Novel T cells with improved in vivo anti-tumor activity generated by RNA electroporation

IVT-mRNA reprogramming of myeloid cells for cancer immunotherapy

In the past decade, in vitro transcribed messenger RNAs (IVT-mRNAs) have emerged as promising therapeutic molecules. The clinical success of COVID-19 mRNA vaccines developed by Pfizer-BioNTech and Moderna, have demonstrated that IVT-mRNAs can be safely and successfully used in a clinical setting, and efforts are underway to develop IVT-mRNAs for therapeutic applications. Current applications of mRNA-based therapy have been focused on (1) mRNA vaccines for infectious diseases and cancer treatment; (2) protein replacement therapy; (3) gene editing therapy; and (4) cell-reprogramming therapies. Due to the recent clinical progress of cell-based immunotherapies, the last direction-the use of IVT-mRNAs as a therapeutic approach to program immune cells for the treatment of cancer has received extensive attention from the cancer immunotherapy field. Myeloid cells are important components of our immune system, and they play critical roles in mediating disease progression and regulating immunity against diseases. In this chapter, we discussed the progress of using IVT-mRNAs as a therapeutic approach to program myeloid cells against cancer and other immune-related diseases. Towards this direction, we first reviewed the pharmacology of IVT-mRNAs and the biology of myeloid cells as well as myeloid cell-targeting therapeutics. We then presented a few cases of current IVT-mRNA-based approaches to target and reprogram myeloid cells for disease treatment and discussed the advantages and limitations of these approaches. Finally, we presented our considerations in designing mRNA-based approaches to target myeloid cells for disease treatment.

Challenges and strategies in relation to effective CAR-T cell immunotherapy for solid tumors

Chimeric Antigen Receptor T cell (CAR-T) therapy has revolutionized cancer treatment, but its application to solid tumors is limited. CAR-T cells have poor incapability of entering, surviving, proliferating, and finally exerting function in the tumor microenvironment. This review summarizes the main strategies related to enhancing the infiltration, efficacy, antigen recognition, and production of CAR-T in solid tumors. Additional applications of CAR-γδ T and macrophages are also discussed. We believe CAR-T will be a milestone in treating solid tumors once these problems are solved.

A multiplexed microfluidic continuous-flow electroporation system for efficient cell transfection

Cellular therapies have the potential to advance treatment for a broad array of diseases but rely on viruses for genetic reprogramming. The time and cost required to produce viruses has created a bottleneck that constricts development of and access to cellular therapies. Electroporation is a non-viral alternative for genetic reprogramming that bypasses these bottlenecks, but current electroporation technology suffers from low throughput, tedious optimization, and difficulty scaling to large-scale cell manufacturing. Here, we present an adaptable microfluidic electroporation platform with the capability for rapid, multiplexed optimization with 96-well plates. Once parameters are optimized using small volumes of cells, transfection can be seamlessly scaled to high-volume cell manufacturing without re-optimization. We demonstrate optimizing transfection of plasmid DNA to Jurkat cells, screening hundreds of different electrical waveforms of varying shapes at a speed of ~3 s per waveform using ~20 µL of cells per waveform. We selected an optimal set of transfection parameters using a low-volume flow cell. These parameters were then used in a separate high-volume flow cell where we obtained similar transfection performance by design. This demonstrates an alternative non-viral and economical transfection method for scaling to the volume required for producing a cell therapy without sacrificing performance. Importantly, this transfection method is disease-agnostic with broad applications beyond cell therapy.

