Targeting IDH2R140Q and other neoantigens in acute myeloid leukemia.

ABSTRACT: For patients with high-risk or relapsed/refractory acute myeloid leukemia (AML), allogeneic stem cell transplantation (allo-HSCT) and the graft-versus-leukemia effect mediated by donor T cells, offer the best chance of long-term remission. However, the concurrent transfer of alloreactive T cells can lead to graft-versus-host disease that is associated with transplant-related morbidity and mortality. Furthermore, ∼60% of patients will ultimately relapse after allo-HSCT, thus, underscoring the need for novel therapeutic strategies that are safe and effective. In this study, we explored the feasibility of immunotherapeutically targeting neoantigens, which arise from recurrent nonsynonymous mutations in AML and thus represent attractive targets because they are exclusively present on the tumor. Focusing on 14 recurrent driver mutations across 8 genes found in AML, we investigated their immunogenicity in 23 individuals with diverse HLA profiles. We demonstrate the immunogenicity of AML neoantigens, with 17 of 23 (74%) reactive donors screened mounting a response. The most immunodominant neoantigens were IDH2R140Q (n = 11 of 17 responders), IDH1R132H (n = 7 of 17), and FLT3D835Y (n = 6 of 17). In-depth studies of IDH2R140Q-specific T cells revealed the presence of reactive CD4+ and CD8+ T cells capable of recognizing distinct mutant-specific epitopes restricted to different HLA alleles. These neo-T cells could selectively recognize and kill HLA-matched AML targets endogenously expressing IDH2R140Q both in vitro and in vivo. Overall, our findings support the clinical translation of neoantigen-specific T cells to treat relapsed/refractory AML.

Engineering T cells to suppress acute GVHD and leukemia relapse after allogeneic hematopoietic stem cell transplantation.

Acute graft-versus-host disease (aGVHD) limits the therapeutic benefit of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and requires immunosuppressive prophylaxis that compromises antitumor and antipathogen immunity. OX40 is a costimulatory receptor upregulated on circulating T cells in aGVHD and plays a central role in driving the expansion of alloreactive T cells. Here, we show that OX40 is also upregulated on T cells infiltrating GVHD target organs in a rhesus macaque model, supporting the hypothesis that targeted ablation of OX40+ T cells will mitigate GVHD pathogenesis. We thus created an OX40-specific cytotoxic receptor that, when expressed on human T cells, enables selective elimination of OX40+ T cells. Because OX40 is primarily upregulated on CD4+ T cells upon activation, engineered OX40-specific T cells mediated potent cytotoxicity against activated CD4+ T cells and suppressed alloreactive T-cell expansion in a mixed lymphocyte reaction model. OX40 targeting did not inhibit antiviral activity of memory T cells specific to Epstein-Barr virus, cytomegalovirus, and adenoviral antigens. Systemic administration of OX40-targeting T cells fully protected mice from fatal xenogeneic GVHD mediated by human peripheral blood mononuclear cells. Furthermore, combining OX40 targeting with a leukemia-specific chimeric antigen receptor in a single T cell product provides simultaneous protection against leukemia and aGVHD in a mouse xenograft model of residual disease posttransplant. These results underscore the central role of OX40+ T cells in mediating aGVHD pathogenesis and support the feasibility of a bifunctional engineered T-cell product derived from the stem cell donor to suppress both disease relapse and aGVHD following allo-HSCT.

Human platelet lysate enhances in vivo activity of CAR-Vδ2 T cells by reducing cellular senescence and apoptosis.

