Targeting CD33 in Chemoresistant AML Patient-Derived Xenografts by CAR-CIK Cells Modified with an Improved SB Transposon System.

The successful implementation of chimeric antigen receptor (CAR)-T cell therapy in the clinical context of B cell malignancies has paved the way for further development in the more critical setting of acute myeloid leukemia (AML). Among the potentially targetable AML antigens, CD33 is insofar one of the main validated molecules. Here, we describe the feasibility of engineering cytokine-induced killer (CIK) cells with a CD33.CAR by using the latest optimized version of the non-viral Sleeping Beauty (SB) transposon system "SB100X-pT4." This offers the advantage of improving CAR expression on CIK cells, while reducing the amount of DNA transposase as compared to the previously employed "SB11-pT" version. SB-modified CD33.CAR-CIK cells exhibited significant antileukemic activity in vitro and in vivo in patient-derived AML xenograft models, reducing AML development when administered as an "early treatment" and delaying AML progression in mice with established disease. Notably, by exploiting an already optimized xenograft chemotherapy model that mimics human induction therapy in mice, we demonstrated for the first time that CD33.CAR-CIK cells are also effective toward chemotherapy resistant/residual AML cells, further supporting its future clinical development and implementation within the current standard regimens.

Interphase Design of Cellulose Nanocrystals/Poly(hydroxybutyrate-ran-valerate) Bionanocomposites for Mechanical and Thermal Properties Tuning.

Poly[(3-hydroxybutyrate)-ran-(3-hydroxyvalerate)] (PHBV) is a bacterial polyester with a strong potential as a substitute for oil-based thermoplastics due to its biodegradability and renewability. However, its inherent slow crystallization rate limits its thermomechanical properties and therefore its applications. In this work, surface-modified cellulose nanocrystals (CNCs) have been investigated as green and biosourced nucleating and reinforcing agent for PHBV matrix. Different ester moieties from the CNCs were thereby produced through a green one-pot hydrolysis/Fisher esterification. Beyond the improved dispersion, the CNCs surface esterification affected the thermal and thermomechanical properties of PHBV. The results demonstrate that butyrate-modified CNCs, mimicking the PHBV chemical structure, brought a considerable improvement toward the CNCs/matrix interface, leading to an enhancement of the PHBV thermomechanical properties via a more efficient stress transfer, especially above its glass transition.

Balance of Anti-CD123 Chimeric Antigen Receptor Binding Affinity and Density for the Targeting of Acute Myeloid Leukemia.

Chimeric antigen receptor (CAR)-redirected T lymphocytes are a promising immunotherapeutic approach and object of pre-clinical evaluation for the treatment of acute myeloid leukemia (AML). We developed a CAR against CD123, overexpressed on AML blasts and leukemic stem cells. However, potential recognition of low CD123-positive healthy tissues, through the on-target, off-tumor effect, limits safe clinical employment of CAR-redirected T cells. Therefore, we evaluated the effect of context-dependent variables capable of modulating CAR T cell functional profiles, such as CAR binding affinity, CAR expression, and target antigen density. Computational structural biology tools allowed for the design of rational mutations in the anti-CD123 CAR antigen binding domain that altered CAR expression and CAR binding affinity without affecting the overall CAR design. We defined both lytic and activation antigen thresholds, with early cytotoxic activity unaffected by either CAR expression or CAR affinity tuning but later effector functions impaired by low CAR expression. Moreover, the anti-CD123 CAR safety profile was confirmed by lowering CAR binding affinity, corroborating CD123 is a good therapeutic target antigen. Overall, full dissection of these variables offers suitable anti-CD123 CAR design optimization for the treatment of AML.

