Targeting CD47 Research Articles

Targeting CD70 in acute myeloid leukaemia: an emerging therapeutic angle in combinatorial treatment

Targeting CD70 in acute myeloid leukaemia: an emerging therapeutic angle in combinatorial treatment

XFab-α4-1BB/CD40L fusion protein activates dendritic cells, improves expansion of antigen-specific T cells, and exhibits antitumour efficacy in multiple solid tumour models.

Additional immunotherapies are still warranted for non-responders to checkpoint inhibitors with refractory or relapsing cancers, especially for patients with "cold" tumours lacking significant immune infiltration at treatment onset. We developed XFab-α4-1BB/CD40L, a bispecific antibody targeting 4-1BB and CD40 for dendritic cell activation and priming of tumour-reactive T cells to inhibit tumours. XFab-α4-1BB/CD40L was developed by engineering an anti-4-1BB Fab arm into a CD40L trimer based on XFab® platform. Characterisation of the bispecific antibody was performed by cell-based reporter assays, maturation of dendritic cell assays, and mixed lymphocyte reactions. The abilities of antigen-specific T-cell expansion and antitumour efficacy were assessed in syngeneic mouse tumour models. Toxicological and pharmacodynamic profiles were investigated in non-human primates. XFab-α4-1BB/CD40L demonstrated independent CD40 agonistic activity and conditional 4-1BB activity mediated by CD40 crosslinking, leading to dendritic cell maturation and T-cell proliferation in vitro. We confirmed the expansion of antigen-specific T cells in the vaccination model and potent tumour regression induced by the bispecific antibody alone or in combination with gemcitabine in vivo, concomitant with improved tumour-reactive T-cell infiltration. XFab-α4-1BB/CD40L showed no signs of liver toxicity at doses up to 51mg/kg in a repeated-dose regimen in non-human primates. XFab-α4-1BB/CD40L is capable of enhancing antitumour immunity by modulating dendritic cell and T-cell functions via targeting 4-1BB agonism to areas of CD40 expression. The focused, potent, and safe immune response induced by the bispecific antibody supports further clinical investigations for the treatment of solid tumours.

Tandem bispecific CD123/CLL-1 CAR-T cells exhibit specific cytolytic effector functions against human acute myeloid leukaemia.

The treatment of refractory and recurrent acute myeloid leukaemia (AML) is still a challenge with poor response rates and short survival times. In an attempt to solve this problem, we constructed a tandem bispecific chimeric antigen receptor (CAR) targeting CD123 and C-type lectin-like molecule 1 (CLL-1), two different AML antigens, and verified its cytotoxic effects in vitro. We established and cultured K562 cell lines expressing both CD123 and CLL1 antigens. Single-target CAR-T cells specific to CD123 and CLL1 were engineered, alongside tandem CD123/CLL1 bispecific CAR-T cells. Flow cytometry was used to determine cell phenotypes, transfection efficiencies, cytokine release, and CAR-T-cell proliferation, and an lactate dehydrogenase assay was used to detect the cytotoxicity of CD123/CLL-1 bispecific tandem CAR-T cells in vitro. Two types of tandem CAR-T cells exhibited significant killing effects on CLL-1 + CD123+ leukaemia cell lines and primary AML tumour cells. The killing efficiency of tandem CAR-T cells in the case of single antigen expression is comparable to that of single target CAR-T cells. When faced with dual target tumour cells, dual target CAR-T cells significantly surpass single target CAR-T cells. CD123/CLL-1 CAR-T cells in tandem targeted and killed CD123- and CLL-1-positive leukaemia cell lines and released a large number of cytokines. CD123/CLL-1 CAR-T cells in tandem can simultaneously target CD123 and CLL-1 on AML cells, demonstrating a significant ability to kill single antigens and multi-target tumour cells. This suggests that CD123/CLL-1 CAR-T cells exhibit significant advantages in the expression of multiple antigens in a wide range of target cells, which may help overcome the challenges posed by tumour heterogeneity and evasion mechanisms.

O-103 - CD38 targeting in aggressive, treatment-refractory cutaneous T-cell lymphomas

O-103 - CD38 targeting in aggressive, treatment-refractory cutaneous T-cell lymphomas

RETRACTED: P-377 CD38 targeting in multiple myeloma

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the authors. This abstract was submitted to the International Myeloma Society and the meeting organizers by the first author without informed consent of all co-authors.