BACKGROUND AIMS: Vγ9Vδ2 T cells are an attractive cell platform for the off-the-shelf cancer immunotherapy as the result of their lack of alloreactivity and inherent multi-pronged cytotoxicity, which could be further amplified with chimeric antigen receptors (CARs). In this study, we sought to enhance the in vivo longevity of CAR-Vδ2 T cells by modulating ex vivo manufacturing conditions and selecting an optimal CAR costimulatory domain. METHODS: Specifically, we compared the anti-tumor activity of Vδ2 T cells expressing anti-CD19 CARs with costimulatory endodomains derived from CD28, 4-1BB or CD27 and generated in either standard fetal bovine serum (FBS)- or human platelet lysate (HPL)-supplemented medium. RESULTS: We found that HPL supported greater expansion of CAR-Vδ2 T cells with comparable in vitro cytotoxicity and cytokine secretion to FBS-expanded CAR-Vδ2 T cells. HPL-expanded CAR-Vδ2 T cells showed enhanced in vivo anti-tumor activity with longer T-cell persistence compared with FBS counterparts, with 4-1BB costimulated CAR showing the greatest activity. Mechanistically, HPL-expanded CAR Vδ2 T cells exhibited reduced apoptosis and senescence transcriptional pathways compared to FBS-expanded CAR-Vδ2 T cells and increased telomerase activity. CONCLUSIONS: This study supports enhancement of therapeutic potency of CAR-Vδ2 T cells through a manufacturing improvement.

Feasibility and preclinical efficacy of CD7-unedited CD7 CAR T cells for T cell malignancies.

Chimeric antigen receptor (CAR)-mediated targeting of T lineage antigens for the therapy of blood malignancies is frequently complicated by self-targeting of CAR T cells or their excessive differentiation driven by constant CAR signaling. Expression of CARs targeting CD7, a pan-T cell antigen highly expressed in T cell malignancies and some myeloid leukemias, produces robust fratricide and often requires additional mitigation strategies, such as CD7 gene editing. In this study, we show fratricide of CD7 CAR T cells can be fully prevented using ibrutinib and dasatinib, the pharmacologic inhibitors of key CAR/CD3ζ signaling kinases. Supplementation with ibrutinib and dasatinib rescued the ex vivo expansion of unedited CD7 CAR T cells and allowed regaining full CAR-mediated cytotoxicity in vitro and in vivo on withdrawal of the inhibitors. The unedited CD7 CAR T cells persisted long term and mediated sustained anti-leukemic activity in two mouse xenograft models of human T cell acute lymphoblastic leukemia (T-ALL) by self-selecting for CD7-, fratricide-resistant CD7 CAR T cells that were transcriptionally similar to control CD7-edited CD7 CAR T cells. Finally, we showed feasibility of cGMP manufacturing of unedited autologous CD7 CAR T cells for patients with CD7+ malignancies and initiated a phase I clinical trial (ClinicalTrials.gov: NCT03690011) using this approach. These results indicate pharmacologic inhibition of CAR signaling enables generating functional CD7 CAR T cells without additional engineering.

Combinatorial antigen targeting strategies for acute leukemia: application in myeloid malignancy.

BACKGROUND AIMS: Efforts to safely and effectively treat acute myeloid leukemia (AML) by targeting a single leukemia-associated antigen with chimeric antigen receptor (CAR) T cells have met with limited success, due in part to heterogeneous expression of myeloid antigens. The authors hypothesized that T cells expressing CARs directed toward two different AML-associated antigens would eradicate tumors and prevent relapse. METHODS: For co-transduction with the authors' previously optimized CLL-1 CAR currently in clinical study (NCT04219163), the authors generated two CARs targeting either CD123 or CD33. The authors then tested the anti-tumor activity of T cells expressing each of the three CARs either alone or after co-transduction. The authors analyzed CAR T-cell phenotype, expansion and transduction efficacy and assessed function by in vitro and in vivo activity against AML cell lines expressing high (MOLM-13: CD123 high, CD33 high, CLL-1 intermediate), intermediate (HL-60: CD123 low, CD33 intermediate, CLL-1 intermediate/high) or low (KG-1a: CD123 low, CD33 low, CLL-1 low) levels of the target antigens. RESULTS: The in vitro benefit of dual expression was most evident when the target cell line expressed low antigen levels (KG-1a). Mechanistically, dual expression was associated with higher pCD3z levels in T cells compared with single CAR T cells on exposure to KG-1a (P < 0.0001). In vivo, combinatorial targeting with CD123 or CD33 and CLL-1 CAR T cells improved tumor control and animal survival for all lines (KG-1a, MOLM-13 and HL-60); no antigen escape was detected in residual tumors. CONCLUSIONS: Overall, these findings demonstrate that combinatorial targeting of CD33 or CD123 and CLL-1 with CAR T cells can control growth of heterogeneous AML tumors.

