The use of induced pluripotent stem cells (iPSCs) has led to a paradigm shift in cellular immunotherapy. By reprogramming somatic cells into a pluripotent state, iPSCs represent a renewable source of diverse cell lineages, including T cells, natural killer (NK) cells, and macrophages.
This ability has significant implications in medical fields, circumventing the limitations of autologous patient-derived products and offering the potential to develop allogeneic ‘off-the-shelf’ cell therapies derived from healthy donor sources.
iPSC-derived T Cells and CAR-T cell therapies
Traditional autologous chimeric antigen receptor (CAR) T cell therapies have prompted major advances in immunotherapy, but these have been limited by factors such as suboptimal T cell fitness, limited patient starting material, and a complicated, expensive manufacturing process.
iPSC technology offers a means of overcoming these production bottlenecks by deriving therapeutic T cells from healthy donor sources. This process involves somatic cell reprogramming prior to directed differentiation toward hematopoietic progenitor cells (HPCs).
Derived HPCs must be cultured under precise conditions, including exposure to Notch ligands like DLL4 and cytokines cocktails (such as IL-2, IL-7, and IL15) that are designed to imitate the thymic environment essential for T cell maturation.
Once cells are differentiated, iPSC-derived T cells undergo CAR engineering to target their specificity towards tumor-associated antigens (TAAs).
Along with their clear benefits in terms of manufacturing, allogeneic iPSC-derived CAR-T products offer a range of therapeutic advantages over their autologous counterparts.
For example, master iPSC banks allow for consistent, scalable production under Good Manufacturing Practice (GMP) conditions. The use of a healthy donor for original cells may also lead to improved cellular fitness, persistence, and anti-tumor potency versus patient T cells.
Multi-antigen CAR targeting improves tumor epitope coverage, while the genomic removal of endogenous T cell receptors (TCRs) and human leukocyte antigen (HLA) molecules are key to the mitigation of risks associated with graft-versus-host disease (GvHD).
Figure 1. Schemic illustration of 2D and 3D protocol for iPSC differentiation to NK cells. Image Credit: ACROBiosystems
iPSC-derived NK cells: Harnessing innate immunity
iPSC-derived NK cell therapy represents a further therapeutic avenue, leveraging NK cells’ innate ability and iPSCs’ unlimited expansion potential. iPSC-NK cells originate from healthy donors (unlike autologous CAR-T), meaning that these can be consistently manufactured via directed differentiation toward the lymphoid lineage.
By imitating in vivo NK cell development, it is possible to differentiate iPSCs into NK cells using cytokines and growth factors that mirror natural NK cell development.
Current advances have resulted in the development of feeder-free differentiation protocols, streamlining the process while simultaneously improving scalability.
These methods utilize stepwise exposure to a range of growth factors, including VEGF, SCF, BMP4, Flt3-L, IL-3, IL-7, and IL15. These growth factors are employed alongside stromal support to guide iPSCs through stages of HPCs to become functional cytotoxic CD56+CD3- NK cells.
Allogeneic NK cells benefit from direct cell-mediated tumor cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC). They can also be engineered with CARs for HLA-independent tumor targeting.
It is important to note that the NK cell lineage offers an advantageous safety profile in comparison to that of T cells, with a lower propensity for GvHD, cytokine release syndrome (CRS), and neurotoxicity.
The future of allogeneic NK cell therapy appears bright, with continuing research being undertaken into NK cells’ safety, efficacy, and applicability in hematological and solid tumor indications.
Work is ongoing to enhance iPSC-derived NK cells’ homing, persistence, and tumor infiltration capabilities and minimize rejection risk in allogeneic settings. The development of CAR-NK cells - a combination of CAR technology with the characteristic cytotoxicity of NK cells - represents an important development in next-generation immunotherapy.
Engineered NK cells have the potential to offer a safer and more effective alternative to CAR-T cell therapy, particularly when treating immunosuppressive solid tumors.
Figure 2. iPSC-derived NK cell therapy schematic diagram. Immune Netw. (Shin) 2020;20(2):e14. Image Credit: ACROBiosystems
iPSC-derived macrophage: An emergent frontier
iPSCs build on the success of T and NK cell engineering platforms, offering the potential to create a new class of cellular immunotherapies in the form of CAR-macrophages (CAR-Ms).
CAR-M therapies leverage macrophages’ inherent abilities. These are versatile immune cells capable of phagocytosis, tissue remodeling, and the exertion of anti-inflammatory effects.
These engineered macrophages can then be redirected to specifically target and eliminate cancer cells, thus offering a promising new means of treating a range of malignancies, including hematological and solid tumors.
By leveraging their capacity for directed differentiation along the myeloid lineage, renewable iPSCs are able to generate mature CD14+CD16+ macrophages by culturing HPCs with growth factors such as M-CSF, GM-CSF, IL-3, and IL-4.
