In vivo CAR-T therapy using lipid nanoparticles (LNPs) represents a transformative advancement in immunotherapy, offering a radical departure from traditional ex vivo cell engineering. Conventional CAR-T therapies, while effective in certain hematological cancers, require the extraction, modification, and reinfusion of a patient’s own T cells, a process that is logistically complex, time-consuming, and expensive. In contrast, in vivo CAR-T therapy proposes a streamlined approach: reprogramming immune cells directly inside the patient’s body.
This innovative method leverages messenger RNA (mRNA) to temporarily instruct T cells to express synthetic receptors, chimeric antigen receptors (CARs), that allow them to identify and destroy disease-associated cells. These mRNA payloads are encapsulated within lipid nanoparticles, a clinically validated delivery system that protects the genetic material, facilitates cellular uptake, and ensures the message reaches the right immune cells. By circumventing the need for viral vectors and personalized cell processing, this technique holds the promise of faster deployment, reduced costs, and improved accessibility.
Furthermore, the transient nature of mRNA expression provides a built-in safety mechanism, reducing the risk of long-term side effects often seen with permanently modified CAR-T cells. This is particularly advantageous for non-cancer indications such as fibrosis, autoimmune disorders, and infectious diseases, where precise temporal control over immune activation is crucial.
In this blog post, we’ll explore the foundations of in vivo CAR-T therapy, examine its underlying technology, discuss current research breakthroughs, address scientific and manufacturing challenges, and consider the future potential of this emerging field. Whether you're a researcher, biotech professional, or simply curious about next-generation therapeutics, this overview will equip you with a deeper understanding of this cutting-edge approach to immune engineering.
Chimeric Antigen Receptor (CAR) T cell therapy is a form of immunotherapy that empowers a patient's own T cells to recognize and attack diseased cells, most commonly cancerous ones. This is achieved by genetically engineering the T cells to express synthetic receptors (CARs) that specifically bind to antigens present on the surface of target cells.
The traditional approach involves extracting T cells from the patient’s blood, modifying them ex vivo using viral vectors to introduce the CAR gene, expanding the engineered cells in culture, and finally reinfusing them back into the patient. While this method has shown remarkable efficacy in treating certain blood cancers like B-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma, it is not without significant drawbacks.
These include the high cost and complexity of individualized manufacturing, the time delay between collection and reinfusion, and the risk of serious side effects such as cytokine release syndrome and neurotoxicity. As a result, researchers are actively exploring more accessible and safer alternatives, among them, in vivo CAR-T therapy.
In vivo CAR-T therapy offers a paradigm shift by bypassing the need for ex vivo cell manipulation. Instead of extracting and engineering T cells in a lab, this approach delivers the genetic instructions directly into the body using lipid nanoparticles loaded with mRNA encoding the desired CAR construct.
Once administered intravenously, these nanoparticles target circulating T cells, enabling them to transiently express the CAR and perform their therapeutic function on-site. This streamlined strategy brings several compelling advantages:
Altogether, in vivo CAR-T therapy represents a more agile, scalable, and potentially safer platform for immune modulation across a range of diseases.
Lipid nanoparticles are central to the in vivo CAR-T strategy. These nanoscale carriers protect mRNA from degradation, facilitate its uptake into target cells, and promote endosomal escape to allow translation in the cytoplasm. LNPs typically consist of four components: ionizable lipids, cholesterol, phospholipids, and PEG-lipids. The ionizable lipid is particularly important, as it becomes positively charged in acidic endosomes, aiding in membrane disruption and cargo release.
To increase specificity, LNPs can be functionalized with antibody fragments targeting T cell markers such as CD5, CD3, or CD7. These antibody-LNP conjugates (Ab-LNPs) allow for selective delivery to T cells, enabling controlled and efficient CAR expression in vivo. Moreover, optimization of LNP composition—such as lipid structure and shielding lipid density, can reduce off-target delivery, enhance immune cell uptake, and minimize liver accumulation.
By combining mRNA payload design with targeted delivery systems, LNPs serve as a modular, tunable vehicle for in vivo immune engineering.
Recent preclinical studies have demonstrated the therapeutic promise of in vivo CAR-T approaches using LNPs. In a 2025 study, researchers delivered mRNA encoding an anti-FAP CAR into mice using CD5-targeted LNPs. This generated CAR T cells in vivo that selectively depleted fibrogenic hepatic stellate cells, significantly reducing liver fibrosis in a model of metabolic dysfunction-associated steatohepatitis (MASH).
Similarly, other studies showcased a modular LNP platform engineered for extrahepatic targeting. These Ab-LNPs successfully transfected T cells in vivo with CAR mRNA, resulting in functional CAR T cells capable of depleting B cells and demonstrating transient, tunable activity. Notably, this approach bypassed hepatic uptake and achieved improved biodistribution through refined LNP chemistry.
Together, these studies validate the feasibility of generating CAR T cells in vivo and provide a framework for treating diseases beyond cancer, including fibrosis and chronic inflammation.
The mechanism behind in vivo CAR-T therapy involves a coordinated sequence of molecular and cellular events:
Because the mRNA is not integrated into the genome, expression is temporary, reducing long-term risks and allowing greater control over treatment dynamics.
While CAR-T therapies originated in oncology, the flexibility and safety profile of in vivo CAR-T opens the door to a wider range of applications beyond cancer:
The versatility and adaptability of the in vivo approach make it a promising candidate for conditions where conventional CAR-T is either too risky or logistically unfeasible.
Despite significant potential, several scientific and technical challenges remain for in vivo CAR-T therapy:
Solving these challenges is crucial to safely advancing this platform into human trials.
As with all novel therapies, in vivo CAR-T must address specific regulatory and safety concerns to move from bench to bedside:
Overall, in vivo CAR-T benefits from being built on validated platforms, but it must meet the same rigorous standards as all advanced therapies.
For in vivo CAR-T therapies to become viable clinical products, robust manufacturing and chemistry, manufacturing, and controls (CMC) strategies are essential. The production of mRNA-loaded LNPs involves intricate steps, each of which impacts the product’s quality, stability, and scalability.
Addressing these manufacturing challenges early in development increases the likelihood of successful scale-up and regulatory approval.
In vivo CAR-T therapies rely on highly efficient gene delivery systems. While LNPs are the current frontrunners, several other delivery platforms are being investigated:
LNPs currently provide the best balance of efficiency, safety, scalability, and clinical validation, particularly in the context of mRNA delivery.
The future of in vivo CAR-T therapy is bright, with several avenues for further innovation:
As formulation chemistry, delivery strategies, and regulatory experience continue to evolve, in vivo CAR-T therapies may become a mainstay of personalized and off-the-shelf immunotherapy.
In vivo CAR-T therapy using lipid nanoparticles is redefining what’s possible in cell and gene therapy. By simplifying the process of CAR generation and eliminating the need for ex vivo manipulation, this approach enables faster, more accessible, and potentially safer immunotherapies.
With promising data in preclinical models of cancer and fibrosis, and ongoing innovation in LNP design and mRNA engineering, the stage is set for rapid advancement toward clinical application. The coming years will be critical for demonstrating efficacy, safety, and scalability, but the foundation has already been laid.
This emerging field holds the potential not just to improve immunotherapy, but to expand its reach to entirely new categories of disease.
When looking to transform you’re in vivo CAR-T vision into a clinical reality be sure to have the formulation, manufacturing, and delivery expertise you can trust.