Clinical CAR-T Cell and Oncolytic Virotherapy for Cancer Treatment.

Immunotherapy has recently garnered success with the induction of clinical responses in tumors, which are traditionally associated with poor outcomes. Chimeric antigen receptor T (CAR-T) cells and oncolytic viruses (OVs) have emerged as promising cancer immunotherapy agents. Herein, we provide an overview of the current clinical status of CAR-T cell and OV therapies. While preclinical studies have demonstrated curative potential, the benefit of CAR-T cells and OVs as single-agent treatments remains limited to a subset of patients. Combinations of different targeted therapies may be required to achieve efficient, durable responses against heterogeneous tumors, as well as the microenvironment. Using a combinatorial approach to take advantage of the unique features of CAR-T cells and OVs with other treatments can produce additive therapeutic effects. This review also discusses ongoing clinical evaluations of these combination strategies for improved outcomes in treatment of resistant malignancies.

Adenovirotherapy Delivering Cytokine and Checkpoint Inhibitor Augments CAR T Cells against Metastatic Head and Neck Cancer.

In solid tumors, chimeric antigen receptor (CAR)-modified T cells must overcome the challenges of the immunosuppressive tumor microenvironment. We hypothesized that pre-treating tumors with our binary oncolytic adenovirus (CAd), which produces local oncolysis and expresses immunostimulatory molecules, would enhance the antitumor activity of HER2-specific CAR T cells, which alone are insufficient to cure solid tumors. We tested multiple cytokines in conjunction with PD-L1-blocking antibody and found that Ad-derived IL-12p70 prevents the loss of HER2.CAR-expressing T cells at the tumor site. Accordingly, we created a construct encoding the PD-L1-blocking antibody and IL-12p70 (CAd12_PDL1). In head and neck squamous cell carcinoma (HNSCC) xenograft models, combining local treatment with CAd12_PDL1 and systemic HER2.CAR T cell infusion improved survival to >100 days compared with approximately 25 days with either approach alone. This combination also controlled both primary and metastasized tumors in an orthotopic model of HNSCC. Overall, our data show that CAd12_PDL1 augments the anti-tumor effects of HER2.CAR T cells, thus controlling the growth of both primary and metastasized tumors.

Improving Chimeric Antigen Receptor-Modified T Cell Function by Reversing the Immunosuppressive Tumor Microenvironment of Pancreatic Cancer.

The adoptive transfer of T cells redirected to tumor-associated antigens via transgenic expression of chimeric antigen receptors (CARs) has produced tumor responses, even in patients with refractory diseases. To target pancreatic cancer, we generated CAR T cells directed against prostate stem cell antigen (PSCA) and demonstrated specific tumor lysis. However, pancreatic tumors employ immune evasion strategies such as the production of inhibitory cytokines, which limit CAR T cell persistence and function. Thus, to protect our cells from the immunosuppressive cytokine IL-4, we generated an inverted cytokine receptor in which the IL-4 receptor exodomain was fused to the IL-7 receptor endodomain (4/7 ICR). Transgenic expression of this molecule in CAR-PSCA T cells should invert the inhibitory effects of tumor-derived IL-4 and instead promote T cell proliferation. We now demonstrate the suppressed activity of CAR T cells in tumor-milieu conditions and the ability of CAR/ICR T cells to thrive in an IL-4-rich microenvironment, resulting in enhanced antitumor activity. Importantly, CAR/ICR T cells remained both antigen and cytokine dependent. These findings support the benefit of combining the 4/7 ICR with CAR-PSCA to treat pancreatic cancer, a PSCA-expressing tumor characterized by a dense immunosuppressive environment rich in IL-4.

Reversal of tumor immune inhibition using a chimeric cytokine receptor.