Redirecting T cells with Chimeric Antigen Receptor (CAR) for the treatment of childhood acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. Nowadays the survival rate is around 85%. Nevertheless, an urgent clinical need is still represented by primary refractory and relapsed patients who do not significantly benefit from standard approaches, including chemo-radiotherapy and hematopoietic stem cell transplantation (HSCT). For this reason, immunotherapy has so far represented a challenging novel treatment opportunity, including, as the most validated therapeutic options, cancer vaccines, donor-lymphocyte infusions and tumor-specific immune effector cells. More recently, unexpected positive clinical results in ALL have been achieved by application of gene-engineered chimeric antigen expressing (CAR) T cells. Several CAR designs across different trials have generated similar response rates, with Complete Response (CR) of 60-90% at 1 month and an Event-Free Survival (EFS) of 70% at 6 months. Relevant challenges anyway remain to be addressed, such as amelioration of technical, cost and feasibility aspects of cell and gene manipulation and the necessity to face the occurrence of relapse mechanisms. This review describes the state of the art of ALL immunotherapies, the novelties in terms of gene manipulation approaches and the problems emerged from early clinical studies. We describe and discuss the process of clinical translation, including the design of a cell manufacturing protocol, vector production and regulatory issues. Multiple antigen targeting and combination of CAR T cells with molecular targeted drugs have also been evaluated as latest strategies to prevail over immune-evasion.

Donor-derived CD19-targeted T cells in allogeneic transplants.

PURPOSE OF REVIEW: Allogeneic hematopoietic stem cell transplantation (HSCT) is still partially ineffective in curing high-risk hematological malignancies, with estimates of relapse rates ranging from 40 to 50%. The purpose of this review is to discuss the emerging therapeutic options for patients with relapsed disease following HSCT based on adoptive immunotherapy using donor-derived T cells genetically engineered to express CD19-specific chimeric antigen receptors (CARs). RECENT FINDINGS: Adoptive cell therapy (ACT) with CAR-modified T cells represents an attractive therapeutic option for further enhancing the graft-versus-leukemia effect. However, CAR-modified T cells are often obtained using apheresis products collected from the patient's own blood, a procedure that has hindered the application of CAR-based therapies into the clinic. Alternative approaches rely on CAR T cells derived from donors rather than the patient's own blood. Therefore, it appears that overcoming the practical limitation of allogeneic T cell-induced graft versus-host-disease is a key to providing access to CAR immunotherapy to all eligible patients. SUMMARY: Donor-derived CD19-CAR T cells may advance the field of CAR immunotherapy by controlling relapse in leukemic patients and improving the range of applications of ACT protocols.

Targeting of acute myeloid leukaemia by cytokine-induced killer cells redirected with a novel CD123-specific chimeric antigen receptor.

Current therapeutic regimens for acute myeloid leukaemia (AML) are still associated with high rates of relapse. Immunotherapy with T-cells genetically modified to express chimeric antigen receptors (CARs) represents an innovative approach. Here we investigated the targeting of the interleukin three receptor alpha (IL3RA; CD123) molecule, which is overexpressed on AML bulk population, CD34(+) leukaemia progenitors, and leukaemia stem cells (LSC) compared to normal haematopoietic stem/progenitor cells (HSPCs), and whose overexpression is associated with poor prognosis. Cytokine-induced killer (CIK) cells were transduced with SFG-retroviral-vector encoding an anti-CD123 CAR. Transduced cells were able to strongly kill CD123(+) cell lines, as well as primary AML blasts. Interestingly, secondary colony experiments demonstrated that anti-CD123.CAR preserved in vitro HSPCs, in contrast to a previously generated anti-CD33.CAR, while keeping an identical cytotoxicity profile towards AML. Furthermore, limited killing of normal monocytes and CD123-low-expressing endothelial cells was noted, thus indicating a low toxicity profile of the anti-CD123.CAR. Taken together, our results indicate that CD123-specific CARs strongly enhance anti-AML CIK functions, while sparing HSPCs and normal low-expressing antigen cells, paving the way to develop novel immunotherapy approaches for AML treatment.

Enforced IL-10 expression confers type 1 regulatory T cell (Tr1) phenotype and function to human CD4(+) T cells.

