Engineered immune cells known as CAR T-cells have revolutionized the treatment of certain blood cancers and offer potential cures for autoimmune diseases. However, traditional ex vivo CAR T-cell therapies are complex, costly, and difficult to deliver. In vivo CAR T-cell generation, which reprograms immune cells directly within the body, is emerging as a promising alternative. Several companies are advancing in vivo CAR T-cell therapies into clinical trials, with the goal of providing faster, better, and cheaper treatments.
Advantages of In Vivo CAR T-Cell Therapy
According to Phil Johnson, CEO of Interius BioTherapeutics, in vivo CAR T-cell generation is significantly faster and more cost-effective than ex vivo methods. The estimated cost of goods for reprogramming cassettes could be as low as $5,000 per dose. Furthermore, in vivo CAR T-cells may be more effective cancer fighters because patients retain intact immune systems and the cells are less exhausted compared to ex vivo CAR T-cells.
Delivery Methods: Lentiviral Vectors vs. Lipid Nanoparticles
Several companies are exploring different gene therapy vectors to deliver CAR payloads to immune cells. Interius, Umoja, and Kelonia are using engineered lentiviral vectors for permanent changes in immune cells, while Capstan, Myeloid Therapeutics, Orbital, and Orna are using lipid nanoparticles (LNPs) with RNA molecules for transient CAR expression. Sanofi has also disclosed three in vivo CAR T-cell programs in preclinical development.
The success of these therapies depends on the vectors, targeted immune cells, CAR payloads, and disease settings. Adrian Bot, CSO of Capstan, anticipates that multiple trials will yield significant data by 2026, potentially reclassifying CAR T-cells as gene therapies.
Lentiviral Reprogramming Strategies
Christian Buchholz, head of molecular biotechnology and gene therapy research group at the Paul-Ehrlich-Institut, drew inspiration from earlier research using measles virus to target cancerous immune cells. He engineered lentiviruses to express antibody-based cell targeting moieties and measles virus glycoproteins to target specific cell types.
Interius has embedded an anti-CD7 antibody fragment into its vector to target CD7+ cells, enabling the targeting of both T cells and NK cells. Umoja uses a multidomain solution to efficiently target a different subset of T cells, achieving a reprogramming efficiency of around 50%.
Clinical Trial Landscape and Safety Considerations
Both Interius and Umoja are enrolling patients in phase I cancer trials. Interius is targeting CD20, while Umoja is advancing a CD19-targeted in vivo CAR T-cell therapy for both CAR-T-naive and CAR-T-exposed patients, as well as a CD22-targeted in vivo CAR T-cell therapy.
Key safety concerns include off-tissue reprogramming, potential for secondary cancers, cytokine release syndrome (CRS), and immune cell-associated neurotoxicity syndrome (ICANS). Researchers will also monitor the immunogenicity profile of in vivo CAR T-cells, as patients are not lymphodepleted before treatment.
Expanding Beyond Cancer: Autoimmune Applications
Beyond cancer, autoimmune applications are also being explored. Interius plans to enter clinical trials for a CD19-targeted in vivo CAR T-cell therapy in autoimmune diseases in 2025. Umoja and IASO Biotherapeutics aim to start testing a CD22-targeted candidate in vivo CAR T-cell therapy in China for autoimmune diseases next year.
Transient Transformations with Lipid Nanoparticles
Capstan and other companies are using mRNA-loaded LNPs for transiently retraining T cells to express a B-cell-killing CAR. LNPs offer advantages in tunability and ease of manufacturing. Capstan is conjugating an anti-CD8 antibody to its vectors to target CD8+ T cells, while overhauling the CAR construct for rapid effect.
Beyond T Cells: Targeting Myeloid Cells
Researchers are also exploring the use of both lentiviral and LNP vectors for reprogramming myeloid cells. Myeloid Therapeutics has two in vivo CAR products in the clinic, targeting solid tumor cells expressing TROP2 or GPC3. Carisma and Moderna are also prioritizing an LNP-based GPC3 CAR macrophage reprogramming cassette for liver cancer. CAR myeloid cells may offer advantages in penetrating and surviving in the tumor microenvironment.