A multiplexed microfluidic continuous-flow electroporation system for efficient cell transfection

Cellular therapies have the potential to advance treatment for a broad array of diseases but rely on viruses for genetic reprogramming. The time and cost required to produce viruses has created a bottleneck that constricts development of and access to cellular therapies. Electroporation is a non-viral approach for genetic reprogramming that bypasses these bottlenecks, but current electroporation technology suffers from low throughput, tedious optimization, and difficulty scaling to large-scale cell manufacturing. Here, we present an adaptable microfluidic electroporation platform with the capability for rapid, multiplexed optimization with 96-well plates. Once parameters are optimized using small volumes of cells, transfection can be seamlessly scaled to high-volume cell manufacturing without re-optimization. We demonstrate optimizing transfection of plasmid DNA to Jurkat cells, screening hundreds of different electrical waveforms of varying shapes at a speed of ~3 s per waveform using ~ 20 μL of cells per waveform. We selected an optimal set of transfection parameters using a low-volume flow cell. These parameters were then used in a separate high-volume flow cell where we obtained similar transfection performance by design. This demonstrates an economical method for scaling to the volume required for producing a cell therapy without sacrificing performance.

Nanoformulations targeting immune cells for cancer therapy: mRNA therapeutics

The approved worldwide use of two messenger RNA (mRNA) vaccines (BNT162b2 and mRNA-1273) in late 2020 has proven the remarkable success of mRNA therapeutics together with lipid nanoformulation technology in protecting people against coronaviruses during COVID-19 pandemic. This unprecedented and exciting dual strategy with nanoformulations and mRNA therapeutics in play is believed to be a promising paradigm in targeted cancer immunotherapy in future. Recent advances in nanoformulation technologies play a prominent role in adapting mRNA platform in cancer treatment. In this review, we introduce the biologic principles and advancements of mRNA technology, and chemistry fundamentals of intriguing mRNA delivery nanoformulations. We discuss the latest promising nano-mRNA therapeutics for enhanced cancer immunotherapy by modulation of targeted specific subtypes of immune cells, such as dendritic cells (DCs) at peripheral lymphoid organs for initiating mRNA cancer vaccine-mediated antigen specific immunotherapy, and DCs, natural killer (NK) cells, cytotoxic T cells, or multiple immunosuppressive immune cells at tumor microenvironment (TME) for reversing immune evasion. We highlight the clinical progress of advanced nano-mRNA therapeutics in targeted cancer therapy and provide our perspectives on future directions of this transformative integrated technology toward clinical implementation.

Scalable continuous-flow electroporation platform enabling T cell transfection for cellular therapy manufacturing

Viral vectors represent a bottleneck in the manufacturing of cellular therapies. Electroporation has emerged as an approach for non-viral transfection of primary cells, but standard cuvette-based approaches suffer from low throughput, difficult optimization, and incompatibility with large-scale cell manufacturing. Here, we present a novel electroporation platform capable of rapid and reproducible electroporation that can efficiently transfect small volumes of cells for research and process optimization and scale to volumes required for applications in cellular therapy. We demonstrate delivery of plasmid DNA and mRNA to primary human T cells with high efficiency and viability, such as > 95% transfection efficiency for mRNA delivery with < 2% loss of cell viability compared to control cells. We present methods for scaling delivery that achieve an experimental throughput of 256 million cells/min. Finally, we demonstrate a therapeutically relevant modification of primary T cells using CRISPR/Cas9 to knockdown T cell receptor (TCR) expression. This study displays the capabilities of our system to address unmet needs for efficient, non-viral engineering of T cells for cell manufacturing.

Development of GPC2-directed chimeric antigen receptors using mRNA for pediatric brain tumors

BACKGROUND

Pediatric brain tumors are the leading cause of cancer death in children with an urgent need for innovative therapies. Glypican 2 (GPC2) is a cell surface oncoprotein expressed in neuroblastoma for which targeted immunotherapies have been developed. This work aimed to characterize GPC2 expression in pediatric brain tumors and develop an mRNA CAR T cell approach against this target.

METHODS

We investigated GPC2 expression across a cohort of primary pediatric brain tumor samples and cell lines using RNA sequencing, immunohistochemistry, and flow cytometry. To target GPC2 in the brain with adoptive cellular therapies and mitigate potential inflammatory neurotoxicity, we used optimized mRNA to create transient chimeric antigen receptor (CAR) T cells. We developed four mRNA CAR T cell constructs using the highly GPC2-specific fully human D3 single chain variable fragment for preclinical testing.