Targeting CD47-SIRPa axis shows potent preclinical anti-tumor activity as monotherapy and synergizes with PARP inhibition

The objective was to correlate CD47 gene expression with resistance to immune checkpoint inhibitors (ICI) in tumor tissue of gynecological cancer (GC). Further, we sought to assess the efficacy of targeting CD47 pathway alone and in combination in pre-clinical ovarian cancer (OC) models. We performed transcriptomic analyses in GC treated with ICI. Signaling pathway enrichment analysis was performed using Ingenuity Pathway Analysis. Immune cell abundance was estimated. CD47 expression was correlated with other pathways, objective response, and progression-free survival (PFS). Anti-tumor efficacy of anti-CD47 therapy alone and in combination was investigated both in-vitro and in-vivo using cell-line derived xenograft (CDX) and patient-derived xenograft (PDX) models. High CD47 expression associated with lower response to ICI and trended toward lower PFS in GC patients. Higher CD47 associated negatively with PDL1 and CTLA4 expression, as well as cytotoxic T-cells and dendritic cells but positively with TGF-β, BRD4 and CXCR4/CXCL12 expression. Anti-CD47 significantly enhanced macrophage-mediated phagocytosis of OC cells in-vitro and exhibited potent anti-tumor activity in-vivo in OC CDX and PDX models. In-vitro treatment with PARPi increased CD47 expression. Anti-CD47 led to significantly enhanced in-vitro phagocytosis, enhanced STING pathway and synergized in-vivo when combined with PARP inhibitors in BRCA-deficient OC models. This study provides insight on the potential role of CD47 in mediating immunotherapy resistance and its association with higher TGF-β, BRD4 and CXCR4/CXCL12 expression. Anti-CD47 showed potent anti-tumor activity and synergized with PARPi in OC models. These data support clinical development of anti-CD47 therapy with PARPi in OC.

B-cell targeting with anti-CD38 daratumumab: implications for differentiation and memory responses.

B cell-targeted therapies, such as CD20-targeting mAbs, deplete B cells but do not target the autoantibody-producing plasma cells (PCs). PC-targeting therapies such as daratumumab (anti-CD38) form an attractive approach to treat PC-mediated diseases. CD38 possesses enzymatic and receptor capabilities, which may impact a range of cellular processes including proliferation and differentiation. However, very little is known whether and how CD38 targeting affects B-cell differentiation, in particular for humans beyond cancer settings. Using in-depth in vitro B-cell differentiation assays and signaling pathway analysis, we show that CD38 targeting with daratumumab demonstrated a significant decrease in proliferation, differentiation, and IgG production upon T cell-dependent B-cell stimulation. We found no effect on T-cell activation or proliferation. Furthermore, we demonstrate that daratumumab attenuated the activation of NF-κB in B cells and the transcription of NF-κB-targeted genes. When culturing sorted B-cell subsets with daratumumab, the switched memory B-cell subset was primarily affected. Overall, these in vitro data elucidate novel non-depleting mechanisms by which daratumumab can disturb humoral immune responses. Affecting memory B cells, daratumumab may be used as a therapeutic approach in B cell-mediated diseases other than the currently targeted malignancies.

Cell targeting and immunostimulatory properties of a novel Fcγ-receptor-independent agonistic anti-CD40 antibody in rhesus macaques

Targeting CD40 by agonistic antibodies used as vaccine adjuvants or for cancer immunotherapy is a strategy to stimulate immune responses. The majority of studied agonistic anti-human CD40 antibodies require crosslinking of their Fc region to inhibitory FcγRIIb to induce immune stimulation although this has been associated with toxicity in previous studies. Here we introduce an agonistic anti-human CD40 monoclonal IgG1 antibody (MAB273) unique in its specificity to the CD40L binding site of CD40 but devoid of Fcγ-receptor binding. We demonstrate rapid binding of MAB273 to B cells and dendritic cells resulting in activation in vitro on human cells and in vivo in rhesus macaques. Dissemination of fluorescently labeled MAB273 after subcutaneous administration was found predominantly at the site of injection and specific draining lymph nodes. Phenotypic cell differentiation and upregulation of genes associated with immune activation were found in the targeted tissues. Antigen-specific T cell responses were enhanced by MAB273 when given in a prime-boost regimen and for boosting low preexisting responses. MAB273 may therefore be a promising immunostimulatory adjuvant that warrants future testing for therapeutic and prophylactic vaccination strategies.

Targeting of CD38 and other NAD-dependent Enzymes in Leukemia Patients

Targeting of CD38 and other NAD-dependent Enzymes in Leukemia Patients

Phase 1 dose escalation study of DSP107, a first-in-class CD47 and 4-1BB targeting fusion protein, in combination with atezolizumab in patients with advanced solid tumors.

