Two birds with one stone: faster, fitter CAR T cells

Chimeric antigen receptor T-cell (CAR T) therapy faces significant barriers to accessible, safe and effective treatment, including lengthy, complex, and costly manufacturing, poor T-cell quality, CAR T–associated toxicities, and suppressive tumor microenvironment. In this issue of Blood, Durgin et al¹ seek to address both challenges of manufacturing complexity and poor T-cell quality using a novel platform for single-day CAR T manufacturing (see figure). Conventional CAR T production takes more than 1 week from initial T-cell activation to the end of ex vivo CAR T expansion.² Moreover, prolonged, strong activation signals used during ex vivo manufacturing have been shown to produce more exhausted, less metabolically-fit CAR T products.³ Additionally, less differentiated CAR Ts have been associated with favorable clinical outcomes.⁴

Single-day CAR T manufacturing protocol involves lentiviral transduction of nonactivated T cells with CAR and IL-18 transgenes and results in more naïve CAR T products, which demonstrate enhanced persistence and antitumor activity in liquid and solid tumor models.

Durgin et al report that nonactivated CAR Ts engineered to secrete interleukin-18 (IL-18) and manufactured in a single day result in improved persistence, antitumor activity, and metabolic fitness in preclinical models. Rather than viewing speed as an end in itself, the authors demonstrate that how CAR Ts are manufactured—specifically, whether T-cell receptor (TCR) activation is imposed ex vivo—fundamentally determines T-cell fate, metabolic competence, and durability. By combining a single day, nonactivated manufacturing platform with IL-18 cytokine armoring, this work argues persuasively that biological quality, not just calendar time, defines the true value of rapid CAR T production. The authors observed enhanced tumor clearance in both liquid and solid tumor models. This study builds on previous work reported by the group on their observations of superior antitumor efficacy of nonactivated CAR Ts compared to activated ones and on the rapid production of nonactivated, highly potent CAR Ts.^5,6

The field for rapid CAR T production is increasingly expanding. Several academic and commercial platforms now support CAR T products manufactured in 1 to 3 days, including systems based on intensified CD3/CD28 activation, streamlined lentiviral transduction, or automated closed-system bioreactors. Several companies have advanced shorter manufacturing platforms to the clinic, including Novartis (T-Charge) and Bristol Myers Squibb (NexT). The process described by Durgin et al is unique in that it both uses lentiviral transduction and does not require prior T-cell activation through the TCR for CAR expression and function. What distinguishes the current study is the demonstration that IL-18 synergizes specifically with the nonactivated manufacturing state of the T cells, rather than simply acting as a generic stimulant. Transcriptomic analyses show that IL-18 further reinforces memory-associated programs (IL7R, KLF2), suppresses exhaustion markers (PDCD1, TOX, and HAVCR2), and enhances biosynthetic and DNA repair pathways. Metabolically, IL-18 armored nonactivated CAR Ts display increased glutamine utilization, polyamine metabolism, and mitochondrial flexibility, suggesting that cytokine armoring here functions less as an effector boost and more as a stability factor that protects and extends T-cell fitness under stress. This group recently published potent activity of IL-18–armored CAR Ts (huCAR T19-IL-18) utilizing a 3-day manufacturing process in a clinical trial for patients with relapsed lymphoma.⁷

Although this platform significantly shortens manufacturing time, it is unclear whether or not it will impact the lengthy vein-to-vein times (from apheresis to CAR T infusion) due to additional factors such as manufacturing capacity or product release testing, as seen in their previous rapid manufacture CAR T trial.⁷ Although in theory, rapid manufacture would shift CAR T production toward decentralized or point-of-care manufacturing, delays due to mandated product release testing and regulatory compliance would remain. Furthermore, additional safety testing would be foreseeable given the potential for residual viral vector, non–T cells, and other impurities to be administered along with the CAR Ts with infusions given just 24 hours after T-cell transduction.⁸ Conventional identity and potency assays, such as CAR surface expression and interferon-gamma release, would also need to be modified for rapid CAR T protocols.

However, this platform of rapid CAR T manufacturing will reduce manufacturing complexity, cost, and staff time. In addition, a major benefit is in the resulting less differentiated CAR T products, allowing for lower doses and further reduction in manufacturing costs as well as improved efficacy and outcomes. There has long been an association between naïve or stem-like T-cell phenotypes and increased persistence and response to CAR T therapy^9,10; rapid CAR T generation from nonactivated T cells as presented by Durgin et al offers a faster, simpler method to promoting naïve T-cell populations compared to lengthy and more complex preselection of memory subsets.

This study advances a clear and provocative thesis: rapid CAR T manufacturing must be judged by the quality of the cellular state it produces, not just by the number of days it saves. By eliminating ex vivo TCR activation and integrating IL-18 armoring, the authors define a CAR T product that is not only faster to manufacture, but intrinsically better equipped for persistence, metabolic resilience, and durable antitumor activity.

Conflict-of-interest disclosure: S.S.K. is an inventor on patents in the field of CAR immunotherapy that are licensed to Novartis (through an agreement between the Mayo Clinic, the University of Pennsylvania, and Novartis), Humanigen/Taran (through the Mayo Clinic), MustangBio (through the Mayo Clinic), Chymal (through the Mayo Clinic), and Immix (through the Mayo Clinic); receives research funding from Kite, Gilead, Juno, Bristol Myers Squibb (BMS), Novartis, Humanigen/Taran, MorphoSys, Tolero, Sunesis/Viracta, LifEngine Animal Health Laboratories Inc, and Lentigen; has participated in advisory meetings with Kite/Gilead, Calibr, Luminary Therapeutics, Humanigen, Juno/BMS, Capstan Bio, Carisma, and Novartis; has served on the data safety and monitoring board with Humanigen and Carisma; and has served as a consultant for Torque, Calibr, Novartis, Capstan Bio, Carisma Therapeutics, JW Therapeutics, and Humanigen.