RESULTS

We identified high GPC2 expression across multiple pediatric brain tumor types including medulloblastomas, embryonal tumors with multilayered rosettes, other central nervous system embryonal tumors, as well as definable subsets of highly malignant gliomas. We next validated and prioritized CAR configurations using in vitro cytotoxicity assays with GPC2-expressing neuroblastoma cells, where the light-to-heavy single chain variable fragment configurations proved to be superior. We expanded the testing of the two most potent GPC2-directed CAR constructs to GPC2-expressing medulloblastoma and high-grade glioma cell lines, showing significant GPC2-specific cell death in multiple models. Finally, biweekly locoregional delivery of 2-4 million GPC2-directed mRNA CAR T cells induced significant tumor regression in an orthotopic medulloblastoma model and significantly prolonged survival in an aggressive orthotopic thalamic diffuse midline glioma xenograft model. No GPC2-directed CAR T cell related neurologic or systemic toxicity was observed.

CONCLUSION

Taken together, these data show that GPC2 is a highly differentially expressed cell surface protein on multiple malignant pediatric brain tumors that can be targeted safely with local delivery of mRNA CAR T cells, laying the framework for the clinical translation of GPC2-directed immunotherapies for pediatric brain tumors.

Promise and pitfalls of allogeneic chimeric antigen receptor therapy in plasma cell and lymphoid malignancies

Chimeric antigen receptor (CAR) T-cell therapy is a promising immunotherapy in haematological malignancies. However, the currently approved products are generated from autologous T cells that require orchestration of several logistically complex steps, which include patient eligibility, apheresis capability, complex manufacturing processes and shipping logistics. Use of third-party donor-derived (allogeneic) effector cells that allows the generation of 'off-the-shelf" CAR T cells (allo-CAR) could circumvent many of the problems associated with autologous CAR T-cell therapy. Several allogeneic products are entering clinical trials, and though early, the results look promising. The recognised potential benefits of allo-CAR do not come without significant challenges, that must be overcome for their widespread use. Alloreactivity, i.e. graft-versus-host disease (GVHD), and rejection of donor T cells is one of the major barriers, while other potential barriers include immunogenicity, unknown in vivo persistence, and CAR T-cell yield. In the present review, we provide a comprehensive review of the challenges associated with autologous CAR, the benefits and potential challenges associated with allo-CAR. Finally, we review the available platforms for allo-CAR for B-cell and plasma cell malignancies.

NKG2D-CAR-transduced natural killer cells efficiently target multiple myeloma

CAR-T-cell therapy against MM currently shows promising results, but usually with serious toxicities. CAR-NK cells may exert less toxicity when redirected against resistant myeloma cells. CARs can be designed through the use of receptors, such as NKG2D, which recognizes a wide range of ligands to provide broad target specificity. Here, we test this approach by analyzing the antitumor activity of activated and expanded NK cells (NKAE) and CD45RA- T cells from MM patients that were engineered to express an NKG2D-based CAR. NKAE cells were cultured with irradiated Clone9.mbIL21 cells. Then, cells were transduced with an NKG2D-4-1BB-CD3z-CAR. CAR-NKAE cells exhibited no evidence of genetic abnormalities. Although memory T cells were more stably transduced, CAR-NKAE cells exhibited greater in vitro cytotoxicity against MM cells, while showing minimal activity against healthy cells. In vivo, CAR-NKAE cells mediated highly efficient abrogation of MM growth, and 25% of the treated mice remained disease free. Overall, these results demonstrate that it is feasible to modify autologous NKAE cells from MM patients to safely express a NKG2D-CAR. Additionally, autologous CAR-NKAE cells display enhanced antimyeloma activity demonstrating that they could be an effective strategy against MM supporting the development of NKG2D-CAR-NK-cell therapy for MM.