2632 Background: DSP107 is a bi-functional fusion protein composed of sequences from the extracellular domain of SIRPα and 4-1BB ligand (4-1BBL). The SIRPα arm targets CD47 overexpressed on tumor cells, blocking the “don’t eat me” checkpoint and anchoring trimeric 4-1BBL to the tumor, which interacts with 4-1BB expressed on activated immune cells. This results in proliferation and conditional activation of effector cytotoxic T-cells in the tumor microenvironment. Thereby, DSP107 triggers both innate and adaptive immune responses. Phase 1 monotherapy dose escalation data demonstrated an excellent safety profile with no binding to red blood cells and no dose limiting toxicities (DLTs), hematological or hepato-toxicities. Here we describe data from the completed DSP107 plus atezolizumab combination dose escalation portion of study NCT04440735. Methods: Adult patients with advanced solid tumors were treated with weekly intravenous DSP107 infusions (1, 3 or 10 mg/kg; N = 6-7 patients/dose cohort) and atezolizumab (1200 mg) Q3W during 3-week treatment cycles. The primary objective was to determine the safety and tolerability of DSP107 in combination with atezolizumab. Restaging imaging was performed every two months and evaluated by RECIST v1.1 criteria. Results: In 19 patients, DSP107 with atezolizumab was well tolerated with no DLTs. Grade 1-2 treatment related adverse events (AEs) were observed in 68% of patients (13/19). The most frequent AEs included diarrhea (21%), fatigue (21%), infusion related reaction (IRR; 16%), nausea, decreased appetite, arthralgia, myalgia and Grade 1 anemia (11% each). IRRs were managed during subsequent infusions by reducing the infusion rate and administering IV fluids. Stable disease (SD) as best response was observed in 8/19 (42%) patients with treatment duration currently up to 10.5 months. At the highest dose of DSP107 (10 mg/kg), 3/7 patients had SD (1 microsatellite stable-colorectal cancer (MSS-CRC) patient with KRAS mutation had 16% target lesion shrinkage and no progression for 7 months). An additional 2 patients with advanced MSS-CRC (with BRAF and KRAS mutations, respectively) demonstrated deep and durable responses (-73 and -76% reduction in target lesions) including disappearance of pulmonary and hepatic target lesions in one patient. These patients currently continue to receive treatment after > 8 and > 6 months, respectively. Conclusions: DSP107 is a novel, CD47 and 4-1BB targeting fusion protein with a differentiated safety, binding and pharmacodynamic profile compared to other CD47 and 4-1BB targeting agents. These Phase 1 data suggest that the combination of DSP107 with PD(L)1 blockade may have anti-tumor activity in cold tumors such as MSS-CRC. Clinical trial information: NCT04440735 .

Targeting CD47 in lymphoid malignancies with CAR T cells.

2513 Background: Despite major therapeutic advances of chimeric antigen receptor (CAR) T cells directed against CD19 in relapsed and refractory non-Hodgkin lymphoma (NHL), two thirds of patients experience relapse within the first two years. Nearly one third of these relapses are associated with CD19 antigen-loss escape thus leveraging alternate CAR targets may improve outcomes. CD47, an anti-phagocytic “don’t eat me” receptor known to be overexpressed in NHL, is an ideal CAR target as it is potentially indispensable for tumor progression. Methods: CD47-CAR binding domains were engineered either as a camelid single variable heavy chain nanobody (CD47-VHH-CAR) or as the CD47 binding domain of cognate receptor SIRPα (SIRPα-CAR), each combined with a CD28 costimulatory domain and a CD3ζ activation domain with two mutated ITAMs (1XX). In vitro co-culture assays were performed with lymphoid mouse tumor cell lines BM185 and A20. For in vivo experiments, syngeneic BALB/c mice were sublethally irradiated for lymphodepletion then injected intravenously with 1x105 luciferase+ BM185 cells. Two days later, mice were injected with 2x106 CAR T cells, and bioluminescence imaging was performed to monitor tumor progression. For bio-localization experiments, CAR T cells were co-transduced with a separate vector encoding luciferase. Results: CD47-CAR T cell expansion in vitro was hindered due to fratricide, which can be rescued by CD47 CRISPR knockout. Both CD47-VHH-CAR and SIRPa-CAR T cells exhibited potent and specific in vitro lysis of BM185 and A20 cells. CD47-VHH-CAR T cells showed transient anti-leukemia activity, however, survival was not significantly prolonged. T cell bio-localization analysis revealed that, compared to CD19-CAR T cells, CD47-VHH-CAR T cells exhibited prolonged retention in the thorax with minimal bone marrow trafficking, suggesting CD47 antigen-specific pulmonary sequestration, and inferior expansion. SIRPα-CAR T cells engineered to secrete pro-inflammatory cytokine IL-18 significantly improved CAR T cell expansion, resulting in bone marrow trafficking and clearance of BM185 tumor. However, recipients of IL-18-secreting SIRPa-CAR T cells experienced lethal CAR T cell-related toxicity. To improve the safety of CD47-CAR T cells, we engineered an NFAT-responsive vector expressing the CD47-CAR modified with E. coli-derived dihydrofolate reductase drug destabilization domain to limit CD47-CAR expression to T cells exposed to the stabilizing antibiotic trimethoprim and receiving a licensing NFAT signal from a CD19-CAR. Conclusions: In vivo activity of CD47-targeting CAR T cells is limited by thoracic retention and limited expansion, which can be partially overcome by overexpression of IL-18, though enhanced toxicity precludes survival prolongation. Our findings suggest that strategies to spatiotemporally restrict CAR expression or activation will be necessary to achieve safe and efficacious CD47-CAR T cell activity.

