety profile, which includes low neurotoxicity rates (with no gr ≥3 events). Deep and durable responses were observed in ≥ 3.0x10 6 CAR-T cells/kg cohorts. Doses of 3.0 and 6.0×10 6 CAR T cells/kg were selected for further study. [Display omitted] DisclosuresZhu: CBMG: Current Employment. Huang: CBMG: Current Employment. Li: CBMG: Current Employment. Lan: CBMG: Current Employment. Chen: CBMG: Current Employment. Humphries: CBMG Ltd: Current Employment. Yao: CBMG: Current Employment, Current holder of stock options in a privately-held company.

Incorporation of 4-1BB Endowed the Potent CD33 Specific Chimeric Antigen Receptor T Cells with Anti-Exhaustion Capacity and Increased Central Memory Compartment

Chimeric antigen receptor (CAR) modified T cells have been an important immunotherapeutic strategy. Efficacy of CAR-T cells may be influenced by the structure of CAR, particularly the costimulator component of CAR. To improve the function of CAR-T cells, different costimulators were incorporated into CAR structures. Studies have shown that CAR-T cells containing 4-1BB costimulator have superior antileukemic efficacy and improved persistence compared with that containing CD28 costimulator. But how costimulators affect CAR-T cell function remained to be further studied. In this study, three different CARs with costimulators CD28, 4-1BB, and both CD28 and 4-1BB targeted the myeloid antigen CD33 (referred to as CD33 28z.CAR-T, CD33 BBz.CAR-T and CD33 28BBz.CAR-T, respectively) were constructed and the antileukemic functions of corresponding CD33 CAR-T cells were reported. In addition, the characteristics related to persistence and function of CAR-T cells were further analyzed.To get CAR-T cells specific for CD33, the murine anti-human CD33 scFv derived from mouse hybridoma cells (clone HIM3-4,which was established in Institute of Hematology and Blood Diseases Hospital, CAMS&PUMC) was cloned into our previously constructed pCDH-CAR plasmids, and transfected into 293T/17 packaging cells with the packaging plasmids to produce lentiviruses. Then T cells from peripheral blood of healthy donors were isolated, stimulated and infected with lentiviruses to get CD33 28z.CAR-T, CD33 BBz.CAR-T and CD33 28BBz.CAR-T, respectively.In vitro antileukemic function of CD33 CAR-T cells was detected by cytotoxic effect on target cells, CAR-T cells degranulation reflected by CD107a expression and cytokines release by ELISA. It showed that all three CD33 CAR-T cells exhibited profound proliferation and potent effector functions against AML cell lines, including specific cytotoxicity at low E:T ratios of 1:8 or even 1:20, LDH release by target cells, distinct degranulation and robust cytokine production. For in vivo effect, human CD33+ leukemia mouse model were established, and then treated with CD33 CAR-T cells, followed by observation of the body weight and overall survival of mouse. Three type CD33 CAR-T cells could all significantly prolong mouse survival without obvious weight loss.Finally, the influences of different costimulators on CAR-T cells efficacy and persistence were explored, phenotypes of three CAR-T cells were assessed by flow cytometry based on memory markers CCR7 and CD45RA and exhaustion markers PD-1, LAG-3, Tim-3 et al. Distinctions among three types CAR-T cells emerged during in vitro expansion. CD33 BBz.CAR-T cells had an increased central memory compartment, which was related to T cell persistence. While CD33 28z.CAR-T cells were effector memory T cells predominant, which were the terminally differentiated T cells. In addition, CD33 28z.CAR-T cells were more inclined to become exhausted compared to CD33 BBz.CAR-T cells, indicated by higher expression of PD-1, LAG-3 and Tim-3.In conclusion, this study reported the high specific cytotoxicity of the CAR-T cells for CD33+ AML cells. Furthermore, this study demonstrated that 4-1BB signaling domain in CARs could endowed CAR-T cells with anti-exhaustion capacity and increased central memory compartment, uncovered the reason that CAR-T cells with 4-1BB performed better in antileukemic function, and further illustrated 4-1BB CAR may be superior to incorporate into T cells to get persistent anti-tumor efficacy especially when transfused to the human body environment.Keywords: Chimeric antigen receptor, CD33, Acute myeloid leukemia, Immunotherapy, Costimulator DisclosuresNo relevant conflicts of interest to declare.

Population Cellular Kinetics of Lisocabtagene Maraleucel, an Autologous CD19-Directed Chimeric Antigen Receptor T-Cell Product, in Patients with Relapsed/Refractory Large B-Cell Lymphoma.