The success of adoptively transferred tumor-directed T cells requires them to survive and expand in vivo. Most tumors, however, employ immune evasion mechanisms, including the production of inhibitory cytokines that limit in vivo T-cell persistence and effector function. To protect tumor-directed T cells from such negative influences, we generated a chimeric cytokine receptor in which the interleukin (IL) 4 receptor exodomain was fused to the IL7 receptor endodomain. We thereby inverted the effects of tumor-derived IL4 so that the proliferation and activation of tumor directed cytotoxic T cells was enhanced rather than inhibited in the tumor microenvironment, resulting in superior antitumor activity. These transgenic T cells were only activated in the tumor environment since triggering required exposure to both tumor antigen (signal 1) and tumor-derived IL4 (signal 2). This selectivity supports future clinical adaptation.

A Case of Foldable Artificial Iris Implantation for Treatment of Postcataract Surgery Aniridia.

We report an approach for managing acquired aniridia induced by intraoperative floppy iris syndrome (IFIS) during cataract surgery. An 81-year-old man with right blurred vision and photophobia symptoms was treated for extensive iris defects due to cataract surgery aniridia. The retained iris for the patient was observed at the 5-10 o'clock position, with the intraocular lens (IOL) inside the capsular bag. Although the aniridia symptoms were successfully addressed by the implantation of a foldable artificial iris (Iris Prosthesis: Ophtec [formerly Reper], Groningen, the Netherlands), the procedure subsequently caused endothelial damage. In summary, while the utilization of the foldable artificial iris can improve aniridia symptoms, further advances in the insertion technique are required.

Novel banana lectin CAR-T cells to target pancreatic tumors and tumor-associated stroma.

BACKGROUND: Cell therapies for solid tumors are thwarted by the hostile tumor microenvironment (TME) and by heterogeneous expression of tumor target antigens. We address both limitations with a novel class of chimeric antigen receptors based on plant lectins, which recognize the aberrant sugar residues that are a 'hallmark' of both malignant and associated stromal cells. We have expressed in T cells a modified lectin from banana, H84T BanLec, attached to a chimeric antigen receptor (H84T-CAR) that recognizes high-mannose (asparagine residue with five to nine mannoses). Here, we tested the efficacy of our novel H84T CAR in models of pancreatic ductal adenocarcinoma (PDAC), intractable tumors with aberrant glycosylation and characterized by desmoplastic stroma largely contributed by pancreatic stellate cells (PSCs). METHODS: We transduced human T cells with a second-generation retroviral construct expressing the H84T BanLec chimeric receptor, measured T-cell expansion, characterized T-cell phenotype, and tested their efficacy against PDAC tumor cells lines by flow cytometry quantification. In three-dimensional (3D) spheroid models, we measured H84T CAR T-cell disruption of PSC architecture, and T-cell infiltration by live imaging. We tested the activity of H84T CAR T cells against tumor xenografts derived from three PDAC cell lines. Antitumor activity was quantified by caliper measurement and bioluminescence signal and used anti-human vimentin to measure residual PSCs. RESULTS: H84T BanLec CAR was successfully transduced and expressed by T cells which had robust expansion and retained central memory phenotype in both CD4 and CD8 compartments. H84T CAR T cells targeted and eliminated PDAC tumor cell lines. They also disrupted PSC architecture in 3D models in vitro and reduced total tumor and stroma cells in mixed co-cultures. H84T CAR T cells exhibited improved T-cell infiltration in multicellular spheroids and had potent antitumor effects in the xenograft models. We observed no adverse effects against normal tissues. CONCLUSIONS: T cells expressing H84T CAR target malignant cells and their stroma in PDAC tumor models. The incorporation of glycan-targeting lectins within CARs thus extends their activity to include both malignant cells and their supporting stromal cells, disrupting the TME that otherwise diminishes the activity of cellular therapies against solid tumors.

Generation of CAR T-cells using γ-retroviral vector.

The generation of chimeric antigen receptor (CAR) T cells requires the transfer of the CAR gene into primary T cells. Among various gene transfer strategies, gammaretroviral vectors have been widely used to generate CAR T cells for both preclinical and clinical settings. Here we describe the detailed method of generating CAR T cells utilizing gammaretroviral vectors. This approach consists of two parallel parts: (1) production of the gammaretroviral particles and (2) gammaretroviral transduction of activated T cells. The gammaretroviral particles are produced by co-transfecting the gammaretroviral vector with packaging plasmids into 293T cells. The manufactured viral particles then efficiently infect activated T cells where the CAR transgene is integrated into host genomic DNA, resulting in stable expression of the CAR molecule on the surface of T cells.