SAR442257, a CD38/CD28/CD3 trispecific antibody, potentiates CAR T‐cell activity against large B‐cell lymphoma

CART cell therapy has significantly improved outcomes of patients with relapsed/refractory large B cell lymphoma (rrLBCL), but many do not experience long term benefit. The mechanisms of failure are multifaceted including CAR T exhaustion. Understanding these mechanisms are likely to identify therapeutic avenues for improving outcomes. 13 rrLBCL tumors (7 CART naïve, 6 CART refractory), were subjected to scRNA-seq. Clustering was performed and frequency, clonal dominance, and expression of major cells and subclusters were compared. The effect of SAR442257, a CD38/CD28xCD3 trispecific antibody, was assessed in cytotoxicity assays and compared to control antibodies without CD38 or CD38/CD3/CD28 targeting regions. RL and HT cell lines were CRISPR modified to knock-out CD19 and isogenic WT used as target cells. CD19 CAR T were constructed from PBMCs of rrLBCL patients obtained at time of apheresis using a construct like axicabtagene ciloleucel. For cytotoxicity assays, cell lines were co-cultured at E:T ratios of 1:1 for 24 h or 48 h. scRNA-seq revealed that CART refractory rrLBCL tumors possessed higher fractions of terminally exhausted LAG3+TIM3+CD38+ CD8 T-cells (CD8TEX) with high expression of T-cell dysfunction and TEX signatures compared to CAR T naïve tumors. CD8TEX were most frequent in CART refractory tumors and enriched within CAR+CD8 T-cells detected. TCR clonotype analysis revealed highly expanded T-cell clones within the CD8TEX cluster, significantly increased clonal dominance, and reduced clonal diversity of CD8TEX cells in CAR T refractory compared to CART naïve tumors. Single cell differential gene expression revealed significantly increased expression of LAG3, TIM3, and CD38 in CD8 T-cells from CART refractory compared to CART naïve tumors. We hypothesized that SAR442257 could boost the activity of CD19 CART-cells from rrLBCL patients through dual antigen targeting of CD19 and CD38 on lymphoma cells and by fratricide of CD38-expressing CD8TEX cells. Cytotoxicity assays showed that SAR442257 significantly increased the killing of CAR T-cells against HT and RL WT (CD19+/CD38+) cells (24-h HT P-value = 3e-4, 24-h RL P-value = 1e-2) that persisted at 48 h. Addition of SAR442257 to CART-cells allowed killing of HT and RL CD19KO (CD19-/CD38+) (24-h HT P-value = 8e-7, 24-h RL P-value = 2e-8) at a level similar to the combination in WT. Addition of antibodies lacking CD38 or CD38/CD3/CD28-targeting regions did not boost cytotoxicity or rescue killing of CD19KO targets. We observed significant T-cell fratricide, which was beneficial or non-detrimental in light of increased lymphoma cell killing. The tumor microenvironment of CART refractory rrLBCL is enriched in clonally expanded and terminally exhausted CD8 T-cells expressing CD38. The CD38/CD28xCD3 trispecific antibody SAR442257 boosted CART-cell activity through recognition of CD38 on the tumor, costimulation of CART-cells, and induced fratricide of CD38+ T-cells. In addition, SAR442257 allowed CD19 CART-cells to kill CD19-/CD38+ LBCL cells. Encore Abstract - previously submitted to EHA 2023 The research was funded by: Sanofi Keywords: Aggressive B-cell non-Hodgkin lymphoma, Bioinformatics, Cellular therapies, Computational and Systems Biology Conflicts of interests pertinent to the abstract. P. Kim Employment or leadership position: Sanofi K. Bisht Employment or leadership position: Sanofi H. Van De Velde Employment or leadership position: Sanofi H. Wang Employment or leadership position: Sanofi

CAR-T cells targeting CD38 and LMP1 and anti-tumor activity against NK/T cell lymphoma.

