Chimeric Antigen Receptor (CAR) T-cell therapy has revolutionized the treatment of certain blood cancers, offering hope to patients with previously limited options. This immunotherapy works by genetically engineering a patient’s own T-cells to express a synthetic receptor that specifically targets cancer cells. The current standard, ex vivo CAR-T therapy, requires a complex and time-consuming manufacturing process outside the body. In vivo CAR-T therapy represents the next technological step, aiming to overcome these limitations by modifying the patient’s T-cells directly within their body. This approach leverages advanced gene delivery systems to create a more accessible, faster, and potentially less toxic cancer treatment option.
Comparing Ex Vivo and In Vivo CAR-T Therapy
The existing ex vivo method involves collecting T-cells from the patient, sending them to a specialized facility for genetic modification and expansion, and then infusing them back into the patient. This process, often called the “vein-to-vein” time, can take several weeks, which is a significant delay for patients with aggressive, rapidly progressing cancers. The high cost of this personalized manufacturing, which can reach hundreds of thousands of dollars per treatment, also limits patient access and places a strain on healthcare systems.
Manufacturing ex vivo products requires specialized Good Manufacturing Practice (GMP) facilities and highly trained staff, further restricting the number of treatment centers that can offer the therapy. Furthermore, patients typically require lymphodepleting chemotherapy before infusion to make space for the new CAR-T cells to thrive, adding a layer of toxicity and risk of infection. The in vivo approach is designed to simplify this entire paradigm.
By delivering the genetic material directly to T-cells inside the body, in vivo CAR-T aims to create an “off-the-shelf” product. This eliminates the need for apheresis, external cell processing, and the lengthy wait time associated with ex vivo manufacturing. This approach increases accessibility and could be administered in a non-specialized hospital setting. Some in vivo platforms are also exploring systems that do not require preconditioning chemotherapy, which could reduce treatment-related toxicity for the patient.
Engineering the Change: Delivery Systems for In Vivo CAR-T
The feasibility of in vivo CAR-T rests on the delivery systems used to modify T-cells within the patient’s bloodstream. These systems must be specific to ensure the CAR gene is delivered only to T-cells and not to other healthy cells, which could cause off-target toxicity. The two primary approaches involve modified viral vectors and non-viral nanocarriers.
Viral vectors, such as modified lentiviruses and adeno-associated viruses (AAVs), are engineered to selectively target T-cell surface markers, such as CD3 or CD8. Lentiviral vectors are particularly noted for their ability to integrate the CAR gene permanently into the T-cell genome, potentially leading to durable expression and long-lasting therapeutic effect. However, this stable integration carries a theoretical risk of insertional mutagenesis, where the viral DNA disrupts a healthy gene.
Non-viral systems, predominantly Lipid Nanoparticles (LNPs), offer an alternative by encapsulating the genetic material, usually messenger RNA (mRNA) or DNA plasmids, for delivery. LNPs can be surface-engineered with targeting ligands to home in on T-cells, achieving cell-specific transduction. An advantage of using mRNA is that it results in transient CAR expression, which can be beneficial for safety as the effect fades over time, potentially allowing for better control over severe side effects like cytokine release syndrome.
The goal across all platforms is to create a vector that is both efficient at transducing T-cells and selective to avoid affecting non-target cells. For example, some companies use targeted LNPs (tLNPs) that deliver an anti-CD19 CAR mRNA preferentially to CD8-expressing cytotoxic T-cells. Other viral vector platforms are modified with T-cell-specific binding components to ensure the genetic payload is delivered only to the intended immune cell population.
Leading Companies and Clinical Pipeline Focus
The development of in vivo CAR-T is being driven by several biotech companies. A major area of focus is on hematological malignancies and the emerging application of CAR-T in autoimmune disorders. Companies are categorized by their chosen delivery technology, typically a modified viral vector or a targeted non-viral system.
Interius BioTherapeutics is advancing a lentivirus-based approach with its lead candidate, INT2104, currently in a Phase 1 clinical trial for B-cell malignancies. This therapy targets CD20-positive B-cells and is engineered to generate both CAR-T and CAR-NK cells in vivo. Interius’s platform is designed to target CD7-positive T and Natural Killer (NK) cells to deliver the CAR transgene without preconditioning chemotherapy.
Umoja Biopharma utilizes its VivoVec platform, which is also a lentiviral vector system, for in vivo CAR-T generation. Their lead oncology candidate, UB-VV111, is a CD19-directed in situ CAR-T that has received Fast Track Designation from the FDA for relapsed/refractory large B-cell lymphoma and chronic lymphocytic leukemia. Umoja is also developing UB-VV400, a CD22-targeted program, and has partnered with AbbVie to explore the potential of its CD19-directed candidates.
Capstan Therapeutics utilizes the non-viral approach, leveraging its CellSeeker targeted Lipid Nanoparticle (tLNP) platform. Their lead candidate, CPTX2309, is an anti-CD19 CAR-T that delivers mRNA via a tLNP to CD8-expressing T-cells. Capstan’s initial Phase 1 trial for CPTX2309 is focused on B cell-mediated autoimmune disorders, demonstrating the versatility of the in vivo approach beyond oncology.
Kelonia Therapeutics uses a lentiviral vector technology, called the iGPS (in vivo Gene Placement System) platform, for targeted gene delivery. Their lead program, KLN-1010, is an anti-BCMA CAR-T therapeutic that entered a Phase 1 study for relapsed and refractory multiple myeloma. This focus on BCMA, a validated target for multiple myeloma, positions Kelonia to potentially overcome the logistical hurdles of current BCMA-targeted ex vivo therapies. Other companies like EsoBiotec, with its BCMA-targeted ESO-T01, are also moving into the clinic.
Regulatory Landscape and Future Development Milestones
The regulatory path for in vivo CAR-T therapies presents challenges due to genetically modifying cells inside the patient. Unlike ex vivo products, where modified cells can be thoroughly tested for quality and safety before infusion, in vivo approaches rely on the predictability of the delivery vehicle. A primary concern for regulators is the risk of off-target effects, where the gene-delivery vector modifies unintended cells or tissues, potentially leading to organ toxicity.
Another regulatory hurdle involves the potential for insertional mutagenesis, particularly with integrating viral vectors like lentivirus, which could cause secondary cancers years later. Authorities, including the FDA, are demanding preclinical data demonstrating the T-cell specificity of the vector and the long-term safety profile. The regulatory framework for gene therapies is evolving to provide clarity for sponsors, including guidance on acceptable trial designs and control strategies.
Key milestones include initial Phase 1 trials to establish safety and a minimum effective dose. Developers must demonstrate that the in vivo generated CAR-T cells are functional and persistent enough to achieve efficacy comparable to established ex vivo products. Scaling of manufacturing is also necessary, as these therapies must be produced as an off-the-shelf biologic. The first demonstration of comparable efficacy in a large patient cohort, potentially without the need for lymphodepleting chemotherapy, will be the validation required for market approval.