Impact of Manufacturing Procedures on CAR T Cell Functionality.

The field of chimeric antigen receptor (CAR) modified T cell therapy has rapidly expanded in the past few decades. As of today, there are six CAR T cell products that have been approved by the FDA: KYMRIAH (tisagenlecleucel, CD19 CAR T cells), YESCARTA (axicabtagene ciloleucel, CD19 CAR T cells), TECARTUS (brexucabtagene autoleucel, CD19 CAR T cells), BREYANZI (lisocabtagene maraleucel, CD19 CAR T cells), ABECMA (idecabtagene vicleucel, BCMA CAR T cells) and CARVYKTI (ciltacabtagene autoleucel, BCMA CAR T cells). With this clinical success, CAR T cell therapy has become one of the most promising treatment options to combat cancers. Current research efforts focus on further potentiating its efficacy in non-responding patients and solid tumor settings. To achieve this, recent evidence suggested that, apart from developing next-generation CAR T cells with additional genetic modifications, ex vivo culture conditions could significantly impact CAR T cell functionality - an often overlooked aspect during clinical translation. In this review, we focus on the ex vivo manufacturing process for CAR T cells and discuss how it impacts CAR T cell function.

Levetiracetam poisoning with acute kidney injury treated with hemodialysis: A case report.

INTRODUCTION: Levetiracetam is a newer second-generation anticonvulsant for the treatment of generalized and partial seizure disorders. Common adverse effects are rhabdomyolysis and neuropsychiatric problems, such as somnolence, dizziness, and mood changes. The present report describes the first case, to our knowledge, of levetiracetam overdose resulting in acute kidney injury for which hemodialysis was required. PATIENT CONCERNS: A 51-year-old man presented with hypotension and disturbance of consciousness with subsequent development of oliguria and elevated creatinine. Based on his history of ingesting a large dose of levetiracetam and the course of the disease, he was considered to have been poisoned by levetiracetam. DIAGNOSIS: Acute kidney injury induced by levetiracetam poisoning. INTERVENTIONS/OUTCOMES: Dialysis was performed for the rapidly progressing renal failure. His renal function improved, and he was weaned from dialysis and discharged home on the 19th day. CONCLUSION: We should be aware of the possibility that severe renal function deterioration may occur in some patients with levetiracetam overdose. It is possible that clinicians underestimate the occurrence of this problem. In cases of acute renal failure in levetiracetam poisoning, induction of dialysis is beneficial.

Off-the-Shelf Chimeric Antigen Receptor T Cells: How Do We Get There?

ABSTRACT: Banked chimeric antigen receptor (CAR) T cells immediately available for off-the-shelf (OTS) application can solve key limitations of patient-specific CAR T-cell products while retaining their potency. The allogeneic nature of OTS cell therapies requires additional measures to minimize graft-versus-host disease and host-versus-graft immune rejection in immunocompetent recipients. In this review, we discuss engineering and manufacturing strategies aimed at minimizing unwanted interactions between allogeneic CAR T cells and the host. Overcoming these limitations will improve safety and antitumor potency of OTS CAR T cells and facilitate their wider use in cancer therapy.

Selectively targeting myeloid-derived suppressor cells through TRAIL receptor 2 to enhance the efficacy of CAR T cell therapy for treatment of breast cancer.