e19529 Background: Natural killer/T-cell lymphoma (NKTCL) is an aggressive lymphoma with poor prognosis. In the past decade, chimeric antigen receptor transduced T (CAR-T) cell therapy has been a promising strategy against hematologic malignancies. Researchers have evaluated the efficacy of CAR-T cell targeting CD38 in multiple myeloma and NKTCL. LMP1 may induce a malignant transformation in B cells and epithelial cells, making it a non-negligible molecule in NKTCL. These suggest the potential clinical administration of CD38 and LMP1 targeting therapy. Methods: Four second-generation CAR-T cells including two single-targeted CAR (CD38-CAR and LMP1-CAR) and two tandem CAR (CD38-LMP1 Tan CAR 1 and Tan CAR 2) were constructed. Then the effects of four CAR-T cells on NKTCL cells were evaluated both in vitro and in vivo. Results: Four CAR-T cells could effectively eliminate malignant target-positive NKTCL cells in vitro. They could be activated and produce inflammatory cytokines in a target-dependent manner. Stimulated by CD38+LMP1+ NKTCL cells, two Tan CAR-T cells produced more IL-13, Granzyme B, IFN-γ and TNF-α than LMP1-CAR-T cells. In vivo test showed that CAR-T cells also exhibit significant anti-tumor effects in a xenotransplant NKTCL mice models. Two Tan CAR-T cells showed higher cytolytic activity against CD38+LMP1+ NKTCL cells than single-targeted CAR-T cells both in vitro and in vivo. Conclusions: We explored the feasibility of CAR-T cell therapy targeting both CD38 and LMP1 molecule. Our results indicated a promising effective therapeutic strategy for NKTCL.

Phase 1 first-in-human study of PF-07257876, a novel CD47/PD-L1 bispecific checkpoint inhibitor, in patients with PD-1/PD-L1-refractory and -naïve advanced solid tumors.

2529 Background: Tumor expression of the antiphagocytic protein CD47 (integrin associated protein) may lead to immunotherapy resistance (IO-R). PF-07257876 is a novel, IgG1, Fc-active, bispecific antibody targeting CD47 and PD-L1 designed to reverse IO-R, decrease anemia risk, and eliminate a priming dose. We report a Phase 1 dose escalation study (NCT04881045) in patients (pts) with advanced solid tumors, both IO-refractory and IO-naïve. Methods: The study enrolled pts ≥18 yrs with advanced non–small-cell lung carcinoma (NSCLC) and squamous cell carcinoma of the head and neck (SCCHN) with PD-L1 expression >1% post anti-PD-1/PD-L1 therapy. Pts with other PD-L1+ tumors known to express CD47 were included (prior IO not required). Pts received PF-07257876 at escalating dose levels in 28-day cycles. Primary objectives were safety (dose-limiting toxicity [DLT] rate), tolerability, and determination of Recommended Phase 2 Dose (RP2D). Secondary and exploratory objectives included pharmacokinetics (PK), blood receptor occupancy (RO), CD47 levels by immunohistochemistry (IHC), tissue biopsy findings, and objective response rate (ORR) per RECIST v.1.1. Results: As of 20OCT2022, 18 pts were enrolled (NSCLC: n = 6; SCCHN: n = 4; other: n = 8). Median (range) age 68 (46–79) yrs. PF-07257876 was given at ascending doses, 150-2400 mg by subcutaneous (SC) injection or SC infusion every 2 weeks. 16 (89%) pts had treatment-related adverse events (TRAEs): Grades 1/2: n = 12 (67%); Grade 3: n = 1 (6%); Grade 4: n = 3 (17%); no Grade 5. Most common TRAEs: injection site reaction/erythema (n = 13, 72%), thrombocytopenia (n = 6, 33%), anemia (n = 5, 28%), and nausea (n = 4, 22%). DLTs occurred in 2 of 3 pts at the highest tested dose (Grade 4 neutropenia and thrombocytopenia, n = 1; Grade 4 thrombocytopenia, n = 1; both pts recovered). One pt with IO-R SCCHN had a confirmed partial response (duration of response 16 wks). ORR was 5.6% (1/18). Drug exposure increase after 1st dose was not dose proportional. Blood RO was > 95% for PD-L1 and > 70% for CD47 with drug exposure. All pts’ baseline CD47 IHC levels were moderate to high. Pharmacodynamics cytokine profiling showed notable dose-response increases of IFNg, TNFa, CXCL9/10, CCL3/4, without IL-6 increase. Conclusions: PF-07257876 was well tolerated with manageable toxicity. Incidence and grade of anemia or thrombocytopenia were manageable. Target engagement of CD47 and PD-L1 in peripheral blood was high. Innate and adaptive cytokine modulation was observed. Antitumor activity was modest. Expansion is ongoing at 1800 mg. Clinical trial information: NCT04881045 .

A first-in-human study of CD123 NK cell engager SAR443579 in relapsed or refractory acute myeloid leukemia, B-cell acute lymphoblastic leukemia, or high-risk myelodysplasia.

