Chimeric antigen receptor (CAR) T-cell and T-cell receptor (TCR) T-cell therapies are promising treatments for a range of cancers, offering hope to patients whose cancers have become refractory to conventional therapeutic options.
Speakers at the recent CAR-TCR Summit Europe in London agreed that despite their efficacy, CAR/TCR-T cell therapy faces challenges that can result in high costs, and limited accessibility.
“Investment in advanced therapies is dropping so drug developers are restricting their pipeline development to save costs,” noted Qian Liu, PhD, head of plasmid engineering & lentiviral vectors (LVVs), WuXi Advanced Therapies. “This means many therapies are slower to reach regulatory approval and commercialization and are usually expensively priced, which restricts market and patient access.”
“With cell therapy many of the cost and time issues are related to manufacturing complexity,” added Victor Vinci, PhD, global VP, product development, Catalent Biologics. “There is variability in the initial quality of the patient’s T cells, as well as the reagents, growth media and range of equipment and automation available for the different production stages, which means there is currently no one size fits all solution for CAR-T manufacturing.”
Optimizing the process
Enhancing manufacturing efficiency is crucial for scaling up production, reducing costs, and ultimately making CAR/TCR-T therapy more accessible to patients. However, the manufacturing process for CAR/TCR-T therapies is complex, involving numerous steps including apheresis, T-cell selection, genetic modification, transduction, expansion, purification, and fill/ finish.
Ali Mohamed, PhD, senior VP, CMC, Immatics, discussed how evaluating different steps in the process had enhanced manufacturing of its ACTengine® IMA203 and IMA203CD8 TCR-engineered cell therapies (TCR-T) that target PRAME (PReferentially expressed Antigen in MElanoma). “ACTengine is our personalized cell therapy approach for patients with advanced solid tumors,” he said.
According to Mohamed, Immatics’ scientists have made several alterations to the standard method of producing TCR-T cells to enhance the manufacturing process. For example, they have moved to a serum-free transduction stage, where serum is not added during transduction and this, Mohamed says: “has significantly increased the numbers of T cells transfected without affecting cell viability, cell expansion, or the cell’s phenotype.”
Another process change that Immatics has made is to remove monocytes and adherent cells by resting T cells in plasticware, such as a CellSTACK, for a few hours. “Monocytes can make up as much as 50 percent of the T cells we collect during apheresis,” explained Mohamed. “They sometimes recognize viral vectors as foreign and destroy them, which can result in their rapid clearance and lower T-cell transduction rates. By removing them we have seen our transduction rates increase significantly.”
The current manufacturing process implements enrichment of CD4 and CD8 T cells using specific antibodies, thereby replacing the adherent cells that have been depleted.
“By selecting CD8 and CD4 cells we can use a defined T cell population at the start of the manufacturing process. This can increase the chances of manufacturing TCR-T cells in sufficient numbers to reach the required cell dose,” pointed out Mohamed.
“In using these three process optimization steps, we can produce TCR-T cells at the recommended Phase II dose (RP2D, 1-10×109 total TCR-T cells) in just 14 days with a seven-day manufacturing process plus seven-day QC release testing. Using our optimized process, we have increased our seeding density and use fewer vessels. All these features help us reduce costs, shorten the turnaround time, and provide the cell products to patients faster while maintaining a manufacturing success rate of over 95%.”
Catalent’s Vinci also stated that process optimization is key for derisking and streamlining a manufacturing pathway. “We have used a Quality by Design (QbD) approach for process optimization and have developed our UpTempo℠ CAR-T cell therapy platform for manufacturing autologous cell therapy,” he told the audience.
According to Vinci, the Catalent platform provides a modular, flexible CAR-T cGMP workflow which utilizes aseptically connected, closed systems including the G-Rex®, Xuri™ and CliniMACS Prodigy® to automate, evaluate, and optimize the manufacturing process. “We produce T-cell therapies that typically have around 90 percent cell viability at harvest. This ensures our manufacturing is efficient which reduces costs,” explained Vinci.
Improving viral gene delivery
To reduce some of the costs involved with manufacturing CAR-T therapies, WuXi Advanced Therapies is developing technologies such as the XOFLX™ packaging and producer cell lines. These cell lines are designed to reduce the cost of producing LVVs, which are commonly used for delivering therapeutic genes in cell therapy as they can efficiently modify T cells in a permanent manner and have a reliable safety profile for this application.