Next-generation immuno-oncology agents: current momentum shifts in cancer immunotherapy

Cancer immunotherapy has reached a critical point, now that immune checkpoint inhibitors and two CAR-T products have received market approval in treating 16 types of cancers and 1 tissue-agnostic cancer indication. Accompanying these advances, the 2018 Nobel Prize was awarded for the discovery of immune checkpoint pathways, which has led to the revolution of anti-cancer treatments. However, expanding the indications of immuno-oncology agents and overcoming treatment resistance face mounting challenges. Although combination immunotherapy is an obvious strategy to pursue, the fact that there have been more failures than successes in this effort has served as a wake-up call, placing emphasis on the importance of building a solid scientific foundation for the development of next-generation immuno-oncology (IO) agents. The 2019 China Cancer Immunotherapy Workshop was held to discuss the current challenges and opportunities in IO. At this conference, emerging concepts and strategies for IO development were proposed, focusing squarely on correcting the immunological defects in the tumor microenvironment. New targets such as Siglec-15 and new directions including neoantigens, cancer vaccines, oncolytic viruses, and cytokines were reviewed. Emerging immunotherapies were discussed in the areas of overcoming primary and secondary resistance to existing immune checkpoint inhibitors, activating effector cells, and targeting immunosuppressive mechanisms in the tumor microenvironment. In this article, we highlight old and new waves of IO therapy development, and provide perspectives on the latest momentum shifts in cancer immunotherapy.

The Emerging Role of In Vitro-Transcribed mRNA in Adoptive T Cell Immunotherapy

Adoptive T cell therapy is a form of cellular therapy that utilizes human immune cells, often empowered by the expression of recombinant proteins, to attack selected targets present on tumor or infected cells. T cell-based immunotherapy has been progressing over the past several decades, and reached a milestone with the recent US Food and Drug Administration (FDA) approval of chimeric antigen receptor T cell therapy for relapsed and refractory leukemia and lymphoma. Although most studies have used viral vectors, a growing number of researchers have come to appreciate in vitro-transcribed (IVT) mRNA for the development, testing, and application of T cell-based immunotherapeutics. IVT mRNA offers inherent safety features, highly efficient recombinant protein translation, and the ability to control pharmacokinetic properties of the therapy. In this review, we discuss the history of IVT mRNA in adoptive T cell therapy, from tumor-infiltrating lymphocytes and T cell receptor-based therapies to chimeric antigen receptor therapy and gene-editing techniques, as well as prior and ongoing clinical trials.

mRNA as novel technology for passive immunotherapy

While active immunization elicits a lasting immune response by the body, passive immunotherapy transiently equips the body with exogenously generated immunological effectors in the form of either target-specific antibodies or lymphocytes functionalized with target-specific receptors. In either case, administration or expression of recombinant proteins plays a fundamental role. mRNA prepared by in vitro transcription (IVT) is increasingly appreciated as a drug substance for delivery of recombinant proteins. With its biological role as transient carrier of genetic information translated into protein in the cytoplasm, therapeutic application of mRNA combines several advantages. For example, compared to transfected DNA, mRNA harbors inherent safety features. It is not associated with the risk of inducing genomic changes and potential adverse effects are only temporary due to its transient nature. Compared to the administration of recombinant proteins produced in bioreactors, mRNA allows supplying proteins that are difficult to manufacture and offers extended pharmacokinetics for short-lived proteins. Based on great progress in understanding and manipulating mRNA properties, efficacy data in various models have now demonstrated that IVT mRNA constitutes a potent and flexible platform technology. Starting with an introduction into passive immunotherapy, this review summarizes the current status of IVT mRNA technology and its application to such immunological interventions.

Epitopes of MUC1 Tandem Repeats in Cancer as Revealed by Antibody Crystallography: Toward Glycopeptide Signature-Guided Therapy