Type 1 regulatory T (Tr1) cells are an inducible subset of CD4(+) Tr cells characterized by high levels of interleukin (IL)-10 production and regulatory properties. Several protocols to generate human Tr1 cells have been developed in vitro. However, the resulting population includes a significant fraction of contaminating non-Tr1 cells, representing a major bottleneck for clinical application of Tr1 cell therapy. We generated an homogeneous IL-10-producing Tr1 cell population by transducing human CD4(+) T cells with a bidirectional lentiviral vector (LV) encoding for human IL-10 and the marker gene, green fluorescent protein (GFP), which are independently coexpressed. The resulting GFP(+) LV-IL-10-transduced human CD4(+) T (CD4(LV-IL-10)) cells expressed, upon T-cell receptor (TCR) activation, high levels of IL-10 and concomitant low levels of IL-4, and markers associated with IL-10. Moreover, CD4(LV-IL-10) T cells displayed typical Tr1 features: the anergic phenotype, the IL-10, and transforming growth factor (TGF)-ß dependent suppression of allogeneic T-cell responses, and the ability to suppress in a cell-to-cell contact independent manner in vitro. CD4(LV-IL-10) T cells were able to control xeno graft-versus-host disease (GvHD), demonstrating their suppressive function in vivo. These results show that constitutive over-expression of IL-10 in human CD4(+) T cells leads to a stable cell population that recapitulates the phenotype and function of Tr1 cells.

Genome Editing in Engineered T Cells for Cancer Immunotherapy.

Advanced gene transfer technologies and profound immunological insights have enabled substantial increases in the efficacy of anticancer adoptive cellular therapy (ACT). In recent years, the U.S. Food and Drug Administration and European Medicines Agency have approved six engineered T cell therapeutic products, all chimeric antigen receptor-engineered T cells directed against B cell malignancies. Despite encouraging clinical results, engineered T cell therapy is still constrained by challenges, which could be addressed by genome editing. As RNA-guided Clustered Regularly Interspaced Short Palindromic Repeats technology passes its 10-year anniversary, we review emerging applications of genome editing approaches designed to (1) overcome resistance to therapy, including cancer immune evasion mechanisms; (2) avoid unwanted immune reactions related to allogeneic T cell products; (3) increase fitness, expansion capacity, persistence, and potency of engineered T cells, while preserving their safety profile; and (4) improve the ability of therapeutic cells to resist immunosuppressive signals active in the tumor microenvironment. Overall, these innovative approaches should widen the safe and effective use of ACT to larger number of patients affected by cancer.

Anti-CD117 CAR T cells incorporating a safety switch eradicate human acute myeloid leukemia and hematopoietic stem cells.

Discrimination between hematopoietic stem cells and leukemic stem cells remains a major challenge for acute myeloid leukemia immunotherapy. CAR T cells specific for the CD117 antigen can deplete malignant and healthy hematopoietic stem cells before consolidation with allogeneic hematopoietic stem cell transplantation in absence of cytotoxic conditioning. Here we exploit non-viral technology to achieve early termination of CAR T cell activity to prevent incoming graft rejection. Transient expression of an anti-CD117 CAR by mRNA conferred T cells the ability to eliminate CD117+ targets in vitro and in vivo. As an alternative approach, we used a Sleeping Beauty transposon vector for the generation of CAR T cells incorporating an inducible Caspase 9 safety switch. Stable CAR expression was associated with high proportion of T memory stem cells, low levels of exhaustion markers, and potent cellular cytotoxicity. Anti-CD117 CAR T cells mediated depletion of leukemic cells and healthy hematopoietic stem cells in NSG mice reconstituted with human leukemia or CD34+ cord blood cells, respectively, and could be terminated in vivo. The use of a non-viral technology to control CAR T cell pharmacokinetic properties is attractive for a first-in-human study in patients with acute myeloid leukemia prior to hematopoietic stem cell transplantation.

Erratum: Anti-CD117 CAR T cells incorporating a safety switch eradicate human acute myeloid leukemia and hematopoietic stem cells.