BACKGROUND: Successful targeting of solid tumors such as breast cancer (BC) using chimeric antigen receptor (CAR) T cells has proven challenging, largely attributed to the immunosuppressive tumor microenvironment (TME). Myeloid-derived suppressor cells (MDSCs) inhibit CAR T cell function and persistence within the breast TME. To overcome this challenge, we have developed CAR T cells targeting tumor-associated mucin 1 (MUC1) with a novel chimeric costimulatory receptor that targets tumor necrosis factor-related apoptosis-inducing ligand receptor 2 (TR2) expressed on MDSCs. METHODS: The function of the TR2.41BB costimulatory receptor was assessed by exposing non-transduced (NT) and TR2.41BB transduced T cells to recombinant TR2, after which nuclear translocation of NFκB was measured by ELISA and western blot. The cytolytic activity of CAR.MUC1/TR2.41BB T cells was measured in a 5-hour cytotoxicity assay using MUC1+ tumor cells as targets in the presence or absence of MDSCs. In vivo antitumor activity was assessed using MDSC-enriched tumor-bearing mice treated with CAR T cells with or without TR2.41BB. RESULTS: Nuclear translocation of NFκB in response to recombinant TR2 was detected only in TR2.41BB T cells. The presence of MDSCs diminished the cytotoxic potential of CAR.MUC1 T cells against MUC1+ BC cell lines by 25%. However, TR2.41BB expression on CAR.MUC1 T cells induced MDSC apoptosis, thereby restoring the cytotoxic activity of CAR.MUC1 T cells against MUC1+ BC lines. The presence of MDSCs resulted in an approximately twofold increase in tumor growth due to enhanced angiogenesis and fibroblast accumulation compared with mice with tumor alone. Treatment of these MDSC-enriched tumors with CAR.MUC1.TR2.41BB T cells led to superior tumor cell killing and significant reduction in tumor growth (24.54±8.55 mm3) compared with CAR.MUC1 (469.79±81.46 mm3) or TR2.41BB (434.86±64.25 mm3) T cells alone. CAR.MUC1.TR2.41BB T cells also demonstrated improved T cell proliferation and persistence at the tumor site, thereby preventing metastases. We observed similar results using CAR.HER2.TR2.41BB T cells in a HER2+ BC model. CONCLUSIONS: Our findings demonstrate that CAR T cells that coexpress the TR2.4-1BB receptor exhibit superior antitumor potential against breast tumors containing immunosuppressive and tumor promoting MDSCs, resulting in TME remodeling and improved T cell proliferation at the tumor site.

Engineered off-the-shelf therapeutic T cells resist host immune rejection.

Engineered T cells are effective therapies against a range of malignancies, but current approaches rely on autologous T cells, which are difficult and expensive to manufacture. Efforts to develop potent allogeneic T cells that are not rejected by the recipient's immune system require abrogating both T- and natural killer (NK)-cell responses, which eliminate foreign cells through various mechanisms. In the present study, we engineered a receptor that mediates deletion of activated host T and NK cells, preventing rejection of allogeneic T cells. Our alloimmune defense receptor (ADR) selectively recognizes 4-1BB, a cell surface receptor temporarily upregulated by activated lymphocytes. ADR-expressing T cells resist cellular rejection by targeting alloreactive lymphocytes in vitro and in vivo, while sparing resting lymphocytes. Cells co-expressing chimeric antigen receptors and ADRs persisted in mice and produced sustained tumor eradication in two mouse models of allogeneic T-cell therapy of hematopoietic and solid cancers. This approach enables generation of rejection-resistant, 'off-the-shelf', allogeneic T-cell products to produce long-term therapeutic benefit in immunocompetent recipients.

WT1 peptide vaccination in combination with imatinib therapy for a patient with CML in the chronic phase.

Although tyrosine kinase inhibitors is effective for dramatically reducing CML cells, it might be difficult to eradicate completely the CML stem cells. We aimed to clarify the safety and effects of WT1 peptide vaccination in combination with imatinib therapy for a CML patient. A 51 year-old male with CML in CP, who showed a resistance against imatinib therapy for 2.5 years, began to be treated with 9 mer modified-type WT1 peptides in combination with standard dose of imatinib. Although every 2-week-administration of WT1 peptides for 22 weeks did not show definite effects on the quantification of bcr-abl transcripts, by changing the administration from every 2 weeks to 4 weeks bcr-abl transcripts decreased remarkably. After 11 months of every 4-week-administration of the peptides and 12 months post cessation of the peptides bcr-abl transcripts achieved to the level below detection by RQ/RT-PCR (complete molecular response). WT1/MHC tetramer(+)CD8(+) CTLs, which appeared after the second administration of WT1 peptides and remained more than 15 in number among 10(6) CD8(+) T cells throughout the administration of WT1 peptides, are still present in the blood on 14th month post cessation of the peptides. An in vitro study as to the cytotoxicity of lymphocytes induced by mixed lymphocyte peptide culture demonstrated that cultured lymphocytes possessed cytotoxicity against WT1 expressing leukemia cells and the cytotoxicity was WT1-specific and MHC class I restricted. The present study showed that WT1 peptide vaccination in combination with TKI is feasible and effective in the therapy for imatinib-resistant CML.