“The industry standard for LVV manufacture is to use four plasmids. A transfer vector containing the gene of interest, two packaging plasmids, and an envelope plasmid,” explained Liu. “What we have done with our XOFLX system is to first develop a Packaging Cell Line, which has all the LVV packaging elements stably integrated into the cells’ genome and only requires transfection of one transfer plasmid for LVV production. Additionally, we developed XOFLX Producer Cell Lines, which have also integrated the LVV genomes containing the therapeutic genes and allow scalable transfection-free LVV production.”
Liu presented data to show that at 10 L scale the XOFLX Packaging Cell Line produced comparable LVV titers when compared to WuXi Advanced Therapies’ conventional LVV production system. A research cell bank and a master cell bank have been created for the Packaging Cell Line. She also showed 1 L LVV production data from XOFLX Producer Cell Lines encoding enhanced green fluorescent protein (eGFP) or a therapeutic transgene, which could be easily scaled up from shake flask production due to the simplified, transfection-free process.
“As our XOFLX system only uses one transfer plasmid or no plasmid at all for LVV production, this reduces the costs of plasmid use and the complexity of LVV manufacturing, which provides cost and quality benefits for drug developers and ultimately for patients,” concluded Liu.
The road less travelled—non viral gene delivery
According to Ting-Wan Lin, PhD, director, business development of GenomeFrontier Therapeutics, the firm is focusing on making advanced affordable cell therapies but is choosing the less well-trodden path of using non-viral cell engineering.
Lin explained the rationale behind this decision: “Despite advances in viral vector design, there are some challenges and/or disadvantages associated with virus-based vectors for gene therapy, such as their intrinsic safety concerns, costly vector manufacturing and limited payload capacity. A non-viral approach for cell engineering can overcome these drawbacks but poses other challenges including poor gene delivery rate, ineffective gene integration, and low cell expansion capacity caused by using electroporation-based gene delivery.”
To overcome the challenges currently encountered using either viral or non-viral cell engineering technologies, GenomeFrontier Therapeutics has developed Quantum Engine™, a technology for facilitating development and manufacturing of high quality, clinical-scale, and virus-free cell and gene therapy products. This system synergistically integrates four platforms, Quantum pBac™, Quantum Nufect™, iCellar™, and G-Tailor™, for therapeutic gene integration, gene delivery, cell expansion, and candidate gene design, respectively.
Lin states: “Quantum pBac, the key platform of Quantum Engine, is our proprietary piggyBac-based transposon, which is potentially safer and much more effective for integrating larger sized gene compared to hyperactive piggyBac, the commercially available piggyBac vector. By finely tuning Quantum pBac along with the other three platforms, we have recently developed a robust Quantum engine, named Quantum CART (qCART), for development and manufacturing of multiplex CARTs.”
Lin presented data demonstrating that qCART™ produced CAR-T cells that yielded higher percentages of CAR+ stem cell memory T cells (TSCMs) with both CD4 and CD8 plus low expression of senescence/ exhaustion markers and good expansion capacity. Furthermore, these CAR-T cells also demonstrated robust anti-tumor efficacy in both lymphoma and gastric solid tumor mice models.
“Our qCART system not only enables us to produce high-quality and clinical scale CAR-T cells with great product consistency in a time- and cost-effective manner, but also is capable of rejuvenating aged and exhausted T-cells in refractory patients,” noted Lin. “Quantum Engine is a powerful technology, enabling us to build cell and gene therapy pipelines by using piggyback and thus riding on the shoulder of giants. Our lead candidate, GF-CART01, a CD20/CD19 targeting CAR-T therapy to treat B cell malignancies has shown promising results in pre-clinical studies of mice and we are looking for partners to work with.”
Enhancing manufacturing efficiency is critical for scaling up production, driving down costs, and increasing the accessibility of CAR-T and TCR-T therapies. Speakers at the CAR-TCR Summit Europe agreed that by embracing closed automated systems and adopting standardization and optimization strategies, manufacturers could overcome existing challenges and realize the full potential of CAR-T cell therapy as transformative treatments.
Sue Pearson, PhD, is a freelance writer based in London.