[This corrects the article DOI: 10.1016/j.omto.2023.07.003.].

Killing of myeloid APCs via HLA class I, CD2 and CD226 defines a novel mechanism of suppression by human Tr1 cells.

IL-10-producing CD4(+) type 1 regulatory T (Tr1) cells, defined based on their ability to produce high levels of IL-10 in the absence of IL-4, are major players in the induction and maintenance of peripheral tolerance. Tr1 cells inhibit T-cell responses mainly via cytokine-dependent mechanisms. The cellular and molecular mechanisms underlying the suppression of APC by Tr1 cells are still not completely elucidated. Here, we defined that Tr1 cells specifically lyse myeloid APC through a granzyme B (GZB)- and perforin (PRF)-dependent mechanism that requires HLA class I recognition, CD54/lymphocyte function-associated antigen (LFA)-1 adhesion, and activation via killer cell Ig-like receptors (KIRs) and CD2. Notably, interaction between CD226 on Tr1 cells and their ligands on myeloid cells, leading to Tr1-cell activation, is necessary for defining Tr1-cell target specificity. We also showed that high frequency of GZB-expressing CD4(+) T cells is detected in tolerant patients and correlates with elevated occurrence of IL-10-producing CD4(+) T cells. In conclusion, the modulatory activities of Tr1 cells are not only due to suppressive cytokines but also to specific cell-to-cell interactions that lead to selective killing of myeloid cells and possibly bystander suppression.

Differentiation of type 1 T regulatory cells (Tr1) by tolerogenic DC-10 requires the IL-10-dependent ILT4/HLA-G pathway.

Type 1 T regulatory (Tr1) cells suppress immune responses in vivo and in vitro and play a key role in maintaining tolerance to self- and non-self-antigens. Interleukin-10 (IL-10) is the crucial driving factor for Tr1 cell differentiation, but the molecular mechanisms underlying this induction remain unknown. We identified and characterized a subset of IL-10-producing human dendritic cells (DCs), termed DC-10, which are present in vivo and can be induced in vitro in the presence of IL-10. DC-10 are CD14(+), CD16(+), CD11c(+), CD11b(+), HLA-DR(+), CD83(+), CD1a(-), CD1c(-), express the Ig-like transcripts (ILTs) ILT2, ILT3, ILT4, and HLA-G antigen, display high levels of CD40 and CD86, and up-regulate CD80 after differentiation in vitro. DC-10 isolated from peripheral blood or generated in vitro are potent inducers of antigen-specific IL-10-producing Tr1 cells. Induction of Tr1 cells by DC-10 is IL-10-dependent and requires the ILT4/HLA-G signaling pathway. Our data indicate that DC-10 represents a novel subset of tolerogenic DCs, which secrete high levels of IL-10, express ILT4 and HLA-G, and have the specific function to induce Tr1 cells.

Green Topochemical Esterification Effects on the Supramolecular Structure of Chitin Nanocrystals: Implications for Highly Stable Pickering Emulsions.

In nature, chitin is organized in hierarchical structures composed of nanoscale building blocks that show outstanding mechanical and optical properties attractive for nanomaterial design. For applications that benefit from a maximized interface such as nanocomposites and Pickering emulsions, individualized chitin nanocrystals (ChNCs) are of interest. However, when extracted in water suspension, their individualization is affected by ChNC self-assembly, requiring a large amount of water (above 90%) for ChNC transport and stock, which limits their widespread use. To master their individualization upon drying and after regeneration, we herein report a waterborne topochemical one-pot acid hydrolysis/Fischer esterification to extract ChNCs from chitin and simultaneously decorate their surface with lactate or butyrate moieties. Controlled reaction conditions were designed to obtain nanocrystals of a comparable aspect ratio of about 30 and a degree of modification of about 30% of the ChNC surface, under the rationale to assess the only effect of the topochemistry on ChNC supramolecular organization. The rheological analysis coupled with polarized light imaging shows how the nematic structuring is hindered by both surface ester moieties. The increased viscosity and elasticity of the modified ChNC colloids indicate a gel-like phase, where typical ChNC clusters of liquid crystalline phases are disrupted. Pickering emulsions have been prepared from lyophilized nanocrystals as a proof of concept. Our results demonstrate that only the emulsions stabilized by the modified ChNCs have excellent stability over time, highlighting that their individualization can be regenerated from the dry state.