Evaluation of cyclin A1-specific T cells as a potential treatment for acute myeloid leukemia.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative option for relapsed or refractory acute myeloid leukemia (AML). However, more than half ultimately experience disease relapse that is associated with a dismal median survival of just 6 months, highlighting the need for novel therapies. In the current study we explore the therapeutic potential of targeting cyclin A1 (CCNA1), a cancer-testis antigen that is overexpressed in malignant blasts and leukemic stem cells. We demonstrate the immunogenicity of this antigen to native T cells, with >90% of donors screened mounting a specific response. The expanded cells were Th1 polarized, polyfunctional, and cytotoxic toward CCNA1+/HLA-matched tumor cell lines. Furthermore, these cells were exquisitely specific for CCNA1 and exhibited no reactivity against other cyclin family members, including CCNA2, which shares 56% homology with CCNA1 and is ubiquitously expressed in dividing cells. Lastly, the detection of CCNA1-specific T cells in AML patients post-HSCT was associated with prolonged disease remission, suggesting the protective potential of such endogenous cells. Taken together, our findings demonstrate the feasibility of targeting CCNA1 and the potential for therapeutic benefit associated with the adoptive transfer of reactive cells.

Modulating TNFα activity allows transgenic IL15-Expressing CLL-1 CAR T cells to safely eliminate acute myeloid leukemia.

BACKGROUND: C-type lectin-like molecule 1 (CLL-1) is highly expressed in acute myeloid leukemia (AML) but is absent in primitive hematopoietic progenitors, making it an attractive target for a chimeric antigen receptor (CAR) T-cell therapy. Here, we optimized our CLL-1 CAR for anti-leukemic activity in mouse xenograft models of aggressive AML. METHODS: First, we optimized the CLL-1 CAR using different spacer, transmembrane and costimulatory sequences. We used a second retroviral vector to coexpress transgenic IL15. We measured the effects of each construct on T cell phenotype and sequential (recursive) co culture assays with tumor cell targets to determine the durability of the anti tumor activity by flow cytometry. We administered CAR T cells to mice engrafted with patient derived xenografts (PDX) and AML cell line and determined anti tumor activity by bioluminescence imaging and weekly bleeding, measured serum cytokines by multiplex analysis. After euthanasia, we examined formalin-fixed/paraffin embedded sections. Unpaired two-tailed Student's t-tests were used and values of p<0.05 were considered significant. Survival was calculated using Mantel-Cox log-rank test. RESULTS: In vitro, CLL-1 CAR T cells with interleukin-15 (IL15) were less terminally differentiated (p<0.0001) and had superior expansion compared with CD28z-CD8 CAR T cells without IL15 (p<0.001). In both AML PDX and AML cell line animal models, CLL-1 CAR T coexpressing transgenic IL15 initially expanded better than CD28z-CD8 CAR T without IL15 (p<0.0001), but produced severe acute toxicity associated with high level production of human tumor necrosis factor α (TNFα), IL15 and IL2. Histopathology showed marked inflammatory changes with tissue damage in lung and liver. This acute toxicity could be managed by two strategies, individually or in combination. The excessive TNF alpha secretion could be blocked with anti-TNF alpha antibody, while excessive T cell expansion could be arrested by activation of an inducible caspase nine safety switch by administration of dimerizing drug. Both strategies successfully prolonged tumor-free survival. CONCLUSION: Combinatorial treatment with a TNFα blocking antibody and subsequent activation of the caspase-9 control switch increased the expansion, survival and antileukemic potency of CLL-1 CAR T-cells expressing transgenic IL15 while avoiding the toxicities associated with excessive cytokine production and long-term accumulation of activated T-cells.