Abnormally O-glycosylated MUC1 tandem repeat glycopeptide epitopes expressed by multiple types of cancer have long been attractive targets for therapy in the race against genetic mutations of tumor cells. Glycopeptide signature-guided therapy might be a more promising avenue than mutation signature-guided therapy. Three O-glycosylated peptide motifs, PDTR, GSTA, and GVTS, exist in a tandem repeat HGVTSAPDTRPAPGSTAPPA, containing five O-glycosylation sites. The exact peptide and sugar residues involved in antibody binding are poorly defined. Co-crystal structures of glycopeptides and respective monoclonal antibodies are very few. Here we review 3 groups of monoclonal antibodies: antibodies which only bind to peptide portion, antibodies which only bind to sugar portion, and antibodies which bind to both peptide and sugar portions. The antigenicity of peptide and sugar portions of glyco-MUC1 tandem repeat were analyzed according to available biochemical and structural data, especially the GSTA and GVTS motifs independent from the most studied PDTR. Tn is focused as a peptide-modifying residue in vaccine design, to induce glycopeptide-binding antibodies with cross reactivity to Tn-related tumor glycans, but not glycans of healthy cells. The unique requirement for the designs of antibody in antibody-drug conjugate, bi-specific antibodies, and chimeric antigen receptors are also discussed.

Safety and Efficacy of Intratumoral Injections of Chimeric Antigen Receptor (CAR) T Cells in Metastatic Breast Cancer

Chimeric antigen receptors (CAR) are synthetic molecules that provide new specificities to T cells. Although successful in treatment of hematologic malignancies, CAR T cells are ineffective for solid tumors to date. We found that the cell-surface molecule c-Met was expressed in ∼50% of breast tumors, prompting the construction of a CAR T cell specific for c-Met, which halted tumor growth in immune-incompetent mice with tumor xenografts. We then evaluated the safety and feasibility of treating metastatic breast cancer with intratumoral administration of mRNA-transfected c-Met-CAR T cells in a phase 0 clinical trial (NCT01837602). Introducing the CAR construct via mRNA ensured safety by limiting the nontumor cell effects (on-target/off-tumor) of targeting c-Met. Patients with metastatic breast cancer with accessible cutaneous or lymph node metastases received a single intratumoral injection of 3 × 107 or 3 × 108 cells. CAR T mRNA was detectable in peripheral blood and in the injected tumor tissues after intratumoral injection in 2 and 4 patients, respectively. mRNA c-Met-CAR T cell injections were well tolerated, as none of the patients had study drug-related adverse effects greater than grade 1. Tumors treated with intratumoral injected mRNA c-Met-CAR T cells were excised and analyzed by immunohistochemistry, revealing extensive tumor necrosis at the injection site, cellular debris, loss of c-Met immunoreactivity, all surrounded by macrophages at the leading edges and within necrotic zones. We conclude that intratumoral injections of mRNA c-Met-CAR T cells are well tolerated and evoke an inflammatory response within tumors. Cancer Immunol Res; 5(12); 1152-61. ©2017 AACR.

Targeting Multiple Tumors Using T-Cells Engineered to Express a Natural Cytotoxicity Receptor 2-Based Chimeric Receptor

Recent developments in cancer treatment are demonstrating the increasing and powerful potential of immunotherapeutic strategies. In this regard, the adoptive transfer of tumor-specific T-lymphocytes approaches can lead to tumor regression in cancer patients. More recently, the use of T-cells genetically engineered to express cancer-specific receptors such as the anti-CD19 chimeric antigen receptor (CAR) continues to show promise for the treatment of hematological malignancies. Still, there is a crucial need to develop efficient CAR-T cell approaches for the treatment of solid tumors. It has been shown that other lymphocytes such as natural killer (NK) cells can demonstrate potent antitumor function—nonetheless, their use in immunotherapy is rather limited due to difficulties in expanding these cells to therapeutically relevant numbers and to suppression by endogenous inhibitory mechanisms. Cancer recognition by NK cells is partly mediated by molecules termed natural cytotoxicity receptors (NCRs). In the present study, we hypothesize that it is possible to endow T-cells with an NK recognition pattern, providing them with a mean to recognize tumor cells, in a non-MHC restricted way. To test this, we genetically modified human T-cells with different chimeric receptors based on the human NCR2 molecule and then assessed their antitumor activity in vitro and in vivo. Our results show that expression in primary lymphocytes of an NCR2-derived CAR, termed s4428z, confers T-cells with the ability to specifically recognize heterogeneous tumors and to mediate tumor cytotoxicity in a mouse model. This study demonstrates the benefit of combining tumor recognition capability of NK cells with T cell effectiveness to improve cancer immunotherapy.