The Past, Present, and Future of Non-Viral CAR T Cells.

Adoptive transfer of chimeric antigen receptor (CAR) T lymphocytes is a powerful technology that has revolutionized the way we conceive immunotherapy. The impressive clinical results of complete and prolonged response in refractory and relapsed diseases have shifted the landscape of treatment for hematological malignancies, particularly those of lymphoid origin, and opens up new possibilities for the treatment of solid neoplasms. However, the widening use of cell therapy is hampered by the accessibility to viral vectors that are commonly used for T cell transfection. In the era of messenger RNA (mRNA) vaccines and CRISPR/Cas (clustered regularly interspaced short palindromic repeat-CRISPR-associated) precise genome editing, novel and virus-free methods for T cell engineering are emerging as a more versatile, flexible, and sustainable alternative for next-generation CAR T cell manufacturing. Here, we discuss how the use of non-viral vectors can address some of the limitations of the viral methods of gene transfer and allow us to deliver genetic information in a stable, effective and straightforward manner. In particular, we address the main transposon systems such as Sleeping Beauty (SB) and piggyBac (PB), the utilization of mRNA, and innovative approaches of nanotechnology like Lipid-based and Polymer-based DNA nanocarriers and nanovectors. We also describe the most relevant preclinical data that have recently led to the use of non-viral gene therapy in emerging clinical trials, and the related safety and efficacy aspects. We will also provide practical considerations for future trials to enable successful and safe cell therapy with non-viral methods for CAR T cell generation.

Transposon-Based CAR T Cells in Acute Leukemias: Where are We Going?

Chimeric Antigen Receptor (CAR) T-cell therapy has become a new therapeutic reality for refractory and relapsed leukemia patients and is also emerging as a potential therapeutic option in solid tumors. Viral vector-based CAR T-cells initially drove these successful efforts; however, high costs and cumbersome manufacturing processes have limited the widespread clinical implementation of CAR T-cell therapy. Here we will discuss the state of the art of the transposon-based gene transfer and its application in CAR T immunotherapy, specifically focusing on the Sleeping Beauty (SB) transposon system, as a valid cost-effective and safe option as compared to the viral vector-based systems. A general overview of SB transposon system applications will be provided, with an update of major developments, current clinical trials achievements and future perspectives exploiting SB for CAR T-cell engineering. After the first clinical successes achieved in the context of B-cell neoplasms, we are now facing a new era and it is paramount to advance gene transfer technology to fully exploit the potential of CAR T-cells towards next-generation immunotherapy.

Multifunctional nanoassemblies target bacterial lipopolysaccharides for enhanced antimicrobial DNA delivery.

The development of new therapeutic strategies against multidrug resistant Gram-negative bacteria is a major challenge for pharmaceutical research. In this respect, it is increasingly recognized that an efficient treatment for resistant bacterial infections should combine antimicrobial and anti-inflammatory effects. Here, we explore the multifunctional therapeutic potential of nanostructured self-assemblies from a cationic bolaamphiphile, which target bacterial lipopolysaccharides (LPSs) and associates with an anti-bacterial nucleic acid to form nanoplexes with therapeutic efficacy against Gram-negative bacteria. To understand the mechanistic details of these multifunctional antimicrobial-anti-inflammatory properties, we performed a fundamental study, comparing the interaction of these nanostructured therapeutics with synthetic biomimetic bacterial membranes and live bacterial cells. Combining a wide range of experimental techniques (Confocal Microscopy, Fluorescence Correlation Spectroscopy, Microfluidics, NMR, LPS binding assays), we demonstrate that the LPS targeting capacity of the bolaamphiphile self-assemblies, comparable to that exerted by Polymixin B, is a key feature of these nanoplexes and one that permits entry of therapeutic nucleic acids in Gram-negative bacteria. These findings enable a new approach to the design of efficient multifunctional therapeutics with combined antimicrobial and anti-inflammatory effects and have therefore the potential to broadly impact fundamental and applied research on self-assembled nano-sized antibacterials for antibiotic resistant infections.