7005 Background: SAR’579 is a trifunctional natural killer (NK) cell engager targeting CD123 antigen and co-engaging NKp46 and CD16a on NK-cells. SAR’579 facilitates the formation of a cytolytic synapse between NK-cells and CD123-positive tumor cells leading to NK-cell activation and tumor cell killing. We herein report preliminary safety and efficacy data of SAR’579 from a phase 1/2 trial in patients with relapsed or refractory acute myeloid leukemia (R/R AML), B-cell acute lymphoblastic leukemia or high risk-myelodysplasia (NCT05086315). Methods: SAR’579 was administered intravenously twice weekly or once weekly (QW), depending on the dose level (DL) for the first 2 weeks of cycle 1 and then weekly for rest of induction cycles. A patient receives approximately three 28-day induction cycles with patients achieving a complete remission (CR) or incomplete hematologic recovery (CRi) per International Working Group criteria transitioning to a 56-day maintenance period with dosing approximately every 29 days. The primary objectives were to establish safety/tolerability and anti-leukemic activity (composite complete remission [CRc] = CR+CRi). Results: With a cutoff date of January 27, 2023, total 23 patients with R/R AML across 6 DLs (3 patients DL1 and 4 each in DL2 - DL6) were included in the safety population. The median age was 70 years (range: 21 - 80) with 9 patients (39.1%) reporting prior hematopoietic stem cell transplantation (HSCT) and 16 (69.6%) had prior exposure to venetoclax. Patients received a median of 2 cycles (range: 1 – 7) for median duration of 7 weeks (range: 1 - 25) and escalating doses of SAR’579 between 10 - 3000 µg/kg/dose in cycle 1 and 100 - 3000 µg/kg QW for the rest of induction cycles. No dose limiting toxicities (DLTs) were observed among the 21 DLT-evaluable patients, until highest dose of 3000 µg/kg QW. The most common treatment emergent adverse events (TEAEs) included infusion-related reactions (n = 10 [43.5%]) and nausea (n = 7 [30.4%]). TEAEs were reported in 22 patients (95.7%) with grade 3/4 adverse events (AEs) in 18 (78.3%) and treatment-related AEs in 16 patients (69.6%), respectively. There were 2 cases of cytokine release syndrome (n = 1 grade 1 and n = 1 grade 2) and no case of immune effector cell-associated neurotoxicity syndrome. No patient reported TEAE leading to permanent discontinuation of SAR’579. The CRc rate was 13.0% (3/23 patients evaluable for response). In DLs with a highest dose of 1000 µg/kg QW, 3/8 (37.5%) patients achieved a CR (2 CR/1 CRi). The median time to first CR/CRi was 16.1 weeks 95% confidence interval (8.1 – Not Estimable [NE]), and the median duration of CR/CRi is NE due to limited follow-up time. Conclusions: SAR’579 was well tolerated up to doses of 3000 µg/kg QW with observed clinical benefit in patients with R/R AML. The trial continues to accrue patients. Clinical trial information: NCT05086315 .

The CD73 immune checkpoint promotes tumor cell metabolic fitness.

CD73 is an ectonucleotidase overexpressed on tumor cells that suppresses anti-tumor immunity. Accordingly, several CD73 inhibitors are currently being evaluated in the clinic, including in large randomized clinical trials. Yet, the tumor cell-intrinsic impact of CD73 remain largely uncharacterized. Using metabolomics, we discovered that CD73 significantly enhances tumor cell mitochondrial respiration and aspartate biosynthesis. Importantly, rescuing aspartate biosynthesis was sufficient to restore proliferation of CD73-deficient tumors in immune deficient mice. Seahorse analysis of a large panel of mouse and human tumor cells demonstrated that CD73 enhanced oxidative phosphorylation (OXPHOS) and glycolytic reserve. Targeting CD73 decreased tumor cell metabolic fitness, increased genomic instability and suppressed poly ADP ribose polymerase (PARP) activity. Our study thus uncovered an important immune-independent function for CD73 in promoting tumor cell metabolism, and provides the rationale for previously unforeseen combination therapies incorporating CD73 inhibition.

A phase 1 dose escalation study of GCC19CART: A novel coupled CAR therapy for patients with metastatic colorectal cancer.