Background and ObjectivesLisocabtagene maraleucel (liso-cel) is a CD19-directed, defined composition, 4-1BB chimeric antigen receptor (CAR) T-cell product administered at equal target doses of CD8+ and CD4+ CAR+ T cells. Large between-subject variability has been noted with CAR T-cell therapies; patient characteristics might contribute to CAR T-cell expansion variability. We developed a population cellular kinetic model to characterize the kinetics of the liso-cel transgene, via quantitative polymerase chain reaction assessment after intravenous infusion of liso-cel, and to understand covariates that might influence liso-cel kinetics in individual patients.MethodsWe employed nonlinear mixed-effects modeling to develop a population cellular kinetic model for liso-cel. The population cellular kinetic analysis was performed using 2524 post-infusion transgene observations from 261 patients with relapsed/refractory large B-cell lymphoma who were treated with a single dose of liso-cel in TRANSCEND NHL 001. Covariates for the analysis included baseline intrinsic factors such as age, baseline disease characteristics, and liso-cel and coadministration factors.ResultsLiso-cel cellular kinetics were well described by a piecewise model of cellular growth kinetics that featured lag, exponential growth, and biexponential decay phases. Population means (95% confidence interval) of lag phase duration, doubling time, time to maximum levels, initial decline half-life, and terminal half-life were 3.27 (2.71–3.97), 0.755 (0.667–0.821), 9.29 (8.81–9.70), 5.00 (4.15–5.90), and 352 (241–647) days, respectively. The magnitude of effect on liso-cel expansion metrics demonstrated that the covariate associations were smaller than the residual between-subject variability in the population.ConclusionsThe covariates tested were not considered to have a meaningful impact on liso-cel kinetics.Clinical Trial RegistrationNCT02631044.

BATF3/MYC axis drives hyper-proliferation of TET2 deficient CAR T cells

Abstract A recent report described a patient presenting a dominant chimeric antigen receptor (CAR) T cell clone at the height of anti-tumor response wherein a TET2 allele was disrupted by the integration of the lentiviral 4-1BB CAR vector (Fraietta et. al. Nature 2018). The enhanced proliferative ability conferred by this chance TET2 disruption opened up the possibility of generating TET2 edited CAR T cells for an enhanced anti-tumor efficacy. We modeled and evaluated loss of TET2 in human T cells engineered to express different CAR receptors in a murine model of human acute lymphoblastic leukemia (ALL). Our results indicate that CAR design plays a critical role in determining anti-tumor efficacy and early stage T cell phenotype upon TET2 disruption. We further observe that TET2 edited CAR T cells, over time, enter a hyper-proliferative state with a near total loss of effector function. The frequency with which TET2 edited T cells achieve hyper-proliferation is dependent on the signaling properties of the CAR receptor. This state is in contrast to the canonical exhaustion state wherein loss of proliferative ability precedes loss of effector function. This hyper-proliferative state shares some transcriptional features with T cell leukemia/lymphoma with sustained upregulation of cell cycle associated factors. Exome analysis identified point mutations and chromosomal aberrations in hyper-proliferative cells, but they were not conserved across different populations. Chromatin accessibility analysis revealed that loss of TET2 sets an epigenetic state that allows for sustained elevated levels of BATF3 which in turn drives a MYC-dependent proliferative program in TET2 deficient CAR T cells.

Updated Follow-up of Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma Treated with Lisocabtagene Maraleucel in the Phase 1 Monotherapy Cohort of Transcend CLL 004, Including High-Risk and Ibrutinib-Treated Patients

Updated Follow-up of Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma Treated with Lisocabtagene Maraleucel in the Phase 1 Monotherapy Cohort of Transcend CLL 004, Including High-Risk and Ibrutinib-Treated Patients

Costs of Postinfusion Monitoring By Site of Care for Patients with Relapsed/Refractory (R/R) Large B-Cell Lymphoma (LBCL) Who Received Third-Line or Later Treatment with Lisocabtagene Maraleucel (liso-cel) in the Transcend NHL 001 and Outreach Trials

Background: Chimeric antigen receptor (CAR) T cell therapy is generally limited to inpatient settings; yet, exploration of outpatient infusion and monitoring is ongoing. Information on health care resource utilization (HCRU) and costs associated with CAR T cell therapy administration is limited and may differ by postinfusion monitoring site. Liso-cel is an investigational, CD19-directed, defined composition, 4-1BB CAR T cell product administered at equal target doses of CD8+ and CD4+ CAR+ T cells. An interim analysis from the OUTREACH study (NCT03744676) observed lower HCRU with outpatient vs inpatient administration (Bachier et al. J Clin Oncol 2020;38:8037). The patient journey after CAR T cell therapy administration may differ for patients with outpatient vs inpatient monitoring and may result in varying costs of care. This study estimated the cost of postinfusion monitoring by site of care for patients with R/R LBCL who received third-line or later treatment with liso-cel in the TRANSCEND NHL 001 (TRANSCEND; NCT02631044) and OUTREACH clinical trials. Methods: This retrospective study analyzed HCRU reported in clinical trial databases from TRANSCEND and OUTREACH. A 2-step microcosting method was used to identify key HCRU and to estimate postinfusion costs: (1) HCRU was analyzed from the index date (day of liso-cel infusion) through the 6-month follow-up; and (2) costs were applied to each HCRU. HCRU included standard inpatient and intensive care unit (ICU) length of stay (LOS), diagnostics (laboratory work and imaging), procedures (dialysis and intubation), and medications (supportive care, prophylactic treatment, and adverse event management). Unit costs were obtained from the health care system (provider) perspective and adjusted to 2020 US dollars. Cost per standard inpatient day ($2,542) was estimated from Healthcare Cost and Utilization Project databases, and cost per ICU day ($7,556) was sourced from Dasta et al (Crit Care Med. 2005;33:1266-77). All medication costs were obtained from REDBOOK (IBM Micromedex) using wholesale acquisition costs. Diagnostic and procedure costs were obtained from the Centers for Medicare & Medicaid Services laboratory fee schedule, physician fee schedule, or outpatient prospective payment system. A payment-to-cost ratio was applied to Medicare payment rates to estimate unit costs. Costs were adjusted to reflect the site of care where the HCRU occurred. A cost ratio was applied to adjust costs from the physician's office/community oncology clinic to the hospital outpatient department (Winfield, Muhlestein, Leavitt Partners; 2017) and from outpatient to inpatient (Meisenberg et al. Bone Marrow Transplant. 1998;21:927-32). Costs were aggregated by HCRU category, specifically medications, diagnostics, procedures, and facility costs. An average total cost by post-liso-cel infusion month was calculated for patients with ongoing status in that month (patients censored due to data cutoff were not included). Analyses were stratified by site of postinfusion monitoring (inpatients vs outpatients). Results: A total of 303 patients with R/R LBCL across the 2 trials received liso-cel and postinfusion monitoring (inpatients, n = 256; outpatients, n = 47). HCRU and LOS, including standard inpatient and ICU days, are shown in the Table. Inpatients had higher rates of inpatient stays (<100% vs 62%) and tocilizumab use (for CRS and/or NE; 20% vs 9%) than outpatients, respectively. Rates of ICU admission, corticosteroid use, vasopressor use, dialysis, and intubation were similar between groups. Median and average LOS in standard inpatient and ICU settings were higher among inpatients. Median (range) total LOS for inpatients and outpatients was 15 (0-88) and 4 (0-77) days, respectively. The estimated mean postinfusion cost of care was $89,535 for inpatients and $36,702 for outpatients. Over 6 months, most costs were incurred in the first month after infusion ($50,369 [56%] for inpatients and $19,837 [54%] for outpatients). Costs were largely driven by facility costs, namely standard inpatient and ICU stays (Figure). Conclusions: Lower overall HCRU was observed with outpatient liso-cel postinfusion monitoring, primarily due to hospitalizations, which resulted in a mean 6-month cost savings of $52,833 (59%) compared with inpatient monitoring. These results are based on national average costs and may not be generalizable to specific institutions. Disclosures Palomba: Regeneron: Research Funding; Juno Therapeutics, a Bristol-Meyers Squibb Company: Honoraria, Research Funding; Genentech: Research Funding; Merck: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Pharmacyclics: Honoraria. Jun:Bristol-Myers Squibb Company: Current Employment, Current equity holder in publicly-traded company. Garcia:Bristol-Myers Squibb Company: Current equity holder in publicly-traded company; Juno Therapeutics, a Bristol-Myers Squibb Company: Current Employment. Lymp:Bristol-Myers Squibb Company: Current equity holder in publicly-traded company; Juno Therapeutics, a Bristol-Myers Squibb Company: Current Employment. McGarvey:Pfizer, Inc.: Ended employment in the past 24 months; BluePath Solutions: Current Employment. Gitlin:BMS: Research Funding. Pelletier:BMS: Current Employment, Current equity holder in publicly-traded company. Nguyen:BluePath Solutions: Current Employment.

Enhancing the Antigen-Sensitivity of the CD22 CAR through Modulation of the Affinity and Linker-Length of the Single-Chain Fragment Variable

The advent of chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of relapsed/refractory acute lymphoblastic leukemia (r/r ALL). CD19 directed CAR T cells have demonstrated the ability to induce complete remissions in up to 90% of r/r ALL patients. Despite this remarkable upfront success, relapse after CAR T cell therapy remains a major obstacle to long term remissions. A major mechanism for relapse after CD19-directed CAR T cell therapy is the recurrence of antigen-negative ALL cells. In recent years, CD22 CAR T cell therapy has emerged as an effective salvage therapy for patients with CD19-negative ALL. In a phase I clinical trial, CD22 CAR T cells were able to induce remission in up to 80% of patients with CD19-negative ALL. Patients achieving remission, who did not undergo a consolidative hematopoietic stem cell transplant, were found to be at high risk of relapse due to downregulation of the CD22 antigen below the threshold required for effective CD22 CAR T cell activity. Thus, strategies to increase the antigen-sensitivity of CD22 CAR T cells have the potential to enhance the induction and duration of remission in ALL patients. As the properties of a CAR that influence sensitivity to antigen are not well defined, we began by testing the impact of increasing the affinity of the single-chain fragment variable (scFv) for the CD22 antigen. T cells from healthy donors were activated and transduced with a second-generation, 4-1BB CAR containing either the standard affinity (SA)-m971 scFv used in the prior clinical trial, or a high affinity (HA) scFv generated by affinity maturation of the m971 scFv. SA- and HA-CD22 CAR T cells were evaluated in vitro and in vivo against clones of the pre-B ALL cell line, NALM6, which express CD22 at wild type levels (CD22WT), sub-physiologic levels (CD22Lo), supra-physiologic levels (CD22Hi) or in which CD22 was deleted (CD22Neg). We found that the amount of CD22 expressed on the leukemia cells resulted in dose-dependent expression of activation markers, such as CD69 and CD25 (p<0.05) on CD22 CAR T cells. Similarly, CAR T cell functions, such as the secretion of interferon-gamma (IFNg, p<0.0001) and interleukin-2 (IL-2, p<0.0001) as well as cytotoxic degranulation (p<0.0001) were all significantly impacted by the amount of CD22 on the surface of NALM6. A similar pattern of antigenic dose-response was seen in the signaling of CAR T cells, with phosphorylation of ERK reflecting the level of CD22 antigen (p<0.001) and correlating with the increased in vivo efficacy of the CAR T cells against CD22WT NALM6, relative to CD22Lo NALM6. Increasing the affinity of the CD22 CAR did not impact the in vivo efficacy against CD22WT NALM6 at either a therapeutic or subtherapeutic dose, however, HA-CD22 CAR T cells significantly prolonged the survival of NSG mice with CD22Lo NALM6, relative to SA-CD22 CAR T cells (p<0.01). The enhanced activity of HA-CD22 CAR T cells against CD22Lo leukemia did not correlate with improved in vitro functionality, as the HA-CD22 CAR T cells surprisingly demonstrated lower IL-2 secretion (p<0.01), lower proliferation (p<0.05) and diminished in vitro lysis of CD22Lo NALM6 (p<0.05), relative to SA-CD22 CAR T cells. ERK phosphorylation, however, was significantly increased in HA-CD22 CAR T cells (p<0.01) and was the only in vitro marker which correlated with the enhanced in vivo activity seen with the affinity-matured CAR. Previous clinical experience has demonstrated the importance of using a short linker (consisting of a single G4S sequence) between the heavy and light chains of the m971 scFv, therefore we next evaluated the impact of linker length on the activity of the HA-CD22 CAR. HA-CD22 CARs were generated with either a short- or long-linker (G4S x1 vs G4S x3, respectively) and evaluated in vitro and in vivo. While the short linker improved proliferation in vitro, there was no significant impact of linker length on cytokine production or lysis of CD22Lo NALM6. In a xenograft model, HA-CD22 CAR T cells with the long-linker demonstrated slower progression of CD22Lo leukemia and significantly prolonged survival of NSG mice with CD22WT leukemia relative to HA-CD22 CAR T cells with the short-linker (p<0.01). Taken together, these studies suggest that increasing the affinity of a scFv is a promising strategy for enhancing CAR sensitivity to low levels of target antigen, with the potential to decrease post-CAR T cell relapses due to antigen downregulation. Disclosures No relevant conflicts of interest to declare.