Anti-human CD117 CAR T-cells efficiently eliminate healthy and malignant CD117-expressing hematopoietic cells.

Acute myeloid leukemia (AML) initiating and sustaining cells maintain high cell-surface similarity with their cells-of-origin, i.e., hematopoietic stem and progenitor cells (HSPCs), and identification of truly distinguishing leukemia-private antigens has remained elusive to date. To nonetheless utilize surface antigen-directed immunotherapy in AML, we here propose targeting both, healthy and malignant human HSPC, by chimeric antigen receptor (CAR) T-cells with specificity against CD117, the cognate receptor for stem cell factor. This approach should spare most mature hematopoietic cells and would require CAR T termination followed by subsequent transplantation of healthy HSPCs to rescue hematopoiesis. We successfully generated anti-CD117 CAR T-cells from healthy donors and AML patients. Anti-CD117 CAR T-cells efficiently targeted healthy and leukemic CD117-positive cells in vitro. In mice xenografted with healthy human hematopoiesis, they eliminated CD117-expressing, but not CD117-negative human cells. Importantly, in mice xenografted with primary human CD117-positive AML, they eradicated disease in a therapeutic setting. Administration of ATG in combination with rituximab, which binds to the co-expressed CAR T-cell transduction/selection marker RQR8, led to CAR T-cell depletion. Thus, we here provide the first proof of concept for the generation and preclinical efficacy of CAR T-cells directed against CD117-expressing human hematopoietic cells.

Sleeping Beauty-engineered CAR T cells achieve antileukemic activity without severe toxicities.

BACKGROUNDChimeric antigen receptor (CAR) T cell immunotherapy has resulted in complete remission (CR) and durable response in highly refractory patients. However, logistical complexity and high costs of manufacturing autologous viral products limit CAR T cell availability.METHODSWe report the early results of a phase I/II trial in B cell acute lymphoblastic leukemia (B-ALL) patients relapsed after allogeneic hematopoietic stem cell transplantation (HSCT) using donor-derived CD19 CAR T cells generated with the Sleeping Beauty (SB) transposon and differentiated into cytokine-induced killer (CIK) cells.RESULTSThe cellular product was produced successfully for all patients from the donor peripheral blood (PB) and consisted mostly of CD3+ lymphocytes with 43% CAR expression. Four pediatric and 9 adult patients were infused with a single dose of CAR T cells. Toxicities reported were 2 grade I and 1 grade II cytokine-release syndrome (CRS) cases at the highest dose in the absence of graft-versus-host disease (GVHD), neurotoxicity, or dose-limiting toxicities. Six out of 7 patients receiving the highest doses achieved CR and CR with incomplete blood count recovery (CRi) at day 28. Five out of 6 patients in CR were also minimal residual disease negative (MRD-). Robust expansion was achieved in the majority of the patients. CAR T cells were measurable by transgene copy PCR up to 10 months. Integration site analysis showed a positive safety profile and highly polyclonal repertoire in vitro and at early time points after infusion.CONCLUSIONSB-engineered CAR T cells expand and persist in pediatric and adult B-ALL patients relapsed after HSCT. Antileukemic activity was achieved without severe toxicities.TRIAL REGISTRATIONClinicalTrials.gov NCT03389035.FUNDINGThis study was supported by grants from the Fondazione AIRC per la Ricerca sul Cancro (AIRC); Cancer Research UK (CRUK); the Fundación Científica de la Asociación Española Contra el Cáncer (FC AECC); Ministero Della Salute; Fondazione Regionale per la Ricerca Biomedica (FRRB).