3547 Background: GCC19CART, the first clinical candidate from the CoupledCAR solid tumor platform, is designed to overcome the limitations of conventional CAR T-cells in solid tumor malignancies by pairing solid tumor CAR T-cells with CD19 targeting CAR T-cells to amplify the proliferation and activation of the solid tumor CAR T component. GCC19CART targets guanylate cyclase-C (GCC), which is expressed in the metastatic lesions of 70%-80% of subjects with colorectal cancers and largely restricted to the intestinal tract. A Phase 1 investigator-initiated clinical trial is underway in China for patients with relapsed or refractory metastatic colorectal cancer who have received at least 2 prior lines of therapy. As of a data cutoff on Jan 28, 2023 21 subjects have been enrolled in 2 dose escalation groups at 5 hospitals in China. Methods: Subjects are screened for GCC expression by immunohistochemistry. Eligible subjects undergo leukapheresis, a single dose of lymphodepleting chemotherapy (fludarabine 30mg/m2 and cyclophosphamide 300mg/m2) 3 days prior to infusion, and then administration of a single infusion of GCC19CART at one of two preassigned doses: 1x106 or 2x106 CAR T-cells/kg. All responses were confirmed by an independent third-party imaging contract research organization. Results: 13 subjects have been enrolled to dose level 1 (1x106 cells/kg) and 8 subjects have been enrolled to dose level 2 (2x106 cells/kg). The most common adverse events were cytokine release syndrome (CRS) in 21/21 subjects (Grade 1 19/21 (90.48%) or Grade 2 2/21 (9.52%)) and diarrhea in 21/21 subjects (Grade 1 6/21 (28.57%) Grade 2 5/21 (23.81%) Grade 3 9/21 (42.86%) or Grade 4 1/21 (4.76%)). All patients with grade 3 and higher side effects were well managed. Immune effector cell-associated neurotoxicity syndrome (ICANS) was observed in 2/21 (9.52%) subjects at Grade 3 or 4 and resolved with corticosteroids. The combined overall response rate (ORR) for both dose levels was 28.6% (6/21). For dose level 1, overall response rate (ORR) was 15.4% (2/13). Two subjects demonstrated a partial response (PR) while 3 additional subjects had partial metabolic response (PMR) on PET/CT with stable disease (SD) or progressive disease (PD) per RECIST 1.1. For dose level 2, The ORR was 50% (4/8). 4 subjects demonstrated a PR and 2 additional subjects had PMR on PET/CT with SD per RECIST 1.1.The median PFS was 1.9 months in the dose 1 group and 6.3 months in the dose 2 group. The median overall survival was 13.3 months in the dose 1 group and 18.3 months in the dose 2 group. Conclusions: Preliminary results demonstrate that GCC19CART has meaningful dose-dependent clinical activity and an acceptable safety profile in relapsed or refractory metastatic colorectal cancer. This trial is ongoing and updated data will be presented. A Phase 1 trial of GCC19CART in the US has opened for accrual and is expected to enroll patients in mid-2022. Clinical trial information: ChiCTR2000040645 .

Translational development of BAFF-R-specific chimeric antigen receptor T-cell therapy targeting B-cell lymphoid malignancies.

e19501 Background: Relapsed and/or refractory (R/R) disease is observed in patients who receive CD19 targeting chimeric antigen receptor (CAR)-T cells to treat B-cell lymphoid leukemias and lymphomas. We generated a novel CAR, MC10029 that targets B-cell activating factor receptor (BAFF-R) to address this unmet medical need. Methods: We engineered a second-generation BAFF-R CAR (MC10029 CAR). The construct includes the single chain variable fragment (scFv) of our newly developed BAFF-R antibody with CD28 costimulatory and CD3ζ signaling domains. We confirmed MC10029 CAR-T cell antigen-specific activation with in vitro degranulation assays and a direct cytolytic assay. We used BAFF-R positive leukemia and lymphoma cell lines in both in vitro and in vivo models to further characterize MC10029 CAR-T cells, and finally, we enriched tumor primary cells from chronic lymphocytic leukemia (CLL) patients as a target for MC10029 CAR-T cells. In preparation for our Phase I clinical trial, we have manufactured three batches of CAR-T cells using a MC10029-encoding lentiviral vector produced under GMP conditions. The production batches of MC10029 CAR-T cells were evaluated for product quality with Viability, Identity and Potency as well as Safety from adventitious viral agents. Antigen specific cytotoxicity of the MC10029 CAR-T cells was confirmed using our standard degranulation assay. Results: MC10029 CAR-T cells elicited in vitro antigen-specific cytotoxicity against Nalm-6 cells, Z138 cells, MEC-1 cells, and a CD19 knock out Nalm-6 model designed to mimic CD19-negative R/R disease. We demonstrated in vivo antitumor effects of MC10029 CAR-T cells in NSG mice challenged with these same cell lines. We showed cytotoxicity of MC10029 CAR-T cells against CLL patients’ tumors. We also showed our quality control results to highlight our clinical trial trajectory. Conclusions: Novel MC10029 CAR-T cells showed broad utility against BAFF-R positive B-cell lymphoid malignancies in a series of in vitro, in vivo, and ex vivo models. With these robust data, we have moved forward to generate clinical grade MC10029 CAR-T cells using cGMP manufacturing and quality protocols in preparation of a MC10029 CAR-T cell Phase I clinical trial.