Safety and Preliminary Efficacy in Patients with Relapsed/Refractory Mantle Cell Lymphoma Receiving Lisocabtagene Maraleucel in Transcend NHL 001

Safety and Preliminary Efficacy in Patients with Relapsed/Refractory Mantle Cell Lymphoma Receiving Lisocabtagene Maraleucel in Transcend NHL 001

Outcomes of Treatment with the Chimeric Antigen Receptor (CAR) T Cell Therapy Lisocabtagene Maraleucel (liso-cel) in the Nonuniversity Setting: Initial Results from the Outreach Study

Outcomes of Treatment with the Chimeric Antigen Receptor (CAR) T Cell Therapy Lisocabtagene Maraleucel (liso-cel) in the Nonuniversity Setting: Initial Results from the Outreach Study

An Anti-Bcma CAR T-Cell Therapy (C-CAR088) Shows Promising Safety and Efficacy Profile in Relapsed or Refractory Multiple Myeloma

Background: C-CAR088, an anti-BCMA CAR T-cell therapy is a novel 2nd generation 4-1BB chimeric antigen receptor T (CAR-T) cell therapy targeting BCMA which is specifically and highly expressed on multiple myeloma (MM) cells. C-CAR088 is manufactured in a serum-free, automated and digital, closed system. Initial, early clinical trial results in patients with R/R MM supported preclinical findings and showed promising efficacy and manageable safety profile (Yao, Blood (2019) 134 (Supplement_1): 50.) Methods: The dose escalation and expansion studies have been conducted at four medical centers in China to evaluate the safety and efficacy of C-CAR088 in patients with R/R MM who were previously treated with at least 2 lines of therapy including proteasome inhibitors (PIs) and IMiDs. C-CAR088 is administered to patients as a single intravenous dose after a standard 3-day cyclophosphamide/fludarabine conditioning regimen. Results: As of July 15, 2020, 24 patients were infused and 21 patients had evaluable data for safety and clinical response at dose levels of 1.0 x 106 CAR-T cells/kg (n=3), 3 x106 CAR-T cells/kg (n=11) and 4.5~6x106 CAR-T cells/kg (n=7). The median vein to vein time was 16 days. The manufacturing success rate was 100%. The median age of patients dosed was 60 years (range: 45-74 years).The median number of prior lines of therapy was 4 (range: 2-12 prior therapies). There were 17 (81%) patients with at least one and 12 (57.1%) patients with at least two high risk cytogenetic tumor changes. Five patients (23.8%) had bridging therapy. C-CAR088 treatment was well tolerated. 20 of 21 (95%) patients had Grade 1-2 CRS and one patient experienced Grade 3 CRS. Median time to CRS was 6.5 days (range: 1-11 days) and median duration of CRS was 5 days (range: 2-10 days). Four patients (19%) received tocilizumab for CRS treatment. Only one patient experienced a Grade 1 neurotoxicity event. No dose-limiting toxicities were observed and all adverse events were reversible. The best overall response (BOR) included 6 complete responses (CRs), 10 very good partial responses (VGPRs) and 4 partial responses (PRs). Median follow-up was 182 days (range: 30-375 days). The median duration of response has not been reached. In the 3 x106 CAR-T cells/kg dose group, 5/11(45%) patients achieved a CR. The C-CAR088 PK profile in peripheral blood showed a trend of a dose dependent profile. AUC0~28day and Cmax increased and Tmax decreased with dose (P<0.05). Conclusion: The clinical trial results in patients with R/R MM treated with C-CAR088 show a favorable safety profile and promising signs of efficacy. We will continue to evaluate these patients to understand the long-term effect of C-CAR088 in multiple myeloma patients. Clinical trial information: NCT04322292、NCT03815383、NCT03751293、NCT04295018 Research Sponsor: Cellular Biomedicine Group, Inc. Disclosures Zhu: Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Zheng:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Yan:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Lv:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Lan:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Yang:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Huo:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Han:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Zhao:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Qin:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Wu:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Yao:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Zhu:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Ren:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Zhang:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Huang:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Humphries:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company. Yao:Cellular Biomedicine Group Inc: Current Employment, Current equity holder in publicly-traded company.