These phagocytic macrophages can be genetically modified to express CARs, effectively redirecting their antigen-presenting, cytotoxic, and immunomodulatory functions towards defined TAAs.
The CAR-M therapy field is still in its early stages, and there are still several limitations and challenges that need to be addressed.
One primary concern is the potential for the immunosuppressive tumor microenvironment (TME) to subvert the anti-tumor functions of CAR-Ms, although preclinical models suggest that CAR-Ms may possess the ability to reprogram the TME.
There is still uncertainty around the efficacy of CAR-Ms as a monotherapy, while combination therapies with other forms of cancer immunotherapy (for example, checkpoint inhibitors or CAR-T) may be required to address the complexities of the TME and ensure improved therapeutic outcomes.
Manufacturing processes, cryopreservation techniques, and repeated dosing regimens for CAR-Ms also require ongoing optimization to maintain persistent and robust anti-tumor surveillance.
Figure 3. CAR-M enhances the anti-tumor cells by increasing expression of inflammatory factors, phagocytosis and antigen presentation ability to T cells. Differentiation (Hang). 2023; 130:51-57. Image Credit: ACROBiosystems
Conclusion
iPSC technology has revolutionized cellular immunotherapy. Developments in this area have enabled the creation of a sustainable source for various immune effector cells, acquiring these from healthy donor sources.
These versatile allogeneic cell therapy platforms continue to progress through clinical testing, and it is anticipated that they will be transformational in terms of improving the treatment landscape for both hematological and solid cancers.
It is also expected that these platforms will result in the development of more effective and better-tolerated immunotherapies for a wide range of indications.
ACROBiosystems is committed to the ongoing development of high-quality cell culture reagents that are key to the clinical stage of immune cell therapy.
Utilizing the company’s strict GMP-grade quality management system, ACROBiosystems has successfully developed a wide range of high-quality GMP-grade growth factors, including VEGF, Flt-3L, DLL4, SCF, IL-2, IL-7, and IL15.
These growth factors have been specifically designed to support iPSC-derived cell therapy development and enable large-scale clinical manufacturing.
References and further reading
- Zhou Y, Li M, Zhou K, Brown J, Tsao T, Cen X, Husman T, Bajpai A, Dunn ZS, Yang L. Engineering Induced Pluripotent Stem Cells for Cancer Immunotherapy. Cancers (Basel). 2022 May 1;14(9):2266. doi: 10.3390/cancers14092266. PMID: 35565395; PMCID: PMC9100203.
- Goldenson BH, Hor P, Kaufman DS. iPSC-Derived Natural Killer Cell Therapies - Expansion and Targeting. Front Immunol. 2022 Feb 3;13:841107. doi: 10.3389/fimmu.2022.841107. PMID: 35185932; PMCID: PMC8851389.
- Sloas C, Gill S, Klichinsky M. Engineered CAR-Macrophages as Adoptive Immunotherapies for Solid Tumors. Front Immunol. 2021 Nov 24;12:783305. doi: 10.3389/fimmu.2021.783305. PMID: 34899748; PMCID: PMC8652144.
- Wang C, Liu J, Li W.’ Off the shelf’ immunotherapies: Generation and application of pluripotent stem cell-derived immune cells. Cell Prolif. 2023 Apr;56(4):e13425. doi: 10.1111/cpr.13425. Epub 2023 Mar 1. PMID: 36855955; PMCID: PMC10068955.
- Kao C-Y, Mills JA, Burke CJ, Morse B, Marques BF. Role of Cytokines and Growth Factors in the Manufacturing of iPSC-Derived Allogeneic Cell Therapy Products. Biology. 2023; 12(5):677. https://doi.org/10.3390/biology12050677
- Hang S, Wang N, Sugimura R. T, NK, then macrophages: Recent advances and challenges in adaptive immunotherapy from human pluripotent stem cells. Differentiation. 2023 Mar-Apr;130:51-57. doi: 10.1016/j.diff.2023.01.001. Epub 2023 Jan 18. PMID: 36682340.
- Shin MH, Kim J, Lim SA, Kim J, Kim SJ, Lee KM. NK Cell-Based Immunotherapies in Cancer. Immune Netw. 2020 Mar 9;20(2):e14. doi: 10.4110/in.2020.20.e14. PMID: 32395366; PMCID: PMC7192832.
Acknowledgments
Produced from materials originally authored by ACROBiosystems.
About ACROBiosystems
ACROBiosystems is a cornerstone enterprise of the pharmaceutical and biotechnology industries. Their mission is to help overcome challenges with innovative tools and solutions from discovery to the clinic. They supply life science tools designed to be used in discovery research and scalable to the clinical phase and beyond. By consistently adapting to new regulatory challenges and guidelines, ACROBiosystems delivers solutions, whether it comes through recombinant proteins, antibodies, assay kits, GMP-grade reagents, or custom services. ACROBiosystems empower scientists and engineers dedicated towards innovation to simplify and accelerate the development of new, better, and more affordable medicine.
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