Efficacy and safety of mitazalimab in combination with mFOLFIRINOX in patients with metastatic pancreatic ductal adenocarcinoma (mPDAC): An interim analysis of the optimize-1 phase 1b/2 study.

4139 Background: Mitazalimab is a human CD40 agonistic IgG1antibody. Targeting CD40 kickstarts the cancer immunity cycle by licensing dendritic cells leading to tumor specific T cell priming and activation. Furthermore, in PDAC CD40 agonists on myeloid cells promote degradation of the desmoplastic tumor stroma, improving influx of T cells and chemotherapeutic agents into the tumor. OPTIMIZE-1 (NCT04888312) is a Phase 1b/2, open label, multicenter study designed to evaluate safety, tolerability, and efficacy of mitazalimab in combination with mFOLFIRINOX (Oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, irinotecan 150 mg/m2, 5-FU 2.4 g/m2) in patients (pts) with previously untreated mPDAC. In the first part of the study (phase 1b), 900 µg/kg mitazalimab was selected as the recommended phase 2 dose (RP2D). Methods: In the first 21 day treatment cycle, mitazalimab was administered IV at RP2D on day 1 and 10 and mFOLFIRINOX infusion started on day 8. In subsequent cycles, treatment followed a 14 day cycle where mitazalimab was always administered 2 days after mFOLFIRINOX. The primary endpoint of this ongoing study is overall response rate (ORR) per RECIST v1.1. Secondary and exploratory endpoints include progression free and overall survival, safety, PK and PD biomarker assessments. Futility was prespecified as ORR≤30% in pts treated at RP2D, based on historical data with FOLFIRINOX (Conroy, 2011). Results: As of December 8, 2022, 43 pts with untreated mPDAC were treated with mFOLFIRINOX and 450 µg/kg (N = 5) or 900 µg/kg (N = 38) mitazalimab and evaluated for safety. The most common grade (Gr) ≥3 TEAEs were neutropenia (16%), fatigue (12%) and hypokalemia (12%). Mitazalimab related Gr >3 AEs were fatigue in 3 (7.9%) pts, hypokalemia in 2 (5.3%) pts, diarrhea in 1 (2.6%) pt, pneumonia in 1 (2.6%) pt, increased ALT in 1 (2.6%) pt, headache in 1 (2.6%) pt, acute kidney injury in 1 (2.6%) pt. 10 pts (23%) experienced infusion reactions (all Gr 1-2) and 5 (12%) pts discontinued treatment due to TEAEs (pneumonia, gastric obstruction, neuropathy, bacteremia). At cutoff, 23 pts were evaluable for futility. Median follow up was 170 days and median exposure was 163 days. 18 pts (78%) remain on treatment, 6 (26%) beyond the 6 month treatment period. ORR was 52.2% (12 partial responses), an additional 8 pts achieved stable disease, resulting in a 91.3% disease control rate. Combination with mFOLFIRINOX had no impact on mitazalimab PK. The PD biomarker profile was consistent with the mode of action of mitazalimab, including upregulation of MCP-1 and IFN-γ. Conclusions: Mitazalimab + mFOLFIRINOX is a feasible regimen with a manageable safety profile. Mitazalimab administered at 900 µg/kg in combination with mFOLFIRINOX shows encouraging antitumor activity in mPDAC, meriting continued development. The study passes futility and continues to full accrual. Clinical trial information: NCT04888312 .

Preclinical Evidence of an Allogeneic Dual CD20xCD22 CAR to Target a Broad Spectrum of Patients with B-cell Malignancies.

Despite the remarkable success of autologous chimeric antigen receptor (CAR) T cells, some patients relapse due to tumor antigen escape and low or uneven antigen expression, among other mechanisms. Therapeutic options after relapse are limited, emphasizing the need to optimize current approaches. In addition, there is a need to develop allogeneic "off-the-shelf" therapies from healthy donors that are readily available at the time of treatment decision and can overcome limitations of current autologous approaches. To address both challenges simultaneously, we generated a CD20xCD22 dual allogeneic CAR T cell. Herein, we demonstrate that allogeneic CD20x22 CAR T cells display robust, sustained and dose-dependent activity in vitro and in vivo, while efficiently targeting primary B-cell non-Hodgkin lymphoma (B-NHL) samples with heterogeneous levels of CD22 and CD20. Altogether, we provide preclinical proof-of-concept data for an allogeneic dual CAR T cell to overcome current mechanisms of resistance to CAR T-cell therapies in B-NHL, while providing a potential alternative to